The Biology and Population Ecology of Nautilus pompilius at Osprey Reef, Coral Sea and the conservation implications of international Nautilus fishing

Andrew Dunstan (2011). The Biology and Population Ecology of Nautilus pompilius at Osprey Reef, Coral Sea and the conservation implications of international Nautilus fishing PhD Thesis, School of Biomedical Sciences, The University of Queensland.

       
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Author Andrew Dunstan
Thesis Title The Biology and Population Ecology of Nautilus pompilius at Osprey Reef, Coral Sea and the conservation implications of international Nautilus fishing
School, Centre or Institute School of Biomedical Sciences
Institution The University of Queensland
Publication date 2011-12
Thesis type PhD Thesis
Supervisor Professor Justin Marshall
Professor Peter Ward
Total pages 239
Total colour pages 49
Total black and white pages 190
Language eng
Subjects 06 Biological Sciences
Abstract/Summary The chambered Nautilus is represented by two extant genera, Nautilus Linnaeus and Allonautilus Ward and Saunders. Species and sub-species of these genera are the subject of speculation as to their threatened status arising from the impacts of targeted fishing for the ornamental shell, jewellery and exotic food market. At present there is a group of nautilid experts communicating with the U.S Fish and Wildlife Service to assess whether such concerns are valid and whether any species of these two genera fit the criteria necessary for listing in the Appendices of the Convention on International Trade in Endangered Species (CITES). This PhD thesis provides current scientific information required by this expert group to enable assessment of the status of nautilid populations. This includes nautilid growth rates, population estimates, movement, localised distribution, fishery impacts and social development and livelihood values of Nautilus fisheries. It also provides a new insight into the life of Nautilus in the wild. Trapping for Nautilus was conducted at Osprey Reef (Coral Sea, Australia) from 1998 - 2008, on 417 occasions, with 2673 individuals of one species, Nautilus pompilius, captured and 252 individuals recaptured. Baited remote underwater video systems (BRUVS) were deployed on 15 occasions and six remotely operated vehicle (ROV) dives from 100-800 m were conducted to record Nautilus presence and behaviour. Maturity, sex and size data were recorded, while measurements of recaptured individuals allowed estimation of growth rates to maturity, and longevity beyond maturity. Sexual dimorphism in size at maturity (males: 131.9SD = 2.6 mm; females: 118.9 7.5 mm shell diameter) was described in a population dominated by mature individuals (58%). Mean growth rates of 15 immature recaptured animals were 0.061 0.023 mm day-1 resulting in an estimate of around 15.5 years to maturation. Recaptures of mature animals after more than five years provided evidence of a lifespan exceeding 20 years. Using program MARK, a small and dispersed population of between 844 and 4467 individuals (14.6-77.4 km-2) dominated by males (83:17 male:female) and comprises few juveniles (<10%) was determined for Osprey Reef N. pompilius. These results provide the first nautilid population and density estimates which are essential elements for long-term management of populations via sustainable catch models. Results from BRUVS deployments now provide confidence for their more widespread use to assess efficiently the size and density of exploited and unexploited Nautilus populations worldwide. Ultrasonic telemetry techniques were employed to track eleven specimens of Nautilus pompilius for variable times ranging from one to 78 days at Osprey Reef, Coral Sea, Australia. Combined with the observational records from ROV dives, the resulting data suggest continuous, nightly movement between depths of 130 to 700 m, with daytime behaviour split between either stasis in relatively shallow (160 to 225 m) depths and active foraging in depths between 489 and 700 m. The findings also extend the known habitable depth range of Nautilus to 700 m, demonstrate juvenile distribution within the same habitat as adults and document daytime feeding behaviour. These data support an hypothesis that, contrary to previously observed diurnal patterns of shallower at night than day, more complex vertical movement patterns may exist in at least this, and perhaps all other Nautilus populations. The studies of Nautilus pompilius at Osprey Reef reveal that this unexploited population is stable from a catch per unit effort (CPUE) basis over 10 years. In contrast, data from a detailed interview questionnaire of Nautilus pompilius fishers and traders in Palawan, Philippines highlight a fishery that is unsustainable. The results from the Philippines show up to 80% declines in reported CPUE from 1980 to the present, fewer than two Nautilus generations, which can be attributed to fishing pressure. Questionnaire responses suggested there is no cultural or historical relevance of Nautilus fishing to local Palawan communities and the fishery only provides approximately 10 - 20 years of economic return before becoming non-viable. Identification of new Nautilus fishing sites and training of locals by buyers from distant depleted fishing areas illustrate how the demand for Nautilus shells has generated this fishing pressure. These findings demonstrate that the Palawan population of Nautilus pompilius fits the criteria for listing as ‘ENDANGERED’ in the International Union for Conservation of Nature (IUCN) Red List and fulfils the requirements for listing within Appendix 1 and 2 of CITES. This project has also developed the techniques to allow rapid and cost-effective estimation of nautilid population density and to gather valuable survey data on fishery catch rates and social value of fishing to the community. The use of Baited Remote Underwater Video Systems is proposed to measure attraction times, numbers and speed of movement of Nautilus to ultimately determine population density and to derive population estimates. These methods form the basis for future research proposed to fill the gaps in knowledge of chambered Nautilus and Allonautilus required for informed decision-making about conservation management.
Keyword Nautilus, population estimates, growth rates, vertical migration, diurnal, fisheries, CITES, demography, Osprey Reef, Coral Sea
Additional Notes 1, 14, 15, 30, 34, 48, 49-50, 52, 54-58, 61, 63, 65, 68, 70, 74, 78-79, 88, 94, 97, 99, 101, 121, 124-127, 130, 132-133, 142, 144, 147-148, 165, 168, 180, 182, 191, 201, 205, 208, 217-218

 
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Created: Thu, 05 Jan 2012, 15:49:18 EST by Mr Andrew Dunstan on behalf of Library - Information Access Service