Energetics and morphology of sockeye salmon: effects of upriver migratory distance and elevation
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. 9·2 to 9·8 MJ kg−1) and fewer eggs (c. 3200 to 3800) than populations making shorter, low elevation migrations (i.e. Weaver and Adams; c. 7·1 to 8·3 MJ kg−1 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 (2·8 to 3·8 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. 4 MJ kg−1 of energy remaining, a level which may reflect a threshold to sustain life.
Document Type: Regular Paper
Forest Sciences Department, 3430 Forest Sciences Centre, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada,
Biological Sciences Department, Simon Fraser University, Burnaby, BC, V5A 1Y6, Canada and
West Vancouver Laboratory, Fisheries and Oceans Canada, West Vancouver, BC, V7V 1N6, Canada
Institute for Resources, Environment, and Sustainability, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada,
Publication date: September 1, 2004