The spawning bed selection of herring Clupea pallasii off Minedomari, Atsuta, on the west coast of Hokkaido, Japan, is discussed in relation to the topography of the rocky shore and wave conditions during the spawning season. From 1998 to 2003, herring have spawned their eggs mainly on the leaves of the seagrass Phyllospadix iwatensis Makino in almost the same site on the rocky shore off Minedomari in the Atsuta area. The site is connected to a valley-like feature offshore. Wave conditions were surveyed at Minedomari during the spawning season in 2000 and the wave height was estimated from 1998 to 2003, except for in 2000, using the correlation of wave height between Minedomari and Ishikari Bay New Port, approximately 18 km south-west of Minedomari. Herring spawned under calm conditions, during which the wave height was approximately 0.5 m off Atusta and Aoshima and was 0.18-1.28 m off Minedomari. The distribution of water particle velocity on the sea bottom surface as a result of ocean waves off the Minedomari area, which was estimated based on the wave height and the topography of the coast, suggested herring could swim easily into the shallower area along the valley-like feature off Minedomari. Therefore, topographical features are thought to be one of the reasons why herring have used Minedomari as a spawning bed. Additionally, seepage of freshwater from the bottom, which was observed in this area, could also be the reason why herring spawn in Minedomari repeatedly.

, The barren grounds, so-called "Isoyake" in Japanese, exist along the southwest coasts of Hokkaido, Japan. In the lsoyake area, the sea urchin, Strongylocentrotus nudus, dominates the rock bed, and results in disappearance of the kelp, Laminaria religiosa, in all except shallow water refuge. In order to develop the technology of kelp afforestation in the Isoyake area, seasonal changes of selected environmental factors, e.g. water movement, temperature, vegetation and grazers were observed continuously during 1998 1999 in Oshoro Bay. The environments for establishment of kelp forest were summarized; sea urchins were removed to deeper zones by strong water movement and kelp buds were protected from overgrazing during winter. Destructive pressure of the sea urchins occurred on kelp beds with little strong water movement and rock bed for kelp (annual algae) was protected from being occupied by perennial algae during summer. The authors propose two methods to increase kelp forest in lsoyake areas: 1) seasonal control of excess grazing pressure using fences and, 2) adjustment of the sea bed depth with concrete blocks and stone which increased wave velocity and therefore reduced urchin orazino pressure.

Seasonal changes in the composition and food habits ofˆsh communities in a Sargassum confusum-dominated bed oŠ the coast of Ishikari, Hokkaido, Japan were examined. Twenty-seven species, a total of 997 individuals, were collected by beach seine surveys from June 2002 to August 2003. Numbers of individuals and species increased in spring to fall compared to winter. A cluster analysis based on stomach contents composition showed that theˆsh communities comprised eight feeding groups: A) phytal amphipods, B) phytal and benthic amphipods, C) benthic polychaetes and phytal amphipods, D) phytal amphipods and isopods, E) benthic copepods and amphipods, F) planktonic copepods, G) phytal mysids and planktonic copepods, and H) phytal mysids feeders. Ontogenetic diet shifts were recognized in Pholidapus dybowskii, Aulichthys japonicus, Hexagrammos otakii and Syngnathus schlegeli, although Blepsias cirrhosus, Neozoarces steindachneri and Zoarchias veneˆcus were included in

This study is aimed at revealing the dietary protein requirement for gonad production in the sea urchin Mesocentrotus nudus, with consideration of protein leaching from diets during seawater immersion. Feeding trials were performed on M. nudus using two diet types with low capacities for protein leaching: starch diets (STG) containing 0–40% gluten in 10%, 5%, and 4% increments (experiments 1–3) and alginate diets (ALG) containing 5–25% gluten in 5% increments (experiment 4). The protein content in the diets was determined after they were immersed in seawater for 24 h or 72 h. The gonad indices of urchins fed STG with 11.4–19.3% protein were significantly higher than those fed STG with 7.8% protein. The protein requirement was estimated to be 12% based on a broken-line regression analysis of urchins fed STG in experiments 1–3. In experiment 4, the gonads became larger as dietary protein content increased from 4.5% to 12.0%, and the sizes were similar to those of urchins fed ALG with 12.0–21.1% protein. The estimated value of 12% was much lower than that reported previously (>20%), indicating that the protein requirement for sea urchin gonad production is modest when the protein-leaching problem is addressed.

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