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Population dynamics reveal conservation priorities of the threatened New Zealand sea lion Phocarctos hookeri

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A Comment and reply to this article was published on 21 April 2016

Abstract

Understanding the life history basis of the population dynamics of threatened species is crucial to their assessment and recovery. Within the Southern Pacific Ocean, the decline and range contraction of New Zealand sea lions (NZSLs) (Phocarctos hookeri) are an exemplary case of a major fisheries and conservation controversy. Despite the use of bycatch reduction measures, the main population of the NZSL has declined since 1998 and its vulnerability to threats is poorly understood. Here we develop a population model for the declining population of the endangered NZSL at the Auckland Islands, New Zealand (\(50^{\circ }30^{\prime }\hbox {S}, 166^{\circ }17^{\prime }\hbox {E}\)), parameterised by mark-recapture data of 2928 female NZSLs spanning 15 years from 1998 to 2012, and provide the first comprehensive analysis of NZSL population dynamics and its relationship to life history. Our model closely predicts the observed trend in population censuses of the main breeding population. We found that the population will continue to decline without effective intervention. Furthermore, we found that the population growth rate is most responsive to changes in survival of adult female NZSLs—the demographic group that is most threatened by fishery bycatch. Nevertheless, inferences about the efficacy of NZSL bycatch reduction measures are still imprecise. Combined, this could explain why the main population of NZSLs continues to decline. Our results emphasise that reliable data on bycatch reduction measures are needed, if they are to be shown to protect key demographic groups of marine mammals.

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References

  • Augé A, Chilvers B, Moore A, Mathieu R, Robertson B (2009) Aggregation and dispersion of female New Zealand sea lions at the Sandy Bay breeding colony, Auckland Islands: How unusual is their spatial behaviour? Behaviour 146(9):1287–1311

    Article  Google Scholar 

  • Baker CS, Chilvers BL, Constantine R, Du Fresne S, Mattlin RH, Van Helden A, Hitchmough R (2010) Conservation status of New Zealand marine mammals (suborders Cetacea and Pinnipedia), 2009. NZ J Mar Freshw Res 44(2):101–115

    Article  Google Scholar 

  • Benton TG, Grant A (1999) Elasticity analysis as an important tool in evolutionary and population ecology. Trends Ecol Evol 14:467–471

    Article  CAS  Google Scholar 

  • Breed AC, Plowright RK, Hayman DT, Knobel DL, Molenaar FM, Gardner-Roberts D, Cleaveland S, Haydon DT, Kock RA, Cunningham AA, et al (2009) Disease management in endangered mammals. In: Management of disease in wild mammals. Springer, Berlin, pp 215–239

  • Breen PA, Hilborn R, Maunder MN, Kim SW (2003) Effects of alternative control rules on the conflict between a fishery and a threatened sea lion (Phocarctos hookeri). Can J Fish Aquat Sci 60:527–541

    Article  Google Scholar 

  • Brussard PF (1991) The role of ecology in biological conservation. Ecol Appl 1(1):6–12

    Article  Google Scholar 

  • Castinel A, Duignan PJ, Pomroy WE, López-Villalobos N, Gibbs NJ, Chilvers BL, Wilkinson IS (2007a) Neonatal mortality in New Zealand sea lions (Phocarctos hookeri) at Sandy Bay, Enderby Island, Auckland Islands from 1998 to 2005. J Wild Dis 43(3):461–474

    Article  CAS  Google Scholar 

  • Castinel A, Grinberg A, Patinson R, Duignan P, Pomroy B, Rogers L, Wilkinson I (2007b) Characterization of Klebsiella pneumoniae isolates from New Zealand sea lion (Phocarctos hookeri) pups during and after the epidemics on Enderby Island, Auckland Islands. Vet Microbiol 122:178–184

    Article  CAS  Google Scholar 

  • Caswell H (2001) Matrix population models, 2nd edn. Sinauer Associates, Sunderland

