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  • 1.
    Eriksson, Hampus
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Managing sea cucumber fisheries and aquaculture: Studies of social-ecological systems in the Western Indian Ocean2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Collecting sea cucumbers to supply the high value Chinese dried seafood market is a livelihood activity available to many people in the Western Indian Ocean (WIO), making it an important part of local economies. These fisheries are generally not successfully managed and tropical sea cucumber fisheries show continuing signs of decline. This thesis takes a social-ecological systems approach to guide better management of sea cucumber fisheries and aquaculture in the WIO. Papers 1 and 2 analyse the fishery situation in Zanzibar and find that in the absence of effective management institutions and income alternatives among fishers, leading to dependence, there are unsustainable expanding processes. Paper 3 compares the unmanaged fishery in Zanzibar to the highly controlled situation in Mayotte. In Mayotte, a protection effect is evident and the commercial value of stocks is significantly higher than in Zanzibar. The analysis of the situation in Mayotte demonstrates the importance of matching the fishery – management temporal scales through prepared and adaptive management to avoid processes that reinforce unsustainable expansion. Paper 4 analyses sea cucumber community spatial distribution patterns at a coastal seascape-scale in Mayotte establishing baseline patterns of habitat utilization and abundance, which can be used as reference in management. Paper 5 reviews the potential for sea cucumber aquaculture in the WIO. The review illustrates that this activity, which is currently gaining momentum, does so based on inflated promises and with significant social-ecological risks. Emphasis for improvements is, in this thesis, placed on the importance of prepared and adaptive institutions to govern and control expanding processes of the fishery. These institutional features may be achieved by increasing the level of knowledge and participation in governance and by integration of sea cucumber resources management into higher-level policy initiatives.

  • 2.
    Eriksson, Hampus
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Sydney, Australia.
    Byrne, Maria
    The sea cucumber fishery in Australia's Great Barrier Reef Marine Park follows global patterns of serial exploitation2015In: Fish and Fisheries, ISSN 1467-2960, E-ISSN 1467-2979, Vol. 16, no 2, p. 329-341Article in journal (Refereed)
    Abstract [en]

    Tropical sea cucumber fisheries follow a predictable pattern of serial depletion. Overfishing is exacerbated in developing countries where management systems lack capacity to control large numbers of fishers influenced by poverty. In contrast, the tropical sea cucumber fishery in Australia's World Heritage listed Great Barrier Reef Marine Park (GBRMP) is operating in a developed high-income country with relatively few licensed fishers to manage. The development of this fishery is reviewed here in a meta-analysis of catches from 1991 to 2011. The fishery expanded to replace high-value teatfish species (Holothuria whitmaei and H.fuscogilva), fished heavily in initial stages of the fishery, with newly commercialized medium-value species such as burying blackfish (Actinopyga spinea) and curryfish (Stichopus herrmanni). These two species now constitute 80% of total catch. The annual average catch of burying blackfish was 208tonnes years 2004-11 and curryfish catches increased rapidly at an average annual pace of 200% from 2007-11. This serial harvest pattern occurred in the absence of baseline studies and without independent resource assessments, information required to inform relevant harvest predictions and to determine fishery impacts. This situation does not support ecologically relevant and adaptive decision-making in management and the unfolding catch patterns in the GBRMP follow those in low-income developing countries. The missing knowledge and lack of data serve as arguments to support precautionary reductions in harvests and extending fallow periods in fishing zones.

  • 3.
    Eriksson, Hampus
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Byrne, Maria
    de la Torre-Castro, Maricela
    Stockholm University, Faculty of Science, Department of Systems Ecology. Stockholm University, Stockholm Resilience Centre.
    Sea cucumber (Aspidochirotida) community, distribution and habitat utilization on the reefs of Mayotte, Western Indian Ocean2012In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 452, p. 159-170Article in journal (Refereed)
    Abstract [en]

