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Wild Fish (wild + fish)
Terms modified by Wild Fish Selected AbstractsIdentifying migratory contingents of fish by combining otolith Sr:Ca with temporal collections of ambient Sr:Ca concentrationsJOURNAL OF FISH BIOLOGY, Issue 3 2006T. S. Elsdon Ambient strontium:calcium (Sr:Ca) concentrations were determined at the temporal scales of months, weeks and days, in summer and winter at two estuarine sites, and experimentally derived correlations between ambient and otolith Sr:Ca were used to estimate the otolith Sr:Ca concentrations of ,resident' black bream Acanthopagrus butcheri. Wild black bream were collected in summer and winter at the end of the temporal water sampling, and their otolith Sr:Ca concentrations were examined. Wild fish were classified as ,resident' if their otolith Sr:Ca matched the predicted concentrations of resident fish, and ,migrant' if this did not occur. In winter, all fish were classified as resident. In summer, all fish were classified as migrants, with fish spending an average of only 16·8% (estuary 1) and 61·1% (estuary 2) of their time at each estuarine location. [source] Predator avoidance behaviour in wild and hatchery-reared brown trout: the role of experience and domesticationJOURNAL OF FISH BIOLOGY, Issue 6 2003D. Álvarez Juvenile brown trout Salmo trutta from natural populations reacted to the presence of piscivorous brown trout by increasing the use of refuges. In contrast, second-generation hatchery fish and the offspring of wild fish raised under hatchery conditions were insensitive to predation risk. The diel pattern of activity also differed between wild and hatchery brown trout. Second-generation hatchery fish were predominantly active during daytime regardless of risk levels. Wild fish, however, showed a shift towards nocturnal activity in the presence of predators. These findings emphasize the potential role of domestication in weakening behavioural defences. They support the idea that the behavioural divergence between wild and domesticated individuals can arise from a process of direct or indirect selection on reduced responsiveness to predation risk, or as a lack of previous experience with predators. [source] Management and Recovery Options for Ural River Beluga SturgeonCONSERVATION BIOLOGY, Issue 3 2010PHAEDRA DOUKAKIS caviar; CITES; criadero; Mar Caspio; puntos de referencia; sobrepesca Abstract:,Management of declining fisheries of anadromous species sometimes relies heavily on supplementation of populations with captive breeding, despite evidence that captive breeding can have negative consequences and may not address the root cause of decline. The beluga sturgeon (Huso huso), a species threatened by the market for black caviar and reductions in habitat quality, is managed through harvest control and hatchery supplementation, with an emphasis on the latter. We used yield per recruit and elasticity analyses to evaluate the population status and current levels of fishing and to identify the life-history stages that are the best targets for conservation of beluga of the Ural River. Harvest rates in recent years were four to five times higher than rates that would sustain population abundance. Sustainable rates of fishing mortality are similar to those for other long-lived marine species such as sharks and mammals. Yield per recruit, which is maximized if fish are first harvested at age 31 years, would be greatly enhanced by raising minimum size limits or reducing illegal take of subadults. Improving the survival of subadult and adult females would increase population productivity by 10 times that achieved by improving fecundity and survival from egg to age 1 year (i.e., hatchery supplementation). These results suggest that reducing mortality of subadults and adult wild fish is a more effective conservation strategy than hatchery supplementation. Because genetics is not factored into hatchery management practices, supplementation may even reduce the viability of the beluga sturgeon. Resumen:,El manejo de pesquerías de peces anádromos en declinación a veces depende estrechamente de la suplementación de poblaciones mediante la reproducción en cautiverio, no obstante la evidencia de que la reproducción en cautiverio puede tener consecuencias negativas y no abordar la causa principal de la declinación. El esturión beluga (Huso huso), una especie amenazada por el mercado de caviar negro y por reducciones en la calidad del hábitat, es manejado mediante el control de la cosecha y suplementación de poblaciones, con énfasis en esta. Utilizamos análisis de producción por recluta y de elasticidad para evaluar el estatus de la población y los niveles de pesca actuales y para identificar las etapas de la historia de vida que son los mejores blancos para la conservación del beluga en el Río Ural. Las tasas de cosecha en años recientes fueron cuatro a cinco veces mayores que las tasas que sustentarían la abundancia de la población. Las tasas sustentables de mortalidad por pesca son similares a las de otras especies marinas longevas como tiburones y mamíferos. La producción por recluta, que es maximizada si los peces son cosechados a la edad de 31 años, podría incrementar significativamente elevando los límites de talla mínima o reduciendo la captura ilegal de subadultos. La mejora de la supervivencia de hembras subadultas y adultas incrementaría la productividad de la población 10 veces más que la mejora obtenida incrementando la fecundidad y supervivencia de huevo a 1 año de edad (i. e., suplementación de poblaciones mediante reproducción en cautiverio). Estos resultados sugieren que la reducción de la mortalidad de peces silvestres subadultos y adultos es una mejor estrategia de conservación que la suplementación. Debido a que la genética no es considerada en las prácticas de manejo en los criaderos, la suplementación incluso puede reducir la