Fisheries conservation on the high seas: linking conservation physiology and fisheries ecology for the management of large pelagic fishes.

Andrij Z Horodysky,John E Graves,Richard W Brill,Steven J Cooke

doi:10.1093/conphys/cov059

Abstract

Populations of tunas, billfishes and pelagic sharks are fished at or over capacity in many regions of the world. They are captured by directed commercial and recreational fisheries (the latter of which often promote catch and release) or as incidental catch or bycatch in commercial fisheries. Population assessments of pelagic fishes typically incorporate catch-per-unit-effort time-series data from commercial and recreational fisheries; however, there have been notable changes in target species, areas fished and depth-specific gear deployments over the years that may have affected catchability. Some regional fisheries management organizations take into account the effects of time- and area-specific changes in the behaviours of fish and fishers, as well as fishing gear, to standardize catch-per-unit-effort indices and refine population estimates. However, estimates of changes in stock size over time may be very sensitive to underlying assumptions of the effects of oceanographic conditions and prey distribution on the horizontal and vertical movement patterns and distribution of pelagic fishes. Effective management and successful conservation of pelagic fishes requires a mechanistic understanding of their physiological and behavioural responses to environmental variability, potential for interaction with commercial and recreational fishing gear, and the capture process. The interdisciplinary field of conservation physiology can provide insights into pelagic fish demography and ecology (including environmental relationships and interspecific interactions) by uniting the complementary expertise and skills of fish physiologists and fisheries scientists. The iterative testing by one discipline of hypotheses generated by the other can span the fundamental-applied science continuum, leading to the development of robust insights supporting informed management. The resulting species-specific understanding of physiological abilities and tolerances can help to improve stock assessments, develop effective bycatch-reduction strategies, predict rates of post-release mortality, and forecast the population effects of environmental change. In this synthesis, we review several examples of these interdisciplinary collaborations that currently benefit pelagic fisheries management.

Highlights

Highly migratory pelagic fishes (including billfishes, tunas and pelagic sharks; Lesser Antilles Pelagic Ecosystem (LAPE) project) are being harvested at or over capacity (Worm et al, 2009), as fisheries fish through food webs to meet the protein demands for a burgeoning human population (Essington et al, 2006)
In the 1970s pelagic longline gear deployments shifted from shallow sets primarily targeting yellowfin tuna (Thunnus albacares) to deeper sets primarily targeting swordfish and bigeye tuna (Thunnus obesus; Lynch et al, 2012); how these shifts in fishers’ behaviours altered the catchability and estimated abundances of target and bycatch species is less clear (Horodysky et al, 2007)
We describe interdisciplinary collaborations regional endothermy of pelagic fishes enables geographical between fish physiologists and pelagic fisheries scientists that and vertical niche expansion and increased access to prey

Summary

Introduction

Highly migratory pelagic fishes (including billfishes, tunas and pelagic sharks; Lesser Antilles Pelagic Ecosystem (LAPE) project) are being harvested at or over capacity (Worm et al, 2009), as fisheries fish through food webs to meet the protein demands for a burgeoning human population (Essington et al, 2006). Stock assessment models of pelagic fishes typically incorporate catch-per-unit-effort (CPUE) time-series data from commercial fisheries, but there have been notable changes in targeted species, areas fished and depth-specific gear deployments over the years (Lynch et al, 2011).

Results

Conclusion