Evaluation of an alternative strategy to enhance salmon populations: Cage rearing wild smolts from Conne River, Newfoundland

Atlantic salmonSalmo salarL., brown troutSalmo truttaL. and Arctic charrSalvelinus alpinus(L.): a review of aspects of their life histories

“…Marine mortality on salmon is commonly believed to be highest in the initial periods that smolts are at sea (Hansen & Quinn 1998; Potter & Crozier 2000) and is consistent with observations on timing of mortality of wild Conne River smolts that were transferred to an estuarine aquaculture grow‐out facility at Roti Bay, Newfoundland (Dempson et al. 1999a).…”

“…1998), as well as altering distribution and behaviour (Drinkwater 2000). In the Conne River smolt rearing experiment (Dempson et al. 1999a), salmon had attained approximately 70% of their subsequent adult 1SW size by the end of October (mean length = 374 mm; mean weight = 780 g).…”

“…The upper level of water ranged from 0 to 5 PSU and surface ice can persist for several months (Sutterlin & Stevens 1992). Aquaculture salmon have been maintained in this environment for a number of years, and over‐winter survival of the wild Conne River reared salmon was similarly high (72% survival from December 31 to May 15) (Dempson et al. 1999a).…”

Use of stable isotopes to distinguish farmed from wild Atlantic salmon, Salmo salar

“…If signatures changed rapidly, or if fish escaped at an early stage, the problem could be analogous to that experienced with the use of scale circuli characteristics to differentiate wild from escaped farmed salmon , with the ease of differentiating between salmon types declining as the time since escapement increases. At Conne River, wild smolts transferred to an estuarine aquaculture rearing site in Bay d'Espoir grew most rapidly from June (mean ¼ 49 g) to August (mean ¼ 565 g), and by October had achieved 82% of their subsequent length and 66% of their weight realised as 1SW fish by June of the following year (Dempson et al 1999). Johnson et al (2002) similarly stated that the rate of change in isotope signatures was proportional to the change in prey signatures as well as the amount of new tissue elaborated as a result of the change in diet.…”

“…In general, aquaculture production of farmed steelhead (Oncorhynchus mykiss) and Atlantic salmon at Bay d'Espoir has increased slowly with annual production of less than 200 t year )1 in the early 1990s to an average of 2129 t from 1998 to 2001 (Fisheries and Oceans Canada: www.dfo-mpo.gc.ca/ communic/statistics/aqua/index_e.htm). This is, in part, the result of the precipitous decline in the returns and survival of salmon to Conne River, Bay d'Espoir, that had been one of the most productive rivers in Newfoundland (Dempson & Stansbury 1991;Dempson et al 1999). Nonetheless, concerns have been registered regarding impacts the industry could have on local stocks of Atlantic salmon (Pepper et al 1998;Whoriskey 1999).…”