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Auswahl der wissenschaftlichen Literatur zum Thema „Spawning strategy“
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Zeitschriftenartikel zum Thema "Spawning strategy"
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van der Meulen, Dylan E., Chris T. Walsh, Matthew D. Taylor und Charles A. Gray. „Habitat requirements and spawning strategy of an estuarine-dependent fish, Percalates colonorum“. Marine and Freshwater Research 65, Nr. 3 (2014): 218. http://dx.doi.org/10.1071/mf13060.
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Determining the links among estuarine hydrography, habitat and spawning of estuarine-dependent fish is essential for understanding reproductive dynamics, recruitment processes and directing conservation efforts. Acoustic tracking was used to evaluate fine-scale spatial and temporal patterns in spawning activity of Percalates colonorum (estuary perch) within the Shoalhaven River, south-eastern Australia. Plankton tows were used to determine the timing of spawning events. Tagged P. colonorum exhibited movements restricted to areas of structurally complex large wooden debris and a concrete ferry landing. Egg counts confirmed that spawning events coincided with adult aggregations, whereas egg abundances peaked at night during the first 2 h of the run-out tide. We postulate that spawning and recruitment success of P. colonorum is attributable to its selective spawning habitats that are (1) structurally complex to provide refuge and protection from predation, as well as congregate prey items, (2) adjacent to deep water of high velocities to maximise egg dispersal and (3) in close proximity to river entrance to facilitate coastal dispersal of eggs and inter-estuarine connectivity of larvae.
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Overholtz, William J. „Harvesting Strategies and Fishing Mortality Reference Point Comparisons for the Northwest Atlantic Stock of Atlantic Mackerel (Scomber scombrus)“. Canadian Journal of Fisheries and Aquatic Sciences 50, Nr. 8 (01.08.1993): 1749–56. http://dx.doi.org/10.1139/f93-196.
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Previous research indicated that density dependence in population-level responses such as growth and predation mortality rate may play a major role in regulating the dynamics of the Northwest Atlantic stock of Atlantic mackerel (Scomber scombrus). Simulation studies, utilizing this compensatory model of the mackerel stock, suggest that expected yields and spawning stock sizes under conditions of constant harvest rate or constant catch would be quite disparate. Yields and spawning stock size would be less variable and slightly larger under a constant catch strategy for catches of mackerel up to approximately 200 000 t. However, a constant harvest rate strategy would provide higher long-term yields and a more stable spawning stock at catches greater than 200 000 t. A comparison of a constant catch policy with F0.1, F20, and Fmax fishing strategies (constant F) suggests that the Fmax and F20 strategies would cause a long-term decline in the spawning stock below the current minimum spawning stock target and provide highly variable yields. A constant catch strategy could produce nearly the same level of yield with considerably less variability and maintain a larger mean spawning stock biomass than the F0.1 strategy.
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MacCall, Alec D., Tessa B. Francis, André E. Punt, Margaret C. Siple, Derek R. Armitage, Jaclyn S. Cleary, Sherri C. Dressel et al. „A heuristic model of socially learned migration behaviour exhibits distinctive spatial and reproductive dynamics“. ICES Journal of Marine Science 76, Nr. 2 (12.07.2018): 598–608. http://dx.doi.org/10.1093/icesjms/fsy091.
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Abstract We explore a “Go With the Older Fish” (GWOF) mechanism of learned migration behaviour for exploited fish populations, where recruits learn a viable migration path by randomly joining a school of older fish. We develop a non-age-structured biomass model of spatially independent spawning sites with local density dependence, based on Pacific herring (Clupea pallasii). We compare a diffusion (DIFF) strategy, where recruits adopt spawning sites near their natal site without regard to older fish, with GWOF, where recruits adopt the same spawning sites, but in proportion to the abundance of adults using those sites. In both models, older individuals return to their previous spawning site. The GWOF model leads to higher spatial variance in biomass. As total mortality increases, the DIFF strategy results in an approximately proportional decrease in biomass among spawning sites, whereas the GWOF strategy results in abandonment of less productive sites and maintenance of high biomass at more productive sites. A DIFF strategy leads to dynamics comparable to non-spatially structured populations. While the aggregate response of the GWOF strategy is distorted, non-stationary and slow to equilibrate, with a production curve that is distinctly flattened and relatively unproductive. These results indicate that fishing will disproportionately affect populations with GWOF behaviour.
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Albers, J. L., und M. L. Wildhaber. „Reproductive strategy, spawning induction, spawning temperatures and early life history of captive sicklefin chubMacrhybopsis meeki“. Journal of Fish Biology 91, Nr. 1 (13.06.2017): 58–79. http://dx.doi.org/10.1111/jfb.13329.
