THE ROLE OF CAPTURE-BASED AQUACULTURE IN AQUACULTURE

PRODUCTION

The system of aquaculture production called capture-based aquaculture has differing characteristics and techniques depending upon the area of the world and species. The use of this aquaculture practice is constantly evolving as demand and technology change.

Use of wild seed for capture-based aquaculture

Aquaculture with seed harvested from the wild is practiced worldwide on a variety of marine and freshwater species. Due to lack of reporting and statistics, it is extremely difficult to make an accurate estimate of the scale of such practices or the percentage of aquaculture production in the freshwater and marine environment which is reliant on the capture of ELP animals from the wild. FAO (2006) has estimated that 20 percent of marine aquaculture production comes from such capture-based aquaculture representing a value of US$1.7 billion. The culture of many freshwater species also relies partly or fully on wild seed because the supply from hatcheries is not adequate to meet demand or because the quality of hatchery produced seed is felt to be inferior to wild caught seed. No estimate has been made for freshwater capture-based aquaculture production. Reports suggest that there is increasingly more use of hatchery-reared seed for many species as the technology improves and due to the diminishing supply of wild seed. The lack of a stable wild seed supply has been a significant obstacle to the further expansion and development of many aquaculture species. The changing nature of seed supply in aquaculture, from wild to hatchery produced, adds to the complexity of developing an accurate estimate of reliance of aquaculture on wild caught seed.

 

While accurate figures on the scale of capture-based aquaculture are not available, a number of papers and reports from around the world provide estimates for individual species which illustrates aquaculture’s continued reliance on wild caught seed. It has been reported that for some freshwater species, such as omnivorous river catfish (Pangasaianodon hypophthalmus) and carnivorous giant snakehead (Channa micropeltes) in Cambodia, that all of the seed is obtained from the wild (APFIC, 2005). In the Philippines, while hatcheries are becoming an increasingly more important source of milkfish fry, Ahmed et al., (2001) estimated that the hatcheries are only supplying approximately 15 to 20 percent of the demand. Although many species of bivalves are routinely produced in hatcheries, the scale of wild spat collection often dwarfs hatchery production (Hair, Bell and Doherty, 2002). It is estimated that up to 95 percent of mussel (Mytilidae) spat is collected from the wild; approximately 15–20 percent of edible oysters (Osteridae); and approximately 50 percent of scallops (Pectenidae). The production of spiny lobsters (mainly Panulirus ornatus) in Asia (China, India, Malaysia, Myanmar, Philippines, Singapore, Taiwan Province of China, Thailand, Viet Nam) is based mainly on the capture of wild juveniles (Hair, Bell and Doherty, 2002; Tuan and Hambrey, 2000). Although hatchery-reared groupers are available, wild-caught juveniles remain the primary source of seed for aquaculture of these species in Asia (Sadovy and Vincent, 2002). Approximately one half to two-thirds of the regional supply of grouper comes from wild-caught adult fish. Major sources of wild-caught grouper are the Philippines, Indonesia, Thailand, and Malaysia. In addition, Australia, Viet Nam, Myanmar, Papua New Guinea and China also supply wild-caught grouper. New supply sources include remote islands in the Indo-Pacific such as Micronesia (Federal State of), Maldives, Solomon Islands, Fiji and Kiribati (Pomeroy, Parks and Balboa, 2006). In Viet Nam, the giant freshwater prawn Macrobrachium rosenbergii, which is indigenous to the Mekong Delta, is becoming an increasingly important cultured species. The culture of this species, especially in rice fields, is based mainly on wild seed collected from rivers and other freshwater bodies (Phuong et al., 2006). The seed for sand goby culture in Viet Nam is obtained primarily from the wild (Phillips, 2002). While not for food, ornamental fish production is an important component of the worldwide aquaculture industry in several nations. Most of the aquaculture production of ornamental fish focuses on freshwater species. Approximately 90 percent of freshwater ornamental fish are captive bred (Bartley, 2000). While marine ornamentals capture higher price, their captive breeding and culture is much less advanced. Only 100 of 800 marine species traded in the pet industry are routinely bred in captivity, with approximately 21 of these being commercially feasible (Tlusty, 2002). As can be seen, many important cultured species still rely on the use of wild organisms as seed material.

