The capture of seabirds and marine mammals in New Zealand non-commercial fisheries

Citation

Abraham, E. R., Berkenbusch, K. N., & Richard, Y. (2010). The capture of seabirds and marine mammals in New Zealand non-commercial fisheries. New Zealand Aquatic Environment and Biodiversity Report No. 64. 52 p.

Summary

Little is known about the nature and extent of incidental captures of seabirds and marine mammals in non-commercial fisheries, either in New Zealand or globally. In New Zealand, participation in recreational fishing is high. A recent survey estimated that 16.5% of the adult population go saltwater fishing during a year, with 2.5% of the adult population (81 000 people) fishing at least once during a week. Because of the intensity of recreational fishing, a small rate of interactions between individual fishers and birds or mammals may have a population-level impact. This report includes a literature review, a brief summary of relevant information from available data sources (including the Hector's dolphin database, and the bird banding database), and the results of a boat ramp survey that sought to quantify how frequently birds were caught by line fishers.

The literature review found three studies that had specifically focused on the catch of protected species in recreational fisheries. All three studies were of set netting, including a study of the catch of shags in nets set in Otago Harbour, a study of the catch of yellow-eyed penguins in set nets in southern New Zealand, and a study of the catch of Hector's dolphin in set nets in Banks Peninsula. During the Otago Harbour study, all seabird captures were recorded in nets set at Portobello over an eight year period. Spotted shags were the most frequently caught species, with the author suggesting that in the worst summer up to 20% of the local population may have been caught in set nets within the harbour. In the studies of yellow-eyed penguins and Hector's dolphins it was also believed that the set net mortalities were having a population level impact on the species concerned.

The literature also contains a range of other examples of seabirds and marine mammals being caught by a variety of recreational fishing methods. As part of the Ornithological Society of New Zealand beach patrol scheme, records are kept of beach cast birds, including those that show evidence of having been killed from fishing. These records encompass a wide range of species, years, and locations, confirming that seabird hookings and entanglements are a common occurrence throughout New Zealand. The Department of Conservation bird banding database contains over 600 records of bands that were returned from fishing. There was little information that could be used to determine whether these birds are caught from recreational or commercial fishing, however. Records of sea lions with hooks and traces consistent with recreational fishing were obtained from the Department of Conservation in Otago.

A boat ramp survey was carried out in collaboration with Blue Water Marine Research during the summer of 2007—08. During the survey, 763 interviews were conducted (654 on the northeast coast, and 109 in Otago). This survey has provided the first quantitative information on the rates of seabird capture by recreational fishers, as well as information on the nature of the interactions. Across all the survey, 47% of fishers recalled witnessing a bird being caught at some stage in the past, and there were 21 birds caught on the day of the interview. This was equivalent to a capture rate of 0.22 (95% c.i.: 0.13 to 0.34) birds per 100 hours of fishing. Observers on 57 charter trips also recorded seabird captures, with a capture rate of 0.36 (95% c.i.: 0.09 to 0.66) birds per 100 fisher hours, similar to the rate found during the boat ramp surveys.

In the northeastern region there were an estimated 4.8 (95% c.i.: 4.4 to 5.2) million fisher hours line fishing from trailer boats in 2004—05. Applying the seabird capture rate from the interviews to this effort results in an estimate of 11 500 (95% c.i.: 6600 to 17 200) bird captures per year. Applying the capture rate to an available estimate of recreational fishing effort in all New Zealand suggests that the number of annual captures in recreational fishing may be 40 000 birds. Although the number of interactions is high, the birds were reported as unharmed in 77% of the capture incidents that were recalled, and only three people reported incidents where the bird died. Because of the qualitative nature of the survey, the fate of birds that have been hooked or tangled remains unclear.

The most frequently reported type of bird caught were petrels, followed by seagulls. Captures of albatrosses, shags, gannets, penguins, and terns were also recalled. The only capture reported from Otago on the day of the boat ramp interview was of an albatross.

Management of the impacts of recreational fishing on protected species has been focused on spatial restrictions, with set net bans being implemented to protect Hector's and Maui's dolphins. There are also opportunities for line fishers to mitigate seabird captures, including ensuring that weighted baits leave the surface rapidly, using barbless hooks, and carrying dehooking equipment to help free hooked birds. For fishers to change their behaviour, they must be made aware of the potential impacts of recreational fishing on seabird populations. Aside from Hector's dolphins, there is currently little attention given by New Zealand governmental or non-governmental agencies to reducing the impacts of recreational fishing on protected species. The scale of the potential problem suggests that the recreational catch of seabirds and marine mammals should have an increased focus.