Academic literature on the topic 'Southern yellowtail'

As with all Sebastes species, yellowtail rockfish ( S. flavidus ) produce larvae with an extended pelagic juvenile phase that can be advected in coastal currents. While dispersal potential is high, previous research on population genetic characteristics of Sebastes species indicates that apparent realized dispersal can be much lower and can exhibit complex patterns of genetic structure. We assayed 812 bp of the mitochondrial cytochrome b gene and six microsatellite loci in ∼1000 yellowtail rockfish collected from 21 sites that span the species range from southern California to southeastern Alaska. An abrupt genetic cline near Cape Mendocino, California, splits the range into a northern and southern stock, and is highly concordant between our mitochondrial (FCT = 0.32, p ≪ 0.001) and microsatellite (FCT = 0.02, p ≪ 0.001) datasets. We show that this pattern may be due to a combination of physical (oceanographic or other barriers to larval dispersal), biological (habitat differences), and historical events. This study, and both intra- and inter-specific evidence from other marine species suggests Cape Mendocino demarcates two regions experiencing divergent evolutionary trajectories, and should be considered in management strategies.

Abstract We evaluated the influence of environmental factors on recruits per spawner (RS) anomalies of 12 New England groundfish stocks. Nonparametric methods were used to analyse time-series of RS anomalies derived from stock-recruitment data in recent assessments. The 12 stocks occur in three geographic regions: the Gulf of Maine (cod Gadus morhua, redfish Sebastes fasciatus, winter flounder Pseudopleuronectes americanus, American plaice Hippoglossoides platessoides, witch flounder Glyptocephalus cynoglossus, and yellowtail flounder Limanda ferruginea), Georges Bank (cod, haddock Melanogrammus aeglefinus, and yellowtail flounder), and Southern New England (summer flounder Paralichthys dentatus, yellowtail flounder, and winter flounder). Randomization tests were applied to detect years when RS anomalies were unusually high or low for comparison with oceanographic conditions such as the 1998 intrusion of Labrador Subarctic Slope water into the Gulf of Maine region. Randomization methods were also used to evaluate the central tendency and dispersion of all RS anomalies across stocks. Average RS anomalies were significantly positive in 1987 across stocks and regions, indicating that environmental forcing was coherent and exceptional in that year. Responses of RS values of individual stocks to lagged and contemporaneous environmental variables such as the North Atlantic Oscillation (NAO) index, water temperature, windstress, and shelf water volume anomalies were evaluated using generalized additive models. Overall, the NAO forward-lagged by 2 years had the largest impact on RS anomalies. This apparent effect is notable because it could provide a leading indicator of RS anomalies for some commercially exploited stocks. In particular, the three primary groundfish stocks on Georges Bank (cod, haddock, and yellowtail flounder) all exhibited positive RS anomalies when the NAO2 variable was positive.

Dietary remains recovered from Australian sea lion (Neophoca cinerea) digestive tracts and regurgitate samples from Seal Bay (Kangaroo Island, South Australia) were used to identify prey species consumed. Four of eight digestive tracts collected (50%) contained prey items located only in the stomach. On the basis of biomass reconstruction of cephalopod prey remains, octopus contributed 40% of the biomass in the samples, giant cuttlefish (Sepia apama) contributed 30% and ommastrephid squids contributed 14% biomass. The remains of several fish species were found in the samples: leatherjacket (Monocanthidae), flathead (Platycephalus sp.), swallowtail (Centroberyx lineatus), common bullseye (Pempheris multiradiata), southern school whiting (Sillago flindersi) and yellowtail mackerel (Trachurus novaezelandiae). Southern rock lobster (Jasus edwardsii) and swimming crab (Ovalipes australiensis) carapace fragments, little penguin (Eudyptula minor) feathers and bones and shark egg cases (oviparous species and Scyliorhinidae sp.) were also identified.

