Journal articles on the topic 'Juvenile survival'
To see the other types of publications on this topic, follow the link: Juvenile survival.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Juvenile survival.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Webb, William C., William I. Boarman, and John T. Rotenberry. "Common Raven Juvenile Survival in a Human-Augmented Landscape." Condor 106, no. 3 (August 1, 2004): 517–28. http://dx.doi.org/10.1093/condor/106.3.517.
Full textAbstract:
AbstractAnthropogenic resource subsidies have contributed to the dramatic increase in the abundance of Common Ravens (Corvus corax) in the western Mojave Desert, California, during the past 30 years. To better understand the effects of these subsidies on raven demography, we examined whether survival to juvenile departure from the natal territory could be predicted by a set of environmental and morphological variables, such as nest proximity to anthropogenic resources and juvenile condition. We captured 240 juvenile ravens over 2 years and marked them prior to fledging. Nest proximity to anthropogenic resources and earlier fledging dates significantly predicted raven juvenile survival to departure from the natal territory. The best-fitting mark-recapture models predicted postdeparture survival as a function of time since fledging, nest proximity to anthropogenic resources, and year hatched. The positive effect of nest proximity to anthropogenic resources influenced postdeparture survival for at least 9 months after fledging, as revealed by the mark-recapture analysis. Annual survival was 47% for first-year, 81% for second-year, and 83% for third-year birds. Our results support the hypothesis that anthropogenic resources contribute to increasing raven numbers via increased juvenile survival to departure as well as increased postdeparture survival. We expect raven numbers to grow in concert with the growing human presence in the Mojave Desert unless raven access to anthropogenic resources is diminished.La Sobrevivencia Juvenil de Corvus corax en un Paisaje Mejorado por HumanosResumen. Los subsidios de recursos antropogénicos han contribuido al aumento dramático de la abundancia del cuervo Corvus corax en el occidente del desierto de Mojave durante los últimos 30 años. Para entender los efectos de estos subsidios en la demografía del cuervo, examinamos si la sobrevivencia hasta la salida de los juveniles del territorio natal podría ser predicha por un conjunto de variables morfológicas y ambientales, tales como su cercanía a los recursos antropogénicos y la condición de los juveniles. En dos años capturamos 240 cuervos juveniles y los marcamos antes que desarollaran plumas de vuelo. La cercanía del nido al punto de subsidio más cercano y las fechas tempranas de emplumamiento predijeron significativamente la sobrevivencia de los juveniles hasta su salida del teritorio natal. Los modelos de marcaje y recaptura más adecuados predijeron la sobrevivencia posterior a la salida del territorio como una función del tiempo desde el momento de emplumamiento, la cercanía al punto más cercano de subsidio y el año de nacimiento. Según el análisis de marcaje y recaptura, el efecto positivo de la cercanía a subsidios antropogénicos influye en la sobrevivencia después de la salida del territorio hasta por lo menos 9 meses después del emplumamiento. La sobrevivencia anual fue de 47% en el primer año, de 81% en el segundo año y de 83% para aves en su tercer año. Nuestros resultados apoyan la hipótesis de que los recursos antropogénicos contribuyen al crecimiento de los números de cuervos aumentando la sobrevivencia juvenil antes y después de su salida de los territorios natales. Esperamos que los números de cuervos aumenten en relación con la presencia humana en el desierto de Mojave a menos que su acceso a los recursos antropogénicos sea disminuido.
2
Gillis, Elizabeth A. "Survival of juvenile hares during a cyclic population increase." Canadian Journal of Zoology 76, no. 10 (October 1, 1998): 1949–56. http://dx.doi.org/10.1139/z98-136.
Full textAbstract:
Snowshoe hares (Lepus americanus) are multilittered synchronous breeders that produce up to four distinct litters of young each summer. I used radiotelemetry to determine the effects of juvenile cohort (i.e., litter group) and food availability on postweaning survival of hares in the southwestern Yukon during the increase phase of a hare cycle. During the study, I monitored 86 juvenile hares from control areas and areas in which supplemental food was provided. Twenty-eight-day survival did not differ between food addition and control areas for any juvenile cohort, and survival rates of juveniles (all cohorts combined) did not differ significantly from those of adults (juveniles: 0.91 per 28 days; adults: 0.93 per 28 days). However, when examined by juvenile cohort, survival of third and fourth litters was significantly lower than that of adults and first and second litters. These differences were the result of differential survival among the juvenile cohorts during a 3-month period in the fall (September-November). Predation was the primary proximate cause of death for weaned juvenile hares, accounting for 86% of deaths.
3
Gardali, Thomas, Daniel C. Barton, Jennifer D. White, and Geoffrey R. Geupel. "Juvenile and Adult Survival of Swainson's Thrush (Catharus Ustulatus) in Coastal California: Annual Estimates Using Capture-Recapture Analyses." Auk 120, no. 4 (October 1, 2003): 1188–94. http://dx.doi.org/10.1093/auk/120.4.1188.
Full textAbstract:
Abstract We estimated annual rates of survival for juvenile and adult Swainson's Thrushes (Catharus ustulatus) using capture-recapture analyses from 22 years of mist-neting data in coastal California (n= 2,651 individual captures). Our apparent survival estimate was 56% for adults and 25% for juveniles. We are the first to estimate an annual juvenile survival rate for a Neotropical migrant using capture-recapture probability estimates. Like most estimates of annual survival, we could not distinguish between dispersal away from our study area (which is likely high for juveniles) and mortality. Hence, survival is underestimated. However, our juvenile survival estimate did not include the period from fledging to independence, a time when mortality can be high. Many researchers have assumed juvenile survival to be half that of adult survival in population models (e.g. source-sink). Our juvenile to adult survival ratio was 45% (95% CI = 27 to 65%). We caution researchers from simply assuming that juvenile survival approximates half of adult survival when modeling populations and suggest using a range of values. Using a range of values is prudent because of the potential for annual variation, site-specific variation, and especially because estimates are imprecise or completely lacking.
4
Spaan, Robert S., Clinton W. Epps, Rachel Crowhurst, Donald Whittaker, Mike Cox, and Adam Duarte. "Impact of Mycoplasma ovipneumoniae on juvenile bighorn sheep (Ovis canadensis) survival in the northern Basin and Range ecosystem." PeerJ 9 (January 19, 2021): e10710. http://dx.doi.org/10.7717/peerj.10710.
Full textAbstract:
Determining the demographic impacts of wildlife disease is complex because extrinsic and intrinsic drivers of survival, reproduction, body condition, and other factors that may interact with disease vary widely. Mycoplasma ovipneumoniae infection has been linked to persistent mortality in juvenile bighorn sheep (Ovis canadensis), although mortality appears to vary widely across subspecies, populations, and outbreaks. Hypotheses for that variation range from interactions with nutrition, population density, genetic variation in the pathogen, genetic variation in the host, and other factors. We investigated factors related to survival of juvenile bighorn sheep in reestablished populations in the northern Basin and Range ecosystem, managed as the formerly-recognized California subspecies (hereafter, “California lineage”). We investigated whether survival probability of 4-month juveniles would vary by (1) presence of M. ovipneumoniae-infected or exposed individuals in populations, (2) population genetic diversity, and (3) an index of forage suitability. We monitored 121 juveniles across a 3-year period in 13 populations in southeastern Oregon and northern Nevada. We observed each juvenile and GPS-collared mother semi-monthly and established 4-month capture histories for the juvenile to estimate survival. All collared adult females were PCR-tested at least once for M. ovipneumoniae infection. The presence of M. ovipneumoniae-infected juveniles was determined by observing juvenile behavior and PCR-testing dead juveniles. We used a known-fate model with different time effects to determine if the probability of survival to 4 months varied temporally or was influenced by disease or other factors. We detected dead juveniles infected with M. ovipneumoniae in only two populations. Derived juvenile survival probability at four months in populations where infected juveniles were not detected was more than 20 times higher. Detection of infected adults or adults with antibody levels suggesting prior exposure was less predictive of juvenile survival. Survival varied temporally but was not strongly influenced by population genetic diversity or nutrition, although genetic diversity within most study area populations was very low. We conclude that the presence of M. ovipneumoniae can cause extremely low juvenile survival probability in translocated bighorn populations of the California lineage, but found little influence that genetic diversity or nutrition affect juvenile survival. Yet, after the PCR+ adult female in one population died, subsequent observations found 11 of 14 ( 79%) collared adult females had surviving juveniles at 4-months, suggesting that targeted removals of infected adults should be evaluated as a management strategy.
5
Dreitz, Victoria J., Wiley M. Kitchens, and Donald L. DeAngelis. "Effects of Natal Departure and Water Level on Survival of Juvenile Snail Kites (Rostrhamus Sociabilis) in Florida." Auk 121, no. 3 (July 1, 2004): 894–903. http://dx.doi.org/10.1093/auk/121.3.894.
Full textAbstract:
Abstract Survival rate from fledging to breeding, or juvenile survival, is an important source of variation in lifetime reproductive success in birds. Therefore, determining the relation-ship between juvenile survival and environmental factors is essential to understanding fitness consequences of reproduction in many populations. With increases in density of individuals and depletion of food resources, quality of most habitats deteriorates during the breeding season. Individuals respond by dispersing in search of food resources. Therefore, to understand the influence of environmental factors on juvenile survival, it is also necessary to know how natal dispersal influences survival of juveniles. We examined effects of various environmental factors and natal dispersal behavior on juvenile survival of endangered Snail Kites (Rostrhamus sociabilis) in central and southern Florida, using a generalized estimating equations (GEEs) approach and model selection criteria. Our results suggested yearly effects and an influence of age and monthly minimum hydrologic levels on juvenile Snail Kite survival. Yearly variation in juvenile survival has been reported by other studies, and other reproductive components of Snail Kites also exhibit such variation. Age differences in juvenile survival have also been seen in other species during the juvenile period. Our results demonstrate a positive relationship between water levels and juvenile survival. We suggest that this is not a direct linear relationship, such that higher water means higher juvenile survival. The juvenile period is concurrent with onset of the wet season in the ecosystem we studied, and rainfall increases as juveniles age. For management purposes, we believe that inferences suggesting increasing water levels during the fledging period will increase juvenile survival may have short-term benefits but lead to long-term declines in prey abundance and possibly wetland vegetation structure.
6
Kershner, Eric L., Jeffery W. Walk, and Richard E. Warner. "Postfledging Movements and Survival of Juvenile Eastern Meadowlarks (Sturnella Magna) in Illinois." Auk 121, no. 4 (October 1, 2004): 1146–54. http://dx.doi.org/10.1093/auk/121.4.1146.
