Body Scars and Dorsal Fin Disfigurements as Indicators Interaction Between Small Cetaceans and Fisheries Around the Mozambique Channel Island of Mayotte

Abstract

Cetacean bycatch in fisheries occur in all oceans of the world and may have both lethal and non-lethal consequences (body injuries). In the lagoon of Mayotte (12o50’S, 45o10’E), in the northern Mozambique Channel, two main types of fisheries occur: handlining (inside the lagoon) and longlining (outside the barrier reef, over the ‘continental’ slope). The level of interactions between small cetaceans and fisheries in this area were characterised using identification photographs taken from July 2004 to April 2008 during dedicated cetacean surveys. Photographs were taken of Indo-Pacific bottlenose dolphins (Tursiops aduncus), melon-headed whales
(Peponocephala electra) and short-finned pilot whales (Globicephala macrorhynchus). Injuries on the dorsal region (especially the dorsal fin) were characterised and related to fisheries or intra-/inter-specific interactions (with sharks and other cetacean species). The results suggest interactions with fisheries involving the three species around Mayotte. The occurrence of interactions was the highest in the most coastal species, i.e. T. aduncus. This study shows that interactions between fisheries and small cetaceans occur at varying levels around Mayotte. It also confirms the utility of scars as indicators of fishery exposure to cetaceans.