Existing and alternative approaches to reducing bycatch of marine mammals

• Main Author: Werner, Timothy Bowen
• Other Authors: Kaufman, Les, Schneider, Chris
• Format: Thesis
• Language: English
• Published: 2024
• Subjects: Wildlife conservation; Fisheries sustainability; Incidental take; baleen whales; Eubalaena glacialis; North Atlantic; North Atlantic right whale
• Online Access: https://hdl.handle.net/2144/48125

Commercial fishing results in the incidental capture, injury, and mortality of marine mammals. Often, this occurs at levels constituting an existential threat to individual populations or species. One solution to this global problem is gear modification, which is generally the preferred strategy of the fishing industry. Gear modifications can sometimes achieve bycatch reduction, but commonly suffer from several important limitations: (a) they are often narrowly focused on individual species or populations, have limited applicability to others, and often carry risks to other marine species and ecosystems; (b) they may be implemented in the absence of adequate scientific assessment of their efficacy; (c) testing new gear can actually subject threatened species to increased bycatch risk, a problem compounded by the extreme difficulty of obtaining adequate sample sizes; and (d) a disproportionate focus of this work occurs in developed countries, even though most of the world’s fishing sector (98%) is located in developing countries, as are many of the marine mammals threatened by bycatch. Here, I present global reviews of techniques for reducing marine mammal bycatch in gillnets, and for large whales in multiple gear types. Next, I present results from a field study in a small-scale non-industrial gillnet fishery, in which the catch and bycatch are compared between traditional gillnets and an alternative gear (pots). The most commercially valuable fish species were caught in both, however with differences in size class selectivity. Switching gears may represent a more promising approach than making incremental modifications to existing ones. Lastly, I employ a new computer model that simulates conflicts between the endangered North Atlantic right whale (Eubalaena glacialis) and fishing lines. The model examined their tensile strength under different entanglement scenarios, as an aid for evaluating the potential of using ropes with reduced breaking strength that are practical for fishing but allow large baleen whales ...