Full textAbstract:
Abstract The postfledging period is the least-studied stage of avian life cycles. Survival during this period has crucial effects on population dynamics. Survival of fledged young may be influenced by dispersal from their nest sites, because juveniles must cope with the hazards of novel environments. To better understand this important life stage, we used radiotelemetry techniques to study postfledging movements and survival of 50 juvenile Eastern Meadowlarks (Sturnella magna) at Prairie Ridge State Natural Area in Jasper County, Illinois, in 1999 and 2000. Juveniles began to move away from the nesting area in the third week after fledging. Most juveniles moved only 1–5 km from their birth site by the end of the study (90 days). Juvenile survival for the first 90 days after fledging was estimated as 56–69%. Mortality was greatest during the first week of the postfledging period, likely because of high rates of predation. Juvenile meadowlarks are flightless at fledging and thus are vulnerable to predators. We did not observe a second peak of mortality, as other studies have shown, at independence or when juveniles began to move away from their nest areas. The present study suggests that immediate postfledging movements may not be related to dispersal to future breeding sites, but rather occur in response to immediate needs for food resources and security from predators. Furthermore, the data suggest that presumed mortality patterns and estimated levels of juvenile survival are suspect; that interspecific variability of juvenile survival and postfledging movements may be considerable; and that detailed, longer-duration field studies are necessary to elucidate this important demographic period.
7
Lougheed, Cecilia, Lynn W. Lougheed, Fred Cooke, and Sean Boyd. "Local Survival of Adult and Juvenile Marbled Murrelets and Their Importance for Estimating Reproductive Success." Condor 104, no. 2 (May 1, 2002): 309–18. http://dx.doi.org/10.1093/condor/104.2.309.
Full textAbstract:
Abstract Juvenile ratios estimated using numbers of hatch year (HY) and after-hatch-year (AHY) Marbled Murrelets (Brachyramphus marmoratus) counted concurrently during at-sea surveys have been used to estimate fecundity in this species. These “concurrent” juvenile ratios assume that HY birds remain in an area, and are likely biased because they do not account for potential differences in emigration rate of HY and AHY birds. We studied the emigration rates of adult and juvenile Marbled Murrelets marked with radio-transmitters. Juveniles had a high emigration rate compared to adults. The weekly local survival rate (ϕ) of newly radio-tagged HY birds was 27%. AHY local survival was 95% during incubation and early chick rearing, suggesting a resident population during the breeding season. We calculated juvenile ratios from 1996–1998 using (1) HY counts corrected for emigration and mean AHY counts around the breeding season peak, and (2) HY and AHY counts from concurrent at-sea surveys. The average “corrected” juvenile ratio (0.13 ± 0.05 SE) was higher than the “concurrent” juvenile ratio (0.04 ± 0.02 SE) but lower than estimates of fecundity from nest monitoring (0.18–0.22). Low juvenile ratios from at-sea surveys could result either from an unknown proportion of nonbreeding birds in the population, or, more likely, from differences in the at-sea distribution of AHY and HY birds. Fluctuation in the timing of the peak number of AHY birds across years might result in an uncorrectable bias in the counts. Because of biases and potential problems, caution is needed when interpreting juvenile ratios from at-sea surveys. Supervivencia Local de Brachyramphus marmoratus Adultos y Juveniles y su Importancia para Estimar Éxito Reproductivo Resumen. Utilizamos los cocientes entre individuos juveniles (nacidos en un año) y adultos (nacidos en años anteriores) de Brachyramphus marmoratus, censados simultáneamente durante conteos en el mar, para estimar la fecundidad de esta especie. Estos cocientes “simultáneos” de individuos asumen que los juveniles permanecen en una misma área, y podrían estar sesgados ya que no toman en cuenta diferencias en las tasas de migración de juveniles y adultos. Estudiamos las tasas de emigración de individuos juveniles y adultos de B. marmoratus marcados con radio-transmisores. Los juveniles tuvieron una tasa alta de emigración comparada con los adultos. La tasa de supervivencia local semanal (ϕ) para juveniles fue del 27%. La tasa de supervivencia local para adultos durante la incubación e inicio de la cría de polluelos fue del 95%, sugiriendo que se trata de una población residente durante la estación reproductiva. Calculamos el cociente entre juveniles y adultos para 1996–1998 utilizando (1) conteos de juveniles corregidos por emigración y promedio de adultos contados durante el pico de la estación reproductiva, y (2) juveniles y adultos contados simultáneamente durante los censos. El cociente “corregido” promedio entre juveniles a adultos (0.13 ± 0.05 EE) fue mayor que el cociente “simultáneo” (0.04 ± 0.02 EE) pero menor que las estimaciones de fecundidad obtenidas por medio del monitoreo de nidos (0.18–0.22). Los bajos cocientes obtenidos de conteos en el mar podrían explicarse por la presencia de una proporción desconocida de aves no-reproductivas en la población, o, más probablemente, por diferencias existentes en la distribución de juveniles y adultos en el mar. Fluctuaciones anuales en la sincronización del período pico de la estación reproductiva podrían introducir error a los conteos de adultos. Debido a estos sesgos y problemas potenciales, es importante interpretar con cautela los cocientes entre juveniles y adultos obtenidos de conteos en el mar.
8
Kerr, Tricia D., Stan Boutin, Jalene M. LaMontagne, Andrew G. McAdam, and Murray M. Humphries. "Persistent maternal effects on juvenile survival in North American red squirrels." Biology Letters 3, no. 3 (March 29, 2007): 289–91. http://dx.doi.org/10.1098/rsbl.2006.0615.
Full textAbstract:
Maternal effects can have lasting fitness consequences for offspring, but these effects are often difficult to disentangle from associated responses in offspring traits. We studied persistent maternal effects on offspring survival in North American red squirrels ( Tamiasciurus hudsonicus ) by manipulating maternal nutrition without altering the post-emergent nutritional environment experienced by offspring. This was accomplished by providing supplemental food to reproductive females over winter and during reproduction, but removing the supplemental food from the system prior to juvenile emergence. We then monitored juvenile dispersal, settlement and survival from birth to 1 year of age. Juveniles from supplemented mothers experienced persistent and magnifying survival advantages over juveniles from control mothers long after supplemental food was removed. These maternal effects on survival persisted, despite no observable effect on traits normally associated with high offspring quality, such as body size, dispersal distance or territory quality. However, supplemented mothers did provide their juveniles an early start by breeding an average of 18 days earlier than control mothers, which may explain the persistent survival advantages their juveniles experienced.
9
Mamuaya, Jimmy, Winda M. Mingkid, Ockstan J. Kalesaran, Hengky J. Sinjal, Reiny A. Tumbol, and John L. Tombokan. "The Survival Rate and Growth of Juvenile Crayfish (Cherax quadricarinatus) With Different Types of Shelter." JURNAL ILMIAH PLATAX 7, no. 2 (July 25, 2019): 427. http://dx.doi.org/10.35800/jip.7.2.2019.24510.
Full textAbstract:
An experiment was designed to assess the relative performance of three shelter types on the survival and growth of red-claw crayfish (Cherax quadricarinatus). A 13 days old juvenile crayfish with an average length of 10 mm were cultured in 400 ml water of glass bowl and were provided with one of 3 types of shelter over 19 days. The various shelter types assessed were dried coconut leaves, bamboo and Hydrilla. Juveniles in each bowl were fed with Artemia twice a day morning and in the afternoon. There was no significant effect (P>0.05) of shelter type on the survival rate; however, there was a significant effect (P<0.05) on growth with dried coconut leaves (5.33%) performing significantly better than Hydrilla (2.33%) and bamboo (2.00%). This experiment showed that the shelter types provided had a significant effect on the growth but not in their survival.Keywords: Survival rate, Growth, juvenile Cherax quadricarinatus, ShelterABSTRAKTujuan penelitian ini adalah untuk menganalisis sintasan hidup dan pertumbuhan juvenil lobster air tawar (C. quadricarinatus) dengan shelter yang berbeda. Juvenil lobster yang berumur 13 hari dengan panjang rata rata 10 mm dipelihara dalam wadah toples kaca dengan diberikan ketiga perlakuan selama 19 hari. Ketiga jenis perlakuan adalah daun kelapa kering, bambu dan Hydrilla. Juvenil diberi pakan Artemia 2 kali sehari yaitu pada pagi dan sore hari. Hasil penelitian menunjukkan ketiga perlakuan tidak berbeda nyata terhadap sintasan hidup (P>0.05), namun berbeda nyata (P< 0.05 ) untuk pertumbuhan dengan daun kelapa kering (5.33%), Hydrilla (2.33%) dan bambu (2%). Penelitian ini menunjukkan bahwa jenis shelter memberikan pengaruh nyata terhadap pertumbuhan namun tidak berbeda nyata untuk sintasan hidup.Kata kunci: Sintasan hidup, Pertumbuhan, Juvenil Cherax quadricarinatus, Shelter
10
Munasik, Munasik, Suharsono Suharsono, J. Situmorang, and Kamiso H. N. "Kerapatan dan Kelulushidupan pada Rekrutmen Karang Pocillopora damicornis (Density and Survivorship on the Recruitment of the brooding coral Pocillopora damicornis)." ILMU KELAUTAN: Indonesian Journal of Marine Sciences 19, no. 3 (September 2, 2014): 171. http://dx.doi.org/10.14710/ik.ijms.19.3.171-180.
