The west coast of North America supports over 9 species of pacific salmon and trout that exhibit an astonishingly wide array of life-history strategies. In the first part of this talk I will consider differentiation of phenotype and life-history among salmonid species, populations, and individuals at the freshwater juvenile rearing stage, and how adaptive differentiation relates to habitat partitioning and associated tradeoffs in phenotype, particularly selection on juvenile growth. Variation among rainbow trout individuals and populations supports the interpretation of a general adaptive tradeoff between selection for high growth vs. active metabolic performance. Life-history and growth differentiation among west coast salmonids can also be interpreted through the lens of evolutionary pressure to escape habitat bottlenecks that limit adult population size.
Stream flow represents a major environmental determinant of juvenile salmonid abundance and a significant regulatory challenge, as domestic and industrial water demands increasingly conflict with flow needs for fish. Despite the need for clear science advice on minimum flows required to support fish production, instream flow science has seen limited evolution over the last 40 years. I will review the potential for bioenergetic modelling of juvenile salmonid growth to be used as a tool to better predict the biological consequences of low stream flows, which are a natural consequence of seasonal summer drought in coastal British Columbia. Low summer flows represent a habitat bottleneck to salmonid production in many coastal streams; this natural bottleneck will be exacerbated by increasing water demands in conjunction with warming temperatures under climate change, reduced snow pack, and eutrophication from urban and agricultural development. Managing for persistence of salmonid-bearing streams in productive landscapes like the lower Fraser Valley requires long-term landscape modelling to anticipate the synergistic consequences of land use and climate change, and to identify the current management actions required to ensure future persistence.
Finally, freshwater and marine ecosystems display strong contrasts in the magnitude and trophic basis of biological production, the drivers of which remain poorly understood. I will consider how contrasting kinetic energy subsidies (physical energy that generates biological production) contribute to differences in the magnitude of benthic production between streams, lakes, and the marine intertidal.
Bio: Jordan Rosenfeld is a Stream Ecology Scientist with the British Columbia Ministry of the Environment based out of UBC. He did his M.Sc. degree at the University of Guelph studying primary production and energy flow in forested streams, and a Ph.D. at UBC studying fish predation effects on benthic invertebrate community structure in coastal streams. He currently does a variety of work related to management of freshwater habitats, including the effects of stream habitat structure on productive capacity for juvenile salmonids, stream restoration, modelling drift-foraging bioenergetics of salmonids, assessing critical habitat of freshwater fish species and risk, and instream flow modelling.
Photo credit: HazelthePikachu from flickr/Creative Commons