    Google Scholar 

  • Childerhouse S (2014) BPM-14-preliminary report for CSP project 4522 NZ sea lion ground component 2013-14 v.1.1. Tech. rep., Department of Conservation, Wellington, New Zealand

  • Childerhouse S, Gales NJ (1998) Historical and modern distribution and abundance of the New Zealand sea lion Phocarctos hookeri. NZ J Zool 25(1):1–16

    Article  Google Scholar 

  • Childerhouse S, Dawson SM, Fletcher DJ, Slooten E, Chilvers BL (2010) Growth and reproduction of female New Zealand sea lions. J Mammal 91(1):165–176

    Article  Google Scholar 

  • Chilvers BL (2008) New Zealand sea lions Phocarctos hookeri and squid trawl fisheries: bycatch problems and management options. Endanger Species Res 5(2–3):193–204

    Article  Google Scholar 

  • Chilvers BL (2010) POP 2007-01 demographic parameters and at-sea distribution of New Zealand sea lions breeding on the Auckland Islands. Conservation services providers progress report. Tech. rep,Department of Conservation, New Zealand

  • Chilvers BL (2012a) Mortality rates clarified: reply to Breen et al (2012). Polar Biol 35:1619–1620

    Article  Google Scholar 

  • Chilvers BL (2012b) Population viability analysis of New Zealand sea lions, Auckland Islands, New Zealand’s sub-Antarctics: assessing relative impacts and uncertainty. Polar Biol 35(10):1607–1615

    Article  Google Scholar 

  • Chilvers BL (2012c) Using life-history traits of New Zealand sea lions, Auckland Islands to clarify potential causes of decline. J Zool 287:240–249

    Article  Google Scholar 

  • Chilvers BL (2015) Phocarctos hookeri. In: IUCN red list of threatened species (IUCN 2015), Version 2015.2. http://www.iucnredlist.org. Accessed 11 July 2015

  • Chilvers BL, MacKenzie DI (2010) Age- and sex-specific survival estimates incorporating tag loss for New Zealand sea lions, Phocarctos hookeri. J Mammal 91(3):758–767

    Article  Google Scholar 

  • Chilvers BL, Wilkinson IS (2008) Philopatry and site fidelity of New Zealand sea lions. Wildlife Res 35:463–470

    Article  Google Scholar 

  • Chilvers BL, Wilkinson IS, Duignan PJ, Gemmell NJ (2005) Summer foraging areas for lactating New Zealand sea lions Phocarctos hookeri. Mar Ecol Prog Ser 304:235–247

    Article  Google Scholar 

  • Chilvers BL, Robertson BC, Wilkinson IS, Duignan PJ (2007a) Growth and survival of New Zealand sea lions, Phocarctos hookeri: birth to 3 months. Polar Biol 30:459–469

    Article  Google Scholar 

  • Chilvers BL, Wilkinson IS, Childerhouse S (2007b) New Zealand sea lion, Phocarctos hookeri, pup production-1995 to 2006. N NZ J Mar Freshw Res 41:205–213

    Article  Google Scholar 

  • Chilvers BL, Wilkinson IS, MacKenzie DI (2009) Predicting life-history traits for female New Zealand sea lions, Phocarctos hookeri: integrating short-term mark-recapture data and population modeling. J Agric Biol Environ Stat 15(2):259–278

    Article  Google Scholar 

  • Chilvers BL, Amey JM, Huckstadt LA, Costa DP (2011) Investigating foraging utilization distribution of female New Zealand sea lions, Auckland Islands. Polar Biol 34:565–574

    Article  Google Scholar 

  • Collins CJ, Rawlence NJ, Prost S, Anderson CNK, Knapp M, Scofield RP, Robertson BC, Smith I, Matisoo-Smith EA, Chilvers BL, Waters JM (2014) Extinction and recolonization of coastal megafauna following human arrival in New Zealand. Proc R Soc B. doi:10.1098/rspb.2014.0097

