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A procedure of classification using a discriminant function analysis was developed to determine the farmed or native natal origin of Atlantic salmon juveniles in the Magaguadavic River, New Brunswick. Farmed juveniles enter this river as escapees from three commercial aquaculture hatcheries. The procedure evaluated measured scale characteristics from the first year of growth, of farmed and native juveniles of known origin, for their power as predictors of derivation. Eight scale characteristics proved to be significant predictors of origin. In a jackknife cross-validation, the function developed from the characteristics proved to be 90.3% accurate in predicting the origin of juvenile Atlantic salmon in the Magaguadavic River. The procedure was then applied to unknown origin juveniles sampled from the Magaguadavic, Waweig and Digdequash rivers in New Brunswick. All of these rivers support hatcheries. Juvenile salmon sampled in the Magaguadavic River in 1996, 1997 and 1998, were determined to be 34%, 63% and 42% of farmed origin, respectively. During 1998, 9% of the juveniles from the Digdequash River were of farmed origin, and 42% of the juveniles in the Waweig River were of farmed origin. The study indicated that substantial numbers of farmed juveniles escaped from hatcheries and occupied juvenile salmon habitat in all three rivers.
Farmed Atlantic Salmon (Salmo salar) have experienced multiple generations of selection pressures different from those experienced by their wild counterparts. Farmed fish escape from aquaculture facilities regularly, and their interbreeding with wild fish can result in lower wild population productivity and altered life history traits. Therefore, understanding the genetic basis of relative performance of farmed, wild, and hybrid salmon is critical to predicting impacts on wild populations from farmed escapees. In my first data chapter, I compared the relative survival, size, morphology, and parr marks of Atlantic Salmon parr (wild, farmed, and reciprocal F1 hybrids) over the first summer of growth at three replicate sites in southern Newfoundland. There was a consistent pattern of relative survival across all sites (wild-mother hybrids > pure wild > pure farmed > farmed-mother hybrids), with wild fish consistently smallest in size, and wild-mother hybrids and farmed fish largest. In addition, I found small differences in body shape related mainly to body depth, and differences among sites for parr mark size. In my second data chapter, I compared lipid and fatty acid profiles at release and recapture for farmed, wild and hybrid parr. There were lipid profile differences among cross types at both time points and in addition, pure farmed fish displayed a greater decrease in storage lipids and certain fatty acids characteristic of freshwater invertebrate prey over the experimental period when compared with other cross types. Overall, there were measurable differences in survival and fitness-related traits among cross types, even over a relatively short experimental period under favourable conditions. Ultimately, this research provides key data on relative cross type performance for North American populations of Atlantic Salmon that may help inform predictive models, and subsequent aquaculture management and mitigation decisions.
Due to egg depositions well below the conservation requirement in recent years, the angling season was closed and there was no First nation allocation of salmon on the Buctouche River as of 1998. Salmon returns in 1999 were calculated from catches and known efficiency of an estuary trapnet operated by Buctouche First Nation. Total large salmon returns were estimated at 244 and total small salmon returns at 114, with respective spawning escapements of 244 and 111. Total egg deposition was estimated at 102% of the conservation requirement. This represents a tripling of the level in 1998, and the first instance in seven assessed years when the requirement may have been met. Juvenile densities on the Buctouche were well below optimum, especially for fry, confirming the low egg deposition observed in 1998. Results from a juvenile survey of four other southeastern New Brunswick rivers indicated that the level of spawning success has been variable and asynchronous. The variability, unpredictability and generally depressed status observed in the Buctouche stock appears to be characteristic of most rivers in the area, and a valid basis for the general management of stocks. The forecast for the Buctouche in 2000 is five year mean of total returns, which is 167 large and 106 for small salmon. With all retention fisheries closed there is only a 3% probability that the egg conservation requirement will be met in 2000.