Culture-based fisheries (CBF) is a practice in which, in general, fish are stocked in small water bodies that are unable to sustain an artisanal fisheries through natural recruitment. CBF has gained popularity in recent years, due to its simplicity in terms of inputs and management and cost effectiveness. Traditionally, in the Asian region, exotic species are used, but countries newly embarking on CBF prefer the use of indigenous species. The shift towards the use of indigenous species was believed to counter negative impacts, perceived or otherwise, brought about by use of exotic species. However, it is also true that hatchery-produced fingerlings that escape can also pose a potential threat to genetic diversity and integrity of their wild counterparts.
At the Regional Workshop on “Culture-based fisheries development in Asia” (this volume), it was clear that the debate on the use of exotic versus indigenous species is still an ongoing topic. This paper entails the pros and cons in the use exotic vs. indigenous species in CBF and steps to be followed when decisions are made on species choice for CBF. The ultimate goal is to improve production whilst maintaining genetic diversity and integrity of the surrounding ecosystems.
A summary of culture-based fisheries developments in Lao PDR based on publications, either in the primary literature, or as manuals and reports posted on the website of the Network of Aquaculture Centres in Asia-Pacific, that have originated from projects funded by the Australian Centre for International Agriculture research (ACIAR) since 1997.
Fish is the most important source of animal protein in Cambodia. On average it makes up more than 75 % of animal protein and in some areas of the country aquatic resources make up 80 % of the available animal protein. Overall, fish consumption is estimated to be around 63 kg/caput/year (FiA, 2013) (whole fish equivalent) and is many times greater than the global average, reflecting the importance of the fisheries sector to the diet and culture of Cambodian people.
The application of culture-based fisheries in Cambodian waters commenced with the initiation of a project under the auspices of the Australian Centre for International Agricultural Research (ACIAR Project FIS/2011/013), coordinated by NACA. For the initial trial, 16 small reservoirs located in four provinces were selected. These reservoirs differed from each other in surface area, mean depth and the catchment land use features, the latter evaluated using GIS software. In choosing the reservoirs, initial consultations with the village communities responsible for the water regime management were held and their agreement obtained for monitoring and cooperating through the trial period. One common feature in all the reservoirs selected, and for that matter in all water bodies in Cambodia, is the provision of a “conservation zone”, generally in the deeper areas of the water body, where fishing is prohibited.
Culture-based fisheries are a form of aquaculture that utilise small water bodies, both perennial and non-perennial, which cannot support a fishery through natural recruitment processes, for food fish production through a stock-recapture strategy. Culture-based fisheries are environmentally friendly as the only external input is seed stock. It also engages a co-management approach utilising the downstream farming communities in most instances already organised into functional entities for dry land agriculture as the principal beneficiaries (De Silva 2003). Culture-based fisheries are an attractive development strategy as it mobilises dry land farming communities (e.g. rice farmers) to use existing water bodies for the secondary purpose of food fish production. The strategies to optimise benefits from culture-based fisheries, however, vary in detail from country to country and across climatic regimes.
Culture-based fisheries activities were conducted over two growth cycles and in all instances the fish production increased above the levels that were obtained prior to the implementation of culture-based fisheries. In this presentation the stocking strategies and the yields obtained are presented. It is believed, however, the yields could be further enhanced by utilisation of the conservation as nursery areas which will be dealt with in a separate presentation.
Fisheries enhancement is defined as technical intervention in the life cycles of fish. Culture-based fisheries (CBF) development is one of the major fisheries enhancement strategies practised in inland reservoirs of Sri Lanka. The extensive availability of inland reservoirs in the country, primarily constructed for irrigation of land crops in ancient times, favours CBF development, which is essentially a development since late 1990s. Water retention period in most small village reservoirs in the country is seasonal and lasts for six to nine months in the year. CBF development in these reservoirs therefore requires fast growing fish species such as Chinese and Indian major carps. Hormone induced captive breeding of major carps in government-owned hatcheries and fingerlings rearing in mini-nurseries, maintained by rural agricultural farmers, are the sources of seed for stocking these village reservoirs.
The CBF in village reservoirs of Sri Lanka is a communal activity involving agricultural farmers without prior experience in fisheries. As such, awareness programs conducted for these farmers have facilitated establishment of CBF in small village reservoirs. The biological productivity of water bodies and socio-economic conditions of rural communities were found to vary from reservoir to reservoir. As such, successful R&D efforts were made for selection of village reservoirs suitable for CBF development, based on the biological productivity-related parameters such as reservoir morphometry, allochthonous input of nutrients through livestock farming, and socio-economic characteristics of rural communities that favour CBF. For CBF development in village reservoirs, correct timing is necessary for fingerling production to suit the monsoonal rainy season when the reservoirs get filled. Climate change impacts, which resulted in a shift in peak monsoonal rainy season were therefore identified together with possible resilience capacities of rural communities for sustainability of CBF.
Dissemination of research findings through various means such as production of a documentary film, publication of a monograph which was translated to several regional languages, and holding a series of regional workshops were instrumental for CBF development at the regional level. The Asian Development Bank funded Aquatic Resources Development and Quality Improvement Project, which contained a significant component for CBF development in inland reservoirs of Sri Lanka, has also been facilitated by R&D efforts mentioned above. The recent efforts to develop CBF in Sri Lanka include establishment of profitable CBF with effective co-management in selected minor perennial reservoirs, and the use of Macrobrachium rosenbergii post-larvae for CBF in many inland reservoirs.
