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Yoneda M.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Yamamoto M.,Kagawa Prefectural Fisheries Experiment Station | Yamada T.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Takahashi M.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Shima Y.,Seikai National Fisheries Research Institute
Journal of the Marine Biological Association of the United Kingdom | Year: 2015

Temperature is one of the most influential factors for the sexual maturation of fishes, but understanding of the extent to which temperature affects the maturational schedules is limited in multiple-spawning fishes over a protracted season. This study examined the effect of temperature on sexual maturation of Japanese anchovy Engraulis japonicus siblings under high and low temperature regimes on different birthdates. The maturation probability differed between the two temperature regimes. Specimens in high temperature regimes matured at much smaller size and younger age than their counterparts. Also, a significant difference in the maturation probability between sexes was found at low temperatures, but not at high temperatures. Our findings show that temperature affects the maturational schedules of siblings of Japanese anchovy, suggesting that the size and age at sexual maturation could differ among cohorts, even in a given sampling location and/or year. Copyright © Marine Biological Association of the United Kingdom 2015. Source


Yamamoto M.,Kagawa Prefectural Fisheries Experiment Station | Nagano T.,Kagawa Prefectural Fisheries Experiment Station | Makino H.,Kagawa Prefectural Fisheries Experiment Station | Ueta Y.,Kagawa Prefectural Fisheries Experiment Station | And 3 more authors.
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2011

Natural infections of adult Neoheterobothrium hirame, a haematophagous monogenean parasite, on Japanese flounder Paralichthys olivaceus in the central Seto Inland Sea off Kagawa Prefecture, Japan, were monitored from 1997 to 2010. N. hirame was found for the first time in the survey area in 1998, and the prevalence rapidly increased annually, reaching a peak level of 52.4? in 2000, then remained at the high level until 2005, and subsequenty suffered a sharp and constant decline until 2010. Occurrences of severely anemic fish were rare and condition factors of the affected fish were not related to N. hirame infection. Whereas the prevalence and intensity of the parasite were statistically irrelevant to the sex or age of the host, they were significantly higher in winter and spring than in summer and fall, indicating a seasonal fluctuation. The prevalence and intensity in the survey area were lower than those reported in the western sea of Japan, which might be affected by environmental factors and biological features of Japanese flounder in this area, including drastic seasonal changes of the water temperature, higher than 25°C in summer and lower than 10°C in winter, and differences in their habitat in the Seto Inland Sea between 0-year-old naïve fish and one-to two-year-old infected fish. Source

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