Healthier lobsters in a marine reserve: effects of fishing on disease incidence in the spiny lobster, Jasus edwardsii

Abstract

Comparison of the health of spiny lobsters (Jasus edwardsii) within and adjacent to a New Zealand marine reserve revealed marked differences in the incidence of a handling-related bacterial infection. Lobsters outside the reserve were significantly more affected by tail fan necrosis than lobsters within the reserve, with up to 17% of the males caught outside the reserve over a 3-year period showing signs of tail fan necrosis, compared with less than 2% within the reserve. The incidence of tail fan necrosis changed abruptly at the marine reserve boundaries, strongly implying repeated handling as the causal agent. The incidence of tail fan necrosis in males increased up to the minimum legal size, consistent with a handling effect. Female lobsters, which comprise only a small proportion of the catch in this area, were comparatively unaffected by tail fan necrosis. There was no significant difference in the recapture rates of individuals tagged either with or without tail fan necrosis, but tagged individuals outside the reserve were more likely to develop tail fan necrosis than tagged individuals within the reserve. These findings have implications for both the dynamics of the lobster populations and their management, and highlight the role of marine protected areas in providing a baseline against which such effects of fishing can be assessed.