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Notes on first attempt at artificial spawning and rearing of early stages with goldblotch grouper, Epinephelus costae (Steindachner, 1875) (CROSBI ID 88478)

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Glamuzina, Branko ; Glavić, Nikša ; Tutman, Pero ; Kožul, Valter ; Skaramuca, Boško Notes on first attempt at artificial spawning and rearing of early stages with goldblotch grouper, Epinephelus costae (Steindachner, 1875) Aquaculture International, 8 (2000), 6; 1-5-x

Podaci o odgovornosti

Glamuzina, Branko ; Glavić, Nikša ; Tutman, Pero ; Kožul, Valter ; Skaramuca, Boško

engleski

Notes on first attempt at artificial spawning and rearing of early stages with goldblotch grouper, Epinephelus costae (Steindachner, 1875)

The goldblotch grouper, Epinephelus costae (Steindachner, 1878), previously known as Epinephelus alexandrinus (Valenciennes, 1828), is a commercially important fish species in Mediterranean, with good market demand and good price (17 USD/kg in Greece). As many other grouper species throughout the world goldblotch grouper is selected as interesting fish for introduction in mediterranean aquaculture (Abelan and Basurco, 1999). The published informations on biology and ecology of this species are very scarce. Only literature about female reproduction cycle and fecundity in the Tunisian waters (Bouain and Siau, 1983), age and growth in Egyptian (Wadie et al., 1981) and Tunisian waters (Bouain, 1986) could be found for the Mediterranean waters. Except information that one commercial producer (Nireus-Greece) keeps broodstock (Abelan and Basurco, 1999), there is no other data about aquaculture of this species. The growth rate of goldblotch grouper in Tunisian water is similar to dusky grouper, Epinephelus marginatus (Lowe, 1834), and comparable with white grouper, Epinephelus aeneus (E. Geoffroy Saint-Hilaire, 1817) during first three years of life cycle (Bouain, 1986). This indicates that according to the good growth rate of dusky grouper (Gracia Lopez and Castello-Orvay, 1995) and white grouper (Hassin et al., 1997) in captivity, goldblotch grouper is a good candidate for mariculture. In this paper we present first results of spawning and trial of rearing of early larval stages of goldblotch grouper, Epinephelus costae. The broodstock consisted of ten females (weight from 4.5-6 kg) raised from wild fingerlings and five sex-reversed smaller males (from 150-450 g) obtained as described earlier (Glamuzina et al., 1998a). The fish were held in concrete tanks with added stones, supplied with ambient seawater (temperature from 13-25 C and salinity 38 ppt). They were fed three times per week with frozen sardines. On the 15th of August 1999 samples of gonads were taken from few females with insertion of a 1.2-mm plastic tube in the oviduct. The obtained samples were examined under the binocular microscope and size of oocytes was measured, showing mean oocyte diameter of 0.795  0.187 m (range 459-975 m). However, more than 60 % of oocytes in all samples were atretic. But, because of presence of significant percent of good oocytes and fact that our samples were from the end of ovary, we started with hormonal treatment. We applied the methodology previously described for dusky grouper (Glamuzina et al., 1998b) and most other grouper species in the world (Tucker, 1994). The human chorionic gonadotropin (HCG) was injected two times, 24 h apart in a total quantity of 2000 IU/kg. Ten hours after the second injection manual stripping was done. The fertilised eggs and hatched larvae were incubated in 300-l plastic tanks with a flow through of ambient seawater (temperature= 25.5 °C; salinity=38 ppt). The larvae were fed with rotifers. We obtained 900 grams of eggs from one treated female ten hours after the second hormonal injection. They were fertilised with the milt from three sex-reversed males. The motility of mixed pool of spermatozoids was 95 %. Next day we stripped around 400 g of eggss, but all of them were overripe. The percent of fertilisation of first batch was 50 %, and dead eggs were mostly overripe, indicating late time of striping and many atretic oocytes. The average diameter of good floated eggs few hours after fertilisation was 926  19 m, with diameters ranged from 890 to 950 m The eggs were transparent and spherical with a smooth chorion and one oil globule. The yolk was unsegmented and homogenous. At 25.5 C, the first cleavage occurred about 1 h after fertilisation. Hatching started 24 h 15 min after fertilisation and lasted next four hours. The average length of newly hatched larvae was 1.76  0.048 mm. Larvae varied from 1.69- 1.85 mm. Goldblotch grouper eggs and larvae are shown in Fig.1. There is no data about eggs and larvae of goldblotch grouper. Among relative Mediterranean species the comparison is presently possible only with dusky grouper. According to all published data about dusky grouper early stages (Spedicato, et al., 1995, Glamuzina, et al., 1998c), the eggs and larvae of goldblotch grouper are bigger. They are also among biggest of all described grouper’s eggs and larvae around the world. However, larval shape, pigmentation patterns and others larval characteristics are similar to dusky grouper and all other groupers of genus Epinephelus. The mouth of the goldblotch grouper started to open 61 h after hatching and was completely functional by 80 h. The maximum gape of the open mouth was between 280-320 m. So, functional mouth opening of goldblotch grouper larvae, based on assumption that it presents only 40 % of maximum mouth opening, was estimated as 112- 128 m. However, beside the fact that mouth gape was bigger than in dusky grouper larvae (Glamuzina, et al., 1998b), we observed similar problems of massive larval mortality linked to poor feeding and formation of crystals in the urinary bladder. The first larval prey is the major problem in rearing of all grouper species, and beside 20 years efforts the technology is not yet developed. Although preys such as oyster trochophores (Watanabe et al., 1996) and small screneed rotifers (Duray et al., 1997) were tested the larval survival is still low and inconsistent. The termination of gonadogenesis and spawning season of goldblotch grouper in conditions of southeastern Adriatic overlaps with dusky grouper. This is different from situation in Tunisian waters, where dusky grouper spawns two months earlier (Bouain and Siau, 1983). Future research on gonadogenesis of goldblotch grouper in captivity will give a better explanation of this difference. The fact that rearing of all world groupers faced with similar problems indicates that breakthrough in rearing of any grouper species, could led to fast development of aquaculture of all others interesting species. The main goal will be development of sustainable culture of new first prey in larval rearing, such as copepods.

egg; goldblotch grouper; Epinephelus costae; larva; reproduction

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Podaci o izdanju

8 (6)

2000.

1-5-x

objavljeno

Povezanost rada

Biologija