Hampus Eriksson

Potential influence of sea cucumbers on coral reef CaCO3 budget: A case study at One Tree Reef

To endure, coral reefs must accumulate CaCO3 at a rate greater or equal than the sum of mechanically, biologically, and chemically mediated erosion rates. We investigated the potential role of holothurians on the CaCO3 balance of a coral reef. These deposit feeders process carbonate sand and rubble through their digestive tract and dissolve CaCO3 as part of their digestive process. In aquarium incubations with Stichopus herrmanni and Holothuria leucospilota total alkalinity increased by 97 ± 13 and 47 ± 7 μmol kg−1, respectively. This increase was due to CaCO3 dissolution, 81 ± 13 and 34 ± 6 μmol kg−1 and ammonia secretion, 16 ± 2 and 14 ± 2μmol kg−1, respectively, for these species. Surveys conducted at a long-term monitoring site of community calcification (DK13) on One Tree Reef indicated that the density of sea cucumbers was approximately 1 individual m−2. We used these data and data from surveys at Shark Alley to estimate the dissolution of CaCO3 by the sea cucumbers at both sites. At DK13 the sea cucumber population was estimated to be responsible for nearly 50% of the nighttime CaCO3 dissolution, while in Shark Alley for most of the nighttime dissolution. Thus, in a healthy reef, bioeroders dissolution of CaCO3 sediment appears to be an important component of the natural CaCO3 turnover and a substantial source of alkalinity as well. This additional alkalinity could partially buffer changes in seawater pH associated with increasing atmospheric CO2 locally, thus reducing the impact of ocean acidification on coral growth.

Contagious exploitation of marine resources

Global seafood sourcing networks are expanding to meet demand. To describe contemporary fishery expansion patterns, we analyzed the worldwide exploitation of sea cucumber (Echinodermata: Holothuroidea) traded via Hong Kong for consumers in China. In just 15 years (1996–2011), the sea cucumber sourcing network expanded from 35 to 83 countries; sea cucumber fisheries serving the Chinese market now operate within countries cumulatively spanning over 90% of the worlds tropical coastlines. The emergence of such fisheries in nations where they were previously absent could not be explained either by their national governance capacity or by their distance from Hong Kong. Surging imports from these new fisheries have compensated for declines in long-standing fisheries elsewhere. The case of commercial sea cucumber trade for the Chinese market exemplifies a new global extraction phenomenon that we call contagious resource exploitation – a fast-moving system resembling a disease epidemic, where long-distance transp...

Mobility, Expansion and Management of a Multi-Species Scuba Diving Fishery in East Africa

Background Scuba diving fishing, predominantly targeting sea cucumbers, has been documented to occur in an uncontrolled manner in the Western Indian Ocean and in other tropical regions. Although this type of fishing generally indicates a destructive activity, little attention has been directed towards this category of fishery, a major knowledge gap and barrier to management. Methodology and Principal Findings With the aim to capture geographic scales, fishing processes and social aspects the scuba diving fishery that operate out of Zanzibar was studied using interviews, discussions, participant observations and catch monitoring. The diving fishery was resilient to resource declines and had expanded to new species, new depths and new fishing grounds, sometimes operating approximately 250 km away from Zanzibar at depths down to 50 meters, as a result of depleted easy-access stock. The diving operations were embedded in a regional and global trade network, and its actors operated in a roving manner on multiple spatial levels, taking advantage of unfair patron-client relationships and of the insufficient management in Zanzibar. Conclusions and Significance This study illustrates that roving dynamics in fisheries, which have been predominantly addressed on a global scale, also take place at a considerably smaller spatial scale. Importantly, while proposed management of the sea cucumber fishery is often generic to a simplified fishery situation, this study illustrates a multifaceted fishery with diverse management requirements. The documented spatial scales and processes in the scuba diving fishery emphasize the need for increased regional governance partnerships to implement management that fit the spatial scales and processes of the operation.

Sea Cucumber Aquaculture in the Western Indian Ocean: Challenges for Sustainable Livelihood and Stock Improvement

The decline in sea cucumber fisheries that serve the Asian dried seafood market has prompted an increase in global sea cucumber aquaculture. The tropical sandfish (Holothuria scabra) has, in this context, been reared and produced with mixed success. In the Western Indian Ocean, villagers often participate in the export fishery for sea cucumbers as a source of income. However, with a growing concern of depleted stocks introduction of hatcheries to farm sandfish as a community livelihood and to replenish wild stocks is being promoted. This review identifies and discusses a number of aspects that constitute constraints or implications with regard to development of sandfish farming in the region. The conclusion is that for sandfish farming to live up to its expectations the possible impacts need to be further studied, and that improved evaluation of ongoing projects is required. In the interim, a precautionary approach toward new enterprise activities is suggested.

