Spawning pattern and type of fecundity in relation to ovarian allometry in the round herring <Emphasis Type="Italic">Etrumeus teres</Emphasis> |
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Authors: | Guido Plaza Hideo Sakaji Hitoshi Honda Yuichi Hirota Kazuya Nashida |
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Institution: | (1) Escuela de Ciencias del Mar, Facultad de Recursos Naturales, Pontificia Universidad Católica de Valparaíso, Avenida Altamirano 1480, Valparaíso, Chile;(2) Kochi Kuroshio Research Laboratory, National Research Institute of Fisheries Science (NRIFS), Fisheries Research Agency (FRA), Sanbashi-dori 6-1-21, Kochi 780-8010, Japan;(3) Stock Assessment Division, National Research Institute of Fisheries Science (NRIFS), Fisheries Research Agency (FRA), 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan;(4) Research Promotion and Development Department, FRA, Minato-Mirai 2-3-3, Nishi-Ku, Yokohama 220-6115, Japan;(5) Tropical Tuna Resources Division, National Research Institute of Far Seas Fisheries (NRIFSF), Fisheries Research Agency (FRA), 5-7-1 Orido, Shimizu, Shizuoka Shizuoka, 424-8633, Japan |
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Abstract: | Spawning pattern (assessed by seasonal changes in ovarian developmental stages) and type of fecundity (assessed by analysis
of oocyte-size frequency distributions) of the round herring Etrumeus teres were studied in relation to ovarian growth and seasonal changes in the gonadosomatic (GSI), hepatosomatic (HSI) and liposomatic
(LSI) index as well as the somatic condition of spawners (CS) in a spawning ground of southern Japan. Except for summer, mature
and recently spawned ovaries occurred all year round. Oogonia and primary oocytes were present in all ovaries, and cortical
alveoli stage (CA) oocytes occurred in all mature, hydrated and partially spent (PS) females (PS: females containing post-ovulatory
follicles). Before hydration, a clutch of larger yolked oocytes, undergoing synchronous growth (range 0.7–1.1 mm), was present
in mature ovaries which was completely separated from a more heterogeneous clutch of oogonia, primary and secondary oocytes
(<0.150 mm) and oocytes in the CA stage (range 0.15–0.60 mm). As vitellogenesis progressed, the yolked clutch increased in
size but the CA oocytes remained arrested. The latter entered into the secondary growth phase when hydration started in the
advanced batch. Ovarian growth was isometric in all developmental stages, validating the use of GSI, which showed a consistent
monthly evolution among years. Spawning stopped in summer (July and August) and peaked in winter and spring. HSI correlated
positively with GSI on both a monthly mean basis (r = 0.76) and individual fish basis (liver weight explained 67–83% of the variability in ovary weight when females were grouped
into 1-unit GSI intervals) suggesting a significant role of liver in vitellogenesis. LSI and CS also showed marked seasonal
changes peaking from summer to middle autumn. Overall results suggest that E. teres is a multiple spawner with a group-synchronous ovarian development and indeterminate annual fecundity, with the three processes
linked to an isometric growth of the ovary. We propose that such a reproductive pattern is an adaptation to produce batches
of large pelagic eggs through a protracted spawning season. |
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