Risk assessments for Hector´s dolphin Population declines of bottlenose dolphins in Fiordland New Zealand sea lion risk analyses     Risk assessments for Hector's dolphin The most recent risk analysis (Slooten 2007) indicates that Hector's dolphin populations will continue to decline under current management. The latest population size estimate is 7,270 (CV 16%) for the South Island population and 111 (CV 44%) for the North Island population, also known as Maui's dolphins. Just taking into account the number of dolphins that have died from entanglement in commercial gillnets, indicates that these populations have declined from an estimated 29,316 (CV 16%) in 1970. Commercial gillnetting expanded rapidly in New Zealand waters in the early 1970s. Under current management, Hector's dolphin populations would continue to decline to 5,475 (CV 20%) by the year 2050. On the other hand, if fisheries mortality is reduced to zero they would recover to 15,411 (CV 16%) by 2050. A recent population model developed by NIWA, in collaboration with fishing industry scientists, makes very similar predictions. They estimate that over 50 years under current management populations would decline to 5,631 and if fishing mortalities were reduced to zero they would recover to 14,650. For more information on the Otago University analysis see: Slooten, E. 2007. Conservation management in the face of uncertainty: Effectiveness of four options for managing Hector's dolphin bycatch. Endangered Species Research 3: 169-179 www.int-res.com/journals /esr/esr-home/ For more information about the NIWA/fishing industry analysis see: www.fish.govt.nz/en-nz/Consultations/Hector+new/default.htm The Department of Conservation and Ministry of Fisheries are currently working on a Threat Management Plan (a draft of which has been released for public comment). Data on the effectiveness of alternative management options, discussed in Slooten (2007), are crucial in informing the Ministers of Fisheries and Conservation in taking important decisions on improved protection for Hector's and Maui's dolphin. A decision is expected in May 2008. Ongoing work on risk analysis for Hector's dolphin includes: 1. The development of an individual-based model with Dr Paul Wade from the US National Marine Fisheries Service. Liz Slooten presented a talk on this in December 2007, at the International Conference on Marine Mammalogy in Cape Town. 2. Development of an integrated Bayesian model for Hector's dolphin. Key Researchers: Liz Slooten, Andrew Gormley                         Population declines of bottlenose dolphins in Fiordland New estimates of population size for bottlenose dolphins in Doubtful sound indicate that the population is declining. Photographic identifications of individual dolphins were used in a census and Mark-Recapture analysis. The Doubtful Sound population appears to have decreased from 69 adults and subadults (95% confidence interval 68-70) in the summer of 1994/1995 to 44 adults and subadults (95% ci 43-45) in the summer of 2006/2007. Calf survival is particularly poor. Risk analyses using the current level of calf survival indicate that the population is not sustainable. The probability of population decline was estimated at 97%. Conservation management to improve calf survival would need to be implemented as soon as possible, and certainly within 5 years. Otherwise, continued decline becomes more likely than population recovery. Potential causes include disturbance from tourism and freshwater input from the Manapouri Power Station. A possible contributing factor is disturbance from biopsy sampling (not by Otago University). The number of stillbirths was especially high immediately following the biopsy sampling and several of the females who lost their calf had apparently been biopsied. Key Researchers: Rohan Currey, David Lusseau, Steve Dawson, Liz Slooten Several papers on the research results outlined above have been submitted for publication.                               New Zealand sea lion Bycatch of NZ sea lions in the southern trawl fishery for squid has increased substantially over the last 5 years, as the method of calculating the annual allowable bycatch has changed. Until 2004 sealion "quotas" were calculated using a method developed by the US National Marine Fisheries Service. This method was developed over the course of a decade of investigation, by a large team of marine mammal biologists and fisheries scientists. Until 2004 an average of 60-70 sealions were allowed to be caught each year. Since then, the quota has increased to around 100 sealions per year, with limits of 115 and 150 in some years. These bycatch limits are based on a management model jointly developed by NIWA and the fishing industry. Problems with the new way of setting quotas include: 1. The model failed to predict recent reductions in pup numbers. 2. The model has great difficulty estimating original population size and maximum population growth rate, producing biologically unrealistic estimates of both. 3.Pups that dies as a consequence of the mother's death are not included in the analysis. 4. The model ignores the fact that the Auckland Islands sea lion population is a small fraction of the original range of the species. 5. The use of sea lion exclusion devices means that no reliable estimates of current bycatch are available. The increase in allowable catches is surprising, given that recent research on the sealions indicates that the population is declining. Key Researchers: Simon Childerhouse, Liz Slooten   References 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) 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. 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., 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) 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) 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., 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)