Effectiveness of vaccination for the control of salmonid rickettsial septicaemia in commercial salmon and trout farms in Chile
Jonathan HappoldRohan SadlerAnne MeyerAlison HillmanBrendan CowledCatriona MackenzieAlicia L. Gallardo LagnoAngus Cameron
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Spawn (biology)
Finding of a nephroblastoma in a juvenile rainbow trout Oncorhynchus mykiss is described; the total body length of the fish was 140 mm and weight 45 g.The fish had been fed dry pellets.The tumour was of a considerable size and weight (28.8 % of the fish's body weight) which caused lordosis of the host's spine.The tumour's expansive growth pushed the internal organs deep into the abdominal part of the body.The tumour structure comprises 2 components: epithelial and mesenchymal.Its epithelia1 parts prevailed, no other structures (myeloblastic.neuroblastic and cartilaginous) being present.The tumour was a demarcated formation with no haemorrhages, no necroses and metastases that would penetrate into the organs.No haematopoietic tissue and no melanin were detected in the neoplastic tissue.
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In the Yakima Spring Chinook supplementation program, wild fish are brought into the Cle Elum Hatchery, artificially crossed, reared, transferred to acclimation sites, and released into the upper Yakima River as smolts. When these fish mature and return to the Yakima River most of them will be allowed to spawn naturally; a few, however, will be brought back to the hatchery and used for research purposes. In order for this supplementation approach to be successful, hatchery-origin fish must be able to spawn and produce offspring under natural conditions. Recent investigations on salmonid fishes have indicated that exposure to hatchery environments during juvenile life may cause significant behavioral, physiological, and morphological changes in adult fish. These changes appear to reduce the reproductive competence of hatchery fish. In general, males are more affected than females; species with prolonged freshwater rearing periods are more strongly impacted than those with shorter rearing periods; and stocks that have been exposed to artificial culture for multiple generations are more impaired than those with a relatively short exposure history to hatchery conditions.
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Chinook wind
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In 2001 hatchery- and wild-origin spring chinook were placed into an observation stream located at the Cle Elum Supplementation Research Facility to compare their reproductive success. Two groups containing both wild- and hatchery fish of both sexes were brought into the stream and allowed to spawn. Their longevity, spawning participation, and reproductive success were assessed. In addition, wild- and hatchery-origin precocious males were also introduced into one of the sections and allowed to spawn. We found that hatchery and wild males generally lived longer than females. In one group hatchery and wild females lived for similar periods of time while in the other wild females lived longer than hatchery fish. Wild females were also more successful at burying their eggs and the eggs they buried had higher survival rates. This result occurred in both groups of fish. Spawning participation in males was estimated by using two statistics referred to as percent gonad depletion (PGD) and percent testes retention (PRT). Both of these measures assumed that loss of testes weight in males would reflect their spawning participation and therefore could be used to estimate reproductive success. Hatchery and wild males had similar PGD and PRT values. One of these measures, PRT, was negatively associated with male reproductive success, confirming the idea that reduction in testes weight can be used as a surrogate measure of a male's ability to produce offspring Fry from the observation stream were collected throughout the emergence period that ran from January through May. Proportionate sub-samples of these fish were removed and microsatellite DNA was extracted from them. Pedigree analyses were performed to ascertain which adult fish had produced them. These analyses disclosed that wild males were more successful at producing progeny in one of the groups. No difference occurred in the other group. Precocial males and jacks fathered fewer progeny than did fish maturing at ages 4 and 5. In addition, male reproductive success was more than twice as variable as that seen in females. Some males apparently never spawned and others produced more than 7,000 offspring an amount that was more than double the quantity generated by the most successful female. Behavioral observations showed that a number of factors besides male origin influenced their reproductive success. One was relative body size; larger males tended to dominate smaller opponents and therefore had greater access to females. However, male dominance was not always related to relative size. The ability to attack and chase opponents was, however, positively related to reproductive success. We also discovered that the reproductive status of females and the social status of males were often reflected by their nuptial coloration. Territorial females typically had a single broad purple black stripe, light green or brown backs and white or gray ventral surfaces. Dominate males on the other hand, were generally a uniform dark brown or black color. The percentage of time that a male possessed a dark color pattern was positively linked to his reproductive success, as was the percentage of time he was observed courting or defending a female. The number of times a male was chased or attacked by a female also affected his reproductive success, in this situation the greater the frequency of such attacks the lower the reproductive success of the male. The pedigree analyses also disclosed that both hatchery and wild precocious males were able to fertilize eggs and produce offspring under natural spawning conditions. In conclusion we found differences in the reproductive competency of hatchery- and wild origin spring chinook. Wild females were better at depositing their eggs and having those eggs produce fry. In one study group wild males were more successful at producing offspring than hatchery males. Additional replications of such evaluations are being carried out to determine if the differences seen can be replicated. A repeat of the work done in 2001, for example, was performed in 2002 and additional studies will take place this coming year.
