PhD Defence: Charles Patrick Lavin

Thesis title​​​:

The cumulative impacts of climate change and fishing on marine communities

Trial lecture topic:

Incorporating resilience of marine fishes to climate change into marine fishery policy

Evaluation Committee:

• R&D Manager Paul Renaud, Akvaplan-niva
• Scientific Researcher Elvira Poloczanska, Alfred Wegener Institute for Polar and Marine Research, Germany
• Professor Pål A. Olsvik, Nord University

Supervisory Committee:

• Main supervisor: Professor Mark J. Costello, Nord University
• Co-supervisor: Professor Henning Reiss, Nord University

Thesis summary​:

Marine water-breathing ectotherms can be negatively impacted by ocean warming and deoxygenation in line with anthropogenic climate change. These environmental changes induce universal responses of marine ectotherms including reductions in body size as well as shifts in geographic distribution. Such responses are required in order for these animals to remain within their evolved thermal niche, as well, obtain sufficient dissolved oxygen from sea water to maintain aerobic metabolism. Yet, such changes will not occur uniformly between species or across biogeographic regions, and thus, the stability of marine communities and food webs can be stressed. Concurrently, persistent fishing pressure can further stress marine community stability, especially through the preferential harvesting of high trophic level species.

This thesis investigated instances of changing body size and geographic shifts of marine ectotherm populations, plus instances of overfishing top predators, between two unique ecoregions, Norway and New Zealand. Novel insight provided in the present thesis into these individual stressors can inform a more wholistic understanding of how cumulative stressors will interact within future scenarios of ocean warming and fishing. Such insight is necessary in order to inform conservation and fisheries management.