Full textAbstract:
Studi rekrutmen karang Pocillopora damicornis telah dilakukan dengan mengamati kerapatan juvenil pada substrat penempelan di dataran terumbu Pulau Panjang, Jepara, Jawa Tengah. Hasil menunjukkan bahwa rekrutmen terjadi sepanjang tahun dan tertinggi pada periode Agustus-Oktober. Laju rekrutmen karang di belakang terumbu (back reef) pada sisi bawah angin (selatan) lebih tinggi daripada di sisi atas angin (utara) Pulau Panjang, tampaknya hal ini berkorelasi dengan kerapatan populasi karang dewasanya. Kerapatan juvenil karang tertinggi pada substrat batu alam terjadi pada sisi bawah permukaan substrat, akan tetapi pertumbuhan juvenil karang tertinggi ditemukan di sisi atas permukaan substrat. Hal ini mengindikasikan bahwa kerapatan juvenil karang berhubungan dengan kelulusan hidup juvenil karang. Semakin tinggi kerapatan juvenil karang P. damicornis maka semakin rendah kelulusan hidup juvenil karang karena terjadinya peningkatan persaingan sesama juvenil karang dan akibat kekurangan cahaya. Kata kunci: rekrutmen, kerapatan, kelulushidupan, karang Pocillopora damicornis Recruitment of the brooding coral Pocillopora damicornis was studied by observing the juvenile density on the settlement plate substrate in reef flat of Panjang Island, Jepara, Central Java. The results show that recruitment occurs throughout the year and the highest in the period from August to October. The rate of recruitment of coral reefs in back reef on the leeward (south) is higher than on the windward (north) of the island, it seems to be correlated with population density of adult corals. The highest density of juvenile corals on natural substrata occurs on the lower side surface of the substrate, but the highest growth of juvenile are found on the upper side surface of the substrate. This indicates that the density of juvenile corals associated with the survival of juvenile corals. The higher density of juvenile corals P. damicornis, the lower the survival of juvenile corals due to an increase in competition among juvenile corals and due to lack of light. Keywords: recruitment, density, survivorship, coral Pocillopora damicornis
11
Lenihan, Colleen, and Dirk Van Vuren. "Growth and survival of juvenile yellow-bellied marmots (Marmota flaviventris)." Canadian Journal of Zoology 74, no. 2 (February 1, 1996): 297–302. http://dx.doi.org/10.1139/z96-037.
Full textAbstract:
We compared patterns of growth in juvenile yellow-bellied marmots (Marmota flaviventris) between 2 years in which precipitation differed, and we determined if mass at entry into hibernation affects over-winter survival. Juveniles exhibited an asymptotic growth pattern with mass gain for a mean of 60.8 days, followed by stable mass until entry into hibernation. Growth ceased in early September, shortly after the end of the plant growing season. Juveniles born in 1991, a year of late snowmelt and low summer precipitation, entered into hibernation at significantly lower mass than juveniles born in 1992. Juveniles born in 1992 survived better despite experiencing a long winter during which they spent more days in hibernation and lost more mass. Overall, heavier juveniles were more likely to survive hibernation. Further, mass at entry into hibernation apparently had a greater effect on over-winter survival than did winter severity.
12
Anderson, Elizabeth M., and Stan Boutin. "Edge effects on survival and behaviour of juvenile red squirrels (Tamiasciurus hudsonicus)." Canadian Journal of Zoology 80, no. 6 (June 1, 2002): 1038–46. http://dx.doi.org/10.1139/z02-087.
Full textAbstract:
Much research has examined parasitism and predation rates on avian nests within the context of edge effects. Few studies, however, have considered the influence that behavioural compensation for high predation risk may have on subsequent survival rates and edge effects. We attempted to determine whether juvenile red squirrels (Tamiasciurus hudsonicus) experience edge effects by comparing the survival and behaviour of individuals born along a forest edge with those of individuals born in the forest interior. A combination of telemetry, direct observation, and livetrapping was used to determine the fate of juveniles born during the summers of 1987 through 1998 and the behaviour of juveniles born during the summers of 1997 and 1998 in Kluane, Yukon. There were no differences in survival between edge and interior juveniles from birth to emergence but there was a trend towards higher survival rates for edge juveniles from emergence to weaning. Behavioural differences between edge and interior juveniles were consistent with these survival differences: edge juveniles spent less time travelling and foraging and more time resting near the time of weaning than did interior juveniles. Edge and interior mothers differed little behaviourally during the early emergence period. The significant differences in juvenile behaviour which we found suggest that behaviour may indeed moderate differences in predation risk between edge and interior habitats and thus should be considered in other studies that examine the influence of edges on survival or nest predation.
13
Lieske, David J., Ian G. Warkentin, Paul C. James, Lynn W. Oliphant, and Richard H. M. Espie. "Effects of Population Density on Survival in Merlins." Auk 117, no. 1 (January 1, 2000): 184–93. http://dx.doi.org/10.1093/auk/117.1.184.
Full textAbstract:
Abstract Accurate estimation of survival probabilities is an important component of population demographics, and it permits a test of the life-history prediction that densities influence population dynamics via suppression of survival rates. As part of a long-term study of urban-nesting Merlins (Falco columbarius), we estimated survival rates and tested for the effects of density dependence based on capture histories from 1,354 individuals (43 males and 110 females caught for the first time as adult breeding birds, and 597 males and 604 females caught for the first time as locally produced nestlings). Overall capture probabilities were 0.55 ± SD of 0.039 per year for adults, 0.10 ± 0.075 per year for juvenile males, and 0.58 ± 0.23 per year for juvenile females. Mean survival rate of adults was 0.62 ± 0.11 per year and did not differ significantly between males and females. Overall juvenile survival rates were 0.23 ± 0.032 for males and 0.055 ± 0.012 for females. Band returns suggest that the discrepancy in survival rates between juvenile males and females resulted from higher natal dispersal of females rather than from lower survival. Survival of adults (but not juveniles) was negatively density dependent, suggesting that density-dependent declines in survival exerted a regulatory effect on population size.
14
Ward, David H., Joel A. Schmutz, James S. Sedinger, Karen S. Bollinger, Philip D. Martin, and Betty A. Anderson. "Temporal and Geographic Variation in Survival of Juvenile Black Brant." Condor 106, no. 2 (May 1, 2004): 263–74. http://dx.doi.org/10.1093/condor/106.2.263.
Full textAbstract:
Abstract First-year survival has important implications for the structure and growth of populations. We examined variation in seasonal survival of first-year Pacific Black Brant (Branta bernicla nigricans) marked late in summer in Alaska at two brood-rearing areas on the Yukon-Kuskokwim Delta (Tutakoke and Kokechik) and one area on the Arctic Coastal Plain to provide insight into the magnitude and timing of mortality during fall migration. First-year survival was lower in early fall (15 July–1 October), when birds fledged from brood-rearing areas and migrated to their primary fall staging area at Izembek Lagoon, Alaska, than during late fall and early winter (1 October–15 February), when birds made a long-distance transoceanic flight (>5000 km) to wintering areas in Baja California, Mexico. When compared to other years, monthly survival during early fall was 20–24% lower in 1992, the year of latest hatch dates and slowest growth of goslings. There was strong evidence to indicate that survival varied geographically within the early fall period. Monthly survival estimates during early fall were lowest for birds from Tutakoke, highest for birds from the Arctic Coastal Plain, and intermediate at Kokechik. Our findings revealed that most juvenile mortality occurred during the first 2 months following banding, and variation in juvenile survival during this period was likely influenced significantly by environmental parameters and habitat conditions on the breeding grounds. Monthly survival estimates during the subsequent 4 months were similar across geographic areas, and long-distance migration was likely the most important contributor to juvenile mortality during this period. Variación Temporal y Geográfica en la Supervivencia de Juveniles de Branta bernicla nigricans Resumen. La supervivencia durante el primer año de vida tiene implicancias importantes para la estructura y el crecimiento de las poblaciones. Examinamos la variación en la supervivencia estacional en individuos añales de Branta bernicla nigricans marcados al final del verano en Alaska en dos áreas de cría del Delta Yukon-Kuskokwim (Tutakoke y Kokechik) y un área en la planicie costera ártica para brindar información sobre la magnitud y el esquema temporal de mortalidad durante la migración de otoño. La supervivencia durante el primer año fue menor a principios del otoño (15 July–1 October), cuando las aves abandonaron las áreas de cría y migraron hacia el área principal de permanencia otoñal en Izembek Lagoon, Alaska, que durante fines de otoño y comienzos del invierno (1 October–15 February), cuando las aves realizaron un vuelo transoceánico de larga distancia (>5000 km) hacia las áreas de invernada en Baja California, México. Comparando con otros años, la supervivencia mensual durante principios del otoño fue un 20–24% menor en 1992, el año con fechas más tardías de eclosión y con crecimiento más lento de los polluelos. Hubo fuerte evidencia para indicar que la supervivencia varió geográficamente a principios del otoño. Las estimaciones mensuales de supervivencia durante principios del otoño fueron menores para las aves de Tutakoke, mayores para las aves de la planicie costera ártica, e intermedias para Kokechik. Nuestros resultados revelaron que la mayoría de la mortalidad juvenil ocurrió durante los dos primeros meses luego del anillado, y la variación en la supervivencia de los juveniles durante este período fue probablemente influenciada de forma significativa por parámetros ambientales y condiciones del hábitat en las áreas de cría. Las estimaciones mensuales de supervivencia durante los cuatro meses siguientes fueron similares para las distintas áreas geográficas, y la migración de larga distancia fue probablemente la causa más importante de mortalidad juvenil durante este período.
15
Van Drunen, Stephen G., Jessica E. Linton, James P. Bogart, and D. Ryan Norris. "Post-emergence survival and dispersal of juvenile Jefferson salamander (Ambystoma jeffersonianum) and their unisexual dependents." Amphibia-Reptilia 42, no. 1 (July 16, 2020): 29–41. http://dx.doi.org/10.1163/15685381-bja10028.
Full textAbstract:
Abstract Understanding population demography and dispersal of species at risk is integral for evaluating population viability, identifying causes of decline, and assessing the effectiveness of recovery actions. In pond-breeding amphibians, juvenile survival and dispersal are key components linked to population and metapopulation stability but little is known about this life stage. We use mark-recapture methods to estimate juvenile daily apparent survival, dispersal distance, and initial dispersal orientation during summer and fall dispersal of endangered Ambystoma jeffersonianum and their unisexual dependents (Ambystoma laterale – jeffersonianum). Over four years (2015-2018), 1018 juveniles (612 bisexual, 406 unisexual) were marked and 192 (19%) were recaptured at least once. Total captures varied widely between years, with the highest number of captures (88% of all individuals) occurring in 2017. Cormack-Jolly-Seber estimates of daily apparent survival were low in all years (0.76-0.95) but was higher for unisexuals than bisexuals. The majority of juveniles (71%) did not disperse further than 10-40 m after which movement appeared to cease. While most juveniles remained close to their natal pond, at least 2% of juveniles in 2017 travelled further than 100 m. Dispersal orientation varied by year and there was no difference in either dispersal orientation or distance between bisexual and unisexual individuals. This work is the first to estimate and compare juvenile survival and dispersal of sympatric A. jeffersonianum and A. laterale – jeffersonianum individuals, the results of which help inform population viability assessment and increase our understanding of juvenile dispersal dynamics and habitat use.
16
Bennett, Ronald P. "Effects of food quality on growth and survival of juvenile Columbian ground squirrels (Spermophilus columbianus)." Canadian Journal of Zoology 77, no. 10 (December 1, 1999): 1555–61. http://dx.doi.org/10.1139/z99-144.
