Author: Derek J. Hamer

Publisher:

Published: 2012

Total Pages: 317

ISBN-13:

Reports of interactions between marine mammals and fisheries are on the increase globally. This is mainly because fishery effort has increased to feed the burgeoning human population and because advances in technology have allowed fisheries to exploit habitats that were until recently inaccessible. Additionally, many marine mammal populations decimated by harvesting over the past few hundred years are recovering and the growing conservation community is paying unprecedented attention to their welfare and conservation generally, with growing interest in their interactions with fisheries. Operational interactions are conspicuous and involve the close contact of marine mammals with fishing gear, either because marine mammals opportunistically or habitually target fishing activities to depredate (i.e. attempt to consume) caught fish, or because marine mammals incidentally encounter fishing gear while foraging naturally. Operational interactions often result in negative outcomes for the conservation and welfare of the marine mammals involved and for the economic viability of the fisheries involved. Marine mammals that become by-caught may receive life threatening injuries from entanglements, or may drown, thus having adverse impacts on small or recovering populations. Fisheries that are targeted by depredating marine mammals may need to replace damaged fishing gear, or may have the catch partially or completely removed, thus having adverse impacts on their economic viability. At the time this body of work commenced, little was being done to address the known or suspected occurrence of operational interactions between marine mammals and several commercial fisheries in the Oceania region. The general aim was to make significant inroads into addressing thesis, by: 1. Reviewing a major fishing method in the two regions in which there are operational interactions with marine mammals; 2. Characterising the nature and extent of depredation and by-catch where operational interactions are known to exist; and 3. Where deemed necessary in those fisheries, developing mitigation strategies and explore their efficacy. Collectively, the five research chapters in this thesis address these aims. They are stand alone case studies of marine mammal depredation and by-catch in commercial fisheries, four of which have already been published in international, peer reviewed journals. The first three research chapters focus on operational interactions involving odontocetes (i.e. toothed whales) and the second two research chapters focus on the otariids (i.e. eared seals).