Changes in the growth of the Japanese sardine Sardinops melanostictus during a period of declining stock size was examined by using sardines sampled from 1990 to 1996 in Tosa Bay, south‐western Japan, one of the main spawning grounds on the Pacific coast of Japan during February and March. The growth parameter k‐values of the von Bertalanffy growth equation of female sardines were small in the 1987–1990 years classes, while the values for the 1991–1992 years classes were larger, which corresponded closely with the decrease in catch of the sardines in south‐western Japan, suggesting that there are density‐dependent effects on the growth of sardines in Tosa Bay. In contrast, the body length decreased since the 1993 years class, but the fatness of female sardines improved after 1993. Since 1994, many I year females with transparent eggs in the ovaries have been collected from Tosa Bay. It is speculated that good nutritional conditions of the 1993 year class led to maturation at an earlier age, and that the decrease of growth from the 1993 year class occurred due to the reduction of resources channeled to growth as a result of the maturation at I year.

To evaluate the impact of temporal variation of primary productivity on the recruitment of Japanese sardine (Sardinops melanostictus) in the Sea of Japan, the phenology of sea surface phytoplankton abundance was estimated from 8 day multiple satellite (SeaWiFS, MODIS‐Aqua, MERIS, and VIIRS) derived sea surface chlorophyll (SSChl) a concentrations from January 1998 to December 2015. Because relationships between SSChl a and in situ chlorophyll a concentrations were significantly different among periods based on the satellite combinations used, maximum and minimum SSChl a concentrations of 1 year were relativized as 1 and 0, respectively. Spatio‐temporal variation of relativized SSChl a concentrations was determined by using empirical orthogonal function (EOF) analysis. Scores in the first EOF mode denoted the basin‐scale variations of SSChl a concentrations in the Sea of Japan, and the major peak from the end of February to the end of May displayed the spring bloom. The logarithm of recruitment per spawner (LNRPS) for sardine was positively affected by delays in the start and end dates of the spring phytoplankton bloom. The delay of the date of the lowest sea surface temperature contributed to the delay of the end of the spring bloom during the period 1998–2015 and elevated the LNRPS during the period 1982–2015. Sardine spawns in the southern Sea of Japan from April to May, hence, delays of the spring bloom prolonged its overlap with sardine larval periods, and thus improved the recruitment of Japanese sardine in the Sea of Japan.

To know a physiological role of vitamin in the development of fish eggs, changes in the contents of ascorbic acid, pantothenic acid, biotin, niacin and vitamin B6, and activities of glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) in developing rainbow trout eggs were determined.The ascorbic acid content rapidly decreased by half level on third day after fertilization, thereafter the vitamin tended to decrease during development. The sac fry, when a substantial amount of the yolk had disappeared, retained the ascorbic acid and was about one fourth of that of the initial eggs. The amounts of thiamine, pantothenic acid and biotin were reduced by half during the course of development, while niacin content tended to increase after hatching. The amounts of vitamin B6 decreased by about 45% during the course of the development. Some variation of the composition were found: the concentration of pyridoxal decreased appreciably, while those of pyridoxal 5'-phosphate, pyridoxamine 5'-phosphate and pyridoxamine increased in the course of development.The activities of GOT and GPT were very low in the early stages of development. After hatching, the activities of the vitamin Be enzymes increased greatly.

The nutrient concentrations at depths of 0–200 m in the southern area of the Japan Sea were investigated at 97 stations during six cruises between June and October in 2013 and 2014. The nutrient concentrations at the surface were depleted to less than 0.1 µM, except for silicates, which remained at 0.8–5 µM, and increased below the nutricline, at depths of 20–125 m. The vertical profiles of nitrate, silicate, and/or phosphate concentrations between 131°30′E–139°40′E and 35°50′N–40°40′N showed a peak in the subsurface layer at 40, 71, and 6 stations, respectively, and nutrient inversions occurred at macroscale widths. The subsurface nutrient maximum occurred at depths of 20–150 m in waters at temperatures of 15–16°C and potential densities of 25.3–25.5 σθ, on average. The depths of the subsurface nutrient maximum were generally associated with a salinity maximum originating in the bottom water of the shallow Tsushima Strait. The nutrient inversions were disturbed by phytoplankton consumption, as indicated by the presence of the subsurface chlorophyll maximum at the same depth or below the salinity maximum at stations without nutrient inversions. Therefore, it was inferred that remineralization of nutrients near the bottom, from the East China Sea to the Tsushima Strait, and horizontal advection by the Tsushima Warm Current below the euphotic layer induced macroscale subsurface nutrient inversions in the southern Japan Sea.

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