Fisheries for Ray (Batoidei) in Western statistical area viia, investigated through the commercial catches.

Abstract

The status of the Irish Sea ray fishery is investigated using commercial catches of rays landed into two ports, Howth and Arklow. Approximately 80 45kg boxes were examined monthly over a year when approximately 100 individuals of each of the four contributing species were aged and measured. The species are R. naevus, montagui, clavata and brachyura. These are inter-mixed and casually segregated into four grades on their length. Weighting factors are provided to raise the sampled numbers to total landings. The frequency distribution of grades at the two ports is established from an analysis of some 5,700 commercial transactions. At Arklow, the pattern is stable from one year to another and apparently seasonal. Arklow boats have a short range. The pattern of landings at Howth is more complex; these vessels have a longer range and probably exploit various ages of rays. Growth in all four species occurs most actively during the summer months, slowing down in the winter. Annulus formation is not readily associated with the conventional birth date of 1 January. Coefficients of total mortality (Z) are high for the four species (0.38-1.00), higher than those found in a recent study of rays in Carmarthen Bay. R. brachyura is the most valuable species. R. naevus is the most numerous, possibly because it has a competitive advantage due to its age at full recruitment being one year later than those of the other three species. The yield of rays increases moving offshore and in a southerly direction in the Irish Sea. Landings into Irish ports by Irish vessels have increased between 1903 and 1985 although, until recently, ray as a percentage of total demersal landings was declining, from the 1950s.