    Article  Google Scholar 

  • Connors BM, Cooper AB, Peterman RM, Dulvy NK (2014) The false classification of extinction risk in noisy environments. Proc R Soc B 281:20132935. doi:10.1098/rspb.2013.2935

    Article  Google Scholar 

  • Cox T, Lewison R, Žydelis R, Crowder L, Safina C, Read A (2007) Comparing effectiveness of experimental and implemented bycatch reduction measures: the ideal and the real. Conserv Biol 21(5):1155–1164

    Article  CAS  Google Scholar 

  • Department of Conservation (2009) New Zealand sea lion species management plan: 2009–2014. Tech. rep., Department of Conservation, Wellington, New Zealand

  • Department of Conservation (2014) New Zealand sea lion demographic database. Department of Conservation, Wellington. http://data.dragonfly.co.nz/nzsl-demographics/v20130701/

  • Eberhardt LL (2002) A paradigm for population analysis of long-lived vertebrates. Ecology 83(10):2841–2854

    Article  Google Scholar 

  • Frankham R (1996) Relationship of genetic variation to population size in wildlife. Cons Biol 10(6):1500–1508

    Article  Google Scholar 

  • Fritz LW, Towell R, Gelatt TS, Johnson DS, Loughlin TR (2014) Recent increases in survival of western Steller sea lions in Alaska and implications for recovery. Endanger Species Res 26:13–24

    Article  Google Scholar 

  • Gelman A (2006) Prior distributions for variance parameters in hierarchical models (comment on article by Browne and Draper). Bayesian Anal 1(3):515–534

    Article  Google Scholar 

  • Gimenez O, Rossi V, Choquet R, Dehais C, Doris B, Varella H, Vila JP, Pradel R (2007) State-space modelling of data on marked individuals. Ecol Model 206(3–4):431–438

    Article  Google Scholar 

  • Hamilton SA, Baker GB (2014) Current bycatch levels in Auckland Islands trawl fisheries unlikely to be driving New Zealand sea lion (Phocarctos hookeri) population decline. Mar Freshw Ecosyst Aquat Conserv. doi:10.1002/aqc.2524

    Article  Google Scholar 

  • Hamilton S, Baker GB (2015) Review of research and assessments on the efficacy of sea lion exclusion devices in reducing the incidental mortality of New Zealand sea lions Phocarctos hookeri in the Auckland Islands squid trawl fishery. Fish Res 161:200–206

    Article  Google Scholar 

  • Heppel SS, Caswell H, Crowder LB (2000) Life histories and elasticty patterns: perturbation analysis for species with minimal demographic data. Ecology 81(3):654–665

    Article  Google Scholar 

  • Kissel AM, Palen WJ, Govindarajulu P, Bishop CA (2014) Quantifying ecological life support: the biological efficacy of alternative supplementation strategies for imperiled amphibian populations. Conserv Lett 7(5):441–4500

    Article  Google Scholar 

  • Lande R (1993) Risks of population extinction from demographic and environmental stochasticity and random catastrophes. Am Nat 142(6):911–927

    Article  Google Scholar 

  • Lande R (1994) Risk of population extinction from fixation of new deleterious mutations. Evolution 48(5):1460–1469

    Article  Google Scholar 

  • Le Boeuf BJ, Campagna C (1994) Protection and abuse of young in pinnipeds. Infanticide and parental care. In: Parmigiani S, vom Saal F (eds) pp 257–276

  • Lewison RL, Crowder LB, Read AJ, Freeman SA (2004) Understanding impacts of fisheries bycatch on marine megafauna. Trends Ecol Evol 19(11):598–604

    Article  Google Scholar 

  • Lewison R, Wallace B, Alfaro-Shigueto J, Mangel JC, Maxwell SM, Hazen EL (2013) The biology of sea turtles. CRC Press, Boca Raton

    Google Scholar 

  • Maloney A, Chilvers BL, Muller CG, Haley M (2012) Increasing pup production of New Zealand sea lions at Campbell Island/Motu Ihupuku: Can it continue? NZ J Zool 39(1):19–29

