Effects of climate change on fisheries : from a global to a regional perspective

Tese de doutoramento, Biologia (Biologia Marinha e Aquacultura), Universidade de Lisboa, Faculdade de Ciências, 2016

The present thesis focused on the effects of climate change on fisheries, both on a global and on a regional scale. Trends in annual catches of fish species in the large marine ecosystems of the world were analysed, taking into account changes in sea surface temperature (SST). The results obtained in this analysis agreed with a poleward shift in distribution of fish species as a response to ocean warming. The Portuguese coast is located in a biogeographic transition zone, where the effects of climate change are higher, which makes it particularly adequate for studies on the effect of climate change on fisheries. Landings of biogeographic groups of fish species were compared, for each Portuguese fleet component: trawl, purse-seine and multi-gear fisheries. Results pointed out to an easier adaptation of multi-gear fisheries to the effects of climate change. A long time series analysis was performed for Setúbal, an important fishing port in central Portugal. In 86 years, mean annual SST has increased 0.9 ºC in the area. The main target species in 2012 were the same as in 1927. However, their landings have changed and have responded to changes in environmental variables, particularly SST. The influence of river drainage on landings of coastal ports in the vicinity of four estuaries was investigated. No significant correlations between river drainage and landings were found, which could be due to a stronger dependence of the food web on the nutrients provided by coastal upwelling. Also, the possible interaction of several other smaller scale factors acting on recruitment of commercial species may mask the effects of river drainage on landings. Recruitment and landings of European sardine (Sardina pilchardus) and Atlantic horse mackerel (Trachurus trachurus), two highly consumed fish species in Portugal, were modelled. Models obtained emphasized the influence of SST and wind strength in landings of these pelagic species. Finally, trends in landings of the most important fishing métiers, as well as the vulnerability and adaptation capacity of Portuguese fisheries to climate change were analysed. A latitudinal pattern in the number of new species found in landings was observed, agreeing with a northward shift of subtropical species. The south coast showed a higher vulnerability to climate change, in terms of both exposure and sensitivity of target species and ecosystems to its effects. Trawl fisheries and multi-gear fisheries may be more adaptable and less vulnerable to climate change than purse-seine fisheries. In fact, the high sensitivity of sardine to the effects of climate change makes purse-seine fisheries particularly vulnerable to climate change. Overall, results responded to the main objective of this thesis of assessing trends and relationships between climate change and fisheries. Suggestions for future research in this subject are also proposed.

Programa operacional Potencial Humano (POPH) do Quadro de Referência Estratégico Nacional (QREN)