The research has shown that mussel seed fishing has a short-term effect on biodiversity. This effect consists primarily of the removal of mussels and their associated predators, such as the beach crab and starfish.
Benthic animals larger than 5 mm were collected with a suction sampler. In total, 41 species were identified on the 40 research locations. Besides the mussel, the most important species were the beach crab, the ragworm, the sand gaper, the American razor shell, the sea anemone, the starfish, the barnacle and the shrimp. The exotic species of Japanese shore crab and Japanese oyster were found in more than 30% of the samples.
The box core was used to collect samples of burrowing benthic animals larger than 1 mm. In total, 140 species were identified. Significant short-term effects were determined for the total density; higher numbers of individuals were found in the sections closed to fishing. The effects of mussel seed fishing differ between the spring and autumn fisheries. More than one year after the spring fishery, more species were found in the open sections, but one year after the autumn fishery, no differences were observed.
In total, 24 fish species were identified on the open and closed sections; the dominant species were goby, butterfish and plaice. It appears that some fish species increase in density after fishing, while other species decrease. Species that increase after fishing are: butterfish, goby, eelpout, small and large pipefish, snailfish, shorthorn sculpin and fivebeard rockling. Increases were also observed in the numbers of plaice, small sand eel, flounder and sole, but these were not statistically significant.
The conclusion is that the effects of the fishery on benthic animals and fish are directly related to the effects on the mussels themselves and the development of the mussel stocks. In addition, many other factors affect the composition of the benthic animal community.