    Article  Google Scholar 

  • Martin TG, Nally S, Burbidge AA, Arnall S, Garnett ST, Hayward MW, Lumsden LF, Menkhorst P, McDonald-Madden E, Possingham HP (2014) Acting fast helps avoid extinction. Acting fast helps avoid extinction. Conserv Lett 5:274–280

    Article  Google Scholar 

  • Melbourne BA, Hastings A (2008) Extinction risk depends strongly on factors contributing to stochasticity. Nature 454(7200):100–103

    Article  CAS  Google Scholar 

  • Meynier L, MacKenzie DDS, Duignan PJ, Chilvers BL, Morel PCH (2009) Variability in the diet of New Zealand sea lions (Phocarctos hookeri) at the Auckland Islands, New Zealand. Mar Mamm Sci 25(2):302–326

    Article  Google Scholar 

  • Mills SL (2012) Conservation of wildlife populations: demography, genetics, and management, 2nd edn. Wiley, Missoula

    Google Scholar 

  • Norris K (2004) Managing threatened species: the ecological toolbox, evolutionary theory and declining-population paradigm. J Appl Ecol 41:413–426

    Article  Google Scholar 

  • Nunney L (1993) The influence of mating system and overlapping generations on effective population size. Evolution 47(5):1329–1341

    Article  Google Scholar 

  • Oosthuizen WC, De Bruyn P, Bester MN, Girondot M (2010) Cohort and tag-site-specific tag-loss rates in mark-recapture studies: a southern elephant seal cautionary case. Mar Mamm Sci 26(2):350–369

    Article  Google Scholar 

  • Oppel S, Hilton G, Ratcliffe N, Fenton C, Daley J, Gray G, Vickery J, Gibbons D (2014) Assessing population viability while accounting for demographic and environmental uncertainty. Ecology 95(7):1809–1818

    Article  Google Scholar 

  • Parsons E, Favaro B, Aguirre A, Bauer AL, Blight LK, Cigliano JA, Coleman MA, Côté I, Draheim M, Fletcher S et al (2014) Seventy-one important questions for the conservation of marine biodiversity. Conserv Biol 28(5):1206–1214

    Article  CAS  Google Scholar 

  • Plummer M (2003) JAGS: a program for analysis of Bayesian graphical models using Gibbs sampling. In: Proceedings of the 3rd international workshop on distributed statistical computing (DSC 2003), pp 20–22

  • Plummer M, Best N, Cowles K, Vines K (2006) CODA: convergence diagnosis and output analysis for MCMC. R News 6(1):7–11

    Google Scholar 

  • Development Core Team R (2011) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna

    Google Scholar 

  • Reijnders PJ, Ries EH, Tougaard S, Nørgaard N, Heidemann G, Schwarz J, Vareschi E, Traut IM (1997) Population development of harbour seals Phoca vitulina in the wadden sea after the 1988 virus epizootic. J Sea Res 38(1):161–168

    Article  Google Scholar 

  • Roberts J, Doonan I (2014) NZ sea lion: demographic assessment of the causes of decline at the Auckland Islands demographic model options—correlative assessment. Tech. rep., NIWA—National Institute for Aquatic and Atmosphere Research, Wellington, New Zealand

  • Robertson BC, Chilvers BL (2011) The population decline of the New Zealand sea lion Phocarctos hookeri: a review of possible causes. Mamm Rev 41(4):253–275

    Article  Google Scholar 

  • Rotella JJ, Link WA, Chambert T, Stauffer GE, Garrott RA (2012) Evaluating the demographic buffering hypothesis with vital rates estimated for Weddell seals from 30 years of mark-recapture data. J Anim Ecol 81(1):162–173

    Article  Google Scholar 

  • Schipper J, Chanson JS, Chiozza F, Cox N, Hoffmann M, Katariya V, Hammond PS (2008) The status of world’s land and marine mammals: diversity, threat and knowledge. Science 322(5899):225–230

