The seasonal and inter-annual variation in chlorophyll a concentration in the Kitanada Bay located at the eastern coast of the Bungo Channel was investigated using the data of oceanographic monitoring conducted by Tsushima town, Ehime Prefecture. The relationship between the variations in physical conditions and chlorophyll a concentration was also investigated. From April to October, the density structure of Kitanada Bay was estuarine type. Low density water spread from the bay head to bay mouth at the surface. On the other hand, it was inverse estuarine type from December to February, cold and high density water plunges along the bottom from bay head to the bay mouth. The chlorophyll a concentration in the bay was low in the inverse estuarine period and high during the estuarine type period especially in the surface layer. The net ecosystem production (NEP) of chlorophyll a was estimated with a box model analysis. The NEP of chlorophyll a amounted around 400 kg chl-a day^-1 in the estuarine type period, but it was around zero in the inverse estuarine period. The integrated NEP of chlorophyll a throughout the year indicates that the Kitanada Bay is a source of chlorophyll a for the offshore water. There was a good relationship between the mean summer chlorophyll a concentration in upper 5 m in and outside of the Kitanada Bay and the bottom water temperature in the offshore region that is an indicator of the activity of the bottom intrusion from the shelf slope. It indicates that the nutrient supply by the bottom intrusion in the Bungo Channel enhances the phytoplankton production even in the shallow tributary bay. It was supposed that the low chlorophyll a production in winter Kitanada Bay was caused by the decline of riverine input of nutrient and stop of nutrient transport from outside of the bay along the bottom due to the inverse estuarine circulation and the absence of bottom intrusion.

We examined the spatial and temporal distribution of copepod nauplii in Ariake Bay. Surface density of copepod nauplii was high in the inner and center part of the bay, and lower toward the outer bay. Nauplii density increased in summer, which attained to over 9000 individuals l^l, and declined in winter. Their density was high in the upper layer (0–5 m depth) during summer and autumn, and the high density was correspondent with high chlorophyll a concentration. Most of the copepodites (including adult stage) were Oithona spp.; they were the most abundant in summer. Chlorophyll a concentration and copepod nauplii density were higher in the neap tide comparing to those in the spring tide, suggesting that differences in oceanographic conditions (eg. transparency and vertical stratification) due to the change in intensity of tidal mixing may strongly control plankton distribution in Ariake Bay.

A method of measuring fish body lengths at a fish market was developed using a photo image analyzing technique. The method was used to obtain total length composition (commercial categories) of the spotted sole, Eopsetta grigorjewi, landed at the fish wholesale market in Shimonoseki, Yamaguchi Prefecture, Japan. The greatest advantage of the method was the freedom given from handling specimens, allowing quick and easy application under various circumstances. Fish total lengths could be measured with very high precision from photographs of individual fish placed on a flat surface. Because spotted sole was packed according to commercial size categories in separate styrofoam containers before landing, accurate total lengths could be obtained relative to the inner length of the container at the same level as that of the fish snout (TL_lb). Major errors in TL_lb arose from fish inclination (caudal fin tip generally located 0-5 cm higher than snout level) and the convex body shape. Fish inclination resulted in an overestimation of length and the convex body in an underestimation. Because these two factors showed a positive relationship, body convexity increasing with fish inclination, the two error factors essentially cancelled each other out, resulting in a minimal overall measurement error. Between 25% and 50% of fish in photographs of packed fish were entirely visible and able to be measured. No significant difference was found in mean lengths between measurements of visible fish only and all individuals in the container. Mean total length TL_N (cm) for each commercial size category N (N: number of sole per container) was formulated by the allometric equation, TL_N=55.9N^-0.23.

We estimated the supply source of anchovy (Engraulis japonicus) larvae caught by the coastal fishery in Ise Bay and the western Enshu-Nada using a spawner-recruit model. In this model, the Ricker curve, which was evaluated to be the most appropriate among some functions, was adopted to show relationships between the monthly catch of larvae and the number of eggs caught in Ise Bay and the western Enshu-Nada. The determination coefficients of the model were 0.188-0.285 (p<0.01) from April to September and 0.052-0.178 (p>0.01) from October to December. Fluctuation of the number of eggs caught in the western Enshu-Nada was similar to that in the other parts of the coastal sea off the Tokai districts. Using the model, we estimated the monthly larval recruits from Ise Bay, the coastal sea off the Tokai districts and the other distant areas, respectively. The estimated value of the mean monthly larval recruits from Ise Bay was over 200 tons from June to September, that from the coastal sea off the Tokai districts was over 200 tons from May to August, excluding July, and that from the other distant areas was over 200 tons in May and July. The seasonal changes of the estimated values of the Ricker parameters and the monthly larval recruits were consistent with the seasonal changes of the anchovy spawning grounds and the rainfall, both of which affect survival and transport of larvae.