Are depredation rates by reef sharks influenced by fisher behaviour?Published on 17. December 2014
Are depredation rates by reef sharks influenced by fisher behaviour?
Magen Schifiliti, Dianne L McLean, Tim J Langlois, Matthew J Birt, Peter Barnes,
Shark depredation (damage to gear and loss of bait or hooked fish by a non-target species) is a common global occurrence. Depredation events by sharks can have negative impacts for the fishers, fishery targeted species and the sharks. It is, therefore important to better understand if learning behaviour of sharks can influence rates of depredation. Recreational fishers within the World Heritage Ningaloo Reef have reported increased rates of depredation by sharks over the last 5 years. This study aimed to determine if sharks are capable of learning to associate intensive recreational fishing activities with a food reward. We also aimed to test if sharks in areas frequently fished were more habituated to recreational fishing activities than those sharks within a no-take marine sanctuary. To simulate fishing activities baited underwater video systems were deployed in the morning (A.M.), midday, and afternoon (P.M.) for six consecutive days in Fished and Unfished sites. A significant decrease in time of arrival and time to first feed of sharks was seen across days at the Fished sites. The Unfished sites had very low numbers of sharks observed (n=3) and therefore was not statistically analysed. The relative abundance of sharks did not significantly increase across days, however there was a negative correlation between lemon sharks (Negaprion sp.) and whalers (Carcharhinus sp.). Our study suggests sharks are capable of being classically conditioned to recreational fishing activities and depredation rates are influenced by fisher behaviour. We have highlighted possible mitigation strategies designed to un-condition sharks to recreational fishing, including modifying fishing practices, use of deterrents based on the sensitivity of shark senses and management strategies. The best approach is likely to be enabling fishers to become more knowledgeable of how and why shark depredation events happen and take appropriate steps to avoid them.