engleski

Hybridisation between Mediteranean groupers

The culture of groupers of genus Epinephelus is focus of intensive research activities in whole world and Mediterranean area. The research in Med. area is still in the early phase when compared to Asia and USA, with four selected and investigated species: Epinephelus marginatus, Epinephelus aeneus, Epinephelus costae and Epinephelus caninus. All research reported problems of larviculture as in other parts of the world, but also difficulties of artificial spawning. One of the ways to improve some problems in the rearing of different fish species is hybridisation in order to improve some characteristics through obtaining “heterosis” effect. The first attempts of hybridisation in grouper culture were done in Asia (Tseng and Poon, 1983). This presentation will describe results of fertilisation and early development of hybridisation between three Mediterranean grouper species. During 1998 and 1999 two hybridisation were made. Crosses among Epinephelus marginatus +x Epinephelus aeneus >and Epinephelus costae +x Epinephelus marginatus > were tested and the results were compared with maternal species. Males of both species were obtained by sex-reversal using 17- methyltestosterone. Percent of fertilisation, speed of embyogenesis, cumulative hatching were observed during egg development. Characteristics of yolk-sac larvae, their growth and survival and efficiency of feeding on rotifers were examined later on. The percent of fertilisation was not statistically different in both hybrid crosses if compared to maternal species. The percent of fertilisation was lower (app. 50%) for E.costae and hybrid E.costae x E. marginatus, but as a result of inappropriate time of stripping. There was no difference in regularity of second and third cleavages of blastodics between hybrids and maternal species, or in speed of embryogenesis. Both hybrid crosses and straight lines newly hatched larvae had similar length and shape, and later on developed similar patterns of pigmentation. All larvae died after ten days, mostly of unsuitable prey and development of large urinary calculus. The fact that hybrids between different Epinephelus species showed no significant differences if compared to maternal species during early development, could be a sign of suitability of these hybrids in future rearing trials.

hybridizations; groupers; early development

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