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Herrmann, B., Mieske, B., Stepputtis, D., Krag, L. A., Madsen, N., and Noack, T. 2013. Modelling towing and haul-back escape patterns during the fishing process: a case study for cod, plaice, and flounder in the demersal Baltic Sea cod fishery. – ICES Journal of Marine Science, 70: 850–863.The survival likelihood of fish escaping through trawl codends may depend on when they escape. It is therefore relevant to investigate when during the fishing process fish actually attempt to escape and do escape from trawl codends. This subject is addressed by modelling data collected during a specially designed experiment. Results demonstrate that the escape process during towing cannot be described sufficiently by a traditional logistic model or something similar. Instead, a model is required that explicitly considers that not all fish necessarily contact the codend netting to attempt escape during the towing phase. A model that accounts for such behaviour is applied and it is demonstrated that this model can adequately describe the size selection process during towing. The overall escape process, which consists of the attempt probability, partial escape during towing, and partial escape during the haul-back phase, is also modelled. This proposed model sufficiently described the observed escape pattern for cod (Gadus morhua), plaice (Pleuronectes platessa), and flounder (Platichtys flesus). For all three species, a significant percentage of the individuals entering the codends during fishing first attempt to escape during the haul-back operation. [ABSTRACT FROM PUBLISHER]

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Abstract: Due to declining cod (Gadus morhua) stocks, the Baltic Sea was one of the first areas regulated by the European Communities where selective escape windows were implemented to improve the exploitation pattern. Increasing discard rates and the potential for a significant increase of the spawning stock and the yield of the fishery are important reasons to further improve the selectivity of the fishery and to asses the potential next step in this process. In this study, we tested three relatively different design concepts, in the Baltic cod pelagic trawl fishery, that are relevant to past or present legislation and that were developed to meet requirements of increased selectivity performance. A standard nominal 135mm diamond mesh codend, a codend with two nominal 125mm bottom windows, and a codend with a nominal 125mm nominal top window were tested using the covered codend method. A Danish and a Swedish commercial vessel were used for the sea trials to account for potential differences between vessels. Potential differences among the three gear variants were assessed by a two-step mixed effects model. The codend catch weight was found to have a significant effect on the selectivity in some cases. We assessed the actual effect of the selectivity performance on the immediate reductions of the proportions of cod being retained below and above the present minimum landing size (MLS) and a potential increased MLS. [Copyright &y& Elsevier]