Causes of tail fan necrosis in the southern rock lobster, Jasus edwardsii

Abstract

Tail fan necrosis (TFN) is a recognised constraint on the advancement of the South Australian rock lobster (Jasus edwardsii) liveholding industry because of a reduction in value of afflicted lobsters. Trials were run in the laboratory and at a shore-based experimental live-holding facility (LHF) to determine the influence of at-sea post-harvest handling, feeding frequency (LHF only), density (LHF only), and temperature (laboratory only) on the advent of the condition. Lobsters were caught during normal fishing operations and either immediately placed in protective fine-mesh nylon bags and stored in the boat's well or placed unbagged in the well. At the laboratory, the tail fans of half the bagged lobsters were deliberately damaged with sterile instruments. At the LHF the TFN level increased significantly over 4 months. The bagged treatment showed significantly less late-stage TFN than unbagged daily or weekly-fed treatments with 60% of bagged lobsters showing no TFN at 4 months. With unbagged lobsters, 50% showed erosion in the <25% category and 30% showed erosion of >25% of the tail fan. Lobster density and feeding frequency had no effect on TFN incidence. In the laboratory, bagged and bagged-damaged treatments had no advanced TFN after the 6-week period suggesting that post-harvest bagging minimises TFN and that inflicting physical damage to lobster tail fans with aseptic instruments does not lead to its development. Temperature had no effect on TFN development. The highest incidence of TFN was found in lobsters given normal post-harvest handling, that is, communal holding in boat holds and tanks (i.e., without bags). These conditions are normally associated with physical damage inflicted by conspecifics. Such damage will presumably also involve infection of wounds by the bacterial flora of the crayfish exoskeleton, leading to development of TFN. © 2005, Copyright Taylor & Francis Group, LLC.