Full textAbstract:
Within a cohort of Columbian ground squirrels (Spermophilus columbianus), most deaths during hibernation usually occur in the first winter. Over-winter survivorship of juvenile Columbian ground squirrels is positively related to prehibernation body mass, which is primarily determined by the growth rate after emergence from natal burrows. This study examined how food quality influences growth and survival of juvenile Columbian ground squirrels. Growth and survival of juveniles in three colonies was measured, and biomass, composition (forb versus grass content), gross energy, crude protein, and digestibility of the summer forage supply were assessed. Differences in biomass and gross energy among colonies did not explain differences in growth and survival of resident ground squirrels. Growth and survival of juveniles was enhanced on sites with higher forb content in the forage supply. Forbs contained 15-40% more protein and were 30-50% more digestible than grasses, but protein levels on all sites were probably in excess of ground squirrels' requirements. This suggests that digestibility was limiting growth and was a more important food-quality indicator for juvenile ground squirrels than either energy or protein.
17
Covas, Rita, Charles R. Brown, Mark D. Anderson, and Mary Bomberger Brown. "Juvenile and Adult Survival in the Sociable Weaver (Philetairus Socius), A Southern-Temperate Colonial Cooperative Breeder in Africa." Auk 121, no. 4 (October 1, 2004): 1199–207. http://dx.doi.org/10.1093/auk/121.4.1199.
Full textAbstract:
Abstract We used capture-recapture analyses to describe juvenile and adult survival from 1993 to 2001 in a population of Sociable Weavers (Philetairus socius), a colonial, cooperatively breeding passerine of southern Africa. We examined temporal variation in survival and the role that the breeding season's length and environmental factors play in determining survival patterns in the population. Annual survival probability (mean ± SE) was 0.66 ± 0.02. In contrast to most passerines, juveniles and adults had similar survival probabilities; survival rates did not vary significantly between years. We found no relationship among temperature, rainfall, and survival. Relatively high survival rates in Sociable Weavers probably result from a benign climate and easy access to food in winter. Juvenile survival may also be enhanced by prolonged parental care and delayed dispersal.
18
Massé, Gérard, Pierre Dumont, and Réjean Fortin. "Survie oeufs–juvéniles et force des classes d'âge des grands brochets (Esox lucius) de la rivière aux Pins, près de Montréal, Québec." Canadian Journal of Zoology 71, no. 2 (February 1, 1993): 368–75. http://dx.doi.org/10.1139/z93-051.
Full textAbstract:
Exhaustive counts of northern pike that use the Rivière aux Pins and of 0+ juvenile pike produced in this river, based on trap net and seine catches, coupled with potential fecundity estimates, allowed survival rates of pike eggs to migrant 0+ juveniles to be evaluated in a natural situation, in 1975, and in a controlled water level situation, in 1976. In 1975, 3393 juveniles aged 0+ were produced from 9 210 900 eggs potentially deposited by 404 females, yielding a 0.037% survival rate. In 1976, 34 062 juveniles aged 0+ were produced from 8 536 800 eggs potentially deposited by 310 females, yielding a 0.399% survival rate. The higher survival rate in 1976 could have resulted from the water level control and (or) from the higher spring waters in 1976. However, 1975 and 1976 both produced strong year classes, suggesting that potential fecundity and 0+ juvenile production on the spawning grounds are not the only factors influencing recruitment in this species.
19
Donelson, Jennifer M., Philip L. Munday, and Mark I. McCormick. "Parental effects on offspring life histories: when are they important?" Biology Letters 5, no. 2 (January 6, 2009): 262–65. http://dx.doi.org/10.1098/rsbl.2008.0642.
Full textAbstract:
Both the parental legacy and current environmental conditions can affect offspring life histories; however, their relative importance and the potential relationship between these two influences have rarely been investigated. We tested for the interacting effects of parental and juvenile environments on the early life history of the marine fish Acanthochromis polyacanthus . Juveniles from parents in good condition were longer and heavier at hatching than juveniles from parents in poor condition. Parental effects on juvenile size were evident up to 29 days post-hatching, but disappeared by 50 days. Offspring from good condition parents had higher early survival than offspring from poor-condition parents when reared in a low-food environment. By contrast, parental condition did not affect juvenile survival in the high-food environment. These results suggest that parental effects on offspring performance are most important when poor environmental conditions are encountered by juveniles. Furthermore, parental effects observed at hatching may often be moderated by compensatory mechanisms when environmental conditions are good.
20
Morgan Davies, J., and Marco Restani. "Survival and Movements of Juvenile Burrowing Owls During the Postfledging Period." Condor 108, no. 2 (May 1, 2006): 282–91. http://dx.doi.org/10.1093/condor/108.2.282.
Full textAbstract:
AbstractBurrowing Owl (Athene cunicularia) populations have declined extensively throughout much of North America, and modeling demography may assist conservation. However, few studies have estimated adult survival, and fewer still have determined juvenile survival. In 2003 and 2004 we monitored survival of 40 radio-tagged juveniles during the postfledging period in the Little Missouri National Grassland, North Dakota, where owls nested in black-tailed prairie dog (Cynomys ludovicianus) colonies. Survival averaged 0.57 (95% CI: 0.41–0.73) prior to autumn migration. Mortality was highest during the first two weeks after nest departure when juveniles were flightless, and two to three weeks later when juveniles became independent. Predation or starvation was implicated in most deaths. Distribution and abundance of escape cover (number of prairie dog burrows within 30 m of nests and size of the natal prairie dog colony) did not affect survival. Body condition and brood size at the time of radio-tagging also did not influence survival. Juvenile owls exhibited nest-centered dispersal, and averaged 108 ± 21 (SE) m and 82 ± 17 m from nests at initiation of migration in 2003 and 2004, respectively. Mean dates of departure from the study area were 2 September (± 3 days) 2003 and 24 August (± 2 days) 2004. Mortality during the postfledging period accounted for approximately two-thirds of mortality in the first year of life.
21
Rehberg, M. J., and J. M. Burns. "Differences in diving and swimming behavior of pup and juvenile Steller sea lions (Eumetopias jubatus) in Alaska." Canadian Journal of Zoology 86, no. 6 (June 2008): 539–53. http://dx.doi.org/10.1139/z08-018.
Full textAbstract:
Reduced juvenile survival caused by prey depletion is one hypothesis for the decline in the western Alaska population of Steller sea lions ( Eumetopias jubatus (Schreber, 1776)). To understand the exposure of young sea lions to these depletions, the swimming and diving behavior of pups, juveniles, and subadults was evaluated relative to prey behavior. Pups made shorter and shallower dives (13 m, 0.9 min) than juveniles or subadults, as expected based on physiological limitations, but juveniles and subadults dived to similar depths and durations (29 m, 1.7 min and 38 m, 2.0 min, respectively). Activity patterns of juveniles and subadults reflected diurnal prey migrations, while pup activity did not. Longitudinal trends in pup dive behavior reflected both physiological and behavioral development, while juvenile dive behaviors reflected seasonal changes in prey availability. Results suggest that adult females must continue to provide nutritional support to pups during winter because of the limited diving ability of these young animals. For this reason, the flexible lactation strategies that allow for longer nursing periods during periods of low prey availability and reduce female fecundity may improve juvenile survival.
22
Price, Amanda J., Wendy Estes-Zumpf, and Janet Rachlow. "Survival of Juvenile Pygmy Rabbits." Journal of Wildlife Management 74, no. 1 (January 2010): 43–47. http://dx.doi.org/10.2193/2008-578.
Full text
23
Afán, Isabel, Joan Navarro, David Grémillet, Marta Coll, and Manuela G. Forero. "Maiden voyage into death: are fisheries affecting seabird juvenile survival during the first days at sea?" Royal Society Open Science 6, no. 1 (January 2019): 181151. http://dx.doi.org/10.1098/rsos.181151.
Full textAbstract:
The study of juvenile migration behaviour of seabird species has been limited so far by the inability to track their movements during long time periods. Foraging and flying skills of young individuals are assumed to be inferior to those of adults, making them more vulnerable during long-distance migrations. In addition to natural oceanographic effects and intrinsic conditions, incidental seabird harvest by human fisheries is one of the main causes of worldwide seabird population declines, and it has been hypothesized that juveniles are particularly vulnerable to bycatch during their first weeks at sea after leaving the nest. We used solar-powered satellite tags to track the at-sea movements of adults and juveniles of Scopoli's shearwater ( Calonectris diomedea ) after the autumn departure from their breeding colony in Chafarinas Islands (southwestern Mediterranean Sea). Eighty per cent of juvenile tags stopped transmitting during the first week at sea, within 50 km of their natal colony, in an area with one of the highest concentrations of fishing activities in the Mediterranean Sea. All adult birds tagged and only 20% of juveniles migrated into the Atlantic and southwards along the coast of West Africa. The two age groups showed different habitat preferences, with juveniles travelling farther from the coast, in windier and less productive waters than adults. We conclude that Scopoli's shearwater juveniles are particularly vulnerable to mortality events, and we highlight that fisheries, along with differential age-related behaviour skills between adults and juveniles, are likely causes of this mortality. Overall, our study highlights the importance of conducting tracking studies during the first stages of juvenile migration.
24
Palomar-Abesamis, Nadia, Marie Antonette Juinio-Meñez, and Matthew James Slater. "Effects of light and microhabitat on activity pattern and behaviour of wild and hatchery-reared juveniles ofStichopuscf.horrens." Journal of the Marine Biological Association of the United Kingdom 98, no. 7 (June 23, 2017): 1703–13. http://dx.doi.org/10.1017/s0025315417000972.
Full textAbstract:
Animals develop behavioural strategies throughout life to improve their survival in nature. Juvenile activity and behaviour of the commercial tropical sea cucumberStichopuscf.horrenswere examined considering factors that may influence survival at this critical developmental stage. Wild juveniles were observedin situto describe diel activity and movement. Wild and hatchery-reared juveniles were observed in the laboratory to evaluate the influence of different light-dark cycles and microhabitats on feeding and sheltering behaviour. All juveniles (4–54 g) displayed a distinct nocturnal activity pattern both in the field and laboratory. Nocturnal activity was strongly associated with feeding and locomotion. Wild and hatchery-reared juveniles were most active at night, displayed intermediate activity during twilight, and minimal to no activity during daytime. Movement rates of wild juvenilesin situwere significantly influenced by time and size to a lesser extent. Under constant light and constant dark for 48 h, juvenile feeding rhythm was endogenously controlled and strongly entrained to natural light-dark cycles. Sheltering was directly affected by light and linked to strong phototactic and thigmotactic reflexes. Juveniles preferred vegetation as shelter compared to coral, sand or open space, and showed equal preference for seagrass and macroalgae. Deviations in behaviour of hatchery-reared juveniles under laboratory conditions indicate some degree of acclimation to an artificial environment with minimal threats and a decreased sensitivity to light. The implications of nocturnal feeding, light-induced sheltering, shelter preferences and acclimation to artificial conditions are discussed in relation to juvenile survival in nature and potential restocking of the species.