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Rifi, Mouna, Gaël Le Pennec, Mohamed Ben Salem und Jamila Ben Souissi. „Reproductive strategy of the invasive cockle Fulvia fragilis in the Bay of Tunis (Tunisia)“. Journal of the Marine Biological Association of the United Kingdom 91, Nr. 7 (14.03.2011): 1465–75. http://dx.doi.org/10.1017/s0025315411000099.
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This study is the first work on the reproductive biology of lessepsian bivalve Fulvia fragilis. Monthly and bimonthly samplings were made in the period from April 2006 to October 2007, at the Bay of Tunis (northern Tunisia). From histological preparations of gonad, a gametogenic scale was drawn up based on eight stages: sexual rest; initiation of gametogenesis; advanced gametogenesis; ripe; partial spawning; advanced spawning; restoration; and spent. After examination of gonad preparations, F. fragilis appeared to be a simultaneous hermaphrodite species. Spawning was continuous all along the year, scarce in winter and with peaks during the rest of the year. The spawning peaks were positively correlated with the rise of the sea surface temperature and the nutrient availability. Furthermore, the presence of oocytes surrounded by spermatozoa in female and male follicles and in male gonoducts was observed. Self-fertilization may occur in this species. High summer mortalities probably due to the combination of vulnerability of the bivalve in response to the reproductive effort and high temperature stress were recorded. The F. fragilis reproduction strategy explains the success of its installation on the Tunisian coast.
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Melvin, Gary D., Robert L. Stephenson und Michael J. Power. „Oscillating reproductive strategies of herring in the western Atlantic in response to changing environmental conditions“. ICES Journal of Marine Science 66, Nr. 8 (23.06.2009): 1784–92. http://dx.doi.org/10.1093/icesjms/fsp173.
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Abstract Melvin, G. D., Stephenson, R. L., and Power, M. J. 2009. Oscillating reproductive strategies of herring in the western Atlantic in response to changing environmental conditions. – ICES Journal of Marine Science, 66: 1784–1792. Herring are broadly distributed in the western Atlantic, but reproductive activity is restricted to the central portion, from Cape Cod to northern Newfoundland. Spawning extends from early spring to late autumn. Two spawning types are recognized: spring spawners and autumn spawners. At the southern extreme, spawning occurs almost exclusively in autumn, whereas in the north, spring spawners prevail. Mid-range, both strategies are common, with spawning occurring throughout the entire season. We postulate that the temporal intra-stock dominance of spawning type is an adaptive reproductive strategy to changing environmental conditions. A conceptual model is presented to describe how reproductive success can oscillate between spawning strategies. In most years, environmental conditions appear to favour one type or the other, although strong year classes can co-occur when conditions are right. The recent change in environmental conditions, characterized by a general warming trend, favours autumn spawners and is consistent with our model. At the distributional extremes, stocks are restricted to a single spawning strategy, and broad-scale environmental changes can introduce large interannual variability and limit the reproductive and recovery potential of a stock. The dependence of a stock on a single spawning season may result in longer times to recover to target levels.
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Hall, D. L., R. Hilborn, M. Stocker und C. J. Walters. „Alternative Harvest Strategies for Pacific Herring (Clupea harengus pallasi)“. Canadian Journal of Fisheries and Aquatic Sciences 45, Nr. 5 (01.05.1988): 888–97. http://dx.doi.org/10.1139/f88-107.
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A simulated Pacific herring (Clupea harengus pallasi) population is used to evaluate alternative management strategies of constant escapement versus constant harvest rate for a roe herring fishery. The biological parameters of the model are derived from data on the Strait of Georgia herring stock. The management strategies are evaluated using three criteria: average catch, catch variance, and risk. The constant escapement strategy provides highest average catches, but at the expense of increased catch variance. The harvest rate strategy is favored for its reduced variance in catch and only a slight decrease in mean catch relative to the fixed escapement strategy. The analysis is extended to include the effects of persistent recruitment patterns. Stock–recruitment analysis suggests that recruitment deviations are autocorrelated. Correlated deviations may cause bias in regression estimates of stock–recruitment parameters (overestimation of stock productivity) and increase in variation of spawning stock biomass. The latter effect favors the constant escapement strategy, which fully uses persistent positive recruitment fluctuations. Mean catch is depressed for the harvest rate strategy, since the spawning biomass is less often located in the productive region of the stock–recruitment relationship. The model is used to evaluate the current management strategy for Strait of Georgia herring. The strategy of maintaining a minimum spawning biomass reserve combines the safety of the constant escapement strategy and the catch variance reducing features of the harvest rate strategy.