Ichthyoplankton and hydrographic surveys of the southern Grand Bank in September of 1986, 1987, and 1988 revealed substantial correspondence between the areal distributions of larvae of three flatfish species and temperature below the thermocline. Depth-averaged densities of American plaice (Hippoglossoides platessoides) were negatively correlated with temperature whereas yellowtail flounder (Limanda ferruginea) and witch flounder (Glyptocephalus cynoghssus) densities were positively correlated with temperature. In spite of large interannual differences in abundance, the larval distributions showed similar structure from year to year. Using estimates of larval age inferred from length frequency distributions and literature values for growth rate, in conjunction with moored current measurements, estimates of spawning times and locations were obtained for each species. These estimates were compared with historical information on the distribution of prespawning fish for each species to examine the hypothesis of passive larval drift. The results indicate that in most, but not all cases, the larval distributions and currents are consistent with passive larval drift for particular growth rates and vertical distributions. However, the observations are not adequate to rule out alternative mechanisms involving behaviour.

The state-space model framework provides a natural, probabilistic approach to stock assessment by modeling the stochastic nature of population survival and recruitment separately from sampling uncertainty inherent in observations on the population. We propose a state-space assessment model that is expanded to simultaneously treat environmental covariates as stochastic processes and estimate their effects on recruitment. We apply the model to southern New England yellowtail flounder (Limanda ferruginea) using data from the most recent benchmark assessment to evaluate evidence for effects of the mid-Atlantic cold pool and spawning stock biomass on recruitment. Based on Akaike’s information criterion, both the cold pool and spawning stock biomass were important predictors of recruitment and led to annual variation in estimated biomass reference points and associated yield. We also demonstrate the effect of the stochasticity of the mid-Atlantic cold pool on short-term forecasts of the stock size, biomass reference point, and stock status.

Paradeontacylix godfreyi n. sp. (Digenea: Sanguinicolidae) is described from the heart of wild yellowtail kingfish, Seriola lalandi Valenciennes, 1833, collected near Port Augusta, northern Spencer Gulf, South Australia. One specimen of P. godfreyi was also collected from the heart of a single wild specimen of S. lalandi captured near Killarney, Victoria. Paradeontacylix godfreyi is distinguished from other species in the genus by a combination of morphological characters including the shape and number of posterior tegumental spines, the number of rows of tegumental spines along the ventral body margin, the maximum number of marginal tegumental spines per row, the number of testes and the extent of the testicular field. Comparisons are made with a Paradeontacylix sp. collected from the heart of wild Samson fish, S. hippos Günther, 1876 from Greenly Island, South Australia and from the heart of wild S. lalandi from Killarney, Victoria. We also document a new host record for P. sanguinicoloides McIntosh, 1934 from the heart of wild S. hippos from Greenly Island, South Australia. The importance of determining potential intermediate hosts for Paradeontacylix species in relation to South Australian S. lalandi aquaculture is discussed.

Abstract Biomass of the yellowtail Seriola quinqueradiata, an important fishery resource in Japan, has increased about threefold over the past 20 years to ∼300 thousand metric tons. We examined the interannual variations in distribution and abundance of S. quinqueradiata larvae [4.2–7.9 mm body length (BL), ∼7 to 18 days after hatching], based on sampling surveys over a broad area of the shelf-break region of the East China Sea (ECS) in April, the main spawning period, over 15 years (2001–2015). High abundances of larvae were found in the northern ECS off the southwestern coast of Kyushu Island throughout the survey period. After 2010, the larvae began to occur abundantly also in the southern ECS south of 29°30′N, indicating a southward expansion of the spawning ground. There has been a significant positive trend of larval abundance over the whole ECS during the 15 years, which was mainly due to the sharp increase in larval abundance in the southern ECS after 2010. Although interannual variation in larval abundance was not related to environmental conditions (temperature, salinity, and chlorophyll a concentration), it was closely correlated with the spawning stock biomass. This indicates that the increasing trend of larvae was related to the increase in egg production in the ECS. Also, the larval abundance showed a weak positive correlation with recruitment, suggesting that the increased larval abundance has, in part, contributed to high recruitment.

