Increasing performance of Thai silver barb 'Puntius gonionotus' through selective breeding

N Pongthana; Nguyen Hong Nguyen; R W Ponzoni

The genetic improvement program of silver barb was conducted at the Pathumthani Fisheries Test and Research Center of Aquatic Animal Genetics Research and Development Institute, Thailand. Between 1998 and 2003 a mass selection program was practiced on the stock of silver barb from the Chao Phraya River, under the project Genetic Improvement of Carp Species in Asia, coordinated by The WorldFish Center. Over five generations, the selection line had significantly (P less than 0.001) greater body weight than that of the control. The magnitude of the response in harvest weight, however, decreased after the third generation. The most likely reason is that it was due to the effects of inbreeding. Therefore, the genetic improvement strategy for silver barb was re-designed. The population that went through five generations of mass selection was refreshed by outcrossing with the local stock from the Mekong River, Thailand, following 22 diallel crosses. A total of 140 full sib family groups were generated by hypophysation technique. The full pedigree has been maintained and selection for increased body weight has been based on the population formed from the best performing individuals of four strain combinations in a complete diallel cross, involving Chao Phraya (C) and Mekong (M) strains. Animal model using Best Linear Unbiased Prediction (BLUP) methodology was used to estimate genetic merit of individuals for selection and replacements. Data was collected over two generations in this newly established population. The main aim of the present study was to obtain preliminary estimates of genetic parameters for body traits in this population. Performance data collected on 3,848 individual fish were analyzed using restricted maximum likelihood method applied to a multi-trait mixed model in Asreml. The heritabilities for body traits (weight, length, depth and width) ranged from 0.25 to 0.32 (s.e. 0.08). The maternal and common environmental effects due to separate rearing of full-sib families before tagging accounted for a relatively large proportion of total variance (27 to 32%). Pair-wise genetic correlations between body traits were very high (0.70 to 0.98). The phenotypic correlations among the studied traits were almost close to one. These results indicate that selection for one of the body traits can achieve substantial direct response in the selection criteria and would result in correlated changes in other measurements of fish performance. The realized response to selection calculated as a percentage of the control, ranged from 4 to 9% for body traits. On-farm testing also showed that the selected fish had greater growth rate than the local strain under various culture conditions in Thailand. During the course of the selection program, seeds of the improved strain of silver barb was also produced and distributed to fish farmers and producers.

Increasing performance of Thai silver barb 'Puntius gonionotus' through selective breeding

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