Conservation management in the face of uncertainty: effectiveness of four options for managing Hector’s dolphin bycatch

Abstract

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 3:169-179 (2007) - doi:10.3354/esr003169 Conservation management in the face of uncertainty: effectiveness of four options for managing Hector’s dolphin bycatch Elisabeth Slooten* Department of Zoology, University of Otago, PO Box 56, Dunedin, New Zealand *Email: liz.slooten@stonebow.otago.ac.nz ABSTRACT: New Zealand’s endemic Hector’s dolphins Cephalorhynchus hectori overlap with gillnet and trawl fisheries throughout their geographic range. The catch rate in commercial gillnets has been estimated using independent observers. No quantitative estimates are available for bycatch in recreational gillnets or trawl fisheries. The catch rate (per dolphin, per km of gillnet, per year) in commercial gillnets was used in a population viability analysis to estimate past and future population sizes. Total population size today (7873, coefficient of variation [CV] 0.16) was estimated at 27% of population size in 1970 (29316, CV 0.16), before a major expansion of commercial gillnetting. The species matches IUCN criteria for ‘endangered’. The North Island subspecies matches criteria for ‘critically endangered’. Current management, which includes 2 protected areas, is not sufficient to halt population declines. Hector’s dolphin populations are predicted to continue declining to 5475 (CV 0.20) by 2050. Creating 4 strategically placed protected areas would allow population recovery towards 1970 levels, with an estimated 47% probability of reaching 50% of 1970 population size by 2050 (proportion of 5000 model runs in which final population size was at or above this reference level). Reducing fisheries mortality to levels approaching zero shows the strongest promise of meeting national and international guidelines for managing dolphin bycatch, with a 59% probability of reaching 50% of 1970 population size by 2050. KEY WORDS: Hector’s dolphin · Fishing · Bycatch · Extinction · Risk · Population viability Full text in pdf format PreviousNextCite this article as: Slooten E (2007) Conservation management in the face of uncertainty: effectiveness of four options for managing Hector’s dolphin bycatch. Endang Species Res 3:169-179. https://doi.org/10.3354/esr003169Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 3, No. 2. Online publication date: August 02, 2007 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2007 Inter-Research.