Metazoan parasites threaten the development and expansion of yellowtail kingfish (Seriola lalandi) sea-cage aquaculture in Australia. There is international speculation that parasite transmission from farmed to wild fish leads to increased incidence of parasitism in wild fish. Conversely, transfer of parasites from wild fish to farmed fish can negatively impact upon the health of farmed fish. Baseline information on the parasite assemblage of wild S. lalandi in Australia will: 1) allow informed judgments to be made in order to responsibly monitor, and perhaps remedy, potentially negative impacts and; 2) enable identification of parasite species of potential harm to the Australian S. lalandi aquaculture industry. I collected wild Seriola spp. (Carangidae) throughout southern Australia and examined them for metazoan parasites. Fifty-six metazoan parasite species are identified, including one new species. A taxonomic listing is provided for the metazoan parasites found. Taxonomic descriptions are made for the blood fluke Paradeontacylix godfreyi n. sp. (Digenea: Sanguinicolidae) and a redescription is provided for the parasitic copepod Naricolax chrysophryenus (Cyclopoida: Bomolochidae). A qualitative risk assessment was devised for the metazoan parasite taxa identified for the sea-cage aquaculture of S. lalandi in South Australia. Risk was interpreted considering the likelihood and consequence of parasite establishment and proliferation. The monogeneans Benedenia seriolae and Zeuxapta seriolae were considered extremely likely to establish and proliferate. Benedenia seriolae also poses high potential negative consequences for cost-effective S. lalandi sea-cage farming. However, the absence of potential mitigation methods and parasite management for Paradeontacylix spp. (Digenea), Kudoa sp. and Unicapsula seriolae (Myxozoa) indicates that these species may also present high negative consequences for S. lalandi aquaculture in Australia. The nature of wild Seriola migrations is critical for an understanding of the potential impact of disease and parasite interactions between wild and farmed fish. A small-scale tagging programme of wild-caught S. lalandi and S. hippos in South Australia provided insight into the movements of these species. Recapture results indicate that large S. lalandi remain in, or return to, northern Spencer Gulf. S. lalandi also move past sea-cage farms in Fitzgerald Bay, northern Spencer Gulf, which is an important consideration in view of potential expansion of the S. lalandi sea-cage industry in Spencer Gulf. There is surprisingly little experimental assessment on parasite transmission from farmed fish to wild fish. Studies assessing parasite interactions between wild and cultured fish employ models to quantify parasite population levels of cultured, wild and escaped fish, while others carry out comparative surveys of parasite prevalence and intensity over time, in areas close to and distant from farming activity. I provide preliminary data on ectoparasite prevalence and intensity on wild S. lalandi in areas close to, distant from and where there is no sea-cage farming in southern Australia. I review methods employed in the northern hemisphere to assess sea-louse transfer between wild and farmed salmon and propose methods for assessing monogenean parasite transmission from farmed to wild S. lalandi in Australia. In summary, this thesis provides insight into the potential for parasite interactions between wild and farmed S. lalandi. I document the parasite assemblage of wild and farmed S. lalandi and wild S. hippos and provide baseline data on ‘natural’ parasite prevalence and intensity. I provide a taxonomic description of a new species of blood fluke. I indicate the likelihood of parasite transfer from wild fish to farmed S. lalandi, and identify parasite taxa with potentially negative consequences for sea-cage aquaculture. I provide the first firm data that wild S. lalandi move past one area where kingfish are farmed in sea-cages in South Australia. Finally, I propose procedures to better understand the potential for monogenean parasite transmission from farmed S. lalandi to wild fish. This thesis reports new information that is important when considering and managing expansion of the S. lalandi sea-cage aquaculture industry throughout Australia. It also provides baseline data on natural parasite levels to enable ongoing monitoring of the potential impacts of the industry on wild fish populations.
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Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2007

