Seasonal variation of reproduction rates and body size of Calanus sinicus in the Southern Yellow Sea, China |
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Authors: | Zhang Guang-Tao; Sun Song; Zhang Fang |
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Institution: | Key Laboratory of Marine Ecology & Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071, China |
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Abstract: | Annual variations of egg production rate (EPR) and clutch sizeof Calanus sinicus, as well as body size of females (prosomelength and dry weight), were investigated at a series of stationsin the Southern Yellow Sea by onboard incubation. Calanus sinicuswas spawning in all the 11 cruises investigated, and the annualvariation of EPR was bimodal. Monthly average EPR was highestfrom May to July, respectively, 5.97, 5.36 and 6.30 eggs female1d1, then decreased dramatically to only 1.37 eggs female1d1 in August and attained the lowest 1.07 eggs female1d1 in October. In November, average EPR increased againto 4.31 eggs female1 d1. Seasonal variation ofclutch size was similar to EPR, except that it decreased graduallyafter August rather than dramatically as did EPR. Prosome lengthof females was maximum in May and minimum in October, but dryweight was highest in November. Monthly average EPR correlatedbetter with prosome length than dry weight, while clutch sizewas rather determined by dry weight of females. It is suggestedthat egg production of C. sinicus was active during two discontinuousperiods when both surface and bottom temperature fell into itsfavorite range (i.e. 1023°C), and different reproductivestrategies were adopted in these two reproductive peaks: otherthan the highest EPR, longer prosome length was also achievedby C. sinicus from May to July, while females in November developedshorter bodies but accumulated more energy for reproduction. |
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