Graduate Thesis Or Dissertation
 

Growth, Condition, and Survival of Larval Arctic Cod and Walleye Pollock in a Warming Ocean

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/9z9034642

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  • Arctic cod (Boreogadus saida) is an ecologically significant species that plays a critical role channeling energy throughout the Arctic marine food web. Arctic cod is uniquely adapted to occupy ice edge habitats, however, a basic understanding of its larval physiology and habitat requirements is lacking due to widespread sea ice cover which limits spring field sampling. Forecasted shrinkage of sea ice habitat could facilitate invasions of non-ice-obligate North Pacific gadids, such as walleye pollock (Gadus chalcogrammus). By assessing the sensitivity of the early life stages of fish species to environmental conditions affecting growth (i.e., temperature and food availability), it is possible to better understand larval survival, and thus the factors dictating success of the population in the face of climate change. To this aim, I conducted laboratory experiments to directly examine the growth and survival of Arctic cod and walleye pollock at two larval stages in response to forecasted changes in temperature and food availability. Critical rates obtained from these experiments demonstrate that larval Arctic cod has a competitive advantage over walleye pollock in terms of growth and survival at low temperatures. However, rising temperatures and altered productivity regimes associated with climate change have the potential to constrain the habitat that is available to Arctic cod. Temperature-dependent growth models developed from this study emphasize the species-specific and stage-specific differences in the growth of larval gadids and provide a baseline for examining temperature-dependent growth in the field. Following laboratory experiments, I examined the morphometric and lipid condition of each species under the same experimental conditions, to investigate the effects of temperature and food availability on larval fish condition and the suitability of different condition indices. Temperature and food availability impacted larval condition and lipid storage in a species-dependent manner. Furthermore, later stage larval condition was more sensitive to changes in prey availability at higher temperatures, indicating that larval condition may be negatively impacted under a climate change scenario of combined warming and reduced availability of lipid-rich prey. Collectively, the physiological rates determined within my thesis will add to a better understanding of the mechanisms affecting condition and survival of gadid larvae at the Arctic-boreal interface. Knowledge of the habitat requirements of these ecological important species is essential for effective resource management, and is key to understanding the broader implications of global change.
  • Keywords: Climate change, Walleye pollock, Arctic cod, Thermal sensitivity, Arctic-Boreal, Condition, Forage fish, Biogeography
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