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Body-element content was measured for three life stages of wild Atlantic salmon Salmo salar from three distinct Newfoundland populations as individuals crossed between freshwater and marine ecosystems. Life stage explained most of the variation in observed body-element concentration whereas river of capture explained very little variation. Element composition of downstream migrating post-spawn adults ( i.e. kelts) and juvenile smolts were similar and the composition of these two life stages strongly differed from adults migrating upstream to spawn. Low variation within life stages and across populations suggests that S. salar may exert rheostatic control of their body-element composition. Additionally, observed differences in trace element concentration between adults and other life stages were probably driven by the high carbon concentration in adults because abundant elements, such as carbon, can strongly influence the observed concentrations of less abundant elements. Thus, understanding variation among individuals in trace elements composition requires the measurement of more abundant elements. Changes in element concentration with ontogeny have important consequences the role of fishes in ecosystem nutrient cycling and should receive further attention. [ABSTRACT FROM AUTHOR]

Dempson JB, Power M. Use of stable isotopes to distinguish farmed from wild Atlantic salmon, Salmo salar. Ecology of Freshwater Fish 2004: 13: 176–184. © Blackwell Munksgaard, 2004 Stable isotopes of carbon and nitrogen ( δ13C and δ15N) were examined in wild and aquaculture origin Atlantic salmon, Salmo salar, to evaluate their utility to identify escaped farmed fish. Samples of muscle tissue obtained from wild Conne River, Newfoundland, salmon were significantly more enriched in nitrogen ( δ15N: mean = 12.75; SD ± 0.38‰) but depleted in lipid corrected carbon ( δ13C′: mean = −20.51; SD ± 0.23‰) by comparison with aquaculture specimens obtained from Bay d'Espoir, Newfoundland ( δ15N = 10.96 ± 0.19‰; δ13C′ = −19.25 ± 0.17‰) resulting in a complete separation of the two groups. Aquaculture specimens differed in δ13C′ from analyses of commercial salmon diet by 0.24‰, within the enrichment range associated with trophic transfers, while the δ15N values in salmon muscle were enriched by 5.01‰. Although differences occurred in direct comparisons of white muscle and adipose tissue ( N = 49), the average δ13C′ and δ15N signatures varied in absolute amounts by only 0.5‰, supporting the use of adipose tissue as a nonlethal means to determine isotopic signatures of Atlantic salmon. [ABSTRACT FROM AUTHOR]

The effects of catch and release angling on survival of Atlantic salmon, Salmo salar L., at Conne River, Newfoundland, were investigated by retaining angled (n =49; experimental group) and trap-caught (n =20; control group) fish in holding cages for up to 40 days. Samples were obtained from 8 June to 4 July, 2000, and partitioned among four water temperature strata. Apart from not being angled, control fish were handled, tagged, and transferred to holding cages in a manner similar to angled salmon. Water temperatures and discharge were monitored throughout the duration of the study. Overall, 8.2% of salmon caught and released died, but 12% died among salmon angled in water temperatures ≥ 17.9 °C. No control fish died. There were no significant differences in time associated with angling, exposure to air, tagging, transfer to holding cages, nor total handling time between salmon that survived vs. those that died. Results of the study should encourage managers to continue to use catch and release as a viable tool in the management of Atlantic salmon stocks. [ABSTRACT FROM AUTHOR]

Potential impacts of climate warming on recreational fishing opportunities were addressed by assessing the frequency and extent that Atlantic salmon, Salmo salar L., rivers in Newfoundland have been closed over a 25-year period (1975 to 1999) because of warm water temperatures and low water levels. On average, approximately 28% of all salmon rivers were temporarily closed annually, with over 70% affected in some years. This has resulted in a loss of 35–65% of the potential fishing days available in some salmon fishing areas with the collective 1995 to 1999 period being impacted the most over the past two decades. Geographically, west and south-west coastal rivers were affected less from environmental closures than east and some south coast fishing areas. A trend for increased closures of rivers related to environmental reasons could reduce the economic importance of the recreational salmon fishery and also make it more difficult to assess the status of Atlantic salmon stocks, which is a requirement for conservation of the resource. [ABSTRACT FROM AUTHOR]

Marine exploitation rates were estimated for nine Newfoundland Atlantic salmon (Salmo salar L.) populations, separately for small and large salmon size components. Estimates were derived using counts of salmon returning to fish counting facilities rather than from tagging studies and thus adjustments were not required to account for tag loss, handling or tagging mortality, or tag reporting rates. For all stocks combined, the overall marine exploitation rate during the period 1984–1991 averaged 45.3% (29.6–57.1%) on small salmon and 74.2% (57.7–83.7%) on large salmon. These estimates are considered minimum values. Concerns related to declining salmon abundance resulted in the closure of the Newfoundland commercial salmon fishery in 1992. Results are discussed in relation to previous estimates derived from tagging, and highlight the importance of accounting for marine exploitation when examining trends in salmon survival and return data even when commercial fisheries have been closed. [ABSTRACT FROM PUBLISHER]