From genes to ecosystems: an eco-evolutionary assessment of alternative harvesting strategies and consequences for fisheries productivity

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We will employ a novel, multidisciplinary approach to assess to what degree eco-evolutionary changes generated by common harvesting approaches affect fisheries productivity. We will blend emerging theory, concepts and new advances in population genomics, eco-evolutionary dynamics and community ecology to conduct a large scale harvest selection experiment based on experimentally-controlled depletions across a series of closed, natural trout populations. Our project will take advantage of the mandate of Parks Canada to actively restore previously fishless alpine lakes where non-native trout were introduced 80-100 years ago. Hence it provides an exceptional opportunity to conduct replicated depletion of natural populations of a socio-economically important fish species groups (salmonids) where they will be removed anyways. These depletions will be used to (i) explore several untested hypotheses about the effects of size-selective harvesting on fisheries productivity and ecosystem function and (ii) characterize the efficacy of an alternative harvesting approach to substantially reduce size-selective effects ('balanced harvesting'). Concurrently, the project will contribute to reaching ecosystem restoration targets using non-poison removal techniques, for one of Canada's most important heritage symbols - the magnificent Rocky Mountain lakes. Trout depletion will simulate (i) commonly occurring size-selective harvesting of large-sized individuals (4 lakes) and (ii) 'balanced harvesting', wherein mortality is distributed across the widest range of sizes in an ecosystem, in proportion to their natural productivity, with the aim that size-selectivity and associated evolutionary changes are minimized (4 lakes); 4 additional, non-depleted lakes will act as controls. Intense size-selective harvesting has taken place in a 13th lake since 2011 and affords a longer-term temporal assessment of genomic change associated with harvesting selectivity. Lakes will be of a similar characteristics and have had a negligible history of fishing prior to trout depletion. Pre- and post-depletion monitoring of a series of response variables/metrics at the gene, population, community and ecosystem levels will be conducted on multiple age-cohorts over successive years.******