Publication Abstract

SpatMan: A spatial management modelling tool for shellfish stocks

E. Bell, M. Bell, M. Smith and J. Addison

There is increasing pressure for the introduction of spatial management regimes, in particular with relation to inshore shellfish stocks. It is unlikely that micro-management of stocks will be supported by full-blown, age-based assessments. Instead regimes are more likely to rely upon semi-permanent measures such as closed seasons and areas or reactive management based upon simple estimates of relative abundance. Investigations into the potential impact of local-scale spatial management should take account of the ability of fishing vessels to move between management areas. A spatial management model was therefore designed to track the decisions and subsequent success of individual fishing vessels in order to evaluate the relative performance of differing management plans. In the model, individual vessels move around a grid of locations populated by sessile organisms (scallops in this example). Each vessel has a daily operational range within which it must find the optimum location to fish, this optimum being based upon the track record of fishing within those grid cells currently open to fishing within the operational area. Grid cells are grouped to form management areas, each with a distinct management regime. Regimes currently implemented are TAC, effort limitation, LPUE limit, rotational closure, permanent closures (Marine Protected Areas), and closed seasons.    Model output includes landings and effort by area as well as track record information by vessel. A simple implementation of the model with just four areas and four vessels can produce complex results, and several realisations of each implementation are required to determine the potential range of results.

Reference

E. Bell, M. Bell, M. Smith and J. Addison (2007) SpatMan: A spatial management modelling tool for shellfish stocks. ICES CM 2007/O