viabilidad del esturión beluga. [source] Does morphological variation between young-of-the-year perch from two Swedish lakes depend on genetic differences?ECOLOGY OF FRESHWATER FISH, Issue 2 2010M. Heynen Heynen M, Hellström G, Magnhagen C, Borcherding J. Does morphological variation between young-of-the-year perch from two Swedish lakes depend on genetic differences? Ecology of Freshwater Fish 2010: 19: 163,169. © 2009 John Wiley & Sons A/S Abstract,,, Different local environmental conditions have often been found to generate phenotypic diversity. In the present study we examined morphological differences between young-of-the-year perch from two lake populations with differences in size-specific predation risk. A common garden setup was used to examine the genetic and environmental components of the morphological variation. We found differences in head and jaw length and slight differences in body depth between the wild young-of-the-year perch from Lake Ängersjön and Lake Fisksjön. The differences found between the wild fish from the two lakes were not maintained under common garden rearing. The observed morphological divergence between the wild young-of-the-year perch from Lake Ängersjön and Lake Fisksjön seems to stem mainly from a plastic response to different environmental conditions in the two lakes. It is clear that the morphological traits are not influenced by direct reaction to the size-specific risk of cannibalism, but probably stem from a combination of different environment characteristics, including resource and habitat use, and the density of other piscivores, such as pike. [source] Validation of daily increment formation and the effects of different temperatures and feeding regimes on short-term otolith growth in Australian smelt Retropinna semoniECOLOGY OF FRESHWATER FISH, Issue 2 2008Z. Tonkin Abstract,,, To aid otolith interpretation of wild fish, we conducted a laboratory study using metalarval Australian smelt (Retropinna semoni) collected from the Murray River, to examine daily increment deposition and the effects of different temperatures and feeding regimes on otolith growth. Daily increment deposition was confirmed by comparing the number of increments from an oxytetracycline mark with the known number of days from marking. After holding fish at two temperature levels and three feeding rates, both food density and temperature were found to have a significant effect on otolith growth, with food density having the greatest influence. Overall trends in final lengths and condition of fish were well represented by recent otolith growth. The results of the experiment have implications for estimating growth histories and its relationship to various environmental conditions. [source] Use of paired fathead minnow (Pimephales promelas) reproductive test.ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2006Part 1: Assessing biological effects of final bleached kraft pulp mill effluent using a mobile bioassay trailer system Abstract Reproductive effects have been recorded in wild fish in waters receiving pulp mill effluent (PME) since the mid to late 1980s. Laboratory assays with fathead minnow (FHM; Pimephales promelas) have been developed to better understand fish responses to PME. However, observations from laboratory studies have been variable, making it difficult to establish cause/effect relationships. A lack of environmental relevance in these laboratory studies may have contributed to the variability observed. The objectives of the present study were, first, to determine the effects of bleached kraft PME (BKME) on FHM under environmentally realistic conditions (i.e., ambient water and effluent quality) and, second, to determine the suitability of pair-breeding FHM to better link BKME-induced changes in indicators at the biochemical, individual, and population levels. A mobile bioassay trailer was situated on-site at a bleached kraft mill for 60 d, allowing supply of both ambient water (Lake Superior, Canada) and final BKME. The reproductive output of FHM was initially assessed for 21 d to obtain baseline data pre-exposure. At the end of the pre-exposure period, selected breeding pairs were exposed to final BKME (100% v/v and 1% v/v) for 21 d. Results demonstrated a stimulatory response pattern at 1% BKME (e.g., increased egg production) compared to control. In the 100% treatment, spawning events were reduced and fewer eggs were produced during the first two weeks of exposure. Exposure to 100% (v/v) BKME also resulted in ovipositor development in males and development of male secondary sex characteristics in females. Obtaining pre-exposure data and use of pair-breeding FHM in this assay gave a sensitive indication of effluent effects and allowed accurate comparisons of endpoints to be made. [source] Run timing and migration routes of returning Atlantic salmon in the Northern Baltic Sea: implications for fisheries managementFISHERIES MANAGEMENT & ECOLOGY, Issue 3 2009A. SIIRA Abstract, Return migration of Atlantic salmon, Salmo salar L., was studied in the Gulf of Bothnia, northern Baltic Sea, by a mark-recapture experiment and catch records from commercial trap-nets. Coastal salmon fishing is regulated by delayed opening of the fishery in consecutive regions based on the assumption that the wild fish migrate before reared ones and the migration is unidirectional and continuous from south to north. Neural network modelling suggested that the migration does not progress linearly from one regulation region to another, but shows variation between origin and sea age among and within regions. Further evidence of the non-linear migration included a noticeable part of salmon on their way to two major estuaries first visiting the northern-most Bothnian Bay before turning back south. Salmon returning to the different homing sites in the north showed no differences in run timing in the southern Gulf whereas the same individual