    The tropical sea cucumber (Aspidochirotida) fishery for the lucrative Asian dried-seafood trade is a multi-species fishery with little ecological knowledge. To improve ecological understanding of the targeted species, the reefs of Mayotte, Western Indian Ocean, were surveyed to document the distribution, species assemblage and habitat utilization of commercial sea cucumbers. This is one of the few reef areas in the region protected from fishing, thus providing an important and unique opportunity to investigate sea cucumber ecology. Twenty-two species were observed. The medium-value Bohadschia atra and the high-value Holothuria nobilis were the most abundant species. Species distribution varied but the density was generally similar across areas and habitats. Multivariate analysis (ANOSIM) indicated that the community was similar between surveyed areas and reef habitats. Diversity was lower in one of the surveyed areas and in the ocean-facing barrier reef habitat. Habitat complexity was not a significant driver of diversity or abundance. A principal component analysis showed that the 6 most common species (B. atra, Holothuria atra, H. fuscopunctata, H. nobilis and Thelenota ananas) were associated with different substrate types. Clustering these species according to substrate variables indicated both habitat utilization overlap and segregation among species, valuable information for spatial planning of fisheries management and conservation. Although unique species were observed in some areas, the present study shows that, at a large spatial scale, the unfished reefs in Mayotte consist of similar commercial sea cucumber communities, an important baseline finding.

  • 4.
    Eriksson, Hampus
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    de la Torre-Castro, Maricela
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Eklöf, Johan
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Jiddawi, Narriman
    Institute of Marine Science, University of Dar es Salaam, Mizingani Rd., PO Box 668, Zanzibar .
    Resource degradation of the sea cucumber fishery in Zanzibar, Tanzania: a need for management reform2010In: Aquatic Living Resources, ISSN 0990-7440, E-ISSN 1765-2952, Vol. 23, p. 387-398Article in journal (Refereed)
    Abstract [en]

    This study assessed the Zanzibar sea cucumber fishery using a multidisciplinary approach. Data was collected by (i) interviewing various groups of actors in the fishery and reviewing management documentation and legislation, (ii) by monitoring catches and (iii) through a visual census of coastal sea cucumber populations in areas open and closed to fishing. The fishery showed clear signs of being unsustainable with high fishing effort, and weak formal and informal management institutions. The fishery operation was characterised by an intricate cross-scale structure with both fishers and sea cucumber products being transported across national borders. The visual census of commercial sea cucumber stocks at three sites open to fishing around Zanzibar showed low densities across the range of sea cucumber value groups including low value species. Furthermore, the diversity of commercial sea cucumber species was lower in fished reefs than on a protected reef. The poor status of the sea cucumber populations was confirmed by the perception of an overfished resource by the interviewed actors active in the fishery. This was also depicted by the paucity of high value species, and high representation of low value and newly commercialised species in fishers catch. We conclude that the current state of Zanzibar’s sea cucumber populations is compromising the fisheries self-replenishment and existence and that the fishery is in urgent need of a complete management reform. 

  • 5.
    Eriksson, Hampus
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    de la Torre-Castro, Maricela
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Olsson, Per
    Stockholm University, Stockholm Resilience Centre.
    Breaking degradation of sea cucumber resources: a social-ecological analysis of the fisheries in Zanzibar and Mayotte Islands in the Western Indian OceanManuscript (preprint) (Other academic)
    Abstract [en]

    Despite increasing research and management attention to tropical sea cucumber fisheries no apparent successes have been documented. To broaden the perspective of recent advances in management tools this study analyses the social-ecological processes in two contrasting sea cucumber fisheries situations, Zanzibar (Tanzania) and Mayotte (France) in the Western Indian Ocean. Zanzibar has an on-going fishery while the fishery in Mayotte operated approximately 10 years before it was closed in 2004. The study compares how different management strategies in Mayotte and Zanzibar were taken to address increasing fishing effort and a declining sea cucumber population. The comparison provide an opportunity learning and reflection. A visual census of stocks shows that the commercial value is nearly 30 times higher in Mayotte than Zanzibar owing to different fishery and management practices. In Mayotte less than 100 people were engaged in the fishery when it was active and the fishery was a comparatively small enterprise. In contrast, over 1000 people collect sea cucumbers as part of an expansive trade network that has developed in Zanzibar. In addition, in this site fishers are dependent on the resource for livelihood and expanding fishery processes have therefore occurred as a response to declines in catch abundance and value. These responses have taken place in the context of insufficient management and reinforce an unsustainable fishery situation difficult to break – referred to as a social-ecological trap. In contrast, management in Mayotte was receptive and adaptive to changes. The closure of the fishery illustrates the importance and positive outcome of matching the fishery – management temporal scales to avoid reinforcing fishery processes and to maintain ecosystem integrity. The multiple fisheries targeting sea cucumbers documented in this study captures how different management approaches and management plans are required, building on an understanding of the social-ecological context of the fishery. In addition, the comparison illustrates the importance of management systems with adequate resources (e.g. human and economic) and functioning information flows for positive management outcomes.  