25
Rahman, M. Aminur, Fatimah Md Yusoff, A. Arshad, and Tsuyoshi Uehara. "Effects of Delayed Metamorphosis on Larval Survival, Metamorphosis, and Juvenile Performance of Four Closely Related Species of Tropical Sea Urchins (GenusEchinometra)." Scientific World Journal 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/918028.
Full textAbstract:
We report here, the effects of extended competency on larval survival, metamorphosis, and postlarval juvenile growth of four closely related species of tropical sea urchins,Echinometrasp. A (Ea),E. mathaei(Em),Echinometrasp. C (Ec), andE. oblonga(Eo). Planktotrophic larvae of all four species fed on cultured phytoplankton (Chaetoceros gracilis) attained metamorphic competence within 22–24 days after fertilization. Competent larvae were forced to delay metamorphosis for up to 5 months by preventing them from settling in culture bottles with continuous stirring on a set of 10 rpm rotating rollers and larval survival per monthly intervals was recorded. Larval survival was highest at 24 days, when competence was attained (0 delayed period), and there were no significant differences among the four species. Larvae that had experienced a prolonged delay had reduced survival rate, metamorphosis success, and juvenile survival, but among older larvae, Em had the highest success followed by Ea, Eo, and Ec. Juveniles from larvae of all four species that metamorphosed soon after becoming competent tended to have higher growth rates (test diameter and length of spines) than juveniles from larvae that metamorphosed after a prolonged period of competence with progressively slower growth the longer the prolonged period. Despite the adverse effects of delaying metamorphosis on growth parameters, competent larvae of all four species were able to survive up to 5 months and after metamorphosis grew into 1-month-old juveniles in lab condition. Overall, delayed larvae of Em showed significantly higher larval survival, metamorphosis, and juvenile survival than Ea and Eo, while Ec showed the lowest values in these performances. Em has the most widespread distribution of these species ranging from Africa to Hawaii, while Ec probably has the most restricted distribution. Consequently, differences in distribution may be related to differences in the ability to delay metamorphosis.
26
Schneck, J. L., and B. Fried. "Effects of snail size on encystment of Echinostoma caproni in juvenile Biomphalaria glabrata (NMRI strain) and observations on the survival of infected snails." Journal of Helminthology 78, no. 3 (September 2004): 277–79. http://dx.doi.org/10.1079/joh2004235.
Full textAbstract:
AbstractThe effects of snail size on encystment of Echinostoma caproni cercariae in neonatal and juvenile Biomphalaria glabrata (NMRI strain) snails were studied. Encystment in neonatal (0.7–1.1 mm shell diameter) and juvenile (2–3 mm shell diameter) snails was compared 24 h post-infection (PI) following individual exposure of snails of each size to 1, 5, 10, 25 and 50 cercariae. Significantly more cysts were recovered from juveniles exposed to 1, 5, 10 and 50 cercariae than from neonatals with comparable exposure. Size of B. glabrata was a major factor in determining cyst burden in this planorbid. Survival of infected versus uninfected neonatals and juveniles was also examined for 7 days. Neonatals exposed to 10 cercariae showed a significant decrease in survival at 3, 6 and 7 days PI when compared to the uninfected controls. There was no significant decrease in the survival of juveniles exposed to 10 cercariae compared to uninfected controls at any time point. Snail size was a factor in mortality associated with echinostome cercarial penetration and encystment.
27
Smallegange, Isabel M., Isabelle B. C. van der Ouderaa, and Yara Tibiriçá. "Effects of yearling, juvenile and adult survival on reef manta ray (Manta alfredi) demography." PeerJ 4 (August 24, 2016): e2370. http://dx.doi.org/10.7717/peerj.2370.
Full textAbstract:
BackgroundThe trade in manta ray gill plates has considerably increased over the last two decades. The resulting increases in ray mortality, in addition to mortality caused by by-catch, has caused many ray populations to decrease in size. The aim of this study was to ascertain how yearling and juvenile growth and survival, and adult survival and reproduction affect reef manta ray (Manta alfredi) population change, to increase our understanding of manta ray demography and thereby improve conservation research and measures for these fish.MethodsWe developed a population projection model for reef manta rays, and used published life history data on yearling and juvenile growth and adult reproduction to parameterise the model. Because little is known about reef manta ray yearling and juvenile survival, we conducted our analyses using a range of plausible survival rate values for yearlings, juveniles and adults.ResultsThe model accurately captured observed variation in population growth rate, lifetime reproductive success and cohort generation time in different reef manta ray populations. Our demographic analyses revealed a range of population consequences in response to variation in demographic rates. For example, an increase in yearling or adult survival rates always elicited greater responses in population growth rate, lifetime reproductive success and cohort generation time than the same increase in juvenile survival rate. The population growth rate increased linearly, but lifetime reproductive success and cohort generation time increased at an accelerating rate with increasing yearling or adult survival rates. Hence, even a small increase in survival rate could increase lifetime reproductive success by one pup, and cohort generation time by several years. Elasticity analyses revealed that, depending on survival rate values of all life stages, the population growth rate is either most sensitive to changes in the rate with which juveniles survive but stay juveniles (i.e., do not mature into adults) or to changes in adult survival rate. However, when assessing these results against estimates on population growth and adult survival rates for populations off the coasts of Mozambique and Japan, we found that the population growth rate is predicted to be always most sensitive to changes in the adult survival rate.DiscussionIt is important to gain an in-depth understanding of reef manta ray life histories, particularly of yearling and adult survival rates, as these can influence reef manta ray population dynamics in a variety of ways. For declining populations in particular, it is crucial to know which life stage should be targeted for their conservation. For one such declining population off the coast of Mozambique, adult annual survival rate has the greatest effect on population growth, and by increasing adult survival by protecting adult aggregation sites, this population’s decline could be halted or even reversed.
28
Hidalgo, Manuel, Alessandro Ligas, José María Bellido, Isabella Bitetto, Pierluiggi Carbonara, Roberto Carlucci, Beatriz Guijarro, et al. "Size-dependent survival of European hake juveniles in the Mediterranean Sea." Scientia Marina 83, S1 (January 9, 2020): 207. http://dx.doi.org/10.3989/scimar.04857.16a.
Full textAbstract:
Most studies on European hake focus on the recruitment process and nursery areas, whereas the information is comparatively limited on the ecology of the juvenile stage (ca. second year of life)—the one most exploited by the Mediterranean trawl fisheries. Using information of the MEDITS programme, we provide a spatial and temporal assessment of the influence of body size and growth on hake survival from recruits (age 0) to juveniles (age 1), along with the impact of surface temperature and chlorophyll variability. At a biogeographic scale, size-dependent survival is supported, with areas with higher mean length of recruits and juveniles yielding higher survival. A similar pattern was observed at interannual level in some western Mediterranean areas, also mediated by a density-dependent effect on growth. However, the most recurrent inter-annual pattern was a negative effect of size on survival, which could be attributed to potential ontogenetic changes in catchability and underrepresentation of intra-annual recruitment pulses that are seasonally inaccessible to the MEDITS survey. Results also evidence that survival in the Alboran and Adriatic seas is dependent on the primary production variability, and that Corsica and Sardinia could be potential feeding grounds receiving juveniles from neighbouring areas. The present study reveals the importance of size- and growth-dependent survival in the juvenile stage of European hake in the Mediterranean Sea.
29
Avilés, Jesus M. "Time budget and habitat use of the Common Crane wintering in dehesas of southwestern Spain." Canadian Journal of Zoology 81, no. 7 (July 1, 2003): 1233–38. http://dx.doi.org/10.1139/z03-105.
Full textAbstract:
In many bird species juvenile inexperience drastically reduces their survival, and parents must provide for them. I tested whether time budget and habitat use in adult wintering Common Cranes (Grus grus) in dehesas (pastoral woodland) of western Spain were affected by the presence of juveniles. Juvenile cranes devote less time to vigilance and spend more time feeding than adults in dehesas. Likewise, juveniles are involved in fewer aggressive encounters than adult cranes. Contrary to expectation, adults accompanied by juveniles devoted the same amount of time to vigilance and feeding and had the same intake rate than adults without juveniles in attendance. However, adult cranes with offspring in attendance were involved in more aggressive encounters than adults without juveniles in attendance when both adult groups were involved in large flocks. In contrast, when adults accompanied by juveniles were in small flocks they were involved in fewer aggressive encounters than adults without juveniles. I also detected a differential use of dehesas by adult cranes that was linked to juvenile presence and explained by the vulnerability of juvenile cranes in intraspecific social relationships. Adults with juveniles in attendance preferred dehesas with livestock where flock sizes were smaller than those in dehesas without livestock, and therefore where they might reduce the number of aggressive encounters with other cranes.
30
O'Donoghue, Mark. "Early Survival of Juvenile Snowshoe Hares." Ecology 75, no. 6 (September 1994): 1582–92. http://dx.doi.org/10.2307/1939619.
Full text
31
Maness, Terri J., and David J. Anderson. "Predictors of Juvenile Survival in Birds." Ornithological Monographs 78, no. 1 (October 2013): 1–55. http://dx.doi.org/10.1525/om.2013.78.1.1.
Full text
32
Justice, Casey, Brian J. Pyper, Raymond C. P. Beamesderfer, Vaughn L. Paragamian, Pete J. Rust, Matthew D. Neufeld, and Susan C. Ireland. "Evidence of density- and size-dependent mortality in hatchery-reared juvenile white sturgeon (Acipenser transmontanus) in the Kootenai River." Canadian Journal of Fisheries and Aquatic Sciences 66, no. 5 (May 2009): 802–15. http://dx.doi.org/10.1139/f09-034.
