Ecological studies on medaka in a remained habitat in Qinhuangdao, Hebei, China

Abstract

Ecological studies were carried out in the remaining habitat for medaka (Oryzias latipes), a marsh in the suburbs of Qinhuangdao City, Hebei Province, China. Sewage released from villages increases the nutrient levels in open water areas of the marsh, while in cattail (Typha angustifolia) and reed (Phragmites communis) beds the nutrient levels are decreased. There are fewer zooplanktons in the cattail and reed beds than in the open water areas. Sampling fishes with trap nets showed that medaka lived in dense populations in the cattail and reed beds, while the other three fish species, wild goldfish (Carassius auratus), topmouth gudgeon (Pseudorasbora parva), and mud loach (Misgurnus bipartitus), occupied the open water areas in the marsh. A little amount of paradise fish (Macropodus chinensis) was also found in the marsh. Japanese freshwater shrimps (Macrobrachium nipponense) were found only in the influx canal from waterworks. Indoor aquarium experiments showed that the wild medaka in this marsh was easily cultured with commercial feed similar to domesticated strains. Some ecological aspects of the medaka were discussed based on the observations of the fish in the marsh