Metazoan parasites threaten the development and expansion of yellowtail kingfish (Seriola lalandi) sea-cage aquaculture in Australia. There is international speculation that parasite transmission from farmed to wild fish leads to increased incidence of parasitism in wild fish. Conversely, transfer of parasites from wild fish to farmed fish can negatively impact upon the health of farmed fish. Baseline information on the parasite assemblage of wild S. lalandi in Australia will: 1) allow informed judgments to be made in order to responsibly monitor, and perhaps remedy, potentially negative impacts and; 2) enable identification of parasite species of potential harm to the Australian S. lalandi aquaculture industry. I collected wild Seriola spp. (Carangidae) throughout southern Australia and examined them for metazoan parasites. Fifty-six metazoan parasite species are identified, including one new species. A taxonomic listing is provided for the metazoan parasites found. Taxonomic descriptions are made for the blood fluke Paradeontacylix godfreyi n. sp. (Digenea: Sanguinicolidae) and a redescription is provided for the parasitic copepod Naricolax chrysophryenus (Cyclopoida: Bomolochidae). A qualitative risk assessment was devised for the metazoan parasite taxa identified for the sea-cage aquaculture of S. lalandi in South Australia. Risk was interpreted considering the likelihood and consequence of parasite establishment and proliferation. The monogeneans Benedenia seriolae and Zeuxapta seriolae were considered extremely likely to establish and proliferate. Benedenia seriolae also poses high potential negative consequences for cost-effective S. lalandi sea-cage farming. However, the absence of potential mitigation methods and parasite management for Paradeontacylix spp. (Digenea), Kudoa sp. and Unicapsula seriolae (Myxozoa) indicates that these species may also present high negative consequences for S. lalandi aquaculture in Australia. The nature of wild Seriola migrations is critical for an understanding of the potential impact of disease and parasite interactions between wild and farmed fish. A small-scale tagging programme of wild-caught S. lalandi and S. hippos in South Australia provided insight into the movements of these species. Recapture results indicate that large S. lalandi remain in, or return to, northern Spencer Gulf. S. lalandi also move past sea-cage farms in Fitzgerald Bay, northern Spencer Gulf, which is an important consideration in view of potential expansion of the S. lalandi sea-cage industry in Spencer Gulf. There is surprisingly little experimental assessment on parasite transmission from farmed fish to wild fish. Studies assessing parasite interactions between wild and cultured fish employ models to quantify parasite population levels of cultured, wild and escaped fish, while others carry out comparative surveys of parasite prevalence and intensity over time, in areas close to and distant from farming activity. I provide preliminary data on ectoparasite prevalence and intensity on wild S. lalandi in areas close to, distant from and where there is no sea-cage farming in southern Australia. I review methods employed in the northern hemisphere to assess sea-louse transfer between wild and farmed salmon and propose methods for assessing monogenean parasite transmission from farmed to wild S. lalandi in Australia. In summary, this thesis provides insight into the potential for parasite interactions between wild and farmed S. lalandi. I document the parasite assemblage of wild and farmed S. lalandi and wild S. hippos and provide baseline data on ‘natural’ parasite prevalence and intensity. I provide a taxonomic description of a new species of blood fluke. I indicate the likelihood of parasite transfer from wild fish to farmed S. lalandi, and identify parasite taxa with potentially negative consequences for sea-cage aquaculture. I provide the first firm data that wild S. lalandi move past one area where kingfish are farmed in sea-cages in South Australia. Finally, I propose procedures to better understand the potential for monogenean parasite transmission from farmed S. lalandi to wild fish. This thesis reports new information that is important when considering and managing expansion of the S. lalandi sea-cage aquaculture industry throughout Australia. It also provides baseline data on natural parasite levels to enable ongoing monitoring of the potential impacts of the industry on wild fish populations.
Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2007