Impacts of fishing on Hector's dolphins Impacts of fishing on New Zealand sea lions New Zealand fur seals and fisheries                                     Impacts of fishing on Hector's dolphins Bycatch of Hector's dolphins has been a serious conservation problem since the early 1970s, due to the introduction of nylon monofilament nets and mechanical net-hauling. The nylon replaced natural fibres which rotted if the nets were lost, whereas nylon nets persist in the water for considerably longer and therefore continue to entangle dolphins, whales and seabirds. Mechanical net-hauling means that boats can handle far larger nets than they used to. In depth research into Hector’s dolphin bycatch started in 1984. Over 230 Hector's dolphins were killed in commercial and amateur gillnets around Banks Peninsula between 1984 and 1988. Population studies indicate that the maximum population growth rate is about 2% and that the number caught in gillnets far exceeded the potential for population growth. As a result of this research, the Department of Conservation created a sanctuary in order to reduce the bycatch of Hector's dolphins. Within the Banks Peninsula Marine Mammal Sanctuary commercial gillnetting is banned year-round and recreational gillnetting is banned during summer when the dolphins are found closest to shore. Recent research indicates that the sanctuary is not large enough to allow the population to recover. Substantial numbers of dolphins are still caught immediately north, south and offshore of the sanctuary. The sanctuary needs to be extended considerably to reduce dolphin entanglements to a sustainable level. The North Island population of Hector's dolphin, also known as Maui’s dolphin, is critically endangered. Recent research shows that the population numbers just over 100 individuals. A protected area has been created to reduce the level of gillnet bycatch for this population. Ongoing concerns include the fact that trawling is not restricted in the protected area, Maui’s dolphins range further south than the protected area and the harbours are not included. Research in the Manukau Harbour shows that Maui’s dolphins regularly use the harbour and that their movements extend well beyond the protected area, where gillnets are banned. Research is now expanding to include the other North Island harbours within the range of Maui’s dolphin. Our most recent risk analysis indicates that under current management Hector's dolphins would continue to decline, to 5,475 (CV 0.20) by 2050. If fisheries mortalities are reduced to zero, populations would recover to 15,411 (CV 0.16) by 2050. This has recently been confirmed by research carried out by National Institute for Water and Atmosphere in collaboration with the fishing industry. Their corresponding estimates are 5,631 and 14,650. The NIWA/fishing industry analysis estimates that there are currently 110-150 Hector's and Maui's dolphins killed in commercial gillnets each year. Plus an unknown number in trawl nets and recreational gillnets. A sustainable level of bycatch, calculated using a method developed by the US National Marine Fisheries Service is less than 10 individuals per year. More detailed summary of recent research on threats to Hector's dolphins Key researchers: Liz Slooten, Steve Dawson, Trudi Webster, Will Rayment, Judy Rodda, Silvia Scali, Elanor Hutchinson, Andrew Gormley                                       Impacts of fishing on New Zealand sea lions The endemic New Zealand sea lion Phocarctos hookeri (also known as Hooker's sea lion) is one of the world's rarest pinnipeds, and has a highly localised distribution. Most of the population is found in the Auckland Islands although some animals disperse as far as the New Zealand mainland, Campbell Island and occasionally Macquarie Island. The species is classified as "threatened" by the IUCN and is a protected species under the NZ Marine Mammal Protection Act. The Auckland Islands population is under threat from bycatch in the Southern Squid fishery that operates on the Auckland Islands shelf. Little is known about the life history of the New Zealand sea lion. This study is quantifying adult female survival and reproductive rates, as well as investigating other behavioural and life history characteristics. It is possible to estimate survival rates, assess the stability of the population and provide information on reproductive rate from population age structure over a short period compared with traditional approaches of long term population monitoring. Through the investigation and calculation of age structure and population parameters it is possible to gain a better understanding of the status and impacts on this threatened species. Key researcher: Simon Childerhouse                                                                                                                         New Zealand fur seals and fisheries Marine mammals, especially seals and sea lions are seen by commercial fishers as competitors for fish. In New Zealand concern about the number of fur seals, and their impact on fishing has led to periodic calls for the population to be culled. At present this species is protected in New Zealand waters, except for bycatch in fishing. New Zealand fur seal numbers appear to be increasing, and they have been found to be re-colonising part of their earlier habitat. As a result, the Department of Conservation contracted us to carry out research into NZ fur seal diet to investigate whether the species is having an impact on target fishing species. Data for this study were derived from seal scats and vomits collected from colonies in the Foveaux Straight area, the Snares Islands, and in northern Fiordland. The data gathered from this work are more complete as they were collected over several seasons. Seals eat a commercially fished species of arrow-squid, however they target a much smaller size than is gathered by the fishing industry, and their other prey species are of little or no interest to commercial and recreational fishers. The conclusions of