Full textAbstract:
We evaluated effects of stocking level and size-at-release on survival rates of hatchery-reared juvenile white sturgeon ( Acipenser transmontanus ) in the Kootenai River using Cormack–Jolly–Seber and related models implemented in Program MARK. A total of 119 768 marked and unmarked hatchery juveniles were released from 1992 to 2006, of which 2938 passive integrated transponder (PIT)-tagged fish were subsequently recaptured. Annual survival rates of marked groups ranged from 0.01 to 0.84 (mean = 0.45) during the first year at large, from 0.48 to 1.0 (mean = 0.84) in the second year, and averaged 1.0 during all subsequent years. First year survival rates declined substantially in recent years, particularly for small fish (<25 cm fork length). Approximately 59% of the variation in first year survival was explained by a negative relationship with estimated juvenile abundance (linear regression, P < 0.01). Length-at-release of individuals explained a substantial proportion of the within-year variation in survival during the first year at large. Our results provide strong evidence of density- and size-dependent mortality in hatchery-reared juvenile white sturgeon in the Kootenai River. Management actions that prioritize the release of fewer, larger-sized fish will likely improve first year survival rates and subsequent recruitment to the spawning-age population.
33
Erlandsson, R., T. Meijer, S. Wagenius, and A. Angerbjörn. "Indirect effects of prey fluctuation on survival of juvenile arctic fox (Vulpes lagopus): a matter of maternal experience and litter attendance." Canadian Journal of Zoology 95, no. 4 (April 2017): 239–46. http://dx.doi.org/10.1139/cjz-2016-0103.
Full textAbstract:
Reproductive experience affects juvenile survival in a wide range of species with possible links to differences in foraging capacity and predation. Using supplementary feeding, we aimed to limit direct effect of prey abundance to investigate indirect effects of small-rodent availability and maternal experience on juvenile summer survival rates in an endangered population of arctic fox (Vulpes lagopus (L., 1758)). We used data spanning 7 years, included a complete small-rodent cycle, comprising 49 litters and 394 cubs. The effect of small-rodent abundance on juvenile survival depended on maternal breeding experience. Cubs born by first-time-breeding females had lower survival rate when small-rodent abundance was low compared with juveniles born to experienced mothers who remained unaffected. It was unlikely due to starvation, as physical condition was unrelated to survival. Instead, we favour the explanation that intraguild predation was an important cause of mortality. There was a negative relationship between survival and amount of time cubs were left unattended, suggesting that parental behaviour affected predation. We propose that a prey switch related to small-rodent abundance caused fluctuations in intraguild predation pressure and that inexperienced females were less able to cope with predation when small rodents were scarce.
34
Indriana, Lisa Fajar, Muhammad Firdaus, Supono, and Hendra Munandar. "SURVIVAL RATE AND GROWTH OF JUVENILE SANDFISH (Holothuria scabra) IN VARIOUS REARING CONDITIONS." Marine Research in Indonesia 42, no. 1 (March 31, 2017): 11. http://dx.doi.org/10.14203/mri.v41i2.156.
Full textAbstract:
Techniques for producing Holothuria scabra or sandfish sea cucumbers from aquaculture have been developed rapidly in the recent years to address the issues of decreasing sandfish population and increasing market demand. During the process of culturing H. scabra, the early stages of sandfish (i.e. larvae and juveniles) are the most critical of the development. Therefore, the Research and Development Division of the Marine Bio Industry – LIPI conducted a study to assess the growth performance of juvenile H. scabra ultured in four different rearing conditions: (i) indoor concrete tank, (ii) indoor fiberglass tank, (iii) outdoor concrete tank with 1 mm hapa mesh, and (iv) outdoor concrete tank with 3 mm hapa mesh. Each of the rearing condition was set with an initial juvenile density of 15 juveniles per tank with a mean initial weight of 14 g, and fed ad libitum with a mixed feed consisting of Enhalus acoroides sea grass, Pennisetum purpureum napier and cow manure. The experiments were conducted for 20 weeks between April 26 - September 23, 2013. After the experimental period, juveniles reared in the outdoor concrete tank with 1 mm mesh show the best performance with respect to their survival rate (48.89 ± 3.85 %),mean final weight (22.07 ± 1.01 g), final biomass (162.05 ± 18.17 g) and specific growth rate (0.15 ± 0.03% per day). Further studies that combine rearing conditions with different bottom substrates as well as investigating the effect of light are needed to optimize the production of H. scabra from aquaculture.
35
Indriana, Lisa Fajar, Muhammad Firdaus, Supono, and Hendra Munandar. "SURVIVAL RATE AND GROWTH OF JUVENILE SANDFISH (Holothuria scabra) IN VARIOUS REARING CONDITIONS." Marine Research in Indonesia 42, no. 1 (March 31, 2017): 11–18. http://dx.doi.org/10.14203/mri.v42i1.156.
Full textAbstract:
Techniques for producing Holothuria scabra or sandfish sea cucumbers from aquaculture have been developed rapidly in the recent years to address the issues of decreasing sandfish population and increasing market demand. During the process of culturing H. scabra, the early stages of sandfish (i.e. larvae and juveniles) are the most critical of the development. Therefore, the Research and Development Division of the Marine Bio Industry – LIPI conducted a study to assess the growth performance of juvenile H. scabra ultured in four different rearing conditions: (i) indoor concrete tank, (ii) indoor fiberglass tank, (iii) outdoor concrete tank with 1 mm hapa mesh, and (iv) outdoor concrete tank with 3 mm hapa mesh. Each of the rearing condition was set with an initial juvenile density of 15 juveniles per tank with a mean initial weight of 14 g, and fed ad libitum with a mixed feed consisting of Enhalus acoroides sea grass, Pennisetum purpureum napier and cow manure. The experiments were conducted for 20 weeks between April 26 - September 23, 2013. After the experimental period, juveniles reared in the outdoor concrete tank with 1 mm mesh show the best performance with respect to their survival rate (48.89 ± 3.85 %),mean final weight (22.07 ± 1.01 g), final biomass (162.05 ± 18.17 g) and specific growth rate (0.15 ± 0.03% per day). Further studies that combine rearing conditions with different bottom substrates as well as investigating the effect of light are needed to optimize the production of H. scabra from aquaculture.
36
Childress, Evan S., Keith H. Nislow, Andrew R. Whiteley, Matthew J. O’Donnell, and Benjamin H. Letcher. "Daily estimates reveal fine-scale temporal and spatial variation in fish survival across a stream network." Canadian Journal of Fisheries and Aquatic Sciences 76, no. 8 (August 2019): 1446–58. http://dx.doi.org/10.1139/cjfas-2018-0191.
Full textAbstract:
Environmental drivers of population vital rates, such as temperature and precipitation, often vary at short time scales, and these fluctuations can have important impacts on population dynamics. However, relationships between survival and environmental conditions are typically modeled at coarse temporal scales, ignoring the role of daily environmental variation in survival. Our goal was to determine the importance of fine-scale temporal variation in survival to population dynamics of stream salmonids. We extended the Cormack–Jolly–Seber model to estimate daily survival rates from seasonal samples of individually marked brook trout (Salvelinus fontinalis) in a stream network. Daily variation in temperature and flow were strongly associated with survival, but relationships varied between juvenile and adult trout and among streams. In all streams, juveniles had higher mortality in warm, low-flow conditions, but in the two larger streams, cold, high-flow conditions also reduced juvenile survival. Adult survival decreased during low flows, particularly in the fall spawning period. Differing survival responses among stream network components to short-term environmental events created shifts in optimal location for maximum survival across life stages, seasons, and years.
37
Ballouard, Jean-Marie, Sébastien Caron, Thibaud Lafon, Laure Servant, Bernard Devaux, and Xavier Bonnet. "Fibrocement slabs as useful tools to monitor juvenile reptiles: a study in a tortoise species." Amphibia-Reptilia 34, no. 1 (2013): 1–10. http://dx.doi.org/10.1163/15685381-00002859.
Full textAbstract:
Most species of tortoises are seriously threatened worldwide. Chelonians are long-lived organisms characterized by slow demographic traits; mathematical modeling estimated that a high rate of juvenile annual survival (i.e. >0.6 on average) is essential for the persistence of populations. Unfortunately, current knowledge about free-ranging juveniles is fragmentary. Under field conditions, young tortoises are very secretive, they remain sheltered beneath bushes, and they escape capture. The resulting lack of information impairs the assessment of key parameters such as juvenile survival, habitat use, or recruitment rate and thus seriously impedes both accurate population viability analyses and conservation planning. Large-scale monitoring of different populations of a threatened species (Testudo hermanni hermanni) confirmed that juveniles are rarely seen in the field. In 2011, we placed corrugated fibrocement slabs as alternative refuges for small tortoises in a densely vegetated study site. Many juveniles sheltered under the space offered by the corrugations; consequently they were easily captured and recaptured. Our results suggest that this simple technique may significantly improve the detectability of juveniles, providing access to the life history traits of this otherwise elusive age cohort. The slabs also provide protection against predators (such as dogs and birds) which further suggests that these refuges may also improve the survival of the smallest and most vulnerable individuals.
38
Valladares, Sonia, and Miquel Planas. "Nutrient Incorporation in First Feeding Seahorses Evidenced by Stable Carbon Isotopes." Animals 11, no. 2 (February 10, 2021): 470. http://dx.doi.org/10.3390/ani11020470.
Full textAbstract:
Nutritional issues are among the most critical factors in the initial survival of juvenile seahorses. Currently, there is a knowledge gap on the relationship between nutrient assimilation and the effects on initial mortalities and growth. In the present study, the stable isotope approach was used to assess the incorporation of two live preys (Artemia and copepods) in juvenile seahorses Hippocampus guttulatus. The changes in stable carbon isotope (δ13C) values were studied through two feeding experiments: feeding on Artemia or copepods (experiment 1), and shifting feeding from copepods to Artemia (experiment 2). In experiment 1, after 24–48 h of feeding, juvenile seahorses exhibited small but progressive changes in δ13C values towards those of the corresponding diet, indicating that the assimilation of the food offered was progressively enhanced from days 2–3. Similarly, in experiment 2, a diet shifting from copepods to Artemia caused an increase in δ13C values, reflecting a switch towards the isotopically enriched new diet (Artemia metanauplii). Differences in the assimilation efficiency of preys offered are discussed based on growth and survival rates. The enhanced growth performances and survivals achieved when the juveniles were fed on copepods could be related to higher efficient assimilation of copepods compared to Artemia. The present study demonstrates that the consumption and further assimilation of preys by juvenile seahorses could be traced using stable carbon isotopes. The research on nutrient assimilation of juvenile seahorses should enhance our knowledge on nutrient processes in developing seahorses for a better understanding of initial ontogeny in the early life stages of the species.