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Rodrigues, Marcelo, Manuel E. Garcí, Jesús S. Troncoso und Ángel Guerra. „Spawning strategy in Atlantic bobtail squid Sepiola atlantica (Cephalopoda: Sepiolidae)“. Helgoland Marine Research 65, Nr. 1 (06.04.2010): 43–49. http://dx.doi.org/10.1007/s10152-010-0199-y.
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Embke, Holly S., Patrick M. Kocovsky, Tatiana Garcia, Christine M. Mayer und Song S. Qian. „Modeling framework to estimate spawning and hatching locations of pelagically spawned eggs“. Canadian Journal of Fisheries and Aquatic Sciences 76, Nr. 4 (April 2019): 597–607. http://dx.doi.org/10.1139/cjfas-2018-0047.
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Identifying spawning and hatching locations is vital to controlling invasive fish and conserving imperiled fish, which can be difficult for pelagically spawning species with semi-buoyant eggs. In freshwater systems, this reproductive strategy is common among cyprinid species, such as Chinese carp species currently threatening the Great Lakes. Following the confirmation that one of these species, grass carp (Ctenopharyngodon idella), was spawning in a Great Lakes tributary, we developed a modeling framework to combine field data with hydraulic models to calculate the most probable spawning and hatching locations for collected eggs. Our results indicate that the estimated spawning location encompassed habitat consistent with spawning sites in grass carp’s native range. Additionally, all eggs were identified to have hatched in the river, increasing the likelihood of successful recruitment. This modeling framework can be used to estimate spawning and hatching locations for Chinese carp species, as well as all pelagic, riverine spawners. Spawning and hatching locations provide key information to researchers about the reproductive requirements of species and to agencies about how best to manage populations for control or restoration.
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Waddy, S. L., und D. E. Aiken. „Intermolt Insemination, an Alternative Mating Strategy for the American Lobster (Homarus americanus)“. Canadian Journal of Fisheries and Aquatic Sciences 47, Nr. 12 (01.12.1990): 2402–6. http://dx.doi.org/10.1139/f90-267.
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American lobster (Homarus americanus) have a dual mating strategy. Although most females mate when they are newly molted, mating can occur at any molt stage if necessary, in the laboratory, virtually all uninseminated preovigerous females mate prior to spawning. Male aggression is a major factor in the success of intermolt mating and males can discriminate between immature and mature females, and between inseminated and uninseminated females. Female receptivity is affected by both ovarian stage and the presence of stored sperm, but not by molt stage. Most females become unreceptive after insemination, but their receptivity returns once the supply of stored sperm is exhausted. Intermolt mating occurs in smaller lobster that for some reason did not mate at molt, and it is an important part of the reproductive strategy of larger lobster. Lobster s[Formula: see text] carapace length frequently spawn twice without molting and often fail to store sufficient sperm to fertilize consecutive spawnings. Intermolt mating ensures these females will produce fertile second broods.
Dissertationen zum Thema "Spawning strategy"
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Adolfsson, Oscar. „Consequences on population dynamics following regained connectivity in pike (Esox lucius) spawning location“. Thesis, Linnéuniversitetet, Institutionen för biologi och miljö (BOM), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-104213.
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Distributional movements of subpopulations may act as a buffer to prevent the loss of a species in a certain area. However, within subpopulations adaptations may evolve that makes the inhabitants of a certain habitat to better cope with prevailing environmental conditions. If such traits are related to reproduction, they may reduce the opportunity of gene exchange between other subpopulations. Also, a lack of adaptations to a specific habitat may be what prevents a group of individuals, arriving from an adjacent habitat, to successfully colonize an area where a previous subpopulation has been lost.This is the report from a field study conducted in the wetland Lake Långsjön, that in 2018 was restored in order to promote the recruitment of anadromous pike (Esox lucius) to the Baltic Sea. Commonly, wetlands that are restored to promote anadromous pike recruitment, are constructed so that they enable spawning migration from the sea towards the wetland and juvenile emigration towards the sea only. In that sense Lake Långsjön is different, from other wetlands restored for the same purpose, due to that it is connected to both the Baltic Sea and an upstream located freshwater lake. By quantifying the migration of pike (spawners and juveniles) in both directions I explore the consequences that the regained connectivity between the Lake Långsjön and the coast may have on the population dynamics within this wetland; (i) whether it is potentially influenced by allowing mixture between pike with different migratory strategies for spawning (anadromous and potamodromous), (ii) what drivers there are of pike fry emigration and how they may influence the pike fry emigration route and (iii) whether or not the pike of potamodromous origin, resident in the upstream located lake, may work as a source, providing the Baltic Sea with pike juveniles. Pike spawners arriving in the wetland were caught in traps between March - April. Pike fry were caught withing the wetland with fyke nets and by netting. Emigrating pike fry were caught in fyke nets. Findings suggest that spawning migration patterns do not differ between anadromous and potamodromous pike. However, the spawners arriving from the Baltic Sea I suggested are to be composed by offspring of potamodromous origin, possibly hatched during the previous season, and that they as juveniles swam downstream. This, in turn, indicates that the potamodromous stock can help establish an anadromous stock in the Baltic Sea. Still, due to the observation of pike fry displaying an emigration behaviour upstream, origin is identified as a factor that may influence the pike fry emigration route. Also, this emigration pattern seems to indicate a heritable trait that has not been described before among pike, that of downstream spawning. The restoration of the wetland and the regained connectivity is key, both for the ability to restock the Baltic Sea with pike juveniles but also to ensure the conservation of a fascinating stock of pike exhibiting a unique spawning strategy
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Teichert, Nils. „Variabilité des traits d’histoire de vie chez les Gobiidae (Sicydiinae) amphidromes de l’île de la Réunion : Sicyopterus lagocephalus (Pallas, 1770) et Cotylopus acutipinnis (Guichenot, 1863)“. Thesis, Pau, 2012. http://www.theses.fr/2012PAUU3024/document.
