Synthesis of ProByFish modelling approach and the effect of TACs for target species on bycatch species

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. 

This report describes the work under the study to analyse of effect of TACs for target species on fishing mortalities of hybrid, valued and collateral bycatch species assuming different management strategies to define TACs for the target species, while no management applies on the bycatch species. The analyses were conducted in a mixed fisheries Management Strategy Evaluation (MSE) framework to examine the probability that single stock TACs are sufficient under natural variability, mixed fishery dynamics and management strategies. The result shows that the effect of changing the species on which to define a TAC are minor compared to the effects concerning the uncertainty around the implementation of the landing obligation.