Fish stocking in Indonesian lakes and reservoirs has been conducted for a long time. Since 1999, culture-based fisheries (CBF) practices based on scientific evidence such as using suitable fish species, consideration of the primary productivity, stocking density, economic evaluation and community participation, have been conducted in some reservoirs and lakes and have showed encouraging results. Potential fish yield of a water body for CBF development is one of the important factors in determining its success. Potential fish yield of some lakes and reservoirs was estimated using a morpho-edaphic index or primary productivity approach, and the water bodies were classified based on morpho-limnological characteristics. Estimated potential fish yield of small reservoirs/lakes with an area between 1.0-200 ha showed the highest potential with an average yield of 2835 ± 623.6 kg/ha/yr compared to the others of lager area. In the future, therefore, development of CBF was highly recommended and prioritised in small reservoirs with an area less than 200 ha, mostly distributed in Sumatera, Java, and Nusa Tenggara with more than 2,000 reservoirs. However, about 80% of those reservoirs were categorised as idle presently.
Sri Lanka is blessed with a large number (>12,000) of irrigation reservoirs. Depending on their hydrological regimes, they are broadly categorised into perennial and seasonal reservoirs and are secondarily used for inland fisheries. Culture-based fisheries (CBF) in seasonal reservoirs was initiated in the 1980’s and it is well documented. The Government of Sri Lanka has recognised CBF as an effective way of increasing fish supplies in rural areas, at affordable prices, while also providing employment and additional income to rural farmers and thereby contributing towards alleviation of poverty. There are around 200,000 ha of perennial reservoirs in Sri Lanka. These reservoirs are divided into three broad size categories, minor (<200 ha), medium (200 - 800 ha) and major (>800 ha). In this paper the impact of introduction of CBF on fish production in minor, medium and major perennial reservoirs are assessed using the fish production data from eight minor, seven medium and two large reservoirs. In all three categories of reservoirs post CBF resulted in very significant increases in fish production, such as for example increases of 206 and 319 % average annual fish production in minor and medium sized reservoirs, respectively.
Available provisions under the Fisheries and Aquatic Resources Act No. 02 (1996) to ensure ownership of the fish harvest to the fisher community, a crucial element in the success of CBF, are also highlighted. Further, the role of fisher community based organisations and fisheries management measures introduced for effecting successful CBF practices are also discussed.
Releasing of giant freshwater prawn (Macrobrachium rosenbergii) for the purposes of stock enhancement and to create a fishery has been conducted in Thailand since the 1980s. In each year, over a hundred million post larvae (30 day old post larvae of ~1 cm) of M. rosenbergii have been released into inland waters nationwide. The stocking density is, generally, about 2,500 prawn larvae/ha. Average age at harvest is around 6 to 8 months, with an average total length of 20 cm. The individual weights can range between 100 and 200 g after a year of release. Common fishing gears are gillnet, long-lines and traps, the latter designed exclusively for M. rosenbergii. Overall, the success of stocking M. rosenbergii is poor since the recapture rate is generally less than 5 %. However, the economic return is high. Average market price of M. rosenbergii is 150 Thai Baht/kg, which is about 3 times more than the average price of marketed freshwater fish. The profit is reported to be as high as 800 %. Moreover, the high market price of M. rosenbergii benefits traders at various levels, job creation and income for all related sectors. Although the economic profit is very high, the low rate of recapture of stocked M. rosenbergii makes this culture-based practice not entirely satisfactory. The major problem is that there are no guidelines in regard to the optimum size of seed for release as well as appropriate time and location to be stocked, that could enhance the rate of return and economic returns.
Lakes amount to 15% of the total freshwater surface area in China and are important for land-based fisheries. More than 10 species are stocked into lakes to increase production and/or improve water quality. The most common species stocked are the Chinese major carps, i.e. silver carp, bighead carp, grass carp and black carp. In recent years, increasing amount of high valued species such as mandarin fish, mitten crab, yellow catfish and culters were stocked. However, the stocking of mandarin fish and mitten crab perhaps are the most successful because stock enhancement of these two species has been systematically conducted.
In this paper, the culture-based fisheries in lakes are presented, with special reference to mandarin fish and mitten crab stocking in lakes in China. The stocking rate of mandarin fish is determined by food consumption rates, which are mainly related to water temperature and fish size, and prey fish productivity. A bioenergetics model of mandarin fish was established to predict the growth and consumption of prey fish in stocked lakes. Impacts of stocked mandarin fish on wild mandarin fish populations are also dealt with. The stocking model of mitten crab in of culture-based fisheries was also determined based on biomass of macrophyte coverage, benthos biomass and ratio of Secchi depth to mean water depth in lakes.
Since increasing attention is being paid to eutrophication of lakes in China, land-based fisheries development now prioritise maintaining integrity of water quality and biodiversity conservation. Integrated stocking of different species and lakes fisheries management are also addressed.
Peter Edwards writes on rural aquaculture: Promising aquaculture practices for sustainable intensification
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Pramod Kiran R.B., Baiju, A., Krishna Sukumaran, Neetha Susan David, Bijukumar, A. and A.R.T. Arasu