RECRUITMENT VARIATION IN ABALONE - ITS IMPORTANCE TO FISHERIES MANAGEMENT

Recruitment failure has been implicated in the decline of several abal one fisheries. Traditionally, fisheries scientists invoke theoretical stock-recruitment relationships to predict trends in abundance of an e xploited stock under various harvest regimes. The empirical evidence i n support of a positive relationship between spawning stock and recrui ts is not strong. A further problem in interpretation of such relation ships is that both 'stock' and 'recruitment' have various definitions in fisheries and ecological literature. The definition of a stock for abalone is not clear. As emphasized in this review, which considers ea ch stage in the Life history of abalone, the abundance of spawners is one of many sources of variation in recruitment. The evidence for inve rtebrates, particularly those with high fecundity, is that recruitment varies independently of the abundance of spawners. This is also the c ase for abalone, where recruits have been measured as the density of i mmediate post-settlement individuals, juveniles, or as adults entering the exploitable stock. A problem with stock-recruitment hypotheses is that they have intuitive appeal. It is considered 'dangerous' to mana ge fisheries under the assumption that a reduction in the number of sp awners by fishing will not affect recruitment. Such danger to abalone stocks has been more recently assessed by egg-per-recruit analyses, wh ereby various harvest strategies are examined relative to reference po ints for egg production. These studies are reviewed and assessed relat ive to the often conflicting aims of managers and scientists. This rev iew of studies of recruitment variation in abalone emphasizes the need for a more rigorous, autecological approach to stock assessment in wh ich field experiments are conducted over realistic spatial and tempora l scales, permitting robust testing of hypotheses.