Research on freshwater fishes

Abstract

Studies on tilapias focused on the refinement of strain comparison methods, refinement and pilot-testing of broodstock improvement procedure, selective breeding and evaluation of red tilapias, genetic variability determination in hatchery-bred tilapia and the development of criteria for tilapia fingerling quality assessment.

On carps, feeding of bighead carp (Aristichthys nobilis) to enhance reproductive performance was done and stunting was applied as a technique in broodstock development. Studies on the tolerance of bighead carp fry to low salinities were conducted. Free-living nematodes were tested as alternative larval food. The culture potential of grass carp in lake-based cages was also determined.

Research on the native catfish (Clarias macrocephalus) focused on endocrine studies during the final stages of maturation. Hatchery techniques were refined by identification of factors that increase fry production. Practical diets were developed for broodstock, hatchery, nursery and grow-out phases. A collaborative project on the ecological impact of African catfish (C. gariepinus) introduction in natural waters was undertaken.

The occurrence of EUS (epizootic ulcerative syndrome) among wild fishes in Laguna Lake decreases the marketability of both wild and cultured fishes from the lake. Hence, the bacteria and virus associated with EUS and their virulence, modes of disease transmission, developmental stages of dermal lesions and hematological changes in severely affected fish were studied.

Laguna Lake, where fish catch and aquaculture production contribute significantly to the country s total freshwater fish production, has been the focus of extensive ecological research in collaboration with other local and foreign research and academic institutions.