Spawn (biology)
Hatchery
Chinook wind
Gonadosomatic Index
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In October of 1997, The construction of the Kalispel Tribal Hatchery was complete. No spawning activity was recorded for the spring of 1998. On June 14, 1999 the first spawn at the Kalispel Tribal Hatchery was successful. A total of seven nests were fertilized that produced approximately 144,000 fry. The second spawn occurred on July 13, 1999 and a total of six nests were fertilized producing approximately 98,0000 fry. The total amount of largemouth bass fry produced at the Kalispel Tribal Hatchery was 242,000.
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5 ACKNOWLEDGEMENTS 10 INTRODUCTION 12 Stocking procedures 12 Atlantic salmon in the wild and in the hatchery: 13 Improving hatchery rearing 16 Release procedures 19 AIMS OF THE THESIS 20 METHODS 22 Study area 22 Study model 22 Rearing conditions 24 Study design 24 RESULTS AND DISCUSSION 30 Effects of enriched rearing 31 Effects of broodstock origin 35 The benefits of the soft release 37 Reflections 37 CONCLUSIONS AND REMARKS 38 REFERENCES 39
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Chinook salmon (Oncorhynchus tshawytscha), hatchery-reared as juveniles, returned to the upper Columbia River Basin in numbers exceeding broodstock and fishery needs during the spring of 2000. Plans to euthanize these adults were opposed by some regional stakeholders, who preferred letting them spawn naturally in streams also used by endangered spring-run chinook salmon. The National Marine Fisheries Service requested that the Independent Scientific Advisory Board review the scientific literature and conclude whether it was biologically sound to permit hatchery-origin adult salmon to spawn in the wild in large numbers. Substantial experimental evidence demonstrates that domestication selection can genetically alter hatchery populations in a few generations and that hatchery-origin adults returning from the ocean and spawning in the wild produce fewer progeny than adults of wild origin spawning in the wild. More limited evidence suggests that interbreeding between hatchery-origin adults and wild fish can reduce the fitness of the wild population. We conclude that decisions whether or not to permit hatchery-origin adults to spawn in the wild should be based on the needs of wild populations and the ability of the habitat to support additional reproduction, not based simply on the availability of hatchery-origin adults returning from the ocean.
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Chinook wind
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Hatchery‐reared and wild roach Rutilus rutilus were correctly classified to their rearing environment in a discriminant function using data on their scale circuli patterns. The discriminant function was then used to classify recaptured R. rutilus by their origin (hatchery‐reared and wild) during a riverine stocking evaluation. At 8 and 18 months post‐stocking, 10 and 7% of fish captured in the vicinity of the stocking site were classified as hatchery‐reared.
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Discriminant function analysis
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The inception of a hatchery program to rebuild a naturalized steelhead (Oncorhynchus mykiss) population in Minnesota waters of Lake Superior gave us the rare opportunity to monitor the success of fry stocking and determine if hatchery ancestry can reduce fitness of stocked fish in the early generations of a stocking program. Through genetic monitoring of two year classes, we determined that hatchery adults produced 1.3-6.2 times as many age-2 juveniles per female than naturally spawning fish. Survival of stocked fry of parents born in a hatchery relative to those of parents born in the wild was 70% in paired-stocking comparisons. These results suggest that stocking local-origin fry can increase the short-term abundance of depleted populations and that fish with no hatchery history are a better source for supplemental stocking. Additionally, sampling small numbers of adults for broodstock created genetically distinct groups, which could potentially cause long-term genetic change in the population. Genetic monitoring of adults will be essential to determining whether differences observed persist through the life cycle of the stocked fish.
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Electrofishing
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Abstract Stocking is an important management tool for enhancing fisheries resources, but its actual contribution to fisheries resources is controversial, taking into consideration both the positive and negative effects. This study compared density and biomass of hatchery (otolith thermal marked) and wild masu salmon parr between stocked and unstocked rivers to evaluate the contribution of stocking with hatchery‐reared fish. Density and biomass of all fish did not differ between stocked and unstocked rivers. Moreover, density and biomass of wild fish in the stocked rivers were lower than those of the unstocked rivers. Density and biomass of hatchery fish in a non‐natural reproducing river were similar with those of all fish in natural reproducing rivers. These results indicate that hatchery stocking does not have positive effects on population density or biomass but replaces wild fish with hatchery fish and that non‐natural reproducing areas are more suitable as stocking sites.
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Population density
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The first three years of this study were used to collect pre-hatchery baseline data on the fishery. The Spokane Tribal Hatchery began stocking kokanee and rainbow trout in 1991 and Sherman Creek Hatchery began stocking by 1992. The estimated number of kokanee (13,986) harvested in 1993 was similar to harvest numbers in the previous years, but the number of rainbow trout (403,277) and walleye (337,413) harvested doubled from estimates made in past years. The stocking of yearling kokanee began in1992, totaling approximately 140,000 yearlings. The yearlings were not expected to begin entering the creel until 1993 with the main harvest in 1994. As a result, it was too early to speculate on the effect of stocking yearlings instead of fry on the creel. The 1993 rainbow trout harvest escalated. The increased number of walleye harvested was believed to be from the increased angler pressure. Kokanee salmon and rainbow trout growth appeared to be similar to previous years. The growth of walleye was less than in year past, but the average size of walleye in the creel increased. The feeding habits of kokanee, rainbow trout and walleye in 1993 were similar to previous years.
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