39
Ahmad, Fakhirah, Syafiuddin Syafiuddin, and Haryati Haryati. "THE QUALITY OF SEAHORSE JUVENILES Hippocampus barbouri AFTER MODIFYING NATURAL FEED Artemia NAUPLII TO Phronima sp." Jurnal Ilmu Kelautan SPERMONDE 5, no. 2 (January 3, 2020): 83. http://dx.doi.org/10.20956/jiks.v5i2.8936.
Full textAbstract:
This study aims to determine the substitution rate of Artemia naupli to Phronima sp., which produces high-quality seahorses H. Barbouri juveniles This research was carried out using CRD (Completed Randomized Design) with five treatments and three replications. The treatments were natural feeding with different levels of substitution, (A) 100% Artemia nauplii, (B) 75% Artemia nauplii+25% Phronima sp. (C) 50% Artemia nauplii +50% Phronima, (D) 25% Artemia nauplii+75% Phronima sp. and (E) 100% Phronima sp. Data were analyzed with Analysis of Variance and W-Tuckey test to determine the significant difference between the treatments. The parameters of the study included the analysis of feed quality (proximate and amino acid analysis) and survival. Results of the ANOVA indicated that the substitution of Artemia nauplii to Phronima sp. had a significant effect (P <0.05) on survival rate. Based on the result of the proximate analysis of Phronima, the protein and fat content is insufficient for juvenile requirements, which only ranged from 37,12% and 3,82%. The results of the amino acid analysis of Phronima, the total of essential amino acids are deficient in juvenile requirements. The treatments of C and D produces the highest survival value of 96,67%. While in E treatment produce the lowest survival value of 63,33%. Based on the juvenile quality analysis, it can be concluded that the use of Phronima as an alternative feed for seahorse juveniles H. barbouri can be given at a substitution rate of up to 75%.
40
Deaker, DJ, B. Mos, C. Lawson, SA Dworjanyn, C. Budden, and M. Byrne. "Coral defences: the perilous transition of juvenile crown-of-thorns starfish to corallivory." Marine Ecology Progress Series 665 (April 29, 2021): 115–25. http://dx.doi.org/10.3354/meps13660.
Full textAbstract:
The transition from the post-settlement herbivorous juvenile to the coral-eating stage of crown-of-thorns starfish (COTS) is a fundamental step to seed population outbreaks that decimate tropical coral reefs. How the highly cryptic juveniles fare during this transition is poorly understood. We show that the juveniles are vulnerable to attack by coral during this ontogenetic diet shift to coral prey. We monitored the condition, growth, and survival of juvenile COTS during the first 3.5 mo on a diet of Acropora sp. In initial encounters, juveniles often withdrew their arms to avoid the defensive nematocysts of the corals. Within the first 67 d of being offered coral, 37.8% of the juveniles experienced various levels of sublethal and lethal damage. Damaged arms were reduced to ~65.4% of the length of an intact arm, but most injured juveniles were able to regenerate their arms with an average predicted recovery time of ~4 mo. Although sublethal damage slowed the growth of injured juveniles, their capacity to regenerate is likely to contribute to the success of this highly prolific species. Despite being the prey of COTS, coral can influence the survival of juveniles, and potentially reduce their ecological impact by prolonging their growth to reproductive maturity, delaying their transition into a coral predator, and thereby hindering recruitment into the adult population.
41
Malison, Rachel L., Lisa A. Eby, and Jack A. Stanford. "Juvenile salmonid growth, survival, and production in a large river floodplain modified by beavers (Castor canadensis)." Canadian Journal of Fisheries and Aquatic Sciences 72, no. 11 (November 2015): 1639–51. http://dx.doi.org/10.1139/cjfas-2015-0147.
Full textAbstract:
Beavers (Castor canadensis) may strongly influence juvenile salmon production by damming spring brooks that are primary rearing habitats on expansive floodplains of large Pacific Rim salmon rivers. We studied three floodplain rearing habitats in the Kwethluk River, Alaska: free-flowing (beaver-free, n = 3) and beaver-influenced (below beaver dams, n = 4) spring brooks and early-successional beaver ponds (n = 4). We analyzed juvenile coho (Oncorhynchus kisutch) and Chinook (Oncorhynchus tshawytschwa) salmon movement, survival, densities, and growth using a multistate robust capture–mark–recapture design. Survival (46% to 80%) and densities (0.9 fish·m−2) were highest in beaver-free spring brooks. Ponds had lower salmon densities, producing less biomass per unit area than beaver-influenced or beaver-free spring brooks (1.87 ± 0.57 g·m−2 vs. 2.98 ± 1.22 and 3.23 ± 0.73 g·m−2). However, ponds covered 2× greater area than either type of spring brook and therefore produced more salmon biomass at the floodplain scale than either type of spring brook (175 kg vs. 149 kg in beaver-influenced spring brooks and 140 kg in beaver-free spring brooks). We conclude that beaver damming of floodplain spring brooks produces bigger juveniles and more total biomass, but spring brooks produce significantly more, albeit smaller, coho and Chinook juveniles. Thus, the presence of beavers on the floodplain increases habitat variation, which provides a larger range of growth opportunities for juvenile salmon.
42
Friska Sitio, Maru Hariati, Dade Jubaedah, and M. Syaifudin. "KELANGSUNGAN HIDUP DAN PERTUMBUHAN BENIH IKAN LELE (Clarias sp.) PADA SALINITAS MEDIA YANG BERBEDA." Jurnal Akuakultur Rawa Indonesia 5, no. 1 (July 16, 2017): 83–96. http://dx.doi.org/10.36706/jari.v5i1.5810.
Full textAbstract:
ABSTRACT The research consisted of two phases, pre research and research phase. Pre research was carrried out to quantify the isoosmotic of Juvenile catfish by conductivity both on media and fish body which purpose to make the curve of the correlation between salinity with conductivity. The research phase was the maintenance of Juvenile Catfish for 20 days to prove isoosmotic value to survival rate, growth and feed conversion. This research used a completely randomized design with 5 treatments and 3 replications. The treatments were media freshwater (control), 2 ppt (P1), 4 ppt (P2), 6 ppt (P3), 8 ppt (P4). The research value showed there was positive correlation between salinity and conductivity. The isoosmotic value for Juvenil Catfish was 5,893 mS/cm or 4,11 ppt salinity. Survival, growth and feed conversion ratio shows the results were not significantly different (P <0,05). Meanwhile, regression equation indicated salinity (X) that optimal for the maintenance of Juvenile Catfish ranging from 2,6 to 5,0 ppt. Keywords : Conductivity, Growth, Isoosmotic, Salinity, Survival rate
43
Crecco, Victor A., and Thomas F. Savoy. "Effects of Biotic and Abiotic Factors on Growth and Relative Survival of Young American Shad, Alosa sapidissima, in the Connecticut River." Canadian Journal of Fisheries and Aquatic Sciences 42, no. 10 (October 1, 1985): 1640–48. http://dx.doi.org/10.1139/f85-205.
Full textAbstract:
We examined the hypothesis that temporal oscillations in zooplankton abundance, river flows, and temperatures in the Connecticut River affect the survival and growth rates of larval and juvenile American shad, Alosa sapidissima, among 5-d cohorts. The relative survival rates between newly hatched shad larvae and juveniles were low among early cohorts (May 21 – June 15), but rose rapidly among later cohorts (June 21 – July 6) when river flows were low and temperatures and zooplankton densities were high. Age of larval and juvenile shad was estimated by counting daily rings on sagittal otoliths and age-specific length increments determined by backcalculation techniques. Cohort-specific growth rates of larval shad increased linearly with rising zooplankton densities, and asymptotically with rising river temperatures and declining flows. By contrast, juvenile growth rates among 5-d cohorts showed no significant linear or nonlinear relationships to water temperatures and flows.
44
Miller, Sara E., Milo Adkison, and Lewis Haldorson. "Relationship of water column stability to the growth, condition, and survival of pink salmon (Oncorhynchus gorbuscha) in the northern coastal Gulf of Alaska and Prince William Sound." Canadian Journal of Fisheries and Aquatic Sciences 69, no. 5 (May 2012): 955–69. http://dx.doi.org/10.1139/f2012-031.
Full textAbstract:
Water column stability has been hypothesized to affect growth and ultimately survival of juvenile fish. We estimated the relationships between stability and the growth, condition, and marine survival of several stocks of pink salmon ( Oncorhynchus gorbuscha ) within Prince William Sound (PWS), Alaska, USA, and the northern coastal Gulf of Alaska (GOA) shelf. There was a stronger correlation among the biological parameters of the fish than between the biological parameters and physical conditions. While stability and fish condition during early marine residence in PWS were important to year-class survival, stability of the water column that juveniles experienced as they migrated to the open waters of the GOA did not play a key role in determining survival to adulthood. Below-average stability just prior to capture within PWS combined with positive fish condition was related to increased year-class survival. Our results are similar to previous studies that concluded that slower and weaker development of stratification with a deeper mixed layer depth may be important for juvenile pink salmon survival in PWS.
45
Deng, Yuxuan, Chengyang Cao, Xiaoqing Liu, Quan Yuan, Cuixia Feng, Haoran Shi, Yao Yang, and Yufeng Wu. "Effect of Total Dissolved Gas Supersaturation on the Survival of Bighead Carp (Hypophthalmichthys Nobilis)." Animals 10, no. 1 (January 18, 2020): 166. http://dx.doi.org/10.3390/ani10010166.
Full textAbstract:
To assess the effect of TDG on the survival of different sizes of pelagic fish, bighead carp (Hypophthalmichthys nobilis) were subjected to TDG supersaturated water at levels of 125, 130, 135, and 140%. The results showed that apparent abnormal behaviours and symptoms of gas bubble disease (GBD) were observed in bighead carp. The survival probability of large and small juvenile bighead carp declined with increasing TDG levels. The median survival time (ST50) values of large juvenile bighead carp were 74.97 and 31.90 h at 130% and 140% TDG, respectively. While the ST50 of small fish were 22.40 and 6.72 h at the same TDG levels. In comparison to the large juvenile bighead carp, the small juvenile bighead carp showed weaker tolerance to TDG supersaturated water. Furthermore, acute lethality experiments after chronic exposure to TDG were initiated to further investigate the effect of TDG on bighead carp. The juveniles were first subjected to 115% TDG supersaturated water for 96 h. After chronic exposure, live fish were immediately transferred to TDG supersaturated water at levels of 125, 130, 135, and 140%. The results demonstrated that no fish died under chronic exposure and few fish exhibited slight GBD symptoms. The ST50 values for bighead carp subjected to acute exposure after chronic exposure were 61.23 and 23.50 h at 130 and 140%, respectively. Compared with the bighead carp subjected to acute exposure, bighead carp subjected to multiple exposures were more vulnerable to TDG.