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Les Sicydiinae amphidromes constituent une part importante des peuplements piscicoles insulaires de la région Indo-Pacifique et sont vulnérables à de nombreuses pressions anthropiques (i.e. pêcherie, dégradation et fragmentation des habitats). La reproduction a lieu en eau douce, puis les jeunes dévalent en mer où ils débutent leur croissance pendant quelques mois avant de coloniser les rivières. L’objectif est d’acquérir des connaissances sur les traits de vie de S. lagocephalus (cosmopolite) et de C. acutipinnis (endémique). Les travaux de terrain démontrent que le choix de l’habitat quotidien est fortement lié aux interactions sociales, alors que l’habitat de fraie montre une forte sélection pour des conditions morphodynamiques favorisant l’oxygénation des oeufs. Les mâles sélectionnent des sites de ponte et gardent les oeufs. L’étude expérimentale de la survie en eau douce confirme que tous les embryons libres possèdent la capacité à rejoindre la mer. L’analyse des traits de vie marins à partir des otolithes des post-larves révèle des variations saisonnières d’âge et de taille au recrutement, en lien avec la croissance et la température marine. L’examen histologique des ovaires permet de décrire les variations spatiales et temporelles de l’activité de reproduction chez les femelles en rivière et de déterminer la fécondité et la taille de première reproduction. Les variations inter et intra-spécifiques des traits de vie sontcomparées en lien avec la répartition géographique des deux espèces. Ces travaux permettent d’identifier des perspectives concrètes dans le domaine de la gestion et de la conservation sur la base des caractéristiques de la stratégie amphidromeAmphidromous Sicydiinae are particularly widespread among fish freshwater assemblages of the Indo-Pacific region and are vulnerable to anthropogenic pressures (i.e. fishery, degradation and fragmentation of habitats). Spawning and hatching happen in freshwater, then offspring drift downstream to the sea where they begin their growth for a few months before recruiting in the rivers. This study aims at acquire knowledge about life traits of S. lagocephalus (cosmopolite) and C. acutipinnis (endemic). Field sampling shows that the usual habitat choice is related to social interactions, whereasspawning habitat shows a strong selection for morphodynamic conditions which favor eggs oxygenation. Males select spawning sites and care for the eggs. The experimental study of freshwater survival confirms that free embryos survival and swimming capacities are enough to drift to the ocean. Marine life history analysis, based on postlarvae otoliths examination, reveals a seasonal variation of both age and size-atrecruitment related to the larval growth rate and the sea temperature. Histological examination of ovaries is used to describe the spatial and temporal variation of reproductive activity of mature females in the rivers, and to determine fecundity and size at first reproduction. Inter and intra-specific variations of life history traits are compared in relation to the respective geographical distribution of both species. This study identifies concrete prospects for management and conservation based on the features of amphidromous life history strategy
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Nakayama, Shinnosuke 1978. „Intraspecific competition among early life stages and the optimal spawning strategy of red drum (Sciaenops ocellatus)“. Thesis, 2009. http://hdl.handle.net/2152/ETD-UT-2009-12-525.
