Phase III – Sea Cucumbers, a poorly understood but important resource: National and Regional Analyses to Improve Management

Sea cucumbers are ecologically and economically important in fisheries as well as potential valuable for aquaculture. In the western Indian Ocean (WIO) sea cucumbers have been traded for centuries and support coastal livelihoods primarily of artisanal fishers. Increased global demand for the processed product (beche-de-mer and trepang) led to overfishing and the reduction in sea cucumber stocks in most nations of the WIO. The primary responses to overfishing have been bans on harvesting and gear restrictions, yet knowledge to underpin these fisheries interventions were often lacking. The project therefore aimed at addressing two broad objectives: (i) to document and evaluate the knowledge available on sea cucumbers in the region in order to gain an understanding of the challenges of sea cucumber fishery in order to guide future research and management interventions. (ii) to fill key gaps in information by conducting research studies on the ecology and biology of sea cucumbers, and socioeconomics of sea cucumbers fishery in five countries in the WIO region. The project was implemented in Kenya, Madagascar, Reunion, Seychelles and Tanzania. Targeted beneficiaries included local communities, scientific community, decision and policy makers, fisheries and conservation managers as well as donors.

Several methods were applied to cover various topics under study. (i) Species inventories were conducted using a comprehensive literature search and field surveys that included walks in shallow lagoons, and snorkeling or SCUBA diving in deeper waters, (ii) Belt transects and timed-search sampling methods were deployed to estimate abundance of sea cucumber, (iii) Sea cucumber samples for biological and reproductive studies were also collected, (iv) Questionnaires, semi-structured interviews, key informant interviews, focus group discussions and network analysis were used to obtain data on socio-economics aspects and fisheries.

Results revealed that the WIO region has a rich and diverse fauna of sea cucumbers. Patterns of biodiversity indicated relatively similar species and diversity in the Comoros (40 species), Kenya (44 species), Reunion (37 species), the Seychelles (35 species) and Tanzania (26 species). Madagascar was the most speciose with 125 species, which is more than three times the number of species in other countries. Sea cucumbers were ubiquitous and common throughout the studied sites but the distribution and abundance were highly variable ranging from less than 1 to 2500 indiv.ha^-1 depending on the species and the site. The most common species were H. atra and H. leucospilota that occurred in the highest densities in Kenya, Reunion and Zanzibar. Although no new species were recorded in the present study several samples were collected during the surveys that require taxonomic investigation. Protected reefs on average had significantly higher densities of sea cucumbers than fished reefs.

The project provided new information on the reproduction of several species including the two most highly commercially valuable species H. scabra and H. fuscogilva. There was no significant relationship between the gonad index and the gutted weight in all but one (H. scabra) studied species. The main mode of reproduction for all the studied species was sexual and highly synchronized between the sexes. Production indicated a general decreasing trend in most countries except Madagascar and Seychelles, where production has remained relatively stable in the last decade. Compared to world production, Area 51 that encompasses most of the countries of the WIO and the Red Sea showed a decrease averaging 29.2% of world production between 1994 and 2004 to 7.8% in 2010. Madagascar nevertheless remained the top exporter of trepan from the WIO comprising 40% of the total production for FAO area 51.

The sea cucumber fishery in the WIO is mainly artisanal and was carried out in different depth habitats depending on accessibility and mode of collection. Fishing occurred mainly in the calm northeast monsoons. It was also established that in Kenya the fishery was conducted by males only, while in Madagascar, Zanzibar and Mozambique also females and children were involved. Generally most fishers had no or had very low level of education (a few years of primary education) with a few with secondary education. Licensing for the collection and trade of sea cucumbers was the primary management tool, which occurred in all the countries except Reunion where sea cucumbers have never been exploited and in Tanzania (mainland) where a ban was in force. The analysis showed that except for closures, most of the management interventions were poorly executed and enforced in most of the countries with the exception of the Seychelles where management of the fishery was generally reported to be more effective. The analysis also showed that most of the national management agencies mandated to manage the sea cucumber fishery lacked the capacity to carry out basic management interventions including surveillance, enforcement and monitoring of the fishery which contributed to further overexploitation of the stocks. Information on reproductive parameters (e.g. size at sexual maturity and reproductive seasons) can be used as a basis for some interventions towards sea cucumber fisheries management in the region.

Future studies can focus on reproductive cycles, population sex ratios and the size at sexual maturity for individual species in the different countries as well as knowledge on larval dynamics and connectivity. Other areas for future studies could include data on growth, mortality and recruitment of individual commercial species that are key for constructing fisheries models. Information on many other socioeconomics aspects of the fishery, especially the factors that affect poor peoples’ livelihoods and the relationships between these factors, global trade and its impact on livelihoods amongst others, are needed. Future studies can also focus on molecular genetics on the phylogeny of sea cucumbers including of species in the region in order to tackle several pending taxonomic queries at the same time enhance capacity for genetic studies in the region. Climate change impacts including increased temperatures and ocean acidification may have a negative influence on sea cucumber populations therefore future studies could focus on the full impact of this and the compounding effects of fishing pressure.