| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1995: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1994: ¥1,100,000 (Direct Cost: ¥1,100,000)
|
|---|
| Research Abstract |
1. Settlement depth and growth in the sea
Settlement was most frequent at the depth of 10m among 5,10,20,30, and 40m in the Mutsu Bay, northern Japan. Barnacles at 10 and 20m in depth grew bigger than the ones at 5m for 15months. Newly settled (1993) and one-year old (1992) classes of barnacles were transplanted and kept for more than two years in Okirai Bay, north-eastern Japan. They grew 32mm in basal diameter for the former and 42mm for the latter after 2 years. This means it takes 3 or 4 years to grow 42mm in size in Okirai Bay.
2. Effect of water temperature on the barnacle growth
The lower the temperature, the bigger newly attached barnacles grew and the more they survived for 200 days among 10,15,20, and 25ﾟC temperature regimes. One-year class barnacles showed the same response to the temperature as those of the 0-year class. Barnacles in 20ﾟC regimes showed gradual decrease in survival. The results show that a temperature lower than 15ﾟC is desirable for this species to sustain their population.
3. Distribution of larvae
Cyprid larvae had already appeared in mid February, and only a fewnaupliar larvae were found in March. Cyprids tended to appear more in the Eastern half of the Mutsu Bay rather than in the Western half of it.
4. Larval rearing and their grazing rates
Diatoms Asterionella japonica and Thalassiosira nordenskioeldii supported good growth of larvae under 10-12ﾟC,1-2 larvae/ml, and irrespective of light. Stirring was needed to scatter the larvae by aeration or by propulsion. Grazing rate to A.japonica was increased with growing the larva from 300 cells/nauplius/h (stage II) to 1700 (stage VI).
5. Artificial substrate for settling
Barnacles were settled on poly vinylchloride (PVC) and rubber plates among seven different artificial substrata tested. A used tire would be a good substratum not only for settlement but also removing barnacles from it.
|