fish showed differences in catch accumulation further north. Run timing estimates indicated only a slight tendency towards earlier migration for wild salmon compared with reared fish. [source] The effect of stocking size on the first winter survival of whitefish, Coregonus lavaretus (L.), in the Gulf of Bothnia, Baltic SeaFISHERIES MANAGEMENT & ECOLOGY, Issue 2 2002E. JOKIKOKKO The anadromous whitefish, Coregonus lavaretus (L.), is the most numerous fish species stocked in the Gulf of Bothnia, Baltic Sea. One-summer-old-whitefish fingerlings are mostly 8,10 cm long when released annually in September,October, whereas the wild whitefish are 10,12 cm at that time. About 6 million, one-summer-old, spray-marked, whitefish were released in the northern and central parts of the Gulf in 1995,1998. To study the effect of the stocking length on the survival of the marked fish, the length of the recaptured whitefish as 1-year-olds was back-calculated. Altogether 1106 whitefish recaptured in the Gulf of Bothnia were analysed. The back-calculated length was slightly greater than the stocking length but not as large as the length of the wild fish. In the central part of the Gulf of Bothnia, where the mean stocking length was more than 10 cm, the back-calculated length was 10.5,11.1 cm. In the northern part of the Gulf the mean stocking length varied between 8.8 and 10.0 cm annually, and the corresponding back-calculated mean lengths were 9.3,9.7 cm. It also seemed that bigger fingerlings started their feeding migration earlier or they migrated faster than the smaller ones to the southern parts of the Gulf of Bothnia. [source] Effects of differences in diet and seasonal changes on the fatty acid composition in fillets from farmed and wild sea bream (Sparus aurata L.) and sea bass (Dicentrarchus labrax L.)INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 5 2008Mustafa Yildiz Summary The effects of dietary fatty acids and seasonal variation on the fatty acid profiles of farmed and wild sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) were determined by analysis of their fillets. Farmed sea bream and sea bass were fed on the same commercial feeds all year. Fatty acid profiles in the fillets reflected the fatty acid profiles of the commercial feeds. The predominant fatty acids in the trial feeds, fillets of farmed and wild sea bream and sea bass were 16:0, 18:1n -9, 18:2n -6, 20:5n -3 and 22:6n -3. The fatty acid profiles in the fillets of farmed sea bream and sea bass did not differ (P > 0.05) except in the winter season compared with those of their wild counterparts. However, the content of eicosapentaenoic acid (20:5n -3), docosahexaenoic acid (22:6n -3) in the fillets of the farmed and wild sea bass were significantly (P < 0.05) higher than the farmed and wild sea bream. The wild sea bream had significantly (P < 0.05) higher total saturated fatty acid and monounsaturated fatty acid (MUFA) levels, and lower total n -6 and n -3 polyunsaturated fatty acid (PUFA) levels in winter than in the summer and spring seasons. Similarly, in the fillets of wild sea bass, total n -3 PUFA levels were significantly (P < 0.05) lower, and the MUFA levels were higher in winter than in the other seasons. These results indicate that the farmed fish fillets were good sources of n -3 PUFA in each of the three seasons. However, wild fish were good sources of n -3 PUFA in the spring and summer. [source] Comparison of wild and cultured gilthead sea bream (Sparus aurata); composition, appearance and seasonal variationsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 5 2002Kriton Grigorakis Major quality parameters, such as muscle composition, fat deposition, muscle fatty acid composition and external appearance were studied in wild and cultured gilthead sea bream. Muscle fat content and total depot fat (peritoneal and perivisceral fat) indicated a seasonal variation with minimum values observed in late spring and maximum in late summer. Gonadosomatic indices of cultured fish were lower than those found in wild specimens. Lipid content of cultured sea bream was much higher than that of wild fish. Differences were also observed in fatty acid profiles. Cultured fish were characterized by higher levels of monoenes, n-9 and 18:2n-6 fatty acids and wild fish by higher levels of saturates, 20:4n-6, n-3 fatty acids and n-3/n-6 ratios. Differences were also noted in the external appearance of fish. [source] The relative roles of domestication, rearing environment, prior residence and body size in deciding territorial contests between hatchery and wild juvenile salmonJOURNAL OF APPLIED ECOLOGY, Issue 3 2003Neil B. Metcalfe Summary 1Interactions between captive-reared and wild salmonids are frequent because hatcheries annually rear millions of fish for release in conservation programmes while many thousands of domesticated fish escape from fish farms. However, the outcome of competition between captive-reared and wild fish is not clear: wild fish may be smaller and less aggressive than hatchery fish, but they have more local experience and a prior residence advantage. Moreover, it is important to know whether any competitive differences are genetic (due to the process of domestication) or due to the rearing environment. 2We therefore examined the factors influencing competition for feeding territories in juvenile Atlantic salmon. We studied the effect of domestication by using three independent stocks of both domesticated and wild-origin fish, all of which were reared in a common hatchery environment. We also used fish from the same wild stocks that had been living in the wild. Territorial contests were staged in stream tank compartments between pairs of fish differing in origin or rearing environment; the relative importance of body size and prior residence was also assessed. 