Ryan Murashige

The paradox of using background phytoplankton during the larval culture of striped mullet, Mugil cephalus L.

Abstract The role of the microalga Nannochloropsis oculata in the rearing of striped mullet ( Mugil cephalus ) larvae was investigated during the first 15 days posthatching. Striped mullet larvae at a density of 20 larvae l −1 were initially provided with rotifers at a density of 10–20 rotifers ml −1 . Rearing took place in two sets of six 30-l tanks that differed only in the addition of phytoplankton (500 000 cells ml −1 ) to one set of tanks. No significant differences in temperature, pH, salinity or dissolved oxygen (DO) were detected between treatments. Un-ionized ammonia (NH 3 ), however, was found to be significantly higher in the tanks stocked with background phytoplankton (range 0.02–0.13 mg l −1 ) as opposed to those that were not ( −1 ). A significant improvement in both larval survival and growth was consistently observed during two independent rearing trials when larvae were reared in the presence of background phytoplankton. The results demonstrate the importance of background phytoplankton during the rearing of striped mullet larvae.

Factors affecting intensive larval rearing of striped mullet, Mugil cephalus

Abstract Experiments were conducted on larvae of Mugil cephalus to determine onset of feeding, temporal changes in food selectivity, initial stocking density of larvae, rotifers and phytoplankton, and the effectiveness of enriching food organisms. Larvae were observed to possess rotifers in their gut at 70 h posthatch. A significant ( P Artemia resulted in significantly higher growth ( P Artemia or rotifers. Initial larval stocking densities were inversely correlated with survival ( r = −0.58, P 3 cells/ml.

Rotifers fed various diets of baker's yeast and/or Nannochloropsis oculata and their effect on the growth and survival of striped mullet (Mugil cephalus) and milkfish (Chanos chanos) larvae

Abstract The rotifer Brachionus plicatilis (S-type Hawaiian strain) was cultured with various combinations of bakers yeast and Nannochloropsis oculata . There were no significant differences in the daily rotifer production and amino acid profiles of the resulting rotifers. The significantly lower levels of fatty acids (C14, C16, C20:4 n −6, C20:5 n −3 and C22:6 n −3) observed in the rotifers were found to correspond with the amount of yeast presented in their diet. The low survival and growth of striped mullet larvae recorded at Day 15 posthatching indicates that rotifers fed only yeast were nutritionally deficient in fatty acids. The fatty acid requirements of mullet, however, appeared to be satisfied with rotifers cultured on a combination of yeast and N. oculata . In contrast, no significant differences in larval milkfish survival and growth at Day 10 posthatching were detected when using rotifers fed the various diets in the larval rearing protocol.

The effect of salinity on the survival and growth of striped mullet (Mugil cephalus) larvae in the hatchery

Abstract Newly hatched striped mullet larvae were exposed to salinities ranging between 17–18, 22–23, 27–28, and 32–35 ppt and reared in 30-l polycarbonate tanks for 15 days posthatching. In addition, newly hatched larvae were exposed to salinities ranging between 22–23 ppt and 32–35 ppt and cultured at their respective salinities in 5000-l tanks until 50 days posthatching. In the small-scale, shortterm experiments, no differences in survival (range: 30.5%–41.0%) were detected across the salinities tested. However, larvae from the 22–23 ppt group were significantly and consistently larger (5.9±0.8 mm total length) than those exposed to the higher salinities (5.4±0.7 mm TL). In contrast, the large-scale, long-term experiments, resulted in no significant differences in survival (29.0%±13.6% and 22.0%±4.6% for the 32–35 and 22–25 ppt groups, respectively) or growth (19.4±5.0 mm TL and 19.9±4.6 mm TL for the 32–35 and 22–25 ppt groups, respectively). No apparent advantage or disadvantage derives from adjusting the salinity during a larval-rearing trial of striped mullet.