Illegal and unreported fishing on abalone—Quantifying the extent using a fully integrated assessment model

Illegal, unregulated and unreported (IUU) fishing is a major problem in many of the world's fisheries. The stocks most severely impacted centre on those characterised by high economic value, such as abalone, as well as long lived and slow growing species such as Patagonian toothfish (Dissostichus eleginoides). Effective management of these stocks as well as assessment of the impacts of IUU fishing on the resources is impeded by the technical difficulties associated with determining the magnitude of the IUU catches. The South African abalone Haliotis midae fishery rates as an extreme example of extraordinarily high levels of illegal and unreported (IU) catch. To assess the level and trends in IU catches, we used a combination of approaches that included collation of confiscation records from law enforcement, development of a novel index (the confiscations per unit policing effort—CPUPE), estimation of illegal catches using a spatial and age-structured assessment model, and cross-checking of model outputs through comparison with trade data on abalone imports in destination countries. The model-predicted 2008 IU estimate was 860 tonnes, more than 10 times the total allowable catch (TAC) for that year, and implied that, on average, 14% of all IU catches are confiscated. Associated management responses included the listing of H. midae on Appendix III of CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora), and a temporary closure of the commercial fishery. We summarise both technical and management lessons to be learnt from this integrated approach to assess and verify the magnitude of IU fishing.