Determining stock status in a complex, benthic-invertebrate fishery: Accounting for the impact of spatial, temporal and fleet dynamics — ASN Events

Determining stock status in a complex, benthic-invertebrate fishery: Accounting for the impact of spatial, temporal and fleet dynamics (#96)

Stephen Mayfield 1 , Ben Stobart 2 , Owen Burnell 1 , Katherine Heldt 2
  1. SARDI, West Beach
  2. SARDI, Port Lincoln

Abalone stocks support valuable fisheries across southern Australia. Two target species – greenlip (Haliotis laevigata) and blacklip (H. rubra) – form large numbers of stocks across their range, but for pragmatism stock status determination is required at a larger spatial scale (e.g. three zones across South Australia). Assigning zone status is complicated by several factors, including individual stocks likely being at different levels of exploitation and risk of overfishing. This is partly due to abalone being hand-harvested through diving by a small but highly mobile fleet, with fishing location driven by numerous factors including weather, market preference for particular abalone, convenience and abalone abundance. Fleet dynamics also pose challenges for catch rate estimation – a key performance indicator – because it can undermine the link between catch rate and abundance. For example, catch rates can change with the proportion of the target species in the catch, remain high with declining abundance (hyperstability), or be depressed by new entrants (hyperdepletion). Using a greenlip abalone fishery as an example, this study shows how these complexities can be overcome and proposes an approach to determining zonal stock status through accounting for catch rate uncertainty, fleet dynamics and variable levels of depletion among stocks.

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