The development of doctor fish, Garra rufa (Heckel, 1843), larvae and the effect of temperature on their growth

The 'doctor fish,' Garra rufa (Heckel, 1843), is an endemic Mesopotamian freshwater species that is legally protected in Turkey against over-harvesting and commercial exploitation. The present study investigated the larval development of G. rufa and the effect of different temperatures (24, 26, 28, 30, 32, 34ºC) on larval growth and survival. Spawners were collected from Kangal (Turkey) and reared in the laboratory for 12 months. Eggs were obtained under intensive aquarium conditions, and the number of eggs and hatched larvae was observed. The mean total length (TL) of the hatched larvae was 5mm (range 5-5.5mm) initially. The mouth opened 2-3days after hatching (DAH). The yolk sac had been totally absorbed, and the larvae started to swim actively 4-5DAH. Embryonic development was completed within 35-36h at 28±1ºC. The morphological metamorphosis was completed and the larvae transformed into juveniles 27-35DAH. The final total lengths of juveniles at 24, 26, 28, and 30ºC were significantly higher (P<0.05) than at 32 and 34ºC, the lengths being 37.93±2.59, 38.41±1.99, 37.84±2.48, 37.97±1.26, 34.938±4.43, and 33.34±2.35 mm, respectively. The maximum total length (38.41±1.99mm) and weight (0.56±0.07g) were attained on the 75thDAH at 26°C. The results indicated that G. rufa tolerated a range of different temperatures. Specific growth rates (SGR%) were 3.54±0.39, 3.49±0.05, 3.22±0.25, 3.39±0.22, 2.59±0.19, and 2.70±0.20 g at 24, 26, 28, 30, 32, and 34°C, respectively (P<0.05). The survival rates (%) were 100, 100, 100, 100, 90, and 90%, respectively (P<0.05). These results may assist in the development of better techniques for larva culture and hence the more successful production of doctor fish.