Trash fish/low valued fish is still the most commonly used feed in marine cage culture in Asia. Use of trash fish is controversial with regard to the sustainability of the farming practices, and related issues on environmental degradation. In this study, the results of farm based trials on Asian seabass (Lates calcarifer) and tiger grouper (Epinephelus fuscoguttatus) to evaluate the efficacies of the use of commercial pellet feed in comparison to trash fish/low valued fish in marine cages in Thailand are presented. In spite of the variations observed in each of the farm sites, the results indicate that the overall growth performances and fish survival rates between the two feed types were similar, for both species. However, better costbenefit and resource use were recorded for fish reared on trash fish/low valued fish. No significant differences were observed in water quality parameters, dissolved oxygen, transparency and ammonia, between sites where pellet or trash fish were used, inside and outside the cages and for both species. The results of the present study are discussed in the light of the current controversies on the use of trash fish/low valued fish in marine cage culture.
Groupers are economically important for aquaculture in Thailand. A novel hybrid grouper (Epinephelus lanceolatus 9 Epinephelus fuscoguttatus) has been successful cross-bred; therefore, the present work aimed to assess the hybrid's traits. The growth performance, strength and tolerance to a pathogenic bacterial infection of this hybrid were compared with its parent species, tiger grouper and giant grouper. The results of all measured growth parameters indicated that the hybrid strain grew fastest followed by giant and tiger grouper respectively. The expressions of the growth-related genes, insulin-like growth factor (IGF) I and II, were also analysed in fish muscle and liver which are the main target organs in fish growth regulation. Among tested species, similar expression patterns of IGF-I and IGF-II were detected in both organs. The levels of these genes in liver and muscle of hybrid and giant grouper were higher than those of tiger grouper comparable with the growth manner. After challenge with Vibrio vulnificus, the immunological parameters, clearance time of Vibrio in haemolymph and survival was measured to verify the fish immunity. Leucocyte number, lysozyme activity and the ability to eliminate the pathogen were very high in hybrid and giant grouper while these parameters were lower in tiger grouper. Correspondingly, the mortality rate of tiger grouper was higher than others and % survival at the end of observation time (15 days post challenge) was lowest in infected tiger grouper. Altogether, the results suggested that the hybrid grouper has desirable traits that will improve cultured grouper.
The vasa gene is specifically expressed in the germ cell lineage, and its expression has been used to study germline development in many organisms, including fishes. In this study, we cloned and characterized vasa as Efu-vasa in the brown-marbled grouper (Epinephelus fuscoguttatus). Efu-vasa contained predicted regions that shared consensus motifs with the vasa family in teleosts, including arginine- and glycine-rich repeats, ATPase motifs, and a DEAD box. Phylogenetic-tree construction using various DEAD-box proteins confirmed that Efu-vasa was clustered in the vasa family. Efu-vasa mRNA was detectable only in gonads, by reverse transcription polymerase chain reaction. Primordial germ cells (PGCs) during early gonad development in larvae were characterized by histological examination and in situ hybridization using an Efu-vasa antisense probe. Migrating PGCs were found in larvae at 9-21 days post-hatching, and rapid proliferation of PGCs was initiated in 36 days post-hatching. These findings provide a valuable basis for optimizing the developmental stages for germ cell transplantation in order to produce surrogate broodstock, which may help in the production of larvae of large and endangered grouper species.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.