Chagos feels the pinch: assessment of holothurian (sea cucumber) abundance, illegal harvesting and conservation prospects in British Indian Ocean Territory

Abstract

ABSTRACT1. Data are analysed from visual censuses of shallow-water holothurians (sea cucumbers) in 72 shallow water transects 100 m  2 m within four atolls of Chagos. Mean holothurian abundance in Diego Garcia, where harvesting is absent, was 18.5 individuals/transect (all transects) and 55.4 individuals/transect (only those containing holothurians). In the three exploited atolls, mean abundance did not exceed 3.5 and 5.2 individuals/ transect, respectively.2. Comparison with data collected during this study and an earlier investigation reveals a marked decline over four years in both mean and maximum density of commercially valuable Stichopus chloronotus and Holothuria atra in Salomon and Peros Banhos, both exploited atolls, and also for Holothuria nobilis in the latter.3. Holothurian counts were also made along an extensive transect (21 km  4 m) encircling Salomon atoll. Abundance showed highly significant negative correlation with fishing pressure, the latter estimated using an ordinal (0-3) scale (R s 5 À0.605, Pp0.01). Harvesting effects were not discernible using data from 200 m 2 transects.4. While recent studies have shown Chagos is virtually pristine regarding contaminant levels, its holothurian resources are under increasing pressure. Results from this study, and examination of Sri Lanka's fishing activity in distant waters, point to heavy and illegal harvesting.5. Stronger measures are needed to control the illegal fishery, to prevent holothurian abundances falling to the nonsustainable levels now prevalent across much of the Indo-Pacific, and to ensure that Chagos remains a biodiversity hotspot and environment of international renown. Use of smaller surveillance vessels would facilitate this.

Reef shark declines in remote atolls highlight the need for multi‐faceted conservation action

“…It is not clear if this variation corresponds to changes in poaching activity in the territory or simply reflects reduced search effort or better avoidance on the part of poachers. It was estimated that the fishery patrol vessel had a success rate of$10% several years ago, with the actual number of poaching vessels, taking sharks and holothurians, working in the archipelago being 30-60 per year (Price et al, 2009). Vessels that are caught fishing often have a large quantity of shark carcasses in their hold (Figure 3).…”

“…A British Indian Ocean Territory Patrol Vessel, whose main activities are fisheries patrols and border protection, has actively patrolled the archipelago since 1996, charged with managing the Mauritian inshore fishery and offshore tuna fishery and detecting illegal fishing vessels. Illegal vessels come principally from Sri Lanka, which visit the archipelago to target sharks (Anderson et al, 1998) and Beche de Mer (Spalding, 2006;Price et al, 2009).…”

Measuring and monitoring compliance in no‐take marine reserves

“…; Price et al . ). Quantities of illegal take were available from law enforcement records in the Mediterranean (Linares et al .…”

“…; Price et al . ). In the marine environment, dynamite blast craters and discarded fishing gears can be recorded as indicators of illegal activity (Guard and Masaiganah ; Russ and Alcala ; Chiappone et al .…”

Coral Reefs of the United Kingdom Overseas Territories

“…Observations were made in 1996, 2006, and 2010 at 20 sites in the outer atolls, and one in Diego Garcia as part of rapid environmental assessments (Price 1999 ;Price and Harris 2009 ;Price et al, in prep.). Driftwood and lost timber from ships was low on beaches in all years, but decreased over time from 1996 to 2006, attributed to use for fuel by illegal fi shing camps on the islands during this period of increasing fi shing pressure (Price and Harris 2009 ;Price et al 2010 ) . 500 m (along the beach) to 250 m 'inland' from the shore.…”