46
Saputra, Adang, Tatag Budiardi, Reza Samsudin, and Naufal Dwi Rahmadya. "Growth performance and survival of snakehead Channa striata juvenile with different stocking density reared in recirculation system." Jurnal Akuakultur Indonesia 17, no. 2 (July 31, 2018): 104. http://dx.doi.org/10.19027/jai.17.2.104-112.
Full textAbstract:
<p align="center"><strong>ABSTRACT</strong></p><p class="Paragraf">Snakehead <em>Channa striata</em> is a local specific fish species and has high economic value. Until now the production of snakehead still reelies on the catch of nature because cultivation of snakehead is still underdeveloped. The main constraint in snakehead fish farming is high mortality on snakehead juvenile rearing phase. This study was conducted to determine the best stocking density on snakehead juvenile rearing to achieve optimal production. The treatments used in this study were stocking density of 1 juvenile/L, 2 juveniles/L, and 3 juveniles/L. Snakehead juveniles with a length of 3.41 ± 0.39 cm and weight 0.28 ± 0.07 g, were reared for 42 days in the aquarium sized 40×40×40 cm with a volume of 40 L. Fishes were fed by bloodworms in ad libitum<em> </em>method. The result showed that the treatments did not affect the survival, growth and the ratio of RNA/DNA of snakehead juvenile. Survival of juvenile snakehead ranged 92.5‒94.58% (P>0.05). The result of water quality measurement showed that it was on optimum condition to supporting snakehead growth at 3 juveniles/L stocking density. Furthermore, recirculation can be use to maintenance water quality for optimum condition. Thus, the rearing of snakehead fish juvenile in the recirculation system can use a stocking density of 3 juveniles/L, and the recirculation system could maintain the water quality in good condition.</p><p class="Paragraf"> </p><p>Keywords: growth, recirculation system, snakehead fish, stocking density, survival rate</p><p> </p><p> </p><p align="center"><strong>ABSTRAK </strong></p><p class="Paragraf">Ikan gabus <em>Channa striata</em> merupakan ikan spesifik lokal dan mempunyai nilai ekonomis tinggi. Sampai saat ini produksi ikan gabus masih mengandalkan tangkapan dari alam karena kegiatan budidaya ikan gabus masih belum banyak berkembang. Kendala utama dalam budidaya ikan gabus adalah tingginya mortalitas pada fase pemeliharaan benih. Penelitian ini dilakukan untuk menentukan padat tebar terbaik dalam upaya memperoleh pertumbuhan dan sintasan terbaik. Perlakuan yang digunakan dalam penelitian ini adalah padat tebar 1 ekor/L, 2 ekor/L, dan 3 ekor/L. Benih ikan gabus dengan panjang rata-rata 3,41± 0,39 cm dan bobot rata-rata 0,28 ± 0,07 g dipelihara selama 42 hari di dalam akuarium berukuran 40×40×40 cm dengan volume air 40 L. Benih ikan gabus diberikan pakan berupa cacing sutera secara ad libitum. Hasil penelitian menunjukkan bahwa penggunaan padat penebaran yang berbeda tidak memengaruhi sintasan dan pertumbuhan dan rasio RNA/DNA benih ikan gabus (P>0,05). Sintasan benih ikan gabus pada akhir pemeliharaan berkisar antara 92,5‒94,58%. Hasil pengukuran terhadap kualitas air pada kepadatan 3 ekor/L masih dalam kondisi optimum untuk mendukung pertumbuhan benih ikan gabus sehingga sistem resirkulasi yang digunakan dapat mempertahankan kualitas air dengan baik. Hasil penelitian menunjukkan pemeliharaan benih ikan gabus pada sistem resirkulasi sebaiknya menggunakan padat tebar 3 ekor/L dan sistem resirkulasi dapat mempertahankan kualitas air dalam kondisi baik.</p><p class="Paragraf"> </p><p class="Paragraf">Kata kunci: ikan gabus, pertumbuhan, padat tebar, sintasan, sistem resirkulasi.</p><p> </p>
47
Lipcius, R. N., D. B. Eggleston, D. L. Miller, and T. C. Luhrs. "The habitat-survival function for Caribbean spiny lobster: an inverted size effect and non-linearity in mixed algal and seagrass habitats." Marine and Freshwater Research 49, no. 8 (1998): 807. http://dx.doi.org/10.1071/mf97094.
Full textAbstract:
The habitat-survival function (HSF) defines changes in survival relative to habitat structure; forms include linear, hyperbolic and sigmoid (threshold) curves, whose consequences on predator–prey dynamics are illustrated by their first derivatives. Survival of two juvenile size classes of Caribbean spiny lobster was evaluated as a function of plant biomass in tethering experiments in mixed algal and seagrass patches adjacent to Bahía de la Ascensión, Mexico, which serves as nursery habitat. The HSF was hyperbolic for algal biomass; even modest increases of algal biomass significantly enhanced lobster survival. The rate of change in survival as a function of algal biomass (i.e. an approximation of the first derivative) was greatest at low-to-moderate levels of habitat structure. Hence, survival in these microhabitats is either low or rapidly changing with alterations in habitat structure, and they should be avoided by juveniles. Seagrass biomass did not significantly influence survival, although its levels were relatively low. Smaller juveniles had significantly higher survival rates than larger juveniles, probably because of the limited availability of appropriately scaled refugia for larger juveniles; large juveniles may display an ontogenetic shift from these habitats to coral reefs because of elevated predation risk as they grow.
48
Jenkins, Kurt J., and N. L. Barten. "Demography and decline of the Mentasta caribou herd in Alaska." Canadian Journal of Zoology 83, no. 9 (September 1, 2005): 1174–88. http://dx.doi.org/10.1139/z05-111.
Full textAbstract:
We evaluated population trends in the Mentasta caribou (Rangifer tarandus (L., 1758)) herd in Wrangell – St. Elias National Park and Preserve, Alaska, from 1990 to 1997 and determined factors contributing to its decline. We postulated that predation-related mortality of adult females and juveniles was the proximate cause of the decline, and that survival of juvenile caribou reflected interactions with winter severity, calving distribution, timing of births, density of caribou, and physical condition of neonates at birth. The population declined at its greatest rate from 1990 to 1993 (r = –0.32) and at a lower rate from 1994 to 1997 (r = –0.09). Recruitment (number of calves/100 females during September) averaged 4/100 during the rapid population decline from 1990 to 1993 and 13/100 from 1994 to 1997. Parturition rate of adult females ranged from 65% to 97%. Survival of adult females and juveniles ranged from 0.77 to 0.86 and from 0.00 to 0.22, respectively. Approximately 43%, 59%, and 79% of all juvenile mortality occurred by 1, 2, and 4 weeks of age, respectively. We confirmed predation-related mortality as the primary proximate cause of population decline, with gray wolves (Canis lupus L., 1758), bears (species of the genus Ursus L., 1758), and other predators accounting for 57%, 38%, and 5%, respectively, of all juvenile mortality, and bears causing disproportionate mortality among 0- to 1-week-old neonates. We supported the hypotheses that timing of birth and habitat conditions at the birth site, particularly mottled snow patterns, affected vulnerability and survival of neonates, and birth mass affected survival of juveniles through summer. We speculate that the population will continue to decline before reaching a low-density equilibrium that is sustained by density-dependent changes in the functional responses of predators.
49
Norghauer, Julian M., Jay R. Malcolm, and Barbara L. Zimmerman. "Juvenile mortality and attacks by a specialist herbivore increase with conspecific adult basal area of Amazonian Swietenia macrophylla (Meliaceae)." Journal of Tropical Ecology 22, no. 4 (July 2006): 451–60. http://dx.doi.org/10.1017/s0266467406003257.
Full textAbstract:
According to the Janzen–Connell model, host-specific natural enemies can promote species coexistence of canopy trees in tropical forests by attacking progeny where they are most concentrated. However, empirical evidence relating negative density-dependent mortality to herbivory and, in particular, attack by specialist herbivores, remains rare. We investigated density dependence in a natural population of Swietenia macrophylla in a south-eastern Amazon forest of Brazil. Across 24 adult trees, we found that initial juvenile densities were positively correlated with basal area of adult conspecifics whereas subsequent survivorship over 1 y for these juveniles declined strongly with increasing basal area of adult conspecifics. For 18 trees with > 5 juveniles surviving for 1 y, further evidence supporting the Janzen–Connell mechanism was obtained in that leaf herbivory and attack by a specialist microlepidopteran moth (Steniscadia poliophaea) increased, and overall foliar condition decreased, with conspecific basal area. Moreover, when differences in mean juvenile size (number of extant leaves) were accounted for, juvenile survival over 1 y decreased with increased specialist leaf herbivory. Collectively, these results indicate that herbivores, in particular S. poliophaea, may contribute to density dependence among S. macrophylla juveniles. We conclude that the survival of juveniles and their probability of recruitment into the canopy is decreased where conspecific adults are largest and/or most numerous and find support for the importance of host-specific pests in driving density dependence among tropical trees.
50
Watanabe, Y., Y. Oozeki, and D. Kitagawa. "Larval parameters determining preschooling juvenile production of Pacific saury (Cololabis saira) in the northwestern Pacific." Canadian Journal of Fisheries and Aquatic Sciences 54, no. 5 (May 1, 1997): 1067–76. http://dx.doi.org/10.1139/f97-013.
Full textAbstract:
Production of larvae in the hatching size-class of Pacific saury (Cololabis saira) was highest in autumn 1990-1994, implying that spawning activity was highest in this season. Growth and mortality rates were stable in the winter-spawned cohorts in Kuroshio waters (south of Honshu); variable rates were found in the autumn- and spring-spawned cohorts in the mixed water region to the northeast. Although no particular period of high mortality was detected through the larval and juvenile stages, overall percent survival through the larval and juvenile stages differed by an order of magnitude among seasons. Production of 40-mm preschooling juveniles was determined by larval production in the smallest size-class in the winter cohort, but by overall percent survival through the larval and juvenile stages in the spring and autumn cohorts. Over the last 44 yr, percentage of winter-spawned cohorts in commercial catches was stable, compared with large interannual variations of autumn- and spring-spawned cohorts. These observations were assumed to stem from stable juvenile production in winter and variable production in autumn and spring, suggesting the possibility of recruitment forecasts of seasonally spawned cohorts of saury based on preschooling juvenile production estimates in the northwestern Pacific.