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Stocking - Helping or Hindering Fisheries Recovery ?? S&TA Briefing Paper: The Effect of Endocrine Disruptors of Fish CEFAS Paper: Impact of intensive in-river aquaculture on wild salmonids In conclusion, the research has indicated that the effluents from fish farms can have significant impacts on Atlantic salmon particularly during sensitive life history stages such as reproduction and smoltification. In addition, effluents from rainbow trout farms may also have a deleterious effect on the macroinvertebrate populations, which include many of the prey items of juvenile salmonids.
Norwegian Salmon Stocking.pdf Abstract: Stocking is undertaken in the River Suldalsla˚ gen, western Norway, to compensate for an estimated annual loss of 20 000 Atlantic salmon smolts, Salmo salar L., caused by regulating the river for hydropower production. The annual contribution to angling catches from stocked hatchery fish varied from 7 to 334 kg, or <15% of the total number caught. Between 160 000 and 250 000 one-summer old fish were stocked, but only between 6 and 10 (<0.005%) were recaptured as adults in the river. Recaptured stocked fish never exceeded 0.03% by number, despite smolts dominating the stocking material in recent years. It is not certain whether the slight increase in catches comes in addition to or at the expense of natural reproduction. In most years more adults were used as parent stock than were caught as offspring. The lack of positive response to stocking is possibly due to lesser age, smaller size and later migration of hatchery smolts, and that seawater tolerance of hatchery smolts is poorly developed, all factors increasing mortality at sea.________________________ From CEFAS Hatchery rearing affects salmonid brains This study explored how rearing conditions influence the development of
two forebrain structures (the olfactory bulb and the telencephalon) in
juvenile Chinook salmon spawned from wild-caught adults. The sizes of the
forebrain structures of fish reared in a conventional hatchery, an ______________________________ Stocked farm-reared brown trout result in greater introgression in the freshwater component in a river compared to the anadromous (sea trout) component, as a result of farm-reared brown trout that became anadromous experiencing high mortality at sea. Given that anadromy is a threshold quantitative trait (i.e heritable), stocking with farm-reared brown trout is likely to increase the freshwater component in a river and reduce the sea trout run. There is no empirical evidence to support the hypothesis that introgression from farm-reared brown trout improves the fitness of wild brown trout populations. For a few populations that have lost genetic variability due to small size and physical isolation or severe bottlenecks it may be advantageous to introduce farm-reared or other non-native brown trout. Such introductions should not exceed one or two individuals per generation. ___________________________
In new research published in the journal Molecular Ecology, researchers
have found scientific evidence that farmed salmon have evolved
genetically differently to wild salmon, therefore backing claims that
any integration of farmed salmon back into the wild through escapees
could have a negative impact on the health of wild salmon populations.
Christian Roberge and Louis Bernatchez, two of the co-authors on this
research paper explain: "Using a 3,557 genes microarray and a unique
set-up in which farmed and wild salmon of the corresponding natural
population were grown in identical conditions, we document for the first
time genome-wide changes in transcription profiles that evolved in
parallel between farmed strains from North America and Europe within
five to seven generations."
"The magnitude of the accumulated differences was of approximately 20% for 1.5% of the expressed genes in juvenile salmon. These findings provide support to the claim that hybridisation with farmed escapees may alter the gene pool of wild salmon, reduce its fitness and accelerate its decline." Adapted from materials provided by Blackwell Publishing Ltd.. _________________________ Restocking of salmonids—opportunities and limitations M.W. Aprahamian et al Abstract Stocking can be a cost effective method of enhancing salmonid populations, in particular where the aim is to restore populations or mitigate against developments. There are risks associated with any intervention and it is suggested that all stockings undergo risk screening in order to identify the high risk areas. The main concern regarding stocking relates to the impact on the genetic fitness of the wild population, and proposals to minimise the impact while still maintaining a fishery are made. To ensure that the greatest benefit from a stocking programme is realised, stocking rates should be optimal for the type of habitat being stocked. How this can be determined is presented together with guidelines for stocking different types of habitat. Benefit, in terms of cost of adult return or per adult fish caught, enables comparisons to be made with other management options. Information on survival rates of wild and hatchery-reared fish, unit cost of production and the economic value of fish and fishing is summarised enabling simple estimates of cost: benefit to be determined. © 2002 Elsevier Science B.V. All rights reserved. ______________________ The role of stocking in recovery of the River Tyne salmon fisheries. N.J. Milner1 et al _______________________________ Management of salmonid fisheries in the British Isles: towards a practical approach based on population genetics A.F. Youngson et al Abstract The evidence for structuring of Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) into distinct reproductive populations and for genetic differentiation and local adaptation is compelling. The effect of genetic variation among populations is demonstrably a factor determining the economic value of salmonid fisheries in the British Isles. Genetic considerations are, therefore, a matter of self-interest for fisheries managers and a shared interest with those advocating more general approaches to the conservation of diversity and variation. The local population is the basic unit of production and, therefore, the preferred unit of management. However, salmonid populations are numerous and many are small. These factors limit practical possibilities for management at the population level. We suggest that this difficulty can be addressed by combining populations in fisheries-biased management units that comprise interchangeable, nested groupings of populations that are both genetically and biologically meaningful. This population-based approach addresses the necessity of managing the fisheries in ways that are consistent with the conservation of adaptive potential in relation to the dynamic aspects of populations, their capacity to respond to changing environmental conditions, and the likelihood that salmonids will remain a worthwhile resource for the future. Crown Copyright © 2002 Published by Elsevier Science B.V. All rights reserved. ________________________________________________________ Resolution by the Parties to the Convention for the Conservation of Salmon in the North Atlantic Ocean to Minimise Impacts from Aquaculture, Introductions and Transfers, and Transgenics on the Wild Salmon Stocks The Williamsburg Resolution ____________________________________ Potential Genetic Interaction Between Wild and Farm Salmon of the Same Species Prepared for: The Office of the Commissioner for Aquaculture Development Fisheries and Oceans, Canada 344 Slater St., Suite 1610 Ottawa, Ontario K1A 0E6 By: R.G. Peterson, Ph.D. 4291 West 16 th Ave.Vancouver, BC V6R 3E5 September 1999
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