3All three stocks of domesticated fish were generally dominant over wild-origin fish when both had been raised in a common hatchery environment. If the wild-origin fish were given a 2-day period of prior residence on the territory this asymmetry in dominance was reversed. However, domesticated fish did not gain any additional advantage from being prior residents. The relative body size of the two contestants had a negligible effect on contest outcomes. 4Truly wild fish (i.e. those of wild origin that had also grown up in the wild) were generally dominant over domesticated or wild-origin fish that had been hatchery-reared. Differences in body size between contestants had no effect on the outcome. 5Synthesis and applications. These results show that, while juvenile farmed Atlantic salmon are inherently more aggressive than wild-origin fish, the hatchery environment reduces their ability to compete for territories with wild resident fish. Rearing salmon in conventional hatcheries for later release into the wild where natural populations already exist may not be a prudent conservation measure; it is preferable to plant eggs or first-feeding fry rather than attempt to ,help' the fish by rearing them through the early life stages. [source] Fishing near sea-cage farms along the coast of the Turkish Aegean SeaJOURNAL OF APPLIED ICHTHYOLOGY, Issue 1 2010O. Akyol Summary This study reports on the yield of commercially important species captured intentionally around and under fish-cage farms using specific types of gear from both sea-cage farmers and artisanal fishermen, and to identify the species composition of these catches. The 2004,2008 research was carried out in 21 fish farms, randomly chosen along the coast of Izmir Province on the Aegean Sea. A total of 91 persons were interviewed, including directors, fishers from the fish farms and artisanal fishermen. The technical characteristics of a special trap used by some fish farmers were diagramed. Total wild fish catch quantities as well the species raised in the sea-cages were recorded. A total of 34 finfish and four invertebrate species were identified from the sea-cage farm fishery. Eight fish species according to the descending quantities raised were bogue (Boops boops), grey mullet (Mugil spp.), blackspot seabream (Pagellus bogaraveo), salema (Sarpa salpa), common two-banded seabream (Diplodus vulgaris), annular seabream (Diplodus annularis), striped seabream (Lithognathus mormyrus) and gilthead seabream (Sparus aurata). Mean quantities of wild fish caught from 2004 to 2008 in a sampled farm were 13 998 ± 210, 34 434 ± 482, 30 116 ± 529, 27 893 ± 429, and 32 366 ± 808 kg, respectively. There were significant differences between fish amounts and years (P < 0.05). [source] Restricted fish feeding reduces cod otolith opacityJOURNAL OF APPLIED ICHTHYOLOGY, Issue 2 2008H. Høie Summary The purpose of this work was to examine the effect of reduced feeding and constant temperature on cod otolith opacity. Three groups of juvenile cod were given restricted food rations at different times for 4 months, resulting in depressed somatic growth. Otolith opacity was measured on pictures of the otolith sections. The otolith carbonate deposited during the experimental period was generally opaque compared to the more translucent otolith material deposited prior to and after the experimental period, when the fish were kept in a pond and in sea-cages at higher temperatures. Large variations in otolith opacity were found between individual fish both within groups and between groups. In two of the three groups significantly more translucent otolith material was deposited in response to reduced feeding. Our results show that variations in feeding and hence fish growth resulted in variation in otolith opacity, but the effect was minor compared to that of variations in ambient temperature. The combined influence of these effects, which both act on fish metabolism, are most likely controlling the seasonal opacity changes observed in wild fish. Our results help explain the variations seen in fish at constant temperatures. [source] Genetic interactions between marine finfish species in European aquaculture and wild conspecificsJOURNAL OF APPLIED ICHTHYOLOGY, Issue 4 2001Youngson The principal species of marine aquaculture in Europe are Atlantic salmon (Salmo salar), sea bass (Dicentrarchus labrax) and sea bream (Sparus auratus). For Atlantic salmon and sea bass, a substantial part of total genetic variation is partitioned at the geographical population level. In the case of sea bream, gene flow across the Azores/Mediterranean scale appears to be extensive and population structuring is not detected. For Atlantic salmon and sea bass, natural population structure is at risk from genetic interaction with escaped aquaculture conspecifics. The locally adaptive features of populations are at risk from interbreeding with non-local aquaculture fish. Wild populations, generally, are at risk from interactions with aquaculture fish that have been subject to artificial selection or domestication. Atlantic salmon is the main European aquaculture species and its population genetics and ecology have been well-studied. A general case regarding genetic interactions can be based on the information available for salmon and extended to cover other species, in the appropriate context. A generalized flow chart for interactions is presented. Salmon escape from aquaculture at all life stages, and some survive to breed among wild salmon. Reproductive fitness in the escaped fish is lower than in native, wild fish because of behavioural deficiencies at spawning. However, as the number of salmon in aquaculture greatly exceeds the number of wild fish, even small fractional rates of escape may result in the local presence of large numbers, and high frequencies, of escaped fish. At present, policy and legislation in relation to minimizing genetic interactions between wild and aquaculture fish is best developed for Atlantic salmon, through