2003 Volume 67 Issue 2 Pages 88-98
Laminaria japonica inhabiting the east coast of the Oshima peninsula and the northeast coast of the Tsugaru strait have been cropped in fishery. Yields of L. japonica in Hakodate located in the central part of the Tsugaru strait have longterm and short-term periodic variations. The Coastal Oyashio water characterized by low temperature and rich nutrient flows into the Tsugaru strait from the Pacific Ocean during winter and spring. To study a relationship between strength of intrusion of the Coastal Oyashio water and variation in yields of L. japonica, current directions and velocities obtained from the ADCP (Acoustic Doppler Current Profiler) mounted in the research vessel Kinseimaru at the eastmouth of the Tsugaru strait were analyzed in relation to the sea-level difference between Fukaura and Hakodate. When sea-level differences were negative, the Coastal Oyashio water flowed into the strait over the cape Shiokubi. Moreover, relationship between sea-level differences averaged from January to March and next-year yields of L. japonica, which were removed the periodic variations under 3 years, showed negative correlation. Consequently, survival rates of young sporophytes were probably controlled by the strength of intrusion of the Coastal Oyashio water. Next, year-to-year variation for yields of L. japonica were reproduced by using the reproductive model taken the strength of intrusion of the Coastal Oyashio water and the effect of gap regeneration for the kelp forest. From model results, we concluded that the strength of intrusion of the Coastal Oyashio water affected the long-term variation of the yields of L. japonica, and the gap regeneration affected the 2 or 3 years variation of the yields ofthat.
