The identification of measures to protect by-catch species in mixed-fisheries management plans (ProByFish): Final Report

The ProByFish study was initiated to assist in the development of methods to evaluate the impact of different fisheries management options on the objectives of the Common Fisheries Policy (CFP). The study developed robust methods to a) define target and bycatch species and b) to divide the bycatch species into valuable and collateral bycatch species, the first generally retained on board and landed and the latter generally discarded. The classification of a species depended on the fleet and area in which the fleet operates. The study also identified species which can only sustain low levers of fishing and proceeded to include examples of these in mixed fisheries models. After the development of stock assessments, reference points and mixed fisheries management strategy evaluation models for a variety of stocks, the study identified the species for which annual catch limits of target species would be sufficient to ensure sustainable exploitation even in the absence of species specific management actions. Then it proceeded to identify measures that will lead to the sustainable development of the bycatch stocks and agreed reference levels to safeguard stocks. The measures included various combinations of single species annual catch limits and annual catch limits afor groups of species on target and valuable bycatch species, gear modifications and spatial management under different implementations of the landing obligation. The management strategy evaluations showed major differences in the results between different implementations of the landing obligation. Under the current implementation, fisheries remained relatively unchanged but a variety of stocks, with cod as the most prevalent example in the Celtic Sea and greater North Sea, remained fished at levels above the level consistent with the maximum long term yield and with a risk of impairing recruitment that exceeded 5%. In contrast, the study found that enforcing the landing obligation fully would safeguard the stocks, but would lead to so-called ‘choke species’ effects. A ‘choke species’ is a species for which the catch opportunity restricts the catches of one or more other species caught together with this species beyond what is compatible with fishing at the levels that provides the maximum sustainable yield of these other species. The ‘choke species’ issue leads to prolonged closures of most demersal fisheries with subsequent socio-economic impacts. The predicted effect of various measures targeted at reducing catches of choke species was mitigated by associated increases in effort as fishing became less effective for several species at the same time. A possible exception to this was gear changes applied to the nephrops fishery. In general, no scenarios predicted stock recovery of all stocks without an associated reduction in fishing effort.