Preliminary investigation of the bycatch of marine birds and mammals in inshore commercial fisheries, Victoria, Australia Original Research Article

Incidental captures of non-target species occur during fishing operations: such bycatches include taxa often quite different from anticipated harvests. Bycatch studies in Australia are limited, and none have involved the essentially inshore, Victorian-based marine fisheries. Results from two mail surveys (August 1996, February 1997) are presented. Questionnaires circulated to 510 and 497 fishers sought information regarding gear type, use, location and effort, and bycatches of birds and mammals. Return rates (34 and 26% respectively) suggested a high level of acceptance. While some fishers considered certain fisheries or gear precluded bycatches, others (25 of 175, and 17 of 130 valid responses) indicated that birds, turtles, seals or dolphins were caught. Taxa reported included species which feed by scavenging, plunge diving or pursuit swimming. Numbers involved were usually small, mostly caught in nets and mainly in Port Phillip Bay; while birds often died, mammals (mainly seals) escaped or were usually released alive. Recoveries of banded seabirds in southeastern Australia (including Victoria), and treatment records at a wildlife shelter, provided alternative details on the effects of fishing. Results presumably indicate minimum bycatch levels. More targeted investigations with on-board observers are required before wider extrapolations are warranted. However, recovery details for some species suggest that fishing may represent a, presumably, additional mortality factor.