the recommendations of the Oslo Agreement developed by the North Atlantic Salmon Conservation Organization and subsequent agreements on their implementation. In future, the potential use of genetically modified fish in aquaculture will make additional policy development necessary. Improved containment is recommended as the key to minimizing the numbers and therefore the effects of escaped fish. Emergency recovery procedures are recommended as a back-up measure in the case of containment failure. Reproductive sterility is recommended as a future key to eliminating the genetic potential of escaped fish. The maintenance of robust populations of wild fish is recommended as a key to minimizing the effects of escaped fish on wild populations. [source] Escape of farmed tilapiines into the wild and entry of wild forms in fishponds, and the possible interactions between wild and farmed tilapiines from a sample of smallholder farms in Central UgandaAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009Matthew Tenywa Mwanja Abstract Seven smallholder fishponds in central Uganda were studied between 2000 and 2001 to investigate the interaction of farmed tilapiines with their wild conspecifics. Emphasis was on the features that facilitate escape of fish and/or entry of fish into the farms and interactions between the farmed and the wild. These included number of species, source of seed, connection between pond and natural watercourses, purpose of the farm, destination of cultured fish and interaction between farmed and wild fish. Fishponds had no screens against entry of wild fish into the farm or escape of farmed fish into the wild and occurred within wetlands close to natural watercourses. Ponds stocked with one fish species were found to have multispecies with some individuals that were apparently intermediate morphs between the species. Fry produced within the growout fishponds was shared with other farmers within and outside the watersheds. This study showed that smallholder farms with little or no control of escape or entry of fish out and into the fishponds, and little or no management present circumstances that facilitate continued movement of tilapiines within and across watersheds in Ugandan waters. The study also indicated possible genetic interaction between farmed and their wild conspecifics through interactions within fishponds. Résumé Sept viviers appartenant à de petits propriétaires ont étéétudiés entre 2000 et 2001 pour rechercher l'interaction entre les tilapiinés d'élevage et ceux qui vivent dans la nature. On insistait sur les caractéristiques qui facilitent la fuite et/ou l'entrée des poissons dans les fermes et les interactions entre les poissons d'élevage et les poissons sauvages. On a étudié le nombre d'espèces, la source de la progéniture, les connections entre les bassins et les cours d'eau naturels, la raison d'être des fermes, la destination des poissons d'élevage et l'interaction entre les poissons d'élevage et les poissons sauvages. Les réservoirs n'avaient pas de filtres pour empêcher l'entrée des poissons sauvages ou la fuite des poissons d'élevage et ils se trouvaient dans des zones humides proches de cours d'eau naturels. Les bassins qui avaient été stockés avec une seule espèce de poissons se sont avérés contenir plusieurs espèces, et certains individus semblaient avoir une morphologie intermédiaire entre différentes espèces. Le fretin produit dans les bassins de croissance était partagé avec d'autres éleveurs dans ou en dehors des bassins versants. Cette étude a montré que les petits élevages qui exercent peu de contrôles sur les entrées ou les sorties de poissons dans et hors des bassins et une gestion nulle ou très réduite, offrent des conditions qui facilitent le déplacement continu des tilapiinés au sein des bassins de rivières et entre eux, dans les eaux ougandaises. Cette étude indique aussi qu'il est possible qu'il existe des interactions génétiques entre les poissons d'élevage et les poissons sauvages de même espèce, au niveau des bassins d'élevage. [source] Effects of angling on post-release mortality, gonadal development and somatic condition of Australian bass Macquaria novemaculeataJOURNAL OF FISH BIOLOGY, Issue 10 2009K. C. Hall This study assessed the protracted effects of two angling treatments (mild and harsh) on the post-release mortality, gonadal development and somatic condition of Australian bass Macquaria novemaculeata in a pond-based experiment. Angled fish were destructively sampled (along with controls) three times: immediately before, and 1 or 4 weeks after release into cages. Compared with the other groups, harshly angled fish had similar, low immediate and short-term mortalities (,5%), but significant delayed mortality (25%) and fed only minimally. None of these fish ejected ingested hooks. Forty-six per cent of captive fish (across all groups) and 20% of wild fish had non-ripening gonads (stage I) prior to, or during, the experiment. In females with ripening ovaries (stages II or III), neither angling treatment significantly reduced standardized gonadal mass. The mean per cent of atretic oocytes increased among females in all groups, but was significantly greater in those that were harshly angled. The results demonstrated that the gonadal development of M. novemaculeata could be suppressed or impaired (by angling, handling and confinement), and that further research is warranted. In particular, the timing and severity of angling in relation to the stage of gonadal development could have important implications for the introduction of temporal restrictions to angling. [source] Different ocean and climate factors control the marine survival of wild and hatchery Atlantic salmon Salmo salar in the north-east Atlantic OceanJOURNAL OF FISH BIOLOGY, Issue 4 2008A. Peyronnet The influence of climate and ocean conditions on the marine survival of 1SW Irish Atlantic salmon Salmo salar