The principal method of fishing for king scallops in Orkney waters is hand collection by divers. Local scallop divers, exploiting small patches of seabed, have reported that these exploited areas are repopulated within the same fishing season, potentially due to immigration from surrounding areas. Studies which quantify the rate of spatial turnover in a scallop population at a small spatial scale have not previously been conducted, and understanding the extent to which scallops move and re-colonise areas could assist in defining a sustainable fishery for scallops in Orkney waters.
Depletion fishing experiments and tagging work was conducted with funding from FISA* to determine the spatial turnover rates of scallops at the scale of individual fishing patches. The main finding of the research was that on average, the scallop population within a previously fished strip of ground 178 m by 4 m increased at a rate of more than 25 % per month due to immigration of scallops, and could be as high as 50 % per month during the summer.
These results suggest that at this small spatial scale, it is possible for a fished ground to be restored to pre-fishing scallop population levels in under a year. This will however depend on the existence of undepleted stocks in areas adjacent to the fishing grounds. Further work is now underway to determine the real implications of this scale of movements on the Orkney scallop stock, which could in turn inform local fisheries management.