1 NOVEMBER 1998
SEED QUALITY BECOMES AN ISSUE FOR FISH FARMERS IN ASIA
Since the introduction and adoption of induced breeding techniques through much of Asia, hatchery seed has become increasingly important to farmers raising fish. The techniques were first applied to carps in China, but technicians sent from India and Vietnam returned in the early 1960's with the basic knowledge to apply at home. Since then, national and international agencies have spread the techniques and funded hatchery construction throughout Asia. Success has been less related to the size and cost of facility construction than adequate training and motivation of hatchery staff; sometimes grandiose plans have not resulted in any sustained availability of fish seed to farmers. A critical step appears to be the adoption of seed production by the private sector.
As quantities have increased and availability of range of species and sizes become commonplace, quality is increasingly becoming an issue.
Part of the problem is the lack of skills of some farmers in identifying good quality fry and fingerlings, and even species identification. Initial findings in the field indicate that there are no standard protocols in identifying good quality seed which can be used by farmers in making decisions when buying.
But how can 'quality' be defined for these vulnerable, sensitive seeds? Quality fish seed will survive, especially the period immediately after stocking in which survival is often poor, and grow within the norms expected of the species without abnormalities. Reports of poor quality are becoming increasingly common. Suchart Ingthamjitr, who recently completed his doctoral thesis at AIT, found that commercial hybrid catfish farmers in Thailand were complaining of poor fish survival and growth in recent years. Fry that were once stocked and managed in fairly standard systems were taking longer to reach marketable weight, and often poor early survival required complete restocking. The outcome was poorer returns for the food fish farmer, a factor that has stimulated their interest in a simple test that can be used to monitor quality. Hatcheries are also interested as competition for business is intense and they typically have to compensate for fry losses. The poor quality of tilapia fry in much of Asia has driven major research efforts to replace them with selected and monosex fish. Slow growth, early maturation and breeding are characteristics of poorer tilapias. However, introduction of improved tilapias that result in fish of sustainable quality for farmers may be problematic. Monosex technologies have significant practical constraints in most developing countries, and mixed-sex fish, which can allow saving of seed, often appear to deteriorate under farmer management. However, identifying the causes and solutions of poor quality is less straightforward than geneticists or fish disease specialists may suggest. Quality problems appear to have multiple causes. Even seed from broodfish or high genetic potential may perform poorly if mishandled at the hatchery or nursery stage. Fish seed producers are increasingly linked to their final customers through networks of private sector traders and there are therefore many potential points where fish seed can suffer physical or physiological trauma. Pathogens and pests can cause quality and survival problems in eggs, hatchlings and larger seed, but these are often related to management within the production and delivery networks.
(excerpts from article by D. Little in AARM Newsletter (Aquaculture and Aquatic Resources Management Program), ISSN 0859-4848, Vol. 3, No. 3: 10-11)