was explored. Generalized additive models (GAM) explained c. 85% of the observed variations in survival and provided an insight into the mechanisms involved. A positive phase of the North Atlantic oscillation (NAO) and increasing sea surface temperatures (SST) were linked to a decrease in S. salar survival. The NAO in the winter before the smolts migration contributed to c. 70% of the deviance in marine survival of wild fish. The abundance of the copepod Calanus finmarchicus in the north-east Atlantic Ocean explained a further 25% of these variations in wild S. salar survival. By contrast, hatchery populations seem to be controlled by additional processes involving coastal SST. The marine recruitment of hatchery S. salar was largely explained (70% of the deviance) by SST close to the Irish coast in the spring before the year of the smolts migration. This study constitutes the first description of the processes controlling marine recruitment for these populations. [source] Effect of density on competition between wild and hatchery-reared Atlantic salmon for shelter in winterJOURNAL OF FISH BIOLOGY, Issue 2004J. E. Orpwood The effect of varying the density of hatchery-reared Atlantic salmon Salmo salar on the ability of single wild fish to occupy a shelter is assessed. Although there was strong density-dependence on sheltering overall, the ability of wild Atlantic salmon parr to occupy a shelter was not affected by the presence of hatchery-reared fish even when outnumbered by four to one. These findings illustrate a competitive asymmetry for shelter in favour of the wild fish at the densities tested. [source] Domestication, comparative biology and interactions of wild and cultured fish: convenor's synthesisJOURNAL OF FISH BIOLOGY, Issue 2004K. Lorenzen Aquaculture is expanding rapidly and many fish species are brought into cultivation, entering a process of domestication with consequences for their morphology, physiology, ecology and evolution. In some species the abundance of cultured populations matches or exceeds that of wild stocks, and interactions between cultured and wild fish can pose significant conservation challenges. At the same time, captive breeding and re-introduction play an important role in the conservation of some of the world's most endangered fishes. Drawing on contributions from the FSBI Symposium and the wider literature, we synthesize current knowledge of the process and extend of fish domestication, interactions between cultured and wild fish, and the use of cultured fish in fisheries enhancement and restoration. We provide a perspective on the role of biological issues within the wider context of aquaculture development and aquatic conservation biology, and conclude with a discussion of promising avenues for further research. [source] Disease interaction between farmed and wild fish populationsJOURNAL OF FISH BIOLOGY, Issue 2004E. J. Peeler This paper reviews the literature on disease interaction between wild and farmed fish and recommends strategies to reduce the disease risks to both populations. Most, if not all, diseases of farmed fish originate in wild populations. The close contact between farmed and wild fish readily leads to pathogens exchange. Aquaculture creates conditions (e.g. high stocking levels) conducive to pathogen transmission and disease; hence pathogens can overspill back, resulting in high levels of challenge to wild populations. This is exemplified by sea lice infections in farmed Atlantic salmon. Stocking with hatchery reared fish or aquaculture escapees can affect disease dynamics in wild populations. Whirling disease has been spread to many wild rainbow trout populations in the US with the release of hatchery reared stock. The greatest impact of aquaculture on disease in wild populations has resulted from the movement of fish for cultivation. Examples of exotic disease introduction following movement of live fish for aquaculture with serious consequences for wild populations are reviewed. The salmon parasite, Gyrodactylus salaris, has destroyed wild salmon populations in 44 Norwegian rivers. Crayfish plague has wiped out European crayfish over much of Europe. Eels numbers have declined in Europe and infection with the swimbladder nematode Anguillicola crassus has in part been blamed. The impact of disease in farmed fish on wild populations can mitigated. Risk analysis methods need to be refined and applied to live fish movement and new aquacultural developments. Appropriate biosecurity strategies, based on risk assessments, should be developed to reduce pathogen exchange and mitigate the consequences. [source] Gonadal maturation in the blackspot seabream Pagellus bogaraveo: a comparison between a farmed and a wild broodstockJOURNAL OF FISH BIOLOGY, Issue 2004V. Micale The blackspot seabream Pagellus bogaraveo(Brünnich, 1768) has been regarded as a possible alternative to traditionally cultured Mediterranean species such as seabream and seabass, due to its high market value and good adaptation to captivity. Broodstock establishment and management represent the first step towards reliable production of eggs and fry, which is required to develop aquaculture of this new species. Two different broodstocks were tested for gonadal maturation and spawning, one constituting of wild fish caught as juveniles and reared in tanks until sexual maturity (4 years), and one assembled from wild adult fish caught during or just before the reproductive season. All fish were maintained under the same rearing conditions and fed the same diet. Gonadal stripping and biopsies were performed weekly to monitor maturation in both males and females. Ovarian samples were staged for maturity on the basis of follicular diameter and migration of germinal vesicle. Sperm samples were tested for density (number of spermatozoa ml,1) and motility. The fish reared in captivity reached ovarian maturity during the breeding