  • 6.
    Eriksson, Hampus
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    de la Torre-Castro, Maricela
    Stockholm University, Faculty of Science, Department of Systems Ecology. Stockholm University, Stockholm Resilience Centre.
    Olsson, Per
    Stockholm University, Stockholm Resilience Centre.
    Mobility, Expansion and Management of a Multi-Species Scuba Diving Fishery in East Africa2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 4, p. e35504-Article in journal (Refereed)
    Abstract [en]

    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. 

  • 7.
    Eriksson, Hampus
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Robinson, Georgina
    Slater, Matthew
    Troell, Max
    Stockholm University, Stockholm Resilience Centre.
    Sea Cucumber Aquaculture in the Western Indian Ocean:  Challenges for Sustainable Livelihood and Stock Improvement2012In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 41, no 2, p. 109-121Article in journal (Refereed)
    Abstract [en]

    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 towards new enterprise activities is suggested. 

  • 8.
    Eriksson, Hampus
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Thorne, Benjamin V.
    Byrne, Maria
    Population metrics in protected commercial sea cucumber populations (curryfish: Stichopus herrmanni) on one tree reef, great barrier reef2013In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 473, p. 225-234Article in journal (Refereed)
    Abstract [en]

    The population ecology of the tropical beche-de-mer sea cucumber Stichopus herrmanni (curryfish) was investigated on One Tree Reef, a no-take protected area in the Great Barrier Reef Marine Park. The size class frequency and density of this species at several sites were determined over 2 years: 2009 and 2011. There was a spatial separation of populations that differed in size and density, but these parameters did not change over the 2 yr of the study, indicating stable population metrics. The spatially heterogeneous population pattern has relevance for fisheries management, as current size limits protect animals with low fecundity that occur in shallow habitat, but make it legal to remove 85% of large, fecund animals in deeper areas. Data for 4 S. herrmanni populations were used to address 2 theories on the potential drivers of population structure: (1) adult migration and (2) phenotypic plasticity in growth with respect to habitat conditions. While connectivity through adult migration appears possible, the size structure and location of some populations indicate that population features are determined by post-recruitment growth in the habitat. The latter likely plays a major role in population dynamics and terminal growth of S. herrmanni. There was no day-night difference in density at fixed transects, indicating that data obtained in daytime surveys was representative. A frequency distribution profile of density data from manta tows is presented as an alternative to using mean density as an assessment indicator in sea cucumber fisheries. S. herrmanni showed a noticeable affinity for reef features, an important finding for improved resolution of spatial planning in management.

  • 9. Friedman, Kim
    et al.
    Eriksson, Hampus
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Tardy, Emmanuel
    Pakoa, Kalo
    Management of sea cucumber stocks: patterns of vulnerability and recovery of sea cucumber stocks impacted by fishing2011In: Fish and Fisheries, ISSN 1467-2960, E-ISSN 1467-2979, Vol. 12, no 1, p. 75-93Article in journal (Refereed)
    Abstract [en]