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This collection of studies was designed to understand the mechanisms and consequences of competition among early life stages of red drum (Sciaenops ocellatus), with a special attention to asymmetric competition and multiple-breeding strategy of parents. The overall hypotheses were that (1) red drum larvae show behavioral interactions, and the magnitude of these interactions is explained by the sizes of the competing individuals, (2) red drum larvae compete for food and habitat use, and the competition is asymmetric as determined by size and behavioral interactions, and (3) the parents can reduce negative effects of competition among larvae and increase larval survival by altering their multiple-spawning traits. The laboratory experiments showed the existence of sociality in red drum larvae. The magnitudes of aggressive behavior, vigilant behavior and shoaling behavior were explained by a combination of absolute and relative phenotypes of competing individuals, such as body lengths and body condition. A new method of combining the laboratory experiments and the foraging theory disentangled interference competition for food from exploitative competition, revealing that both absolute and relative body lengths of competing individuals influence feeding efficiencies. In addition, vigilant behavior decreased feeding efficiency regardless of body sizes. The competitor size and behavioral interactions between individuals had different effects on competition for habitat use: the existence of larger individuals prevented the newly settled larvae from entering preferred habitats, whereas the aggressive behavior from the occupants of preferred habitats moved newly settled larvae to the unpreferred habitats. Finally, computer simulations using an individual-based model revealed that as interference competition among larvae increased, the number of spawning events and the spawning interval of the parents increased to lessen competition and maximize total survival of offspring.text
Buchteile zum Thema "Spawning strategy"
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Hahn, Ernst Moritz, Mateo Perez, Sven Schewe, Fabio Somenzi, Ashutosh Trivedi und Dominik Wojtczak. „Model-Free Reinforcement Learning for Branching Markov Decision Processes“. In Computer Aided Verification, 651–73. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-81688-9_30.
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AbstractWe study reinforcement learning for the optimal control of Branching Markov Decision Processes (BMDPs), a natural extension of (multitype) Branching Markov Chains (BMCs). The state of a (discrete-time) BMCs is a collection of entities of various types that, while spawning other entities, generate a payoff. In comparison with BMCs, where the evolution of a each entity of the same type follows the same probabilistic pattern, BMDPs allow an external controller to pick from a range of options. This permits us to study the best/worst behaviour of the system. We generalise model-free reinforcement learning techniques to compute an optimal control strategy of an unknown BMDP in the limit. We present results of an implementation that demonstrate the practicality of the approach.
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„Conservation, Ecology, and Management of Catfish: The Second International Symposium“. In Conservation, Ecology, and Management of Catfish: The Second International Symposium, herausgegeben von JOSEPH N. STOECKEL und RICHARD J. NEVES. American Fisheries Society, 2011. http://dx.doi.org/10.47886/9781934874257.ch22.
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<em>Abstract</em>.—Captive spawning is a strategy to bolster populations of rare madtoms <em>Noturus</em> spp., but very little is known regarding their reproductive development in captivity. The primary goal of this research was to develop methods to stimulate gonadal maturation of captive madtoms. We used the nonimperiled margined madtom <em>N. insignis</em> as a model species to investigate the effects of photothermal regimes on gonadal development and reproductive hormones. We also evaluated testicular development of madtoms injected with common carp <em>Cyprinus carpio</em> pituitary extract (CPE). Changing photoperiod, but not temperature, was required to induce oocyte maturation in a high percentage of captive female margined madtoms. Gonadosomatic index (GSI) values of captive females were similar to those of gravid wild fish collected during or just prior to the spawning season with the time to maturation of oocytes shortened by as much as 3 months. Many of the captive males developed large, square-shaped heads with swollen cephalic epaxial muscles as spawning conditions approached, but their GSI values were not different from those of fish sampled at other times of the year. Injections of CPE increased the GSI value and vascularization of testes but not the number of spermatozoa. In general, sperm production in mature male madtoms was enigmatic in captive and wild fish, inasmuch as motile sperm were observed only once. The heads of margined madtom spermatozoa are slightly ovate (4.3 0.2 μm long and 3.6 0.2 μm wide). The tails are centrally attached to the head and are more than 112.5 μm long. A pronounced, collar-like midpiece encircles the posterior portion of the head and anterior portion of the tail. Plasma testosterone concentrations in males peaked just prior to the spawning season at 6.5 ng/mL, but levels were not correlated with male GSI values. Plasma 17β-estradiol levels in females peaked just prior to the spawning season at 15 ng/mL and were correlated with gonadosomatic values.
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„Life in the Slow Lane: Ecology and Conservation of Long-Lived Marine Animals“. In Life in the Slow Lane: Ecology and Conservation of Long-Lived Marine Animals, herausgegeben von Robert W. Chapman, George R. Sedberry, John C. McGovern und Bradley E. Wiley. American Fisheries Society, 1999. http://dx.doi.org/10.47886/9781888569155.ch13.