season of the wild stock. Eggs were obtained by stripping from both farmed and wild specimens, but appeared degenerated as a result of being retained too long in the ovarian cavity due to the absence of spontaneous spawning. Spermiation was prolonged in the farmed fish, but appeared to be blocked in the wild breeders after first sampling. However, the sperm was very viscous and the motile spermatozoa did not exceed 10%. [source] Density-dependent growth in hatchery-reared brown trout released into a natural streamJOURNAL OF FISH BIOLOGY, Issue 5 2004L. F. Sundström Hatchery-reared brown trout Salmo trutta stocked in a natural stream in addition to resident wild brown trout grew more slowly than those stocked with an experimentally reduced density of brown wild trout. In both cases, hatchery-reared brown trout grew more slowly than resident wild fish in control sections. Mortality and movements did not differ among the three categories of fish. The results showed that growth of stocked hatchery-reared brown trout parr was density-dependent, most likely as a consequence of increased competition. Thus, supplementary release of hatchery-reared fish did not necessarily increase biomass. [source] Predator avoidance behaviour in wild and hatchery-reared brown trout: the role of experience and domesticationJOURNAL OF FISH BIOLOGY, Issue 6 2003D. Álvarez Juvenile brown trout Salmo trutta from natural populations reacted to the presence of piscivorous brown trout by increasing the use of refuges. In contrast, second-generation hatchery fish and the offspring of wild fish raised under hatchery conditions were insensitive to predation risk. The diel pattern of activity also differed between wild and hatchery brown trout. Second-generation hatchery fish were predominantly active during daytime regardless of risk levels. Wild fish, however, showed a shift towards nocturnal activity in the presence of predators. These findings emphasize the potential role of domestication in weakening behavioural defences. They support the idea that the behavioural divergence between wild and domesticated individuals can arise from a process of direct or indirect selection on reduced responsiveness to predation risk, or as a lack of previous experience with predators. [source] Physiological effects of dominance hierarchies: laboratory artefacts or natural phenomena?JOURNAL OF FISH BIOLOGY, Issue 1 2002K. A. Sloman Studies of fish behaviour have demonstrated the existence of social interactions that result in dominance hierarchies. In environments in which resources, such as food, shelter and mates, are limited, social competition results in some fish becoming dominant and occupying the most profitable positions. This behaviour has been observed in natural environments and also in many laboratory-based experiments. When two fish have been confined in a small tank, one of them usually has exhibited behaviour that suggests it is dominant over the other submissive animal. Physiological consequences of social interaction can be seen in both dominants and subordinates but are more extreme in the subordinate. However, this scenario is without doubt an artificial situation. Fewer experiments have been conducted using laboratory experiments that are more socially and physically complex than those experienced by dyads in tanks. In simple fluvial tanks, through which water is recirculated, the physiological responses of fish to social competition have generally been qualitatively similar to those recorded among dyads. However, when environmental disturbances, complex resource distributions, increase in water flushing, presence of predators and competing species of fish have been included in experimen-tal designs, there have been fewer, diminished or no physiological dierences between dominant and subordinate fish. There have been very few studies of physiology in relation to dominance in natural habitats, and those that have been conducted suggest that under some circumstances hierarchies may cause less intense physiological responses than have been suggested based on results of laboratory studies in simple environments. Possible reasons for these variations are discussed. The need is identified for a well structured experimental approach to the investi-gation of the causes and consequences of hierarchies if the ecology of wild fish is to be modelled eectively based on physiological processes. It is also suggested that the further development and application of techniques for monitoring physiologies of fish in the wild is important. [source] Developmental change in RNA: DNA ratios of fed and starved laboratory-reared Japanese flounder larvae and juveniles, and its application to assessment of nutritional condition for wild fishJOURNAL OF FISH BIOLOGY, Issue 4 2001W. S. Gwak Starved Japanese flounder Paralichthys olivaceus larvae were characterized by relatively lower levels of RNA content throughout their early life stages. Significant differences in the RNA: DNA ratios were found between fed and starved fish, and appeared to increase as starvation proceeded. Ontogenetic changes in RNA: DNA ratios were clearly observed during metamorphosis, especially decreasing during the period from the late-metamorphic to postmetamorphic stages. The criteria established from these laboratory experiments, were applied to the nutritional condition of wild larvae and juveniles collected in Wakasa Bay, Sea of Japan in 1994 and 1995 by measuring RNA and DNA content. Starved fish were mainly found in stage I (settling stage) fish during the late season of settlement in 1995. This suggests that starvation could be associated with settlement in Japanese flounder. [source] Susceptibility of selected freshwater fish species to a UK Lactococcus garvieae isolateJOURNAL OF FISH DISEASES, Issue 10 2009M Algöet Abstract Gram-positive cocci recovered from diseased rainbow trout from a farm in England were