FISHERIES RESEARCH INSTITUTE,MOA,TAIWAN

This study successfully induced spawning and fertilization of the olive flounder (Paralichthys olivaceus) in an artificial feeding environment using temperature stimulation, achieving a fertilization rate of 81.2%. The fertilized eggs of the fish were buoyant and semi-transparent, with an average diameter of 0.94 ± 0.01mm and an oil globule averaging 0.16 ± 0.01 mm in diameter. These eggs hatched at 32 hr after fertilization (Temperature = 22 ± 1℃; salinity = 33–35 psu). The newly hatched larvae averaged about 2.12 ± 0.03 mm in total length. The larvae (3.47 ± 0.76 mm) were fed with rotifers (Brachionus plicatilis) from the 3rd day post hatching (DPH). A microalgae (Nannochloropsis oculata) was added to stabilize the water quality and nourish the rotifers. The average total length of the 6 DPH fry was 4.58 ± 0.18 mm. Artemia (Artemia spp.) were used as a feed additive for nutrition enrichment. The average total length of the 18 DPH fry was 5.82 ± 0.21 mm. Then, the coronary fin on the head of each larva began to grow. At this time, we continued to use the artemia for nutrition enrichment. The average total length of the 24 DPH fry was 8.38 ± 0.11 mm; their swimming was tilted and the relative position of their eyes began to change. When the eyes were on the same side at 38 DPH (13.88 ± 1.26 mm), the fry began to metamorphose to the benthic stage. The salinity level was then set to 5–40 psu. In the salinity test, it was found that a significantly higher hatching rate (77.8 ± 1.4%) was obtained at 30 psu (p < 0.05). Furthermore, through salinity tests with different incubation times (24, 48, or 72 hr), this study found that the 20 psu and 30 psu tests had an optimum survival rate of 72% and 75%, respectively, at 72 hr of treatment.