Fishing diseased abalone to promote yield and conservation

Abstract

Past theoretical models suggest fishing disease-impacted stocks can reduce parasite transmission, but this is a good management strategy only when the exploitation required to reduce transmission does not overfish the stock. We applied this concept to a red abalone fishery so impacted by an infectious disease (withering syndrome) that stock densities plummeted and managers closed the fishery. In addition to the non-selective fishing strategy considered by past disease-fishing models, we modelled targeting (culling) infected individuals, which is plausible in red abalone because modern diagnostic tools can determine infection without harming landed abalone and the diagnostic cost is minor relative to the catch value. The non-selective abalone fishing required to eradicate parasites exceeded thresholds for abalone sustainability, but targeting infected abalone allowed the fishery to generate yield and reduce parasite prevalence while maintaining stock densities at or above the densities attainable if the population was closed to fishing. The effect was strong enough that stock and yield increased even when the catch was one-third uninfected abalone. These results could apply to other fisheries as the diagnostic costs decline relative to catch value.

Managing marine disease emergencies in an era of rapid change

“…Direct mitigation of economic impacts of diseases can include revising stock-recruitment fishery models to explicitly account for disease [56] and ensuring biosecurity practices reduce or eliminate transport of infected individuals and product. Both the Pacific herring and Tanner crab industries have used stock assessment models that include disease and adjust allowable catch to account for disease-induced mortality [32,38].…”

Communicating about ocean health: theoretical and practical considerations

“…As discussed in detail elsewhere in this issue [2][3][4], research over the past few decades has documented the existence of infectious diseases afflicting a variety of ocean-dwelling species, including coral reefs [5 -7], abalone [8,9], sea stars [10] and oysters [11], among others. Matters of ocean health are deeply intertwined with the health and well-being of human societies [12], given that oceans provide valuable ecosystem services-including carbon sequestration, coastal erosion protection and valuable animal protein for over a billion of the world's poorest people [13]-that depend on healthy and well-functioning marine ecosystems.…”

Managing marine mollusc diseases in the context of regional and international commerce: policy issues and emerging concerns

“…Weighing the degree of harm along with the likelihood of harm provides a basis for assessing risk that can be used to make informed decisions while following the precautionary principle's guidance of taking action to avoid or reduce harm [72]. Managers and practitioners may ultimately disagree, but risk analysis ensures that there is a rational basis for their disagreement.…”