Depending on population, wild Fraser River sockeye salmon Oncorhynchus nerka travel distances of <100 km to >1100 km and ascend elevations ranging from near sea-level to 1200 m to reach spawning areas. Populations embarking on distant, high elevation migrations (i.e. Early Stuart, Chilko and Horsefly populations) began their upriver spawning migrations with higher densities of somatic energy (c. 9Á2 to 9Á8 MJ kg À1) and fewer eggs (c. 3200 to 3800) than populations making shorter, low elevation migrations (i.e. Weaver and Adams; c. 7Á1 to 8Á3 MJ kg À1 gross somatic energy and c. 4300 to 4700 eggs). Populations making difficult upriver migrations also had morphologies that were smaller and more fusiform than populations making less difficult migrations, traits that may facilitate somatic energy conservation by reducing transport costs. Indeed, fish travelling long distances expended less somatic energy per unit of migratory difficulty than those travelling shorter distances (2Á8 to 3Á8 kJ v. 10-1400 kJ). Consistent with evolutionary theory, difficult migrations appear to select for energy efficiency but ultimately fish making more difficult migrations produce fewer eggs, even when differences in body length have been accounted for. Despite large among-population differences in somatic energy at the start of upriver migration, all populations completed migration and spawning, and subsequently died, with c. 4MJkg À1 of energy remaining, a level which may reflect a threshold to sustain life.

This study compared the flesh quality of farmed and wild sources of British Columbia (BC) salmon with respect to concentrations of polychlorinated biphenyl compounds, polychlorinated dibenzodioxins/dibenzofurans and their associated toxic equivalents, total mercury (THg), methylmercury (MeHg), and selected fatty acids of known importance for human health viz., omega-3 (n-3) highly unsaturated fatty acids (n-3 HUFAs) and (n-6) fatty acids. Skinned fillets from known sources of farmed Atlantic, coho, and chinook salmon (n = 110) and wild coho, chinook, chum, sockeye, and pink salmon (n = 91) were examined. Atlantic salmon contained higher PCB concentrations (means, 28-38 ng/g) than farmed coho or chinook salmon, and levels in these latter species were similar to those in wild counterparts (means, 2.8-13.7 ng/g). PCB levels in Atlantic salmon flesh were, nevertheless, 53-71-fold less than the level of concern for human consumption of fish, i.e., 2000 ng/g as established by Health Canada and the U.S. Food and Drug Administration (US-FDA). Similarly, THg and MeHg levels in all samples were well below the Health Canada guideline (0.5 microg/g) and the US-FDA action level (1.0 microg/g). On average, THg in farmed salmon (0.021 microg/g) was similar to or lower than wild salmon (0.013-0.077 microg/g). Atlantic salmon were a richer source (mean, 2.34 g/100 g fillet) of n-3 HUFAs than the other farmed and wild sources of salmon examined (means, 0.39-1.17 g/100 g). The present findings support the recommended weekly consumption guidelines for oily fish species (includes all BC salmon sources) for cardio-protective benefits as made by the American Heart Association and the UK Food Standards Agency.

This study assessed the suitability and cost e⁄cacy of an equal blend of canola oil (CO) and poultry fat (PF) as a supplemental dietary lipid source for juvenile Atlantic salmon. Quadruplicate groups of Atlantic salmon ( $ 400 g) held in 4000 L outdoor ¢breglass tanks supplied with running (35^40 L min À1 ), aerated (dissolved oxygen, 7.88^10.4 mg L À 1 ), ambient temperature (8.6^10.9 1C) sea water (salinity, 263 5 g L À1 ) were fed twice daily to satiation one of three extruded dry pelleted diets of equivalent protein (488^493 g kg À1 dry matter) and lipid (2672 74 g kg À1 dry matter) content for 84 days. The diets were identical in composition except for the supplemental lipid (234.7 g kg À1 ) source viz., 100% anchovy oil (AO; diet COPF-0),70.2% AO and 29.8% CO and PF (diet COPF-30), and 40.3% AO and 59.7% CO and PF (diet COPF-60). Atlantic salmon growth rate, feed intake, feed e⁄ciency, protein and gross energy utilization, percent survival and whole body and ¢llet proximate compositions were not a¡ected by diet treatment. Cost per kilogram weight gain was about 10% less for ¢sh fed diet COPF-60 than for diet COPF-0. Percentages of saturated fatty acids in dietary and ¢llet lipids varied narrowly. Moreover, percentages of 18:1n-9, monounsaturated fatty acids, 18:2n-6, n-6 fatty acids,18:3n-3, and ratios of n-6 to n-3 fatty acids in the £esh lipids were directly related to the dietary level of CO and PF whereas 22:6n-3, the total of 20:5n-3 (eicosapentaenoic acid; EPA) and 22:6n-3 (docosahexaenoic acid; DHA), and n-3 fatty acids revealed the opposite trend. Percentages of 22:6n-3, EPA and DHA, and n-3 fatty acids were signi¢cantly depressed in ¢sh fed diet COPF-60 versus diet COPF-0.We conclude that a 1:1 blend of CO and PF is an excellent cost-e¡ective dietary source of supplemental lipid for Atlantic salmon in sea water.