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51.
There is a low nutrient level in the Aoshan Bay. In June 1999, the chemical adjustmentand control experiment was made in the Aoshan Bay. Following tracts investigation was carried out before the experiment and on the 1st, 2nd, 4th, 5th, 6th and 45th day/after the experiment. While the variance of amount of phytoplankton, the replacement of superior species and the species composition of phytoplankton were researched. The results show that the amount of phytoplankton in the Aoshan Bay rises gradually after the experiment. Ceratium macroceros Cleve of pyrophyta was the dominant species before the experiment, its dominant index was 37.7%. Six days after the experiment, its dominant index dropped to 17.6% . Meanwhile the dominant index of Asterionella japanics Cleve rose from 7.1% to 39.2% , it became the first dominant species. Forty-five days after the experiment, the amount of phytoplankton in the Aoshan Bay was 5.15 to 137.32 times more than that in 1997. 相似文献
52.
The food consumption and ecological conversion efficiency of a species marine pelagic andsmall size fish, Hyporhamphus sajori, were determined by using in situ stomach content method presented by Eggers. The results showed that: (1) the fish was taken in food all day, so empty-stomach rate was very low, taking up about 4.5% of the total determined fish number. However, the fish still has significant daily feeding rhythm. A feeding peak was found 0:00 o'clock at night, but feeding level was always high in the daytime; (2) relationship between instantaneous food content in stomach and corresponding time could be described as S_t = a ·e ~(-b ·t). There was not significant difference of instantaneous gastric evacuation rate between two determinations, with average value being 0.13 × 10~(-2)g/ (g·d) (wet weight); (3) the daily food consumption tended to change in irregular waving form, with average value being (10.16×l0~(-2)±1.19×l0~(-2) g/ (g·d) (wet weight) or (55.56 × 10~(-2) ±6.51 × 10~(-2) kJ/ 相似文献
53.
东海虾类的生态群落与区系特征 总被引:6,自引:0,他引:6
有关东海的虾类,刘瑞玉(1959,1963,1964)、董聿茂(1959,1980,1986)等已做过大量的调查研究。近10多年来,由于东海传统的主要经济鱼类资源衰退,捕食虾类的鱼类减少,因此,使虾类生存空间扩大,这有利于虾类资源的繁衍生长,使虾类资源发生量增多,数量增长较快。东海区三省一市近几年虾类产量达到80×104~90×104t,其中浙江省为60×104~70×104t,拖虾作业已成为东海区一大作业方式,对促进海洋捕捞业的发展起重要作用。20世纪80年代中后期,我们开展了东海虾类资源开发调查,尔后又继续与拖虾生产船相结合进行监测调查,积累了一些资料,本文就东海虾类生态群落结构与区系特征进行探讨。 相似文献
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探讨淡水养殖尤其是大水域网箱养鱼中由于投饵方式的不当和投饵量过多导致过剩饵料沉积引起水域环境污染的解决方法。本研究利用鱼类的听觉生物学特性,参考音响驯化技术的有关参数,结合投饵用400 Hz正弦波连续音对鲤(Cyprinus carpioLinnaeus)进行了音响驯化实验。结果表明,最初放声时,实验鱼产生惊愕反应,迅速离声源而去;但驯化6 d后,实验鱼在放声后迅速游向声源,摄食时间由最初的150 s缩短到实验后期的60 s。整个实验阶段放声组与对照组摄食时间差异极显著(P<0.01),摄食率和特定生长率无显著差异(P>0.05)。根据实验鱼的生长参数,求得了参考投饵量曲线和方程。本实验结果为音响驯化技术在淡水鱼养殖中的推广应用提供了基础数据。 相似文献
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A Santa Marta JG Ferreira GC Pitcher J Lencart e Silva 《African Journal of Marine Science》2020,42(2):151-166
The carrying capacity for bivalve shellfish culture in Saldanha Bay, South Africa, was analysed through the application of the well-tested EcoWin ecological model, in order to simulate key ecosystem variables. The model was set up using: (i) oceanographic and water-quality data collected from Saldanha Bay, and (ii) culture-practice information provided by local shellfish farmers. EcoWin successfully reproduced key ecological processes, simulating an annual mean phytoplankton biomass of 7.5 µg Chl a l–1 and an annual harvested shellfish biomass of about 3 000 tonnes (t) y–1, in good agreement with reported yield. The maximum annual carrying capacity of Small Bay was estimated as 20 000 t live weight (LW) of oysters Crassostrea gigas, or alternatively 5 100 t LW of mussels Mytilus galloprovincialis, and for Big Bay as 100 000 t LW of oysters. Two production scenarios were investigated for Small Bay: a production of 4 000 t LW y–1 of mussels, and the most profitable scenario for oysters of 19 700 t LW y–1. The main conclusions of this work are: (i) in 2015–2016, both Small Bay and Big Bay were below their maximum production capacity; (ii) the current production of shellfish potentially removes 85% of the human nitrogen inputs; (iii) a maximum-production scenario in both Big Bay and Small Bay would result in phytoplankton depletion in the farmed area; (iv) increasing the production intensity in Big Bay would probably impact the existing cultures in Small Bay; and (v) the production in Small Bay could be increased, resulting in higher income for farmers. 相似文献
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