Værdioptimering af fiskefangsten i dansk blandet fiskeri (VærdiFisk) - forbedret kvalitet og selektion som følge af redskabsudvikling

The FishValue-project (VærdiFisk) led to the development of a vertically divided codend with prospects of increasing the income in the Danish mixed fishery in several ways. Separation of fish and Nephrops (Nephrops norvegicus) in an upper and lower codend, respectively, led to a significant improvement of the quality of fish, fillets and Nephrops compared to the standard codend. With different mesh sizes in the upper and lower codend and use of square meshes in both codends, it was possible to customise the selection of fish and Nephrops separately and at the same time retain the most valuable catch. Design and placement of a grid in the lower codend gave an effective separation of all the four fish species investigated in addition to Nephrops when compared to the first version of the experimental codend.
When separated in a different codend than Nephrops, the skin of both roundfish and flatfish were glossier and lost less scales. Due to increased selectivity in both codends, small individuals were returned to the ecosystem during fishing rather than being discarded. The reduced codend catch weight may explain the reduction in bruises in fish and loss of claws in Nephrops. The best texture was observed in fish and filets from fish caught in the upper codend. A possible explanation for this is a reduction in stress. As shown in previous studies, fish exposed to ante mortem stress can accelerate the onset and resolution of rigor mortis. If this is the case for the fish caught in the upper codend, there may be a potential of prolonging the shelf life of fish caught in trawls.
Fish from the upper codend did not obtain higher prices at the fish auction despite the increased quality. This does not, however, exclude the possibility of obtaining better prices for higher quality as measured by the quality parameters included in this study. There are many factors other than quality that governs the price at the auction, e.g. the amount of fish at the action, the size of the lot where small quantities like the ones in the project typically obtain lower prices, the demand in the market, and the product portfolio of the exporters present.
In addition to being more selective, the experimental codend had 10% higher catch rate of Nephrops compared to the standard codend. This more efficient fishery gives less fuel consumption per kilogram Nephrops caught, and may, if evaluated over longer time periods, imply less impact on the sea bottom than when fishing with the standard codend.