this study were made available to conservation managers, and for public education. Bycatch of marine mammals in fishing operations has become an issue of great international concern. The last twenty years have seen a spectacular increase in middle depth and deepwater trawl fisheries in New Zealand, with a corresponding increase in the bycatch of marine mammals. Substantial numbers of New Zealand fur seals and New Zealand sea lions are killed in these fisheries each year. Data on the population biology of both species are limited and because of this the impact of the bycatch cannot be estimated reliably. Key parameters which are currently unknown for both species include age at sexual maturity, birth rate, maximum age, and annual survival rate. Current population size of fur seals is also unknown. Key researcher: James Holborow   References Bejder, L. and Dawson, S.M. Abundance, residency and habitat utilisation of Hector's dolphins in Porpoise Bay, New Zealand. New Zealand Journal of Marine and Freshwater Research 35: 277-287. 2001. Bräger, S., Dawson, S.M., Slooten, E., Smith, S., Stone, G.S. and Yoshinaga, A. Site fidelity and along-shore range in Hector’s dolphin, an endangered marine dolphin from New Zealand. Biological Conservation 108: 281-287 (2002) Burkhart, S.M. and Slooten, E. Population viability analysis for Hector's dolphin (Cephalorhynchus hectori): A stochastic population model for local populations. New Zealand Journal of Marine and Freshwater Research 37: 553-566 (2003) Cameron, C., Barker, R., Fletcher, D., Slooten, E. and Dawson, S. Modelling survival of Hector’s dolphins around Banks Peninsula, New Zealand. Journal of Agricultural, Biological and Environmental Statistics 4(2): 126-135 (1999) Darby, J.T. and Dawson, S.M. Incidental bycatch of yellow-eyed penguins (Megadyptes antipodes) in gillnets in New Zealand waters 1979-1997. Biological Conservation 93(3): 327-332. 2000 Dawson, S., Pichler, F., Slooten, E., Russell, K. and Baker, C.S. The North Island Hector’s dolphin is vulnerable to extinction. Marine Mammal Science 17 (2): 366-371 (2001) Dawson, S.M. 2002. Cephalorhynchus dolphins. pp. 200-203 in: “Encyclopedia of Marine Mammals” (Perrin, W.F., Würsig, B. & Thewissen, J.G.M, eds.). Academic Press. San Diego. 2002 [ISBN 0-12-551340-2] Dawson, S.M. and Lusseau, D. Pseudoreplication problems in studies of dolphin and porpoise reactions to pingers. Marine Mammal Science 21(1). 175-176. 2005 Dawson, S.M. and Slooten, E. Management of gillnet bycatch of cetaceans in New Zealand.  Journal of Cetacean Research and Management  7: 59-64 (2005) Dawson, S.M. Dolphins and whales. Pp.336-338 in The Natural History of Southland (Darby, J.T, Fordyce, R.E, Mark, A., Probert, K., and Townsend, C.R. eds), Otago University Press. Dunedin. 2003. [ISBN 877133-51-5] Dawson, S.M., Read, A. and Slooten, E. Pingers, porpoises and power: Uncertainties with using pingers to reduce bycatch of small cetaceans. Biological Conservation 84(2): 141-146 (1998) Dawson, S.M., Slooten, E., DuFresne, S., Wade, P. and Clement, D. Small-boat surveys for coastal dolphins: Line-transect surveys for Hector's dolphins (Cephalorhynchus hectori). Fishery Bulletin 201: 441-451 (2004) Dickie, G.S, and Dawson, S.M. Age, growth and reproduction in New Zealand fur seals. Marine Mammal Science 19(1): 173-185. 2003. Fletcher, D., Dawson, S. and Slooten, E. Designing a mark-recapture study to allow for local emigration. Journal of Agricultural, Biological and Environmental Statistics 7(4): 1-8 (2002) Gormley, A.M., Dawson, S.M., Slooten, E. and Bräger, S. Capture-recapture estimates of Hector’s dolphin abundance at Banks Peninsula, New Zealand. Marine Mammal Science 21: 204-216 (2005) Martien, K.K., Taylor, B.L., Slooten, E. and Dawson, S. A sensitivity analysis to guide research and management for Hector’s dolphin. Biological Conservation 90: 183-191 (1999) McConkey, S.D., Lalas, C., and Dawson, S.M. Moult and changes in body shape and pelage in known-age male New Zealand sea lions. New Zealand Journal of Zoology 29:53-61. 2002. Pichler, F., Baker, C.S., Dawson, S.M. and Slooten, E. Geographic isolation of Hector’s dolphin populations described by mitochondrial DNA sequences. Conservation Biology 12(3): 676-682 (1998) Pichler, F.B., Slooten, E. and Dawson, S.M. Hector’s dolphins and fisheries in NZ: a species at risk? Pages 153-173 In: Marine mammals and humans: towards a sustainable balance. N.J. Gales, M.A. Hindell & R. Kirkwood (eds), Collingwood,  Victoria, CSIRO (2003) Rayment, W., Dawson, S.M., Slooten, E. and Childerhouse, S.J. Offshore distribution of Hector’s dolphin at Banks Peninsula.  Department of Conservation Research and Development  Series, 232, 23 p. (2006) Slooten, E. Conservation management in the face of uncertainty: Effectiveness of four options for managing Hector's dolphin bycatch. Endangered Species Research 3: 169-179 (2007) www.int-res.com/journals /esr/esr-home/ Slooten, E., Dawson, S.M. and Rayment, W.J. Aerial surveys for coastal dolphins: Abundance of Hector’s dolphins off the South Island west coast, New Zealand. Marine Mammal Science 20: 117-130 (2004) Slooten, E., Dawson, S.M., Rayment, W.J. and Childerhouse, S.J. A new abundance estimate for Maui’s dolphin: What does it mean for managing this critically endangered species?  Biological Conservation 128: 576-581 Available online 18 November (2005) Slooten, E., Dawson, S.M., Rayment, W.J. and Childerhouse, S.J. Distribution of  Maui’s dolphin, Cephalorhynchus hectori maui. New Zealand Fisheries Assessment Report 2005/28,  21p. Published by Ministry of Fisheries, Wellington (2005) Slooten, E., Fletcher, D. and Taylor, B.L. Accounting for uncertainty in risk assessment: Case study of Hector's dolphin mortality due to gillnet entanglement. Conservation Biology 14: 1264-1270 (2000) Slooten, E., Rayment, W.J. and Dawson, S.M. Offshore distribution of Hector’s dolphins at Banks Peninsula: Is the Banks Peninsula Marine Mammal Sanctuary large enough?  New Zealand Journal of Marine and Freshwater  Research 40(2): 333-343 (2006)