Evaluating the effect of real-time closures on cod targeting

Needle, C. L., and Catarino, R. 2011. Evaluating the effect of real-time closures on cod targeting. – ICES Journal of Marine Science, 68: 1647–1655. Under its Conservation Credits scheme to reduce cod mortality, the Scottish Government has implemented a system of real-time closures (RTCs) since 2008. These are relatively small, temporarily closed areas (50–225 square nautical miles per RTC, closed for 21 d) that are triggered by high cod catches. An important step in evaluating their effectiveness is to determine the response of vessels to RTCs, because the conservation benefit would be reduced if vessels moved to areas of greater cod abundance following closures. Abundance indices from research-vessel surveys and commercial-vessel observer trips are combined to create a time- and space-dependent relative cod-importance index (RCII). Vessel monitoring system data from Scottish vessels fishing during 2008/2009 are used to construct RCII profiles for each vessel, which are then used to determine whether the areas to which vessels move have a higher or a lower RCII, and how far away they move when an RTC is activated. We show that the RCII of the areas moved to tends to be lower than that of the RTC and that vessels travel farther when moving away from a closure than when moving back after reopening. Although not conclusive, this result indicates that RTCs may impact beneficially on cod mortality.