Browsing by Author "Nakagawa, Heisuke"
ArticleThe lipid content and fatty acid composition were examined in the liver, eye, muscle, brain and intraperitoneal fat body (IPF) of hatchery-bred and wild-caught orange-spotted grouper, Epinephelus coioides. The cultured and wild grouper were classified into three different body weights (small, medium and large size), and submitted to lipid content and fatty acid analysis. Muscle lipid in cultured grouper increased lineally with growth, but that of wild fish decreased. The amount of lipid in the IPF in cultured fish was higher than wild fish. Lipid content and essential fatty acids in cultured fish showed significant change with growth. All organs in the early growth stage of cultured fish seemed to contain poor arachidonic acid (AA) than the wild fish. The liver of small sized cultured fish contained low AA and docosahexaenoic acid (DHA), but no profound change was found in AA during growth of fish. While the proportion of DHA in the liver and IPF increased with growth in cultured fish, muscle DHA decreased with growth. The difference in fatty acid composition between cultured and wild fish disappeared with growth.
ArticleJD Toledo, H Kurokura & H Nakagawa -
Nippon Suisan Gakkaishi, 1991 - Japanese Society of Fisheries ScienceCryopreserevation of different strains of Brachionus plicatilis symmetrical stage embryos was conducted. One S-type strain, namely Yashima-S (YS), and three L-type strains, namely Yashima-L (YL), Nagasaki (NG), and Hamana (HA), were used. Symmetrical stage embryos in 10% DMSO-28‰ sea water solution were frozen at -196°C using a two-step freezing procedure; the embryos were first cooled slowly from -5°C to -20°C at a rate of 0.3°C/min and then cooled rapidly by direct transfer to liquid nitrogen. Frozen samples were thawed in a gently stirred water bath at room temperature. A mean survival rate of 36% after 30 days storage in liquid nitrogen of HA strain was significantly lower than YS (55%), YL (58%), and NG (54%), and is due likely to its relatively larger embryo volume. There was no significant difference in the intrinsic rate of increase (r) between strains among clones taken from the cryopreservation or unfrozen control group. The results also indicate that various strains of B. plicatilis embryos can be cryopreserve without seriously altering their reproductive capability. The freezing method described could be of great potential in aquaculture and in future studies on rotifer genetics.
Effects of salinity, aeration and light intensity on oil globule absorption, feeding incidence, growth and survival of early-stage grouper Epinephelus coioides larvae JD Toledo, NB Caberoy, GF Quinitio, CH Choresca & H Nakagawa -
Fisheries Science, 2002 - Springer VerlagA series of experiments were conducted to examine the effects of salinity, aeration and light intensity on oil globule absorption, feeding incidence, and growth and survival of early-stage Epinephelus coioides larvae. Newly hatched larvae were transferred to 40-L aquaria at a density of 1500 individuals/aquarium. Larvae were exposed to different levels of aeration (0 mL/min per L, 0.62 mL/min per L, 1.25 mL/min per L, 2.50 mL/min per L, or 3.75 mL/min per L); salinity (8 ppt, 16 ppt, 24 ppt, 32 ppt, or 40 ppt); and light intensity (0 lx, 120 lx, 230 lx, 500 lx, or 700 lx) for 4–6 days. Twenty larvae were sampled daily at 11:00 hours to measure for total length (TL), oil globule volume, and feeding incidence. Survival rates were determined by counting the total number of larvae remaining in each aquarium at the end of the experiment. Significantly higher survival rates (P < 0.05) were observed at aeration levels of 0.62 mL/min per L and 1.25 mL/min per L, at salinity levels of 16 ppt and 24 ppt, and at light intensities of 500 lx and 700 lx. The influence of aeration level, salinity and light intensity on oil globule absorption, feeding incidence, and growth and survival of early-stage grouper larvae are discussed.