ADHOC - Evaluation of Proposed Amendments to the North Sea Flatfish Multiannual Plan

In 2007, the European Commission (EC) adopted Council Regulation No 676/2007, establishing a multiannual plan for fisheries exploiting stocks of plaice and sole in the North Sea. In 2010 IMARES provided a thorough simulation Management Strategy Evaluation (MSE) of the EU management plan for sole and plaice in the North Sea. This evaluation (Miller and Poos, 2010) as well as a subsequent STECF evaluation (Simmonds et al., 2010b) found the plan to be precautionary while providing high long term yields. In April 2012, IMARES, through ICES, received a special request from the Netherlands to evaluate whether a number of proposed amendments to the plan are in accordance with the precautionary principle and MSY approach. In sum-mary, the proposed amendments comprise a change in the target fishing mortality for sole from 0.20 to 0.25 and ceasing reductions of the Maximum Allowable Effort. The current report provides the response to this special request.

The evaluation of the multiannual plan is carried out using a numerical simulation model to study the interplay between the biological dynamics of the stocks and the dynamics of the fleet. The biological operating model consists of age structured popu-lation models of the ‘true’ plaice and sole stocks in the North Sea, following current stock delineations (see WGNSSK, 2012). The effects of the fishery on the two stocks is modeled as the combined effect of three different fishing fleets: a BT2 Dutch beam trawl fleet (80mm mesh, targeting plaice and sole), a Dutch fleet with gears other than BT2 (targeting plaice) and a fleet for the other countries (targeting plaice).

A number of management strategies were tested under various scenarios, including differing assumptions on biology and fleet behavior. For the main purpose of re-sponding to the special request a comparison is done between the current manage-ment plan (“CurMP”) and the proposal for an amended management plan (“Proposal”) under a “BaseCase” scenario. Subsequent scenarios examined sensitivity of the results to several assumptions incorporated in the biological operating model (alternative stock perception as a starting point and different levels of stock produc-tivity: “WorstCase” and “BestCase”) and in the fleet operating model (differences in effort deployment and inclusion of technological creep: “DepEffLeast”,“DepEffMost” and “TechCreep”).

Under base case assumptions, the proposed amendments to the current management plan are in accordance with the precautionary approach and consistent with the prin-ciples of MSY. Further scenarios indicate that the proposed management plan is ca-pable of prevent collapse of the stocks under very low productivity and of generating high yields under high productivity regimes.