The combined effects of water temperature and salinity on the settlement rate and density (spats/cm 2 ) of Crassostrea gigas pediveliger larvae were studied under the hatchery conditions. Four water temperatures (20.0, 23.0, 26.0 and 29.0℃) were tested at three salinities (20.0, 30.0 and 40.0). The optimum water temperature by salinity conditions were 29.0℃ and 20.0, 30.0 which significantly (P ＜ 0.05) the highest mean (±S.D) larval settlement rate of 43.1 ± 0.1%, 42.1 ± 0.1%, respectively. But the combination of water temperatures and salinities for settlement density was not effected, but each factor as water temperature (29.0℃), salinity (40.0) was shown significantly high and low settlement density, respectively (P ＜ 0.05). The statistics result of settlement density frequency was appeared: mode (1.2-2.3 spats/cm

Twelve species of food microalgae were investigated to clarify the digestion index of Crassostrea gigas larvae using epifluorescence microscopy to choose an appropriate diet for artificial seed production in hatchery. An experiment was conducted using 1 (D shaped stage), 4 (Early umbo stage), 8 (umbo stage) and 12 (Full grown stage) days old larvae. larvae were stocked in 1 L flasks at 5 individuals/mL and fed 10×10 4 algal cells/mL of each species individually. Prior to larvae were fed for 3 h and then were observed under the microscope to detect ingestion; larvae were then sieved and replaced in 1 L flasks containing filtered seawater and were observed after Therefore, it is assumed that food microalgae showing the high digestion such as I. galbana should be supplied to the early umbo stage larvae, and then after the umbo larval stage, the mixed microalgae with diatoms and light green algae should be supplied to the full grown stage larvae to increase the digestion of their larvae.Keywords: Digestion index, Epifluorescence microscopy, oyster, Crassostrea gigas, microalgae, larval development. 서 론현재

Aquaculture is challenged by a number of constraints with future efforts towards sustainable production. Global climate change has a potential damage to the sustainability by changing environmental surroundings unfavorably. The damaging parameters identified are water temperature, sea level, surface physical energy, precipitation, solar radiation, ocean acidification, and so on. Of them, temperature, mostly temperature elevation, occupies significant concern among marine ecologists and aquaculturists. Ocean acidification particularly draws shellfish aquaculturists' attention as it alters the marine chemistry, shifting the equilibrium towards more dissolved CO 2 and hydrogen ions (H + ) and thus influencing signaling pathways on shell formation, immune system, and other biological processes. Temperature elevation by climate change is of double-sidedness: it can be an opportunistic parameter besides being a generally known damaging parameter in aquaculture. It can provide better environments for faster and longer growth for aquaculture species. It is also somehow advantageous for alleviation of aquaculture expansion pressure in a given location by opening a gate for new species and aquaculture zone expansion northward in the northern hemisphere, otherwise unavailable due to temperature limit. But in the science of climate change, the ways of influence on aquaculture are complex and ambiguous, and hence are still hard to identify and quantify. At the same time considerable parts of our knowledge on climate change effects on aquaculture are from the estimates from data of fisheries and agriculture. The consequences may be different from what they really are, particularly in the temperature region. In reality, bivalves and tunicates hung or caged in the longline system are often exposed to temperatures higher than those they encounter in nature, locally driving the farmed shellfish into an upper tolerable temperature extreme. We review recent climate change and following environment changes which can be factors or potential factors affecting shellfish aquaculture production in the temperate region.

We determined the effects of neuroactive compounds known as synthetic larval settlement inducers on the settlement of the Pacific oyster C. gigas pediveliger on the larval collector. Six types of the inducers, serotonin (5-HT), γ-amino butyric acid (GABA), L-3,4-dihydroxyphenylalanine (L-DOPA), norepinephrine, epinephrine and methyl bromide (MB) were tested. All the chemicals induced larval settlement, MB being the most effective with settlement rate of 42.7 ± 2.7%, followed by GABA (35.4 ± 2.0%), 5-HT (29.1 ± 2.2%), L-DOPA (19.2 ± 2.1%), epinephrine (15.2 ± 0.9%), and norepinephrine (11.0 ± 1.2%). The chemicals γ-amino butyric acid and methyl bromide were also better in terms of settled density on the collector with their respective density of 1.97 ± 1.42 and 2.37 ± 1.86 ind/cm 2 , reminiscent of being most effective candidates for a larval settlement inducer in the oyster hatchery. Keywords