4.2. From minimum landing sizes of fish to minimum fishing sizes of fish
Historically, an important element when deciding on minimum mesh sizes in bottom trawl has been the objective of utilising the growth potential of the individual fish, and letting each fish spawn at least once before it is caught [20]. The minimum landing sizes of fish have often been set at levels where on average 75% of the fish below that size are expected to swim through the meshes, whereas 25% are captured (and discarded if the minimum landing size is enforced). The introduction of a discard ban led to a conceptual change with regard to the interpretation and function of permissible minimum sizes of fish. The minimum sizes of the fish that are actually fished have replaced the minimum landing sizes in technical regulations; for example, fishing sizes are crucial elements in the decision rules for RTCs. The focus on reduction of potential discards has also been an invitation to revisit – and if possible harmonise or improve – the connection between mesh sizes, allowed minimum fish sizes and the actual commercial minimum market sizes. For targeted fisheries, for example, there is no obvious reason why it should be legally permissible to take fish that are smaller than what is commercially accepted in the market. Hence, the option of increasing the minimum mesh size in trawls accordingly should be considered. For mixed fisheries the situation is, admittedly, more complex.