POPULATION INDEXES OF REPRODUCTION AND RECRUITMENT IN LOLIGO-FORBESI (CEPHALOPODA, LOLIGINIDAE) IN SCOTTISH AND IRISH WATERS

1. As a preliminary step towards a fishery management strategy for the squid Loligo forbesi, indices of reproduction, egg production and rec ruitment were derived for this species in Irish (1991-93) and Scottish (1990-95) waters to give a quantitative estimate of peaks in spawning and fishery recruitment. 2. The indices were derived by combining lan dings or catch per unit effort (CPUE) data with the estimated proporti ons of mature squid (reproducers) and immature squid (recruits) to giv e an index of the number of squid spawning in and recruiting to the fi shed population each month. 3. The reproductive index peaked between N ovember and December in Irish waters and between December and January in Scottish waters, earlier than predicted by simply examining peaks i n the proportion of mature squid. 4. The index of recruitment showed p eaks in the autumn in both Irish and Scottish waters, but there was al so an additional April peak in Scottish waters. The two periods of rec ruitment in Scottish waters, together with a decrease in the size of m ature females during the spawning season, are not compatible with a si ngle breeding season and possible explanations for this are discussed. 5. By helping to define the timing of the fishing season (to avoid ov erfishing) and by providing estimates of natural mortality (for assess ment of population size), the indices provide important input for popu lation models for fisheries management of squid and short-lived fish s pecies. 6. A possible model for a directed fishery for L. forbesi is p roposed. In the model, the start of the fishing season is delayed to p revent growth overfishing and the season curtailed during spawning to prevent recruitment overfishing. However, on the basis of the indices developed here, this leaves only a narrow time window in which such a fishery could operate.