Apostolos Mihelakakis

Spawning in captivity and early life history of cultured red porgy, Pagrus pagrus

Abstract Spawning in captivity of the red porgy, Pagrus pagrus, was studied at ambient temperature and photoperiod during one breeding season. Spawning lasted 114 days from February 12 to June 5, 1997, within a temperature range of 12.2°C and 18.5°C. The total number of eggs collected during the spawning period was estimated at 77 million of which 14.3% were sinking and 85.7% were buoyant. The percentage of fertilized buoyant eggs was generally high (95–100%). Mean egg diameters ranged from 0.991 to 1.093 mm within a temperature range of 12.2–14.5°C and decreased rapidly with increasing water temperature from 14.5°C to 18.5°C. Larval development, growth, and morphological changes were described from day 0 to day 34. Larvae were reared intensively in 2 m 3 tank under a constant photoperiod (18 h light and 6 h dark), and fed initially on rotifers, followed by Artemia nauplii and weaned onto an artificial diet. A green water technique was applied using Nannochloropsis sp. Larvae completed yolk absorption on day 4 after hatching. Feeding began on day 3. Absorption of the oil globule was completed by day 7. Notochord flexion started on day 20 at about 7.0 mm total length (TL). Transformation from larval to juvenile stage occurred between days 23 and 32 after hatching, at a mean TL of 12.7±1.2 mm. Initial swim bladder inflation occurred between day 5 and day 7 after hatching.

Effects of salinity and temperature on incubation period, hatching rate, and morphogenesis of the silver sea bream, Sparus sarba (Forskål, 1775)

Abstract Effects of salinity and temperature on eggs of silver sea bream (Sparus sarba) were studied in laboratory experiments. Naturally fertilized eggs were incubated under 60 different combinations of constant temperature (13.0, 15.0, 18.5, 22.0 and 23.5°C) and salinity (8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48 and 52‰). Incubation period, hatching period, hatching rate, abnormalities and total length of newly hatched larvae were investigated. The relation between incubation period and temperature was expressed for salinity levels of 24, 28, 32, 36, 40 and 44‰. Hatching occurred between 12 and 52‰ and between 13.0 and 23.5°C. Higher hatching rates of normal larvae were observed at 18.5°C between 20 and 36‰ and at 22.0°C between 28 and 32‰. Largest larval size was observed at 22.0°C and between 28 and 36‰. Using multiple regression analysis the calculated maximum yield of normal larvae was 66.7% at 19.4°C and 31.4‰.

SHORT COMMUNICATION Effects of salinity and temperature on incubation period, hatching rate and morphogenesis of the red sea bream

The red sea bream, Pagrus major, which is widely distributed throughout the Far East, is the most important species of the family Sparidae for marine aquaculture in Japan (Ochiai and Tanaka, 1986). The total production of market-size red sea bream in Japan was over 72 000 tonnes (t) in 1993, with approximately 28% of the fish being derived from cultivation (Taya, 1995). In 1995 about 30 million red sea bream juveniles were produced: about 22 million being used for restocking into coastal waters, and the remainder were on-grown in commercial farms (Morita, 1997). In southern Japan, the natural spawning season starts at the end of February and lasts until early June, when water temperatures are within the range 15–23 °C (Higuchi, 1977). In captivity, the spawning season of the red sea bream starts in April and comes to an end in June (Harada, 1969; Kitajima, 1978). Although there are several reports, published mostly in Japan, on aspects related to red sea bream culture, relatively little is known about the environmental requirements of the early life stages of this species. Some effects of temperature and salinity on the embryonic development of red sea bream eggs were described by Matsuura and Kakuda (1980) and Yoo et al. (1991), while Apostolopoulos (1976) provided some information about the combined effects of these factors on the hatching of red sea bream eggs. The current study was undertaken to provide information about the effects of salinity and temperature combinations on the length of the incubation period, hatching rate and appearance of newly hatched larvae of the red sea bream. The experiments were carried out at the Fishery Research Laboratory of Kyushu University in 1994. Naturally spawned eggs were collected from a broodstock tank of 3 m3 water capacity during the spawning season (which in Kyushu is early April to June), washed carefully with fresh filtered seawater and transferred directly to the experimental room. Water temperature in the spawning tank during the experimental period ranged from 16.5 to 20.0 °C, and salinity corresponded to the normal salinity of water in the adjacent bay (29.0–32.5‰). Ten trials were conducted to test

Effects of feeding rate on growth, feed utilization and body composition of red porgy fingerlings: preliminary results

APOSTOLOS MIHELAKAKIS1,∗, TAKAO YOSHIMATSU2 and CHRISTOS TSOLKAS3 1Provimi Western Greece A.B.E.E., 20 km National Road Agrinio – Arta, 30009 Agrinio, Greece; 2Laboratory of Advanced Animal and Marine Bioresources, Graduate School of Bioresources and Bioenvironmental Sciences, Kyushu University, Hakozaki, 812-8581 Fukuoka, Japan; 3Pharmaserve – Lilly A.B.E.E., 15 km National Road Athens – Lamia, 14564 Kiffisia, Greece; *Author for correspondence (e-mail: mihelaka@otenet.gr)