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<em>Abstract.</em> —Individuals of many aquatic species produce millions of offspring in a single spawning event, engage in several such events during a spawning season, and may be reproductively active for many years. Out of all of this activity only two offspring must reach reproductive age in order for the species to maintain its numbers. The genetic consequences of this high-risk strategy have been discussed in previous work. At least five null hypotheses concerning the relationship between reproductive output and the distribution of genetic variation can be constructed from theoretical considerations and the biology of weakfish <em>Cynoscion regalis, </em> spotted sea trout <em>Cynoscion nebulosus</em> , and red drum <em>Sciaenops ocellatus</em> . In this paper, we test four of these hypotheses and provisionally reject three. These results indicate the variance in reproductive output tends to reduce effective population size and lead to apparent (and misleading) fine-scale population structure in long-lived species.
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„Propagated Fish in Resource Management“. In Propagated Fish in Resource Management, herausgegeben von BARRY BEREJIKIAN, THOMAS FLAGG und PAUL KLINE. American Fisheries Society, 2004. http://dx.doi.org/10.47886/9781888569698.ch20.
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<em>Abstract.</em>—Captive broodstocks have been initiated for maintenance and recovery of imperiled anadromous salmonid populations because they can provide a rapid demographic boost and reduce short-term extinction risk. As with captive propagation programs for other vertebrates, difficulties with reintroduction to the natural environment may impede success in achieving the program’s objectives. Strategies for reintroduction of anadromous salmonid captive broodstocks in the United States and Canada include release of captively reared adults (currently four programs), stocking their offspring as eyed eggs (two programs), parr (six programs), or smolts (nine programs). Captive broodstock programs that release adults considered the management objectives of (i) evaluating of different reintroduction strategies, and (ii) spreading the risk of failure of any one particular strategy to be much more important than programs that do not release adults. This distinction indicates that the programs releasing adults consider the strategy to be an experimental one that may serve to offset potential risks associated with juvenile release options. However, the finding that preventing extinction was considered to be very important in adult and juvenile release programs alike indicates that programs releasing adults believe the strategy, at a minimum, will not impede that objective. We summarized the salmonid literature on (1) natural and sexual selection during reproduction, (2) homing and straying, (3) rearing effects on social behavior, (4) domestication, and (5) survival as it relates to biological trade-offs of different reintroduction strategies for captive broodstocks. The adult release strategy provides potential biological benefits that include the opportunity for natural and sexual selection to occur on the spawning grounds—selection that is relaxed during artificial spawning. Adult release and egg stocking may reduce potential for unnaturally high straying rates and may minimize domestication selection of the offspring compared to programs that artificially spawn adults and release their offspring as smolts. The potential benefits of adult and egg releases must be weighed against (and may be offset by) the greater F1 production that could be achieved by releasing hatchery-reared smolts. A variety of reintroduction strategies will likely continue to be appropriate for captive broodstock programs.
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„Challenges for Diadromous Fishes in a Dynamic Global Environment“. In Challenges for Diadromous Fishes in a Dynamic Global Environment, herausgegeben von Midori Iida, Shun Watanabe und Katsumi Tsukamoto. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781934874080.ch23.
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<em>Abstract</em>-<em>Sicyopterus japonicus </em>is unique because it is the only temperate amphidromous goby of the subfamily Sicydiinae. Life history and migration characteristics of <em>S. japonicus</em>, including seasonal changes of condition factor, spawning season, hatching size, oceanic larval duration, recruitment season, and size at recruitment, were examined in the temperate region of western Japan and were compared with those of other Sicydiinae species, all of which inhabit the tropics and subtropics. The condition factor varied seasonally, with peaks in July and November. The spawning season of <em>S. japonicus </em>ranged from July to September, with a peak in July-August, and was shorter than that of other species that normally spawn from 7 to 12 months/year. The hatching size (1.5 mm total length) was similar to other Sicydiinae, but oceanic larval duration (range: 173-253 d) was longer than most other species. The long larval duration and single annual reproduction period suggest that it is adapted to longdistance oceanic dispersal. The recruitment season (about 4 months) is the shortest known among the Sicydiinae, but its size at river entry (mean: 26.3 mm standard length) was similar to other species. The shorter reproductive and recruitment seasons for <em>S. japonicus </em>probably indicate that its migration strategy is determined by seasonal changes in the temperate region. Sicydiinae species have larger clutch sizes and smaller hatching sizes compared to other temperate amphidromous families such as the Galaxiidae, Osmeridae, and Cottidae. Sicydiinae species have no nondiadromous forms, suggesting that they may have a migration strategy with a high oceanic dependency that facilitates oceanic dispersion.
