Register      Login
Marine and Freshwater Research Marine and Freshwater Research Society
Advances in the aquatic sciences
Shopping Cart: ( empty )
You are here: Home > Journals > MF > MF09303
RESEARCH ARTICLE
Contents Vol 61(9)

Demographic analysis of the pelagic thresher shark, Alopias pelagicus, in the north-western Pacific using a stochastic stage-based model

Wen-Pei Tsai A C , Kwang-Ming Liu B D and Shoou-Jeng Joung A
+ Author Affiliations
- Author Affiliations

A Department of Environmental Biology and Fisheries Science, National Taiwan Ocean University, Keelung 202, Taiwan.

B Institute of Marine Affairs and Resource Management, National Taiwan Ocean University, Keelung 202, Taiwan.

C Current address: Institute of Oceanography, National Taiwan University, Taipei 106, Taiwan.

D Corresponding author. Email: kmliu@mail.ntou.edu.tw

Marine and Freshwater Research 61(9) 1056-1066 https://doi.org/10.1071/MF09303
Submitted: 3 December 2009  Accepted: 2 April 2010   Published: 23 September 2010

Abstract

The pelagic thresher shark, Alopias pelagicus, like most large sharks produces a low number of offspring (two embryos per litter). However, there is no accurate information on its population status. To improve the accuracy of population simulations, a stochastic stage-based birth-flow model was constructed to assess the stock status of the pelagic thresher in the north-western Pacific. Based on the best biological information available, its life history was represented as four stages: neonates, juveniles, subadults, and adults. Results indicated that, without mortality from fishing, the stock would clearly increase (mean annual population growth rate (λ) = 1.058 year–1, 95% CI = 1.014–1.102 year–1). When current fishing mortality was taken into account, a decrease in population was indicated (λ = 0.979 year–1, 95% CI = 0.921–1.030 year–1) with a projected reduction of 34.3% over 20 years. These results suggest that the stock is overexploited. Simulations using various management measures showed that the population will remain steady under these protection options. However, this species is extremely vulnerable to overexploitation and is especially sensitive at the juvenile and adult stages, implying that nursery closures or size limit management measures are urgently needed to ensure the sustainable utilisation of the stock.

Additional keyword: stock assessment.


Acknowledgements

We would like to thank Dr Chi-Lu Sun of National Taiwan University and Dr Sheng-Ping Wang of National Taiwan Ocean University for their constructive suggestions. We acknowledge Nanfangao and Chengkung Fishermans Associations for providing the longline shark catch and weight data. We also thank three anonymous reviewers for their helpful comments, which greatly improved this manuscript. This study was financially supported by the National Science Council of the Republic of China under Contract No. NSC96-2313-B-019-008 and NSC97-2313-B-019-002-MY2.


References

Aires-da-Silva, A. , and Gallucci, V. F. (2007). Demographic and risk analyses applied to management and conservation of the blue shark (Prionace glauca) in the North Atlantic Ocean. Marine and Freshwater Research 58, 570–580.
| Crossref | GoogleScholarGoogle Scholar | Au D. W., Smith S. E., and Show C. (2008). Shark productivity and reproductive protection, and a comparison with teleosts. In ‘Sharks of the Open Ocean: Biology, Fisheries and Conservation’. (Eds E. K. Pikitch and M. Camhi.) pp. 298–308. (Blackwell Publishing: Oxford.)

Branstetter S. (1990). Early life-history implications of selected carcharhinoid and lamnoid sharks of the northwest Atlantic. In ‘Elasmobranchs as Living Resources: Advances in the Biology, Ecology, Systematics, and the Status of the Fisheries’. (Eds H. L. Pratt, S. H. Gruber and T. Taniuchi.) pp. 17–28. (US Department of Commerce: Washington, DC.)

Brewster-Geisz, K. K. , and Miller, T. J. (2000). Management of the sandbar shark, Carcharhinus plumbeus: implications of a stage-based model. Fishery Bulletin 98, 236–249.
Burgman M. A., Ferson S., and Akçakaya H. R. (1993). ‘Risk Assessment in Conservation Biology. Population and Community Biology Series 12.’ (Chapman & Hall: London.)

Cailliet, G. M. (1992). Demography of the central California population of the leopard shark (Triakis semifasciata). Australian Journal of Marine and Freshwater Research 43, 183–193.
| Crossref | GoogleScholarGoogle Scholar | Campana S., Joyce W., Marks L., and Harley S. (2001). Analytical assessment of the porbeagle shark (Lamna nasus) population in the northwest Atlantic, with estimates of long-term sustainable yield. Canadian Stock Assessment Research Document 2001/067, Ottawa, Ontario.

Carlson, J. K. , and Baremore, I. E. (2002). Changes in biological parameters of Atlantic sharpnose shark, Rhizoprionodon terraenovae, in the Gulf of Mexico: evidence for density-dependent regulation? NAFO SCR Document 02/128. (North Atlantic Fisheries Organization: Darmouth, Canada.)  ,
Caswell H. (2001). ‘Matrix Population Models. Construction, Analysis, and Interpretation.’ 2nd edn. (Sinauer Associates: Sutherland, MA.)

