Effects of photoperiod on survival and growth of the marine pejerrey Odontesthes argentinensis larvae.

摘要

Fertilized eggs of pejerrey (Odontesthes argentinensis) were collected at Cassino Beach, Rio Grande, Brazil, and transferred to the Laboratory of Mariculture at FURG. After hatching, groups of 100 larvae were distributed in 12 larviculture tanks (15 litres) placed in a water bath. Four photoperiod regimens were tested for 21 days: 0L:24D, 12L:12D, 18L:6D and 24L:0D (L: light; D: dark), each treatment being replicated three times. Larvae were fed with newly hatched Artemia nauplii. Water salinity, temperature and the number of dead larvae were registered every day in the morning. In order to maintain water quality, sedimented residues were siphoned out and 80% of the water was renewed every day. Seawater provided to the tanks was filtered (5 mm) and was constantly aerated using air stones. Larvae were anaesthetized with benzocaine (25 ppm), weighed on an electronic scale to the nearest 0.01 g and measured under a stereomicroscope to the nearest 0.01 mm every 7 days (n=530 per tank). At the same time, the digestive tract was examined for the presence of food. Survival, daily specific growth rate and Fulton's condition factor were calculated. It was shown that larval survival was not significantly affected by photoperiod (P