Publication Abstract

A comparison of management tools for multiple objective fisheries management; towards reconciling fisheries production and conservation management.

 

Moving towards an ecosystem based approach to management requires simultaneously considering multiple objectives for the marine environment. Long lived, slow growing and late maturing species are particularly vulnerable to the impacts of fishing. This is highlighted by significant declines, and even regional extirpation, of some long lived elasmobranchs in European waters. Thus there is a desire to understand how fisheries can be best managed to meet conservation objectives for vulnerable fishes with the least impact on commercial fishing operations.

This study provides a general analysis of the relative ability of different management tools to achieve dual objective, fisheries and conservation, management using a spatially explicit 2-species age structured population model incorporating a ‘commercial’ species and a ‘conservation’ species. The management tools considered within the model were effort limitation, closed areas and mesh size regulation; comparative simulations were run using management tools individually and in combination. To examine the implications of differing relative mobility between the commercial and conservation species, the model was run under different assumptions about the mobility of the species.

When management tools were used individually, closed areas were considered optimal when the conservation species is less mobile that the commercial species; conversely effort control was considered optimal when the conservation species is more mobile than the commercial species. When the conservation and commercial species are equally mobile effort control and closed area management provide similar outcomes, with the optimal management strategy depending on the absolute level of mobility. By itself increasing mesh size provided little benefit as to provide meaningful benefits to the conservation species the mesh size had to be increased so large that almost no commercial catch was taken. Using management tools in combination allowed the greatest yield to be taken whilst maintaining the conservation species at acceptable levels.

W. Le Quesne*

European Marine Biology Symposium, Edinburgh, 23-27 Aug 2010