Chen, S. , and Watanabe, S. (1989). Age dependence of natural mortality coefficient in fish population dynamics. Nippon Suisan Gakkai Shi 55, 205–208.
Compagno L. J. V. (1984). ‘FAO Species Catalogue. Vol. 4. Sharks of the World. An Annotated and Illustrated Catalogue of Shark Species Known to Date.’ FAO Fisheries Synopsis, No. 125, Vol. 4, Part 2, pp. 251–655. (FAO: Rome.)

Cortés, E. (1995). Demographic analysis of the Atlantic sharpnose shark, Rhizoprionodon terraenovae, in the Gulf of Mexico. Fishery Bulletin 93, 57–66.
Cortés E. (2004). Life-history patterns, demography, and population dynamics. In ‘Biology of Sharks and their Relatives’. (Eds J. C. Carrier, J. A. Musick and H. R. Heithaus.) pp. 449–470. (CCR Press: Boca Raton, FL.)

Cortés, E. (2007). Chondrichthyan demographic modeling: an essay on its use, abuse, and future. Marine and Freshwater Research 58, 4–6.
| Crossref | GoogleScholarGoogle Scholar | Ebert T. A. (1999). ‘Plant and Animal Populations: Lessons in Demography.’ (Academic Press: San Diego, CA.)

Ehrlén, J. , van Groenendael, J. , and de Kroon, H. (2001). Reliability of elasticity analysis: reply to Mills et al. Conservation Biology 15, 278–280.
Heppell S. S., Crowder L. B., and Menzel T. R. (1999). Life table analysis of long-lived marine species with implications for conservation and management. In ‘Life in the Slow Lane: Ecology and Conservation of Long-lived Marine Animals. Proceedings of American Fisheries Society Symposium 23, Bethesda, MD’. (Ed. J. A. Musick.) pp. 137–148. (American Fisheries Society: Bethesda, MD.)

Heppell, S. S. , Pfister, C. , and de Kroon, H. (2000a). Elasticity analysis in population biology: methods and applications. Ecology 81, 605–606.
Lassen H., and Medley P. (2001). Virtual population analysis – a practical manual for stock assessment. FAO Fisheries Technical Paper 400. (FAO: Rome.)

Liu, K. M. , and Chen, C. T. (1999). Demographic analysis of the scalloped hammerhead, Sphyrna lewini, in the northwestern Pacific. Fisheries Science 65, 219–224.
Liu K. M., Chen C. T., and Joung S. J. (2001). A study of shark resources in the waters off Taiwan. In ‘Proceedings of the Joint Taiwan-Australia Aquaculture and Fisheries Resources and Management Forum’. (Eds I. C. Liao and J. Baker.) pp. 249–256. (Taiwan Fisheries Research Institute: Keelung, Taiwan.)

Liu, K. M. , Chang, Y. T. , Ni, I. H. , and Jin, C. B. (2006). Spawning per recruit analysis of the pelagic thresher shark, Alopias pelagicus, in northeastern Taiwan waters. Fisheries Research 82, 56–64.
| Crossref | GoogleScholarGoogle Scholar | Otter Research (2007). ‘An Introduction to AD Model Builder Version 4 for Use in Nonlinear Modeling and Statistics.’ (Otter Research: Sidney, BC.)

Pauly, D. (1980). On the interrelationships between natural mortality, growth parameters, and mean environmental temperature in 175 fish stocks. Journal du Conseil International pour l’Exploration de la Mer 39, 175–192.
Simpfendorfer C. A. (1999). Demographic analysis of the dusky shark fishery in southwestern Australia. In ‘Life in the Slow Lane: Ecology and Conservation of Long-lived Marine Animals. Proceedings of American Fisheries Society Symposium 23, Bethesda, MD’. (Ed. J. A. Musick.) pp. 149–160. (American Fisheries Society: Bethesda, MD.)

Sminkey, T. R. , and Musick, J. A. (1995). Age and growth of the sandbar shark, Carcharhinus plumbeus, before and after population depletion. Copeia 1995, 871–883.
| Crossref | GoogleScholarGoogle Scholar | Smith S. E., Rasmussen R. C., Ramon D. A., and Cailliet G. M. (2008b). The biology and ecology of thresher sharks (Alopiidae). In ‘Sharks of the Open Ocean’. (Eds E. K. Pikitch and M. Camhi.) pp. 60–68. (Blackwell Publishing: Oxford, UK.)

The MathWorks (2000). ‘Using MATLAB. Version 6 (Release 12).’ (The MathWorks, Inc.: Natick, MA.)

Wang, S. P. , Sun, C. L. , Punt, A. E. , and Yeh, S. Z. (2007). Application of the sex-specific age-structured assessment method for swordfish, Xiphias gladius, in the North Pacific Ocean. Fisheries Research 84, 282–300.
| Crossref | GoogleScholarGoogle Scholar |