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„Propagated Fish in Resource Management“. In Propagated Fish in Resource Management, herausgegeben von VAUGHN L. PARAGAMIAN und RAYMOND C. P. BEAMESDERFER. American Fisheries Society, 2004. http://dx.doi.org/10.47886/9781888569698.ch32.
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<em>Abstract.</em>—In 1994, the Kootenai River white sturgeon <em>Acipenser transmontanus </em>was listed in the United States as an endangered species. Under provisions of the Endangered Species Act, a recovery plan was prepared and included two main recovery measures: (1) mitigation of spring flows for spawning and early life rearing, and (2) implementation of a conservation aquaculture and breeding plan to prevent extinction and sustain year-classes. The hatchery program was controversial and intended as a short-term measure as the flow mitigation strategy for wild fish developed. It called for the release each year of up to 1,000 white sturgeon from each of 10–12 families. It was believed that the mitigation of spring flows from Libby Dam would rapidly bring about recovery. However, after 8 years of flow mitigation and intensive monitoring and evaluation, it became apparent that recovery needs were more complex. Flow releases were not at the expected magnitude and habitat issues became a significant concern because the spawning location of sturgeon did not appear suitable (silt and sand) for adequate survival of eggs and larvae. Recruitment of wild fish was extremely low, while survival of hatchery sturgeon was higher than expected. Hatchery fish soon became abundant out numbering juvenile wild sturgeon by about 400:1. Assessment of sturgeon demographics, with extinction risk models, provided evidence that the wild population would be extinct within three decades and the population would be comprised almost exclusively of hatchery fish. Population projections described a significant near-term bottleneck in spawner numbers as the wild population diminished but hatchery fish had not yet matured. Managers are faced with a contentious dilemma of elevating the importance of the hatchery program by taking a higher proportion of the remaining wild spawners, escalating the number of hatchery releases, which could result in increasing the risk of inbreeding depression, loss of genetic diversity, genetic swamping, disease magnification, long term domestication, and intraspecific competition with wild recruits, compromising recovery. However, without significant hatchery intervention, the population could become a museum piece with no management options to benefit anglers. There will be disagreements, but risks must be considered, and we propose some compromises that may ease the intrusion of hatchery fish and provide management options.
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„Benthic Habitats and the Effects of Fishing“. In Benthic Habitats and the Effects of Fishing, herausgegeben von Peter W. Barnes, Guy W. Fleischer, James V. Gardner und Kristen M. Lee. American Fisheries Society, 2005. http://dx.doi.org/10.47886/9781888569605.ch15.
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<strong><em>Abstract. </em></strong>As part of a strategy to reestablish native stocks of lake trout <em>Salvelinus namaycush</em>, six areas of offshore and coastal Lake Michigan benthic habitat were mapped with a bathymetric laser system. This allowed us to visualize and map morphologic detail by at least an order of magnitude over existing data. Decimeter elevation–bathymetric data, referenced to the International Great Lakes datum of 1985, were obtained on a 4-m grid over a total area of about 200 km<sup>2</sup> in water depths from 0 to 30 m. Based on the laser-derived morphology, regional geology and sparse samples, three geologic regimes were used for substrate–habitat classification: (1) bedrock carbonates of Silurian through Devonian age, indicated by bedding scarps and lineations at or near the surface at all of the mapped areas; (2) glacial deposits that appear as compacted clay till lineations and cobble and boulder moraines with outwash features; and (3) modern sand deposits seen in thin down-drift (to the east) bedforms, sand sheets, and depositional lobes. Preferred spawning substrate—clean cobble and gravel deposits with adjacent deep water—is present in sections of all mapped areas. However, laser data cannot discern cleanliness, and video data indicate the cleanliness on this substrate may be compromised by recent algal and mussel growth.
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„Biology, Management, and Protection of North American Sturgeon“. In Biology, Management, and Protection of North American Sturgeon, herausgegeben von Susan C. Ireland, Paul J. Anders und John T. Siple. American Fisheries Society, 2002. http://dx.doi.org/10.47886/9781888569360.ch17.