Historical perspective on capture-based aquaculture

A variety of species groups and aquaculture production systems that have evolved based on the collection of gravid females or wild-caught seed show that harvest occurs at life history stages ranging from planktonic (pre-settlement) post-larvae to large juveniles. This historical evolution is changing for many species and production systems, however, as the harvest of wild seed has often been unsustainable and unable to support higher production demands as hatchery produced seed has become more available and of higher quality and less expensive. In many cases, the technological progress in hatchery technology has displaced capture-based aquaculture as a source of seed. The following discussion highlights the historical and technological shifts occurring in the culture of many species which were once fully dependent upon wild caught seed.
In Viet Nam, before 1997, the supply of “Tra/Basa” fingerlings relied on wild seed. Recent successes in Pangasius breeding (Pangasianodon hypophthalmus and Pangasius boucourti) have led to more farmers stocking hatchery-reared catfish. About three billion fry were produced in 2004. High seasonal demand for the fry led to an insufficient supply. From the end of 2003 to the beginning of 2005, the price of fry increased two fold. There is concern that the multi-breeding of broodstock in the hatcheries has led to lower quality of fish seed (Sinh, 2005). Increasingly in the Mekong Delta, prawns are coming from hatcheries, as demand for post-larvae rises. Whether this is because of diminishing wild supply, or high demand, or a combination of both, is not known. From the limited information available, there appears to be no evidence that juvenile collection is a wasteful use of the resource, although other species are discarded in the process (Phillips, 2002).
Collection of seed, in particular shrimp seed, involved a significant bycatch of larval fish and crustaceans that was discarded, further damaging wild stocks. Larsson, Folke and Kautsky (1994) estimated that 872–2 300 km2 of mangrove was required to supply post-larvae to Colombia shrimp farms in 1990, equating to 20–50 percent of the countries mangrove forest. In response, state-run hatcheries, often supported with external assistance, were established to supply seed to emerging aquaculture sectors, however, in many cases these hatcheries were often poorly managed, producing low numbers of poor quality seed; furthermore, production cycles were often poorly matched to farmers needs and the timely distribution of seed was problematic (Bunting, 2006).
In Bangladesh, the demand for shrimp fry increased with the rapid expansion of the shrimp industry after the mid-1980s. According to the Department of Fisheries, there are 40 Upazilas (sub-districts) under 12 coastal districts along the 710 km long coastal area where shrimp fry are collected (DOF, 2004). The increased fishing pressure on the fry fishery has long been thought to be contributing to the gradual decline in abundance and distribution of mother shrimp causing serious damage to the productivity of coastal and marine fisheries. Moreover, a huge number of eggs, larvae and juveniles of non-target fish and shrimp harvested during shrimp fry collection are included in the bycatch. Overfishing of these fisheries has occurred to the extent that fishing in the artisanal sector is no longer remunerative. The penaeid shrimp stock in particular is over-exploited in all three fisheries, but the fry fishery in particular removes an estimated 90 percent of the Panaeus monodon fry stock.
Mud crab aquaculture has been practiced for many years in Southeast Asia, based primarily on capture and fattening of juvenile crabs from the wild. There is an unmet demand for mud crabs and this has led to over-exploitation in many areas. Difficulties with obtaining wild caught juveniles for farming operations, plus concerns of further over-exploitation, have led to major investment in research into hatchery techniques. Of the four species of mud crabs (Scylla serrata, Scylla paramamosain, Scylla tranquebarica and Scylla olivacea), hatchery technology is only being developed or researched for S. serrata and S. paramamosain (Allen and Fielder, 2003).
In Cambodia, traditional cage culture first developed as an activity integrated with fisheries rather than agriculture, possibly more than a century ago. It subsequently spread to Thailand, Viet Nam and, more recently, to the Lao People’s Democratic Republic. Older literature sometimes states that it is indigenous to Thailand but mentions Siem Riep province, previously in Siam but now in Cambodia. The traditional and intensive cage culture of the region developed in association with the “live boats” of fishers which have water-filled holds used to hold and transport the catch. Initially, it was entirely dependent upon wild fish both as seed and feed. Integration may also be at the livelihood level, as cage farmers, especially small-scale ones, may also be fishers and collect their own seed and feed (So et al., 2005). The most important fish species in Cambodia’s cage culture system is the strictly carnivorous giant snakehead (Channa micropeltes). Supply of giant snakehead seed for cage culture mainly depends on the seasonal wild seed availability in the floodplains of the Great Lake using scoop nets (So et al., 2005). Pond aquaculture has developed gradually in Cambodia in the last decade. Two major fish species, the omnivorous river catfish (Pangasaianodon hypophthalmus) and the carnivorous hybrid clariid catfish (Clarias batrachus and Clarias gariepinus) are stocked in ponds. Wild river catfish seed are collected by both the farmers and fishers from fishing lots, bag net or dai, and other small-scale fishing grounds in the Great Lake, Tonle Sap, Mekong and Bassac rivers; while hatchery hybrid catfish seed is imported from Viet Nam (So et al., 2005).
Ahmed et al. (2001), reporting on the results of an assessment of milkfish fry in the Philippines state that there is a strong perception among the fry gatherers that milkfish fry production from natural stocks is declining. The reasons given for the decline are: pollution, loss or degradation of coastal habitats, overexploitation of fishery resources and a decline in the sabalo (fully grown milkfish) population. Data generated by the study based on a one-year catch monitoring record show a declining trend in catch during both peak and lean months when compared to the historic data for the same site. On the other hand, Ahmed et al. (2001) found that there are indications of a growing demand for fry in recent years. This is attributable to two factors. The first is a shift from traditional or extensive culture systems to semi-intensive and intensive or high-density culture systems. The second is the shift from prawn farming to milkfish farming. This shift is due to the collapse of the prawn farming industry. It was concluded that fry availability from the wild is highly seasonal and its abundance fluctuates over time and space. The natural supply is unable to cope with the year round demand for fry for grow-out operations, even though the producers use various mechanisms (e.g. stunting the fry in nurseries or staggering the production cycle) to even out the gaps in the supply of fry. This indicates a need to develop a framework for monitoring natural fry resources and to develop greater local participation over the management of fry gathering activities. Hatcheries are seen as an increasingly important source of supply of fry for milkfish aquaculture. While the supply from the wild is decreasing, hatcheries are improving their technology for fry and fingerling production. This could mean competition for fry gatherers. Most milkfish producers, however, place a higher value on wild caught fry relative to hatchery-bred, so there is still a good market for the fry from the wild.
The live reef food fish (LRFF) trade, primarily consisting of groupers (Serranidae), wrasses (Labridae) and snappers (Lutjanidae), markets live fish for consumption in restaurants and markets, largely in Asia. Fish are supplied from capture of market sized fish, full-cycle mariculture, and grow-out from wild seed. Most live fish for the LRFF trade are currently wild-caught due to the limited supply from full-cycle mariculture. It is estimated that hundreds of millions of wild-caught seed fish are traded annually to supply grow-out operations, primarily from Thailand, Philippines and Indonesia. Only a small proportion of species desired in the LRFF trade can be hatchery-reared, with several important species still sourced exclusively from the wild. The latter include the coral trout, Plectropomus leopardus, the squaretailed coralgrouper, P. areolatus, the camouflage grouper, Epinephelus polyphekadion, and the humphead wrasse, Cheilinus undulates (Sadovy, Donaldson and Graham, 2003; Pomeroy, 2007).

