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Climate and fishing effects on the distribution and size structure of exploited fish populations
climate change,spatial distribution,size structure,fishing effect,life history traits,
|Publication Year :||2018|
Climate and fishing effect on the exploited populations is an important research topic. Although the global meta-analysis indicates a general pattern of poleward distributional shifts in response to rising temperatures, the specific responses have varied among species. The size structure of exploited populations is simultaneously affected by both climate and fishing, but what determines the relative contribution of the two remains unknown. More importantly, the dynamics of distribution and size structure of exploited populations may be interwoven because of the ontogenetic habitat shift of fish. Therefore, a framework to incorporate these two demographic aspects is urgently needed to gain the whole picture for understanding exploitation population’s response to climate and fishing effect.
In my thesis, I use three different approaches to investigate climate and fishing effects on the distribution and size structure of the exploited fish populations. The first chapter describes the general phenomenon and set the research scene. The second chapter describes how fish with different life history traits respond differently at interannual and decadal scales of climate change, using the bottom trawl fishery in the Japan Sea as an example. The results indicate that the distributional changes of species in response to decadal climate variability are best explained by asymptotic length, which indicates that warming has greater negative effects on larger fishes in the Japan Sea. The third chapter focuses on the size structure of exploited fish population, with emphasis on applying variation partitioning to disentangle the synergetic effect of climate and fishing. The results show that fishing has the most prominent effect on the size structure of exploited stocks. In addition, the fish stocks experienced higher variability in fishing displayed a greater response to temperature in their size structure, suggesting that fishing may elevate the sensitivity of exploited stocks in responding to environmental effects. The variation partitioning approach provides complementary information to univariate size-based indicators in analyzing size structure. The fourth chapter examines how the change in spatial distribution at different life stages is affected by climate change in exploited fish populations. I found adult stage generally move faster as response to temperature change than juvenile stages. Also, the species whose adults and juveniles move toward the same direction are more likely to have more overlapping in distribution among the two life stages, indicating that adults and juveniles of given species occupying similar niches are more likely to have similar response.
Overall, this study concludes that size structure and distribution are related in the response of the exploited population to climate and fishing effects. It would be necessary to examine both for a better understanding the responses of exploited populations. These results may provide useful information for ecosystem-based fisheries management in light of climate change.
|Appears in Collections:||海洋研究所|
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