    Identifying rates of change in the abundance of sea cucumbers under differing management regimes is fundamental to estimating commercial yields, identifying ecological interactions and facilitating management. Here, we review the status of sea cucumber stocks from a range of Pacific Island countries (Samoa, Tonga, Palau, Fiji and Papua New Guinea), some of which have had a moratorium on exports for up to a decade. We use a time-series approach to look at variation in sea cucumber presence, coverage and density from survey and re-survey data. Results give an appreciation of variation between 'high' status (less impacted) and depleted stocks. Survey data show marked declines in coverage and abundance as a result of artisanal fishing activity, and although species groups were not lost at a country level, local extirpation and range restriction was noted. Resilience and 'recovery' following cessation of fishing varied greatly, both among locations and among the species targeted. Worryingly, even after extended periods of moratorium, the density of some species was markedly low. In many cases, the densities were too low for commercial fishing, and may be at a level where the effective population size is constrained due to 'Allee' affects. From these results, we suggest that management regimes presently employed are generally not well aligned with the level of response to fishing mortality that can be expected from sea cucumber stocks. New adaptive, precautionary approaches to management are suggested, which would allow more timely interventions to be made, while refined information on stock dynamics is sought.

  • 10. Schneider, Kenneth
    et al.
    Silverman, Jacob
    Woolsey, Erika
    Eriksson, Hampus
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Byrne, Maria
    Caldeira, Ken
    Potential influence of sea cucumbers on coral reef CaCO(3) budget: A case study at One Tree Reef2011In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 116, p. G04032-Article in journal (Refereed)
    Abstract [en]

    To endure, coral reefs must accumulate CaCO(3) 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 CaCO(3) balance of a coral reef. These deposit feeders process carbonate sand and rubble through their digestive tract and dissolve CaCO(3) as part of their digestive process. In aquarium incubations with Stichopus herrmanni and Holothuria leucospilota total alkalinity increased by 97 +/- 13 and 47 +/- 7 mu mol kg(-1), respectively. This increase was due to CaCO3 dissolution, 81 +/- 13 and 34 +/- 6 mu mol kg(-1) and ammonia secretion, 16 +/- 2 and 14 +/- 2 mu mol 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 CaCO(3) by the sea cucumbers at both sites. At DK13 the sea cucumber population was estimated to be responsible for nearly 50% of the nighttime CaCO(3) dissolution, while in Shark Alley for most of the nighttime dissolution. Thus, in a healthy reef, bioeroders dissolution of CaCO(3) sediment appears to be an important component of the natural CaCO(3) turnover and a substantial source of alkalinity as well. This additional alkalinity could partially buffer changes in seawater pH associated with increasing atmospheric CO(2) locally, thus reducing the impact of ocean acidification on coral growth.

  • 11. Thorne, Benjamin V.
    et al.
    Eriksson, Hampus
    Stockholm University, Faculty of Science, Department of Systems Ecology. University of Sydney.
    Byrne, Maria
    Long term trends in population dynamics and reproduction in Holothuria atra (Aspidochirotida) in the southern Great Barrier Reef; the importance of asexual and sexual reproduction2013In: Journal of the Marine Biological Association of the United Kingdom, ISSN 0025-3154, E-ISSN 1469-7769, Vol. 93, no 4, p. 1067-1072Article in journal (Refereed)
    Abstract [en]

    Population density and the presence of fission products of Holothuria (Halodeima) atra were investigated in surveys taken over 5 years (2006-2010) in the Capricorn Bunker Group, Southern Great Barrier Reef. These surveys were undertaken to document population density over time and assess the potential that asexual reproduction contributes to population maintenance. Over the 5 years a low incidence of fission was evident year-round, with an increase in July and August (13 and 27% of the population, respectively). There was a positive correlation between population density and the presence of fission products across all surveys. Although density fluctuated, there was no significant difference between months or sites. Despite the potential increase that might be expected from fission followed by regeneration, density fluctuated around a mean of 0.77 ind. m(-2). Examination of gonads of the small (asexual and sexual reproduction) and large (sexual only) morphs of H. atra indicated a difference in reproductive pattern. Many small morphs lacked gonads during winter and, when they developed gonads, the gonad index (GI) was low. The GI pattern of the small morph indicated that they spawned in summer. In comparison the large morph had conspicuous gonads through the year. The GI of the large morph was high in winter and summer indicating greater, more prolonged spawning activity in these individuals.

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