Carp-based aquaculture, which continues to dominate inland aquaculture in Asia, in the past tended to be limited to areas close to wild seed supplies. This may explain the tendency for fish seed production to be concentrated close to the rivers where hatchlings were harvested. The development and adoption of modern hatchery technologies and additional species has begun to change the nature of fish seed supply but the distribution of private sector hatchery and nursery operates often remain clustered (Edwards, Little and Demaine, 2002).
There is continued interest in developing methods for new ornamental freshwater species as well as advancing the culture of marine species. Size selectivity and sex selectivity in the marine ornamentals trade is a concern. For many species, juveniles and sub-adults are more desirable than adults due to their coloration patterns and their more suitable size for home aquaria (Job, 2005). Culture of ornamental fish and invertebrates is now recognized as a feasible alternative to a wild harvest of specimens. Many collecting localities currently limit either the number of fish or the number of species taken, or both. A long history of destructive collecting practices, combined with poor husbandry after collection, has damaged the long term health of reefs with subsequent negative impacts on the potential for harvesting animals and the associated economic benefits of this harvest. Cultivation can help sustain the ornamental fish industry, restore exploited and impacted wild populations and minimize future use conflicts. In addition, mounting pressure from conservation groups and governments restricts the collection of wild organisms which leaves aquaculture as the only means to satisfy market demand for these products (Tlusty, 2002).