Publications
Prepared by
Biodiversity Group Environment Australia in consultation with the Threat Abatement Team
Environment Australia, 1998
ISBN 0 642 21420 4
There are a number of sources of seabird mortality which arise from interactions with longline vessels, including:
This is the most common form of incidental mortality (Murray et al. 1993). Brothers (1991) documented this mortality in seabirds on Japanese longline vessels operating in the AFZ. The mortality arising from this source is usually quantified by counting birds which are on hooks when the line is hauled. This underestimates the rate of by-catch because:
These two sources of error are significant and are difficult to quantify and serve to reduce the accuracy of by-catch data.
The likelihood of seabirds being caught on longlines depends on the type of fishing activity and gear used. For example, the availability of baited hooks to seabirds depends upon a number of factors, which include the buoyancy of the line and bait, weight on the end of the line, speed of deployment and boat speed and degree of shielding of the line from bird attacks.
Huin and Croxall (in press) record seabirds being hooked during line hauling and either escaping or being released alive. Injuries sustained may account for the injured birds found dying at breeding colonies by Weimerskirch and Jouventin (1987).
Seabirds can become entangled in longline branch lines or collide with the mainline above the water to the stern of the fishing vessel. Brothers (1995) recorded birds being caught on hooks adjacent to the bait they were attempting to catch.
Regurgitated longline hooks have been recorded near albatross nests at South Georgia. It is possible that these hooks come from either:
Brothers (1995) recorded hooks in 9.4% of grenadier discarded as fish by-catch from the south Atlantic Dissostichus fishery. 23% of the discarded heads of the target species in that fishery also contained hooks.
| Fishery | Target Species | Fishing Areas (see diagrams) |
Fishing Seasons | Methods and Equipment | Effort (hooks/yr in 1995/6) |
Relative Rate of Seabird By-catch |
| Foreign (Japanese) Tuna Longline |
Southern Bluefin Tuna (SBT) Thunnus maccoyii, Yellowfin Tuna T. albacores, Big eye Tuna T. obesus and Albacore T. alalunga Broadbill |
SBT - Southern Waters (Tas) Other tuna species - off NSW, Tasmania, WA and Qld |
Dependent on Bilateral Access Agreement but usually May - July SBT. June - Sept other species |
Pelagic drifting horizontal set longlines | East Coast 6.8 million West Coast 1.4 million Tasmania 1.48 million |
High3 |
| Domestic Tuna Longline | Southern Bluefin Tuna Thunnus maccoyii, Yellowfin Tuna T. albacares, Big eye Tuna T. obesus and Albacore T. alalunga Broadbill |
Predominantly near Continental Shelf but expanding seaward | May - Feb SBT. All year with some fishery-by-fishery seasonality |
Pelagic drifting horizontal set longlines | East Coast 3.7 million West Coast 580,000 Tasmania 370,000 |
High3 |
| South East Non Trawl Fishery: Dropline and Trotline |
Deep sea trevalla (blue eye) (Hyperoglyphhe antarctica)
Other finfish species |
Commonwealth waters off southern Qld, NSW, Victoria, SA and Tasmania | Permits are issued 1 January to 31 December (fishing takes place all year round) | Vertically set demersal dropline and trotlines | Low2/ Insufficient data | |
| South East Non Trawl Fishery: Longline |
Ling (Genypterus sp) Other finfish species |
Commonwealth waters off southern Qld, NSW, Victoria, SA and Tasmania | Permits are issued 1 January to 31 December (fishing takes place all year round) | Horizontal set demersal longlines | Low2/ Insufficient data | |
| Southern Shark Fishery: Longline |
School shark (Galeorhinus galeus) & Gummy shark (Mustelos antarcticus) | Commonwealth waters off Victoria, SA and Tasmania | Permits are issued 1 July to 3 June each year (fishing takes place all year round) | Horizontal set demersal longlines | 2.4 million | Low1 |
| Tropical Shark Fishery: Longline |
Tropical pelagic shark species | Northern waters | Surface or floatline set horizontal longline | Unknown |
Table 1 summarises the target fish species, fishing areas, fishing seasons, methods and equipment and effort for oceanic longline fisheries operating in Australian waters. These fisheries vary in their impact on seabirds. Statistically robust data on seabird by-catch are scarce because most data come from observers on fishing vessels tasked with recording data on fishing operations, not on non-fish by-catch. High relative rates of by-catch are defined as being a regularly reported by-catch rate exceeding 0.1birds/1000 hooks. Many fisheries have limited or no interactions with seabirds due to the method of operation or the location of activity.
1 based on anecdotal accounts provided by Tasmanian Parks and Wildlife Service
2 based on documented accounts but insufficient data exists to quantify catch rates with accuracy
3 based on documented accounts and able to be quantified with some degree of accuracy
Given the high parental investment in raising a chick by albatrosses and other seabirds, it is likely that the death of a breeding adult would also result in the death of the egg or chick. In addition, there is often a considerable delay before new partnerships are formed and lower reproductive success in new pairings between albatrosses has been reported. The remaining parent is therefore less likely to breed successfully in the years following the death of their mate.
There have been reports of seabirds being shot by crew on longline vessels and recreational fishers (Adams 1992, Tomkins 1985). The rate or incidence of mortality from shooting is not known. This deliberate take of seabirds is illegal under the Commonwealth National Parks and Wildlife Conservation Act 1975 and equivalent State/Territory legislation.
The distribution of pelagic longline fishing effort in the Australian fishing zone for 1997 is summarised in figures below. These figures were compiled by Australian Fisheries Management Authority.
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