Abstract

The Pitcairn Islands, located in the central South Pacific, contain near-pristine marine ecosystems which support unique fish assemblages, together with both endemic and threatened species. Pitcairn itself is the only inhabited island in the group and, before this study, the environmental impact of local fisheries was unclear, with little data to inform conservation and management. In 2014–2015 coastal fish populations were assessed using a mixed methods approach: a newly introduced system of fishers’ catch monitoring and Baited Remote Underwater Video Systems (BRUVS). Thirty-nine BRUVS deployments recorded 88 species in total, with small-bodied herbivores (e.g., Kyphosus pacificus) and mesopredators (e.g., Xanthichthys mento) dominating a “bottom heavy” assemblage. Several large pelagic predators were recorded, but reef-associated predators were rare with only one shark observed. Pitcairn’s top predator assemblage was relatively impoverished compared to global “pristine” sites, including other islands within the Pitcairn group. Top predator scarcity may be explained by local artisanal fisheries, which have historically targeted sharks and other large reef carnivores, and these taxa may not have recovered despite subsequent declines in fishing pressure. The dominant small-bodied species may have proliferated as a result of diminished top predator populations. Subsequent to BRUVS sampling, a local fisheries officer post was created to collate catch data from coastal fishers. Regular returns were obtained from over half of the active fishers (representing approximately 80% of catches), with K. pacificus also dominating catches and the small grouper Epinephelus fasciatus frequently targeted. Thirty fish species were represented in the recorded catch over a 12 month period. Results were shared with the local community, providing a basis for the cooperative design of a Fisheries Management Plan. This plan ensured traditional fisheries could continue in a sustainable manner within Coastal Conservation Zones around each of the four Pitcairn Islands, established within the large, no-take Marine Protected Area designated in 2016, covering the entire Pitcairn Exclusive Economic Zone. Monitoring of Pitcairn’s artisanal fisheries should be continued beyond this one-off study in order to inform adjustment of the Fisheries Management Plan, as the ongoing island fishery may still have consequences for long-term sustainability, particularly for pelagic species caught in coastal waters which remain a significant data gap.

Highlights

  • The Pitcairn Islands are a UK Overseas Territory (UKOT) consisting of four small, extremely remote islands in the central South Pacific

  • Sampling Effort Forty-two Baited Remote Underwater Video Systems (BRUVS) deployments were completed in the shallow coastal waters of Pitcairn Island (Figure 3), of which 39 produced valid samples

  • Deployment depths ranged from 7 to 33 m and the mean depth sampled was 19 m (± 7.39 sd.) Algae and rock-dominated substrates accounted for 38% and 33% of habitat classifications, respectively, whilst coral and sand accounted for 15% and 13% of classifications. 2,769 individual fishes from 26 families were sampled, 88 species were identified and 95% of individuals were identified to species level, with 3% identified to family level and 2% to genus level, respectively

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Summary

Introduction

The Pitcairn Islands are a UK Overseas Territory (UKOT) consisting of four small, extremely remote islands in the central South Pacific. The islands’ isolation has helped to ensure that their marine ecosystems have remained in near-“pristine” condition, largely unaffected by human activities (Sala et al, 2012), this isolation has contributed to a dearth of available data on the Pitcairn Islands marine environment compared to other UKOTs. Whilst marine species diversity in the Pitcairn Islands is low compared to the Coral Triangle, some 6,000 km to the west, the presence of corals is noteworthy given the islands’ southern location just south of the Tropic of Capricorn, at the south-eastern extreme of the Indo-Pacific province (Irving and Dawson, 2012). The marine ecosystems of the Pitcairn Islands are considered to have “outstanding” value owing to their relatively untouched condition and biological uniqueness (Friedlander et al, 2014)

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