Bycatch Estimates of Dugongs and Dolphins: Results from an Interview Survey of Fishermen in Brunei Bay, Malaysia

Abstract

Bycatch refers to the unintentional capture of non-targeted animals during fishing activities.  Worldwide, bycatch poses a significant threat to marine mammal species. In the Southeast Asian region, information on bycatch is particularly scarce, and there is little indication that the issue is adequately addressed anywhere in the region. To address this knowledge gap, we conducted face-to-face interview surveys across fishing communities in the Malaysian side of the Brunei Bay. We collected two datasets of marine mammal bycatch incidences from two different groups of fishermen (N=90 of 356 reported dugong data, 0.3%, and N=62 of 146 reported dolphin data, 0.4%), to estimate the levels of mortalities of the marine mammals. More than four fifths (82.1%) of respondents reported that they have accidentally captured at least one marine mammal (25.0% dugong and 42.5% dolphin) throughout their lifetime as a fisherman, with the highest frequency of occurrence being reported by fishers using gillnets (53.5% and 38.7%, respectively). Our interview results suggest an annual bycatch of 0.22 (95% CI = 0.13 to 0.32) for dugongs and 0.65 (95% CI = 0.40 to 0.88) for dolphins in the Malaysian Brunei Bay. Findings from this study provides important data to guide fisheries resource managers in providing protection and conservation efforts the endangered marine mammal populations.