Livelihoods and Fisheries Governance in a Contemporary Pacific Island Setting

Inshore marine resources play an important role in the livelihoods of Pacific Island coastal communities. However, such reliance can be detrimental to inshore marine ecosystems. Understanding the livelihoods of coastal communities is important for devising relevant and effective fisheries management strategies. Semi-structured household interviews were conducted with householders in Langalanga Lagoon, Solomon Islands, to understand household livelihoods and resource governance in fishing-dependent communities. Households were engaged in a diverse range of livelihoods. Fishing, shell money production and gardening were the most important livelihoods. Proximity to an urban centre influenced how households accessed some livelihoods. Perceptions of management rules varied and different reasons were cited for why rules were broken, the most common reason being to meet livelihood needs. Current models of inshore small-scale fisheries management that are based on the notion of community-based resource management may not work in locations where customary management systems are weak and livelihoods are heavily reliant on marine resources. An important step for fisheries management in such locations should include elucidating community priorities through participatory development planning, taking into consideration livelihoods as well as governance and development aspirations.

Echinoderms piggybacking on sea cucumbers: benign effects on sediment turnover and movement of hosts

Abstract Sea cucumbers (Holothuroidea) are known to host ectocommensal animals but echinoderm epibionts have never been reported nor their effects on hosts appraised quantitatively. At one location in New Caledonia, we found a high number of ophiuroids (Ophiothela cf. danae) and synaptid sea cucumbers (Synaptula media and Synaptula sp.) living on the bumpy external body wall of sea cucumbers, Stichopus herrmanni. Rates of midday sediment defecation (mean: 23 g h−1) and short-term displacements (mean: 60 cm h−1) by the hosts were not significantly affected by the number of echinoderm commensals they carried. The frequent relationships at the location suggest that such facultative commensalism between echinoderms could be more common than previously understood. Appreciable numbers of scaleworms, crabs and shrimps on the sea cucumbers show that sea cucumbers can act as hosts to echinoderms and other epibiotic taxa, bolstering the notion that they play important ecological roles in reef ecosystems.

Lessons for resource conservation from two contrasting small-scale fisheries

Abstract Small-scale fisheries present challenges to management due to fishers’ dependency on resources and the adaptability of management systems. We compared social-ecological processes in the sea cucumber fisheries of Zanzibar and Mayotte, Western Indian Ocean, to better understand the reasons for resource conservation or collapse. Commercial value of wild stocks was at least 30 times higher in Mayotte than in Zanzibar owing to lower fishing pressure. Zanzibar fishers were financially reliant on the fishery and increased fishing effort as stocks declined. This behavioral response occurred without adaptive management and reinforced an unsustainable fishery. In contrast, resource managers in Mayotte adapted to changing fishing effort and stock abundance by implementing a precautionary fishery closure before crossing critical thresholds. Fishery closure may be a necessary measure in small-scale fisheries to preserve vulnerable resources until reliable management systems are devised. Our comparison highlighted four poignant lessons for managing small-scale fisheries: (1) diagnose the fishery regularly, (2) enable an adaptive management system, (3) constrain exploitation within ecological limits, and (4) share management responsibility.

Rotational harvesting is a risky strategy for vulnerable marine animals

Sea cucumber fisheries exemplify resource systems under intense exploitation pressure from lucrative Asian markets. Plaganyi et al. (1) model the performance of rotational harvests of sea cucumbers on the Great Barrier Reef (GBR) and advocate it globally. We support their aim to evaluate management models but believe the tenets of the strategy are flawed, key model inputs bias the outputs, and inferences to other coastal fisheries are overreaching. These shortcomings set a risky approach for managing coastal resources, especially those with vulnerable life-history traits, such as sea cucumbers (2).

Chinese trader perceptions on sourcing and consumption of endangered seafood

Growing trade networks through globalisation have expanded governance of local environments to encompass multiple scales. The governing role of market actors, such as traders and consumers in importing countries, has been recognized and embraced for sustainable seafood sourcing and trade. The perceptions that affect the conduct of these actors are a potential influence on governance of distal environments. In this paper we investigate the perceptions of sea cucumber traders in China. Sea cucumbers are an important global fishery commodity predominantly traded to China, the world’s largest seafood market, and seven traded species are endangered globally. We examine what traders and consumers in China perceive as important issues in seafood markets, and where they perceive the responsibility for sustainable fisheries to lie, to interpret what scope there is for sustainability to become an important issue in China’s seafood markets. We find that clusters of perceptions about cultural status, quality, health and food safety, and country of origin influence decisions that consumers make. These norms are rooted in sociocultural practice and drive current trade strategies. While traders do want to mitigate risks and secure supplies, food safety, product quality and country of origin are viewed as more important concerns than stock sustainability. Responsibility for sustainable fishing is perceived to be that of national governments in production countries. Trading practices and consumer perceptions together pose a serious challenge to sustainable seafood markets, further confounded by clandestine cross-border grey trade into China.