Diving into fisher experience: Do new entrants and fleet turnover depress catch rates in abalone (Haliotis laevigata and H. rubra) fisheries

Abstract

A fisher’s experience may provide greater efficiency and enhanced catches through time. Compared to new entrants to the fishery, experienced fishers often have developed tactics: the advantage of knowing ‘the best’ fishing grounds, having established efficient fishing practices, and developing relationships and trust within their fishing community. The influence of experience on catch rates, a key indicator of abundance, may be particularly strong in fisheries such as abalone, which rely on hand-collection and local knowledge for catches. We investigated diver records for greenlip (Haliotis laevigata) and blacklip (Haliotis rubra) abalone fisheries in South Australia to 1) examine annual catch rates (CPUE) and the number of diver entrants among licenses, 2) determine if CPUE of new diver entrants is lower than average fleet CPUE, and 3) establish relationships between CPUE and experience. We additionally simulated fleet turnover in the South Australian Western Zone Abalone Fishery by randomly replacing 25 %, 50 %, and 75 % of daily CPUE records with new diver catch rates and applied decision rules in the proposed abalone harvest strategy that allow for, and if needed account for, the impacts of new divers on catch rates. Catch rates varied among licenses and, on average, each license had less than one diver entrant per year (i.e., on average 5–20 % fleet turnover). During the first three years post-entry, annual license catch rates were generally 3–10 % lower than fleet catch rates, and license CPUE was positively correlated to experience in both greenlip and blacklip fisheries. However, depressed catch rates of entrants were unlikely to impact fleet trends given the small proportion of new entrants annually, and in cases where new divers impact CPUE, the proposed harvest strategy enables adjustment of recommended catches at a fine spatial scale prior to calculating the total allowable commercial catch. Of greater concern is ≥ 50 % fleet turnover, which, during simulations of the Western Zone Fishery, depressed fleet CPUE by ∼1 kg/hr or more; a reduction that is sufficient to result in lower recommended catches and, if such exceptional circumstances were to occur, may require modification of harvest strategy application. Assessing fisher experience as a driver of catch rate, builds a greater understanding of primary indicators for stock assessment and, together with appropriate decision-making tools, provides a more reliable management outcome.