Quantifying the rare: Baselines for the endangered Napoleon Wrasse, Cheilinus undulatus, and implications for conservation

Abstract

The Napoleon wrasse, an endangered fish (Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix II, 2004), is a valuable component of the Chinese live reef fish trade. Only Indonesia legally exports up to 2000 Napoleon fish annually, with each fish weighing between 1 and 3 kg. Information on natural abundance and fish sizes was required to determine sustainable export quotas. Hence, an underwater visual survey method, using GPS‐based multi‐kilometre transects, was tailored for this uncommon wide‐ranging fish. Transects totalling 430 km were run between 2005 and 2016 at nine locations. Six locations were resurveyed between six and nine years later, which was long enough to allow for recruitment and maturation. Fish density and sizes across locations were inversely related to fishing intensity, and densities increased significantly between surveys. Low density (0.04‐0.86 fish hectare‐1) and few adult‐sized fish were in heavily fished locations. Higher densities occurred (0.86‐4.0 fish hectare‐1) in lightly/unfished locations, where evidence of recruitment was also seen. Nowhere were many male-sized (>1 m long) fish present. At Karas Is., where fishing ceased between surveys, clear sign of recovery was seen after 9 years. Comparison of survey data from 11 Indo‐Pacific countries indicated that in Indonesia adult densities were lower at comparable levels of fishing pressure than elsewhere. Densities of 5 fish hectare−1 or more are more typical of lightly fished or unfished areas across the Pacific, which is greater than the highest density of 4 fish hectare−1 noted in this study at Banda Islands. Low densities of the species, despite the presence of adult‐sized fish, in Bunaken Marine Park probably reflects the continuance of fishing both within and adjacent to the park. Conservation options include improved implementation of CITES regulations by Indonesia, through tighter export controls and the tagging of legally exported fish, the activation of the National Plan of Action, a temporary moratorium to restore reproductive capacity, and more marine protected areas.

The Bird's Head Seascape Marine Protected Area network—Preventing biodiversity and ecosystem service loss amidst rapid change in Papua, Indonesia

“…In both North and South Raja Ampat MPAs, fish biomass increased within sustainable use zones, suggesting that these MPAs are balancing sustainable fishing with biodiversity conservation. Fish biomass trends are not representative of all BHS MPAs, as MPAs with established monitoring programs have greater management capacity, although our results broadly reflect other recent BHS reef fish studies (e.g., Mudjirahayu, Rembet, Ananta, Runtuboi, & Sala, 2017;Brown et al, 2018;Sadovy de Mitcheson, Suharti, & Colin, 2019;Text S3). Global studies have indicated that healthy coral reefs without fishing typically sustain 1,000 kg/ha of fish biomass (Karr et al, 2015;MacNeil et al, 2015;McClanahan et al, 2019), so it is encouraging that North Raja Ampat sustainable fishing areas maintain fish biomass above this level.…”

Isolated reefs support stable fish communities with high abundances of regionally fished species

“…We recorded high abundances of C. undulatus and B. muricatum at the Rowley Shoals; the Cocos (Keeling) Islands were the only other location with a notable number of these species. Both species are sensitive to fishing pressure, being large-bodied, slow-growing, and late-maturing (Bellwood & Choat, 2011;Fenner, 2014;Hamilton et al, 2019;Sadovy de Mitcheson et al, 2019). The ecological roles of these iconic species contribute to healthy ecosystem function.…”

Phylogeography and Conservation Biogeography of the Humphead Wrasse, Cheilinus undulatus

“…Some of the trade out of Indonesia and into Hong Kong and mainland China, the major importers, however, is illegal and in excess of the quota (Wu and Sadovy de Mitcheson 2016), which implies that some of the supplying fisheries are likely to be unsustainable. Studies clearly indicate that overfishing is still occurring despite an export quota and national management measures in place for the species (Sadovy de Mitcheson 2015, Sadovy de Mitcheson et al 2019, although there are some signs of recovery after the CITES listing. Field studies in eight locations over nine years show that, wherever fished, there are few adults, hardly any over 80 cm (i.e., males) and only small numbers of juveniles present (Sadovy de Mitcheson et al 2019).…”

“…Studies clearly indicate that overfishing is still occurring despite an export quota and national management measures in place for the species (Sadovy de Mitcheson 2015, Sadovy de Mitcheson et al 2019, although there are some signs of recovery after the CITES listing. Field studies in eight locations over nine years show that, wherever fished, there are few adults, hardly any over 80 cm (i.e., males) and only small numbers of juveniles present (Sadovy de Mitcheson et al 2019). Adults and abundance levels closer to unexploited levels were only found where the species is unfished or where fishing stopped although recruitment was noted in both lightly and medium fishing pressure sites.…”

“…In both cases, MPAs need to be properly sited, oceanographically, in suitable adult and juvenile habitat (which can include coral reef areas and specific settlement habitats such as Sargassum spp. ), large enough (at least 20 km of reef is recommended; Green et al 2015, Sadovy de Mitcheson et al 2019), and where spawning occurs, especially if these are important sources of eggs and larvae in the region, to conserve this wide-ranging species, and to appropriately manage fishing pressure where the species is exploited.…”