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<em>Abstract.</em>—The white sturgeon population <em>Acipenser transmontanus</em> in the Kootenai River was listed as endangered by the U.S. Fish and Wildlife Service (USFWS) in 1994 due to postglacial isolation and the virtual lack of recruitment since 1974. The Kootenai River White Sturgeon Conservation Aquaculture Program was initiated to preserve genetic variability, begin rebuilding natural age-class structure, and prevent extinction while measures are identified and implemented to restore natural recruitment. The program is part of a comprehensive recovery strategy detailed in the USFWS recovery plan for the Kootenai River population of white sturgeon. A breeding plan, including culture methods to minimize potential detrimental effects of conventional stocking programs, has been implemented to guide recovery, population management, and the systematic collection and spawning of wild adults before they are lost from the wild breeding population. Between 1990 and 2000, 33 families were produced from the mating of 51 wild white sturgeon broodstock. Genetic analysis indicated that five mitochondrial control region length variants represented in the wild white sturgeon population were represented in similar frequencies in the wild white sturgeon broodstock. A total of 2,702 hatchery-reared white sturgeon were released into the Kootenai River between 1992 and 1999. White sturgeon juveniles approved for release had no diagnostic disease symptoms and less than or equal to 10% prevalence of endemic pathogens. A total of 398 hatchery-reared fish were recaptured in the wild (14.7% of 2,702 stocked; single recapture events) during the 1993–1999 sampling period. The Kootenai River Conservation Aquaculture Program is currently meeting its objectives of reducing the threat of population extinction by providing frequent year classes from native broodstock, representing inherent within-population genetic diversity in its broodstock and progeny, and minimizing the introduction of disease into the recipient wild population.
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„From Catastrophe to Recovery: Stories of Fishery Management Success“. In From Catastrophe to Recovery: Stories of Fishery Management Success, herausgegeben von Miratori Kim, Elizabeth R. Bageant, Shakuntala H. Thilsted und Kathryn J. Fiorella. American Fisheries Society, 2019. http://dx.doi.org/10.47886/9781934874554.ch14.
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<i>Abstract</i>.â€â€Home to nearly 500 aquatic species, Cambodian freshwater fisheries are among the world’s most diverse (Baran 2005). These diverse fisheries support the livelihoods and the food and nutrition security of millions of Cambodian people. However, these fisheries also face a range of threats, including conflicts with dam projects that disrupt fish movement and spawning, increasing harvest pressure, and unpredictable flood seasons. Rice-field fisheries support as much as 30% of all fish catch in Cambodia and are the site of a unique management strategy that has been implemented to sustainably improve fish catch and strengthen community governance: community fish refuges (CFRs). Community fish refuges have been encouraged by the government of Cambodia and are community-managed protected areas designed to increase fish productivity and protect biodiversity. We use governance scores to examine how support for CFRs from 2012 to 2015 has improved their governance across five dimensions (structure, planning, representation, fundraising, and networking) and the relationship between governance and fish biomass within CFRs. We find some associations between the governance scores and the biomass and biodiversity of the refuges, suggesting that improving governance may affect fishery productivity in this setting. Important lessons learned include (1) that supporting community leadership and technical knowledge enables communities to better understand and justify the underlying reasons for management actions and negotiate their implementation; (2) that in changing ecosystems, community-based approaches allow communities to responsively adapt to the unique, localized environmental conditions they face; (3) that community-based approaches capitalize on a community’s unique knowledge of their ecological setting and community; and (4) that engagement of community leadership with the wider fisheries context is essential to facilitating and encouraging community efforts.
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„Propagated Fish in Resource Management“. In Propagated Fish in Resource Management, herausgegeben von WALLACE E. JENKINS, THEODORE I. J. SMITH und MICHAEL R. DENSON. American Fisheries Society, 2004. http://dx.doi.org/10.47886/9781888569698.ch3.
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<em>Abstract.</em>—Some fisheries managers have reservations concerning marine stock enhancement programs as they believe that stock supplementation is not a proven management strategy. Further, they consider the perceived risks of disease introductions, genetic degradation, and other possible negative impacts unacceptable for an unproven technology. The red drum <em>Sciaenops ocellatus </em>is a highly popular sport fish throughout southern U.S. waters, but population abundance has been drastically reduced due to overharvesting. For more than a decade, South Carolina has been evaluating the impact of stocked red drum in the overall management plan to restore abundance of this species. Findings to date conclude that stocked fish behave similarly to wild fish, sex ratio and survival of stocked fish is similar to wild fish, stocking effects are additive and increase local population size, growth of wild cohorts is not impacted by presence of stocked fish, stocked fish enter into the adult population, and negative genetic impacts are not likely in a properly managed program. Over this same time period, experiments conducted in Texas and Florida have also addressed many of the critical uncertainties associated with red drum stocking. Data from these three states have demonstrated that responsibly managed stocking programs can increase local abundance while not displacing wild red drum or causing loss of genetic diversity. In spite of these encouraging findings, stocking should not be considered as a panacea or total solution to population restoration. Nursery and spawning habitats must be vigorously protected and regulations must be maintained to prevent overfishing if long-term sustainability is to be achieved. Similarly, based on data collected to date, stocking may not be the pariah that some managers perceive. Indeed, it will only be through additional controlled studies that the role of stocked red drum can be quantitatively assessed as a management tool.