characterized by different methods, including pulsed field gel electrophoresis, as virulent Lactococcus garvieae serogroup 2 (pulsotype A1). Groups of rainbow trout were kept at a range of temperatures and injected intraperitoneally (i.p.) with one of the UK isolates, L. garvieae 00021. The 18 °C and 16 °C groups showed 67% and 28% mortality, respectively, by day 27 post-injection. Fish kept at 14 °C or lower were less susceptible (,3% mortality). Raising the temperature of all groups to 18 °C at day 27 post-injection did not result in recurrence of the disease, even though viable bacteria were recovered from all groups 42 days later. Grayling were highly susceptible, with 65% mortalities when challenged with 200 colony forming unit fish,1 by i.p. injection and 37% mortalities when exposed to effluent water from tanks containing affected rainbow trout. Other fish species tested, Atlantic salmon, brown trout and seven cyprinid species, were less susceptible. Viable L. garvieae was isolated from the internal organs of all species tested at the end of the trials, suggesting that they may pose a threat as possible carriers to susceptible farmed and wild fish. [source] Genetic analysis of aquabirnaviruses isolated from wild fish reveals occurrence of natural reassortment of infectious pancreatic necrosis virusJOURNAL OF FISH DISEASES, Issue 7 2009I Romero-Brey Abstract In this study, we report the sequencing of the whole genome [including the 5, and 3, non-coding regions (NCR) of both segments A and B] of seven birnavirus strains isolated from wild fish from the Flemish Cap (FC) fishery at Newfoundland, Canada. From analysis and comparison of the sequences, most of the FC isolates clustered with the North American reference strains West Buxton (WB), Dry Mill and Jasper. One strain was included in the same genotype as the European strain Ab. In addition, at least in one case cohabitation of both type strains in an individual fish was demonstrated. These results clearly suggest the acquisition of the viruses from two different sources. The prevalence of the American type is easily explained by the close proximity of this fishing bank to the American coast whereas, although surprising, the presence of the European type strain could be because of migration of fish from European waters. In one strain, segment A and B sequences were typed differently (WB and Ab, respectively). These findings indicate natural reassortment between two strains of aquabirnaviruses in a host. [source] An investigation into the prevalence of Renibacterium salmoninarum in farmed rainbow trout, Oncorhynchus mykiss (Walbaum), and wild fish populations in selected river catchments in England and Wales between 1998 and 2000JOURNAL OF FISH DISEASES, Issue 2 2008E Chambers Abstract A cross-sectional survey of Renibacterium salmoninarum infection in farmed rainbow trout (RBT) and wild fish populations was carried out in 10 farms and six river catchments, respectively, in England and Wales. The majority of the wild fish were sampled in 1998 and the farmed fish in 2000. Grayling, Thymallus thymallus, and brown trout, Salmo trutta, were the main wild species sampled. Two fish, one grayling and one salmon, Salmo salar, were R. salmoninarum culture-positive, compared with 40 confirmed polymerase chain reaction-positive wild fish. The highest prevalence of R. salmoninarum infection was found in grayling in rivers with RBT farms with a history of R. salmoninarum infection. One hundred and fifty fish were sampled from each RBT farm, but none of the fish was found to be R. salmoninarum -positive. Evidence was found, for the first time, for the presence of R. salmoninarum in an eel, Anguilla anguilla. [source] Caligus elongatus Nordmann genotypes on wild and farmed fishJOURNAL OF FISH DISEASES, Issue 2 2007Ø Øines Abstract Two mitochondrial genotypes have been described for Caligus elongatus Nordmann in Norway. This article reports on the distribution of C. elongatus mitochondrial cytochrome C oxidase 1 genotypes from wild fish hosts from the SE Norwegian coast. For comparison, lice from areas with fish farming were included in the study. The genotype distribution of 841 lice from wild coastal (n = 535), wild North Sea pelagic (n = 26), farmed (n = 160) and wild hosts in areas of fish farming (n = 89) is presented. The genotype frequencies of C. elongatus on wild coastal hosts varied significantly between spring and autumn. Lice from these fish show a large proportion of genotype 1 lice in March,June every year. Genotype 2 lice were found more frequently in autumn. Genotype 1 was clearly associated with the lumpfish, Cyclopterus lumpus L. The genotype frequency appeared to be different in areas with aquaculture. Caligus elongatus from farmed fish and wild fish caught close to Atlantic salmon fish farms in Norway were predominantly genotype 1 in autumn. Genotypes of C. elongatus on the SE coast of Norway vary according to season and fish species. Factors involved in the encounter between fish and lice are important for the establishment of lice on their hosts. [source] Association with Underwater Structures in Hatchery-reared and Wild Red Snapper Lutjanus campechanus JuvenilesJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 2 2003Reiji Masuda Behavioral observations were conducted with red snapper juveniles to improve release strategies for stock enhancement of this species. Association with an underwater structure was compared between hatchery-reared and wild juveniles using video recording. Both hatchery-reared and wild fish tended to stay inside the structure in the daytime and outside it at night. Hatchery-reared fish spent longer periods inside the structure in the daytime, hut showed less association with the structure at night compared to the wild fish. We concluded that association behavior is innate but can be fine-tuned through experience. [source] | ||||||||||||||||