Appraisal of the whelk Buccinum undatum fishery of the Southern Irish Sea with proposals for a management strategy

A small occasional fishery for whelk in the southern Irish Sea expanded in the early 1990s, particularly in 1993, to provide meat for the Far East. Between 1990 and 1993 the weight of whelk delivered by a fisherman to factory per day remained stable but the fishing effort increased by 44%. The quality of landings declined, increasing proportions of smaller whelk being retained. The most heavily fished populations apparently display a Lee effect. An age at length key was prepared from 3,081 individuals and is used to transform length to age frequencies within the area of interest. The weight compositions of graded samples, abstracted from processors' financial accounts, were converted to population numbers. The age of full recruitment is reckoned to be five years over the area of interest although it may fall to four in the most intensely fished whelk patches. A Thompson-Bell yield per recruit curve has Fmax at F=0.3. Only one fishery, at the northern fringes of the fishing area, has an F value (read from the catch curve) of less than this. F values of fisheries at the centre and south of the exploited area are all situated on the negative slope of the yield per recruit curve. Male maturation occurs at a length of 70 - 80 mm in the least and 50 mm in the most exploited populations. Thus, a measure to protect broodstock would require a size limit of approximately 70 - 80 mm which would, coincidentally, approximate the size for maximum sustainable yield. It would also have a catastrophic effect on the existing fisheries. A size limit of 50 mm is already in force