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Commercially valuable sea cucumbers are potential co-culture species in tropical lagoon environments, where they may be integrated into established aquaculture areas used for seaweed farming. In the current study, wild-caught juvenile sea cucumbers, Holothuria scabra, and red seaweed Kappaphycus striatum were co-cultured on Zanzibar, United Republic of Tanzania. Sea cucumbers (97 g +- 31 SD, n = 52) were cultured in mesh enclosures at initial cage stocking densities of 124 +- 21 SD and 218 +- 16 SD g m^-2 under seaweed culture lines. Over 83 days, individual growth rate (1.6 g d^-1 +- 0.2 SD) of sea cucumbers at low stocking density was significantly higher (v2 = 8.292, d.f. = 1, P = 0.004) than at high-stocking density (0.9 g d^-1 +- 0.1 SD). Seaweed individual growth rates [6.27 (+-0.3 SE) g d^-1 ] were highest in co-culture with sea cucumber at low density but did not differ significantly from high sea cucumber density or seaweed monoculture treatments (v2 = 3.0885, d.f. = 2, P = 0.2135). Seaweed growth varied significantly (v2 = 35.6, d.f. = 2, P < 0.0001) with sampling period, with the final sampling period resulting in the highest growth rate. Growth performance for seaweed and sea cucumbers (v2 = 3.089, d.f. = 2, P = 0.21 and v2 = 0.08, d.f. = 1, P = 0.777 respectively), did not differ significantly between monoculture and co-culture treatments, yet growth in co-culture was comparable with that reported for existing commercial monoculture. Results indicate H. scabra is a highly viable candidate species for lagoon co-culture with seaweed. Co-culture offers a more efficient use of limited coastal space over monoculture and is recommended as a potential coastal livelihood option for lagoon farmers in tropical regions.

Coastal aquaculture of seaweeds and prawns has developed in Tanzania during the past two decades. Farming of Eucheuma seaweeds commenced in 1989 along the east coast of Zanzibar and it has since expanded to other areas. This form of aquaculture does not pollute the environment with feeds, wastes or other chemicals, although there are some negative interactions causing inhibition of surrounding biota, but which appear to be relatively mild. Monoculture may result in some self-inhibition and disease vulnerability over time. The socio-economic impacts of seaweed farming was initially overwhelmingly positive, providing income to women from relatively poor remote villages. Annual production reached 7000 tonnes, constituting an important earning of foreign exchange. However, monopoly control by a few international corporations recent years has led to reduced prices being paid to producers. Aquaculture of penaeid prawns has also been attempted in Tanzania. A huge project was proposed for the Rufiji mangrove delta, but met strong opposition from local communities, government managers, scientists, journalists, lawyers and environmental NGOs. Although it was clear that the consequences of the project would have been seriously deleterious, the government approved it. Conclusions are drawn from the lessons learned through Tanzanian and international experiences, and suggestions are put forward concerning principles for the development of more ecologically viable and socially just aquaculture development.

In rapidly developing countries, where large sections of the population are highly dependent on marine resources, coastal livelihoods are vulnerable to sudden shocks and long-term change. National policy can attempt to mitigate this vulnerability within a multi-level framework by addressing the three aspects of vulnerability (exposure, sensitivity, adaptive capacity) through well-documented interventions. This article reviews the Indonesian policy framework for coastal and marine policy interventions that either directly or indirectly address different dimensions of coastal livelihood vulnerability. The findings show that the policy environment for addressing coastal livelihood vulnerability is heavily based on developing adaptive capacity and to a certain extent sensitivity without adequately addressing exposure, the initial cause of vulnerability. In addition, the complexities and inconsistencies within the Indonesian governmental structures, as well as more general issues of funding gaps and poor coordination, mean that policies created at national level rarely filter down to provide the intended benefits to coastal communities. It is recommended that practitioners and policymakers engage in a more cohesive and balanced approach to addressing livelihood vulnerability in coastal management by focusing more on the causes of the disease, exposure, rather than healing just the symptoms.

The commercial exploitation of seaweeds in India has started in 1966. At present the seaweeds are exploited in Gujarat coast and many localities in Tamil Nadu.