    Article  CAS  Google Scholar 

  • Sólymos P (2010) dclone: data cloning in R. R J 2(2):29–37

    Google Scholar 

  • Southwel C (2008) Lobodon carcinophaga, In: IUCN red list of threatened species (IUCN 2013), Version 2013.2. IUCN red list of threatened species downloaded at 26th March 2014. www.iucnredlist.org

  • Su YS, Yajima M (2012) R2jags: a package for running jags from R. R package version 0.03-08. http://CRAN.R-project.org/package=R2jags

  • Tenan S, Pradel R, Tavecchia G, Igual JM, Sanz-Aguilar A, Genovart M, Oro D (2014) Hierarchical modelling of population growth rate from individual capture–recapture data. Methods Ecol Evol 5:606614. doi:10.1111/2041-210X.12194

    Article  Google Scholar 

  • Thompson FN, Berkenbusch K, Abraham ER (2013) Marine mammal bycatch in New Zealand trawl fisheries, 1995–96 to 2010–11. New Zealand aquatic environment and biodiversity report 105, Ministry for Primary Industries—Manatu Ahu Matua, New Zealand

  • Thorpe AS, Stanley AG (2014) Determining appropriate goals for restoration of imperilled communities and species. J Appl Ecol 48:275–279

    Article  Google Scholar 

  • Werner T, Kraus S, Read A, Zollet E (2006) Fishing techniques to reduce the bycatch of threatened marine mammals. Mar Technol Soc J 40(3):50–68

    Article  Google Scholar 

  • Wilkinson I, Burgess J, Cawthorn M (2003) New Zealand sea lions and squid: managing fisheries impacts on a threatened marine mammal, vol 2006, 5th ed, Books Online, pp 192–207

  • Wilmhurst JM, Anderson AJ, Higham TFG, Worthy TH (2008) Dating the late prehistoric dispersal of Polynesians to New Zealand using the commercial Pacific rat. Proc Natl Acad Sci 105(22):7676–7680

    Article  Google Scholar 

  • Wootton JT, Pfister CA (2013) Experimental separation of genetic and demographic factors on extinction risk in wild populations. Ecology 94(10):2117–2123

    Article  Google Scholar 

  • Young TP (1994) Natural die-offs of large mammals: implications for conservation. Conserv Biol 8(2):410–418

    Article  Google Scholar 

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Acknowledgments

This work used data from a long-term study approved by the Department of Conservation Animal Ethics Committee (approval AEC86, 1 July, 1999) and funded through the New Zealand Department of Conservation’s Conservation Services Programme. We thank Scott Jarvie, Cláudia Faustino and Anthony Davidson for helpful and critical comments on the manuscript. We thank the University of Otago for funding. Martin Krkošek thanks the Natural Sciences and Engineering Research Council of Canada.

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  1. B. Louise Chilvers

    Present address: WILDBASE, Institute of Veterinary, Animal and Biomedical Science, Massey University, Palmerston North, New Zealand

Authors and Affiliations

  1. Department of Zoology, University of Otago, PO Box 56, Dunedin, 9054, New Zealand

    Stefan Meyer & Bruce C. Robertson

  2. Department of Conservation, PO Box 10-420, Wellington, 6011, New Zealand

    B. Louise Chilvers

  3. Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada

    Martin Krkošek

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  1. Stefan Meyer
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Correspondence to Stefan Meyer.

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Electronic supplementary material

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227_2015_2695_MOESM1_ESM.pdf

Online Resource A: Model selection on the effect of the breeding status on adult female NZSL survival and recapture 64.0KB

Online Resource B: State and observation process matrices of the CJS model for female NZSLs 140.0KB

Online Resource C (C1 and C2): Posterior distributions of the CJS model for female NZSLs 3.23KB

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Meyer, S., Robertson, B.C., Chilvers, B.L. et al. Population dynamics reveal conservation priorities of the threatened New Zealand sea lion Phocarctos hookeri . Mar Biol 162, 1587–1596 (2015). https://doi.org/10.1007/s00227-015-2695-8

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