Midway evaluation in Biology - Michelle Valliant

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Title of thesis: Distribution, movement, and behavior of inshore and offshore juvenile Atlantic cod (Gadus morhua) in nearshore waters

Student: Michelle Valliant

Doctoral committee: Dr. Guðbjörg Ásta Ólafsdóttir,  Director & Research Scientist, Research Centre of the Westfjords, University of Iceland 
Dr. Snæbjörn Pálsson,  Professor at the Faculty of Life and Environmental Sciences, University of Iceland
Dr. Kalina Hristova Kapralova, Research Specialist, The Institute for Experimental Pathology at Keldur, University of Iceland
Dr. Carla Brandt Freitas, Senior Scientist, Institute of Marine Research, Norway

Abstract

In a changing world, accounting for intraspecific phenotypic variation is essential for effective conservation as variation within species may facilitate adaptation and persistence. Atlantic cod (Gadus morhua) exhibits substantial variation in migration and movement among populations and individuals, and maintaining migratory diversity is particularly important for management and conservation. Atlantic cod differ in many ecologically important genes and inhabit distinct environments, occupying contrasting temperature and depth regimes, and in Iceland cod comprises distinct ecotypes—offshore (frontal) and inshore (coastal). However, the development of these ecotypes and migratory strategies during early life remains poorly understood. In partially migratory species, migration decisions arise from interactions between intrinsic (within an individual) and extrinsic (outside influence) factors, highlighting the importance of examining juvenile ecotypes in the context to their site origin. We examined juvenile cod (1-3 year olds) differences in distribution, seasonal migration, timing of departure from nursery grounds, and behaviour. Specifically, using acoustic telemetry, we test whether ecotype, body size or origin of catch influence fjord residency, horizontal and vertical movements, and activity patterns, and whether temperature interacts with ecotype and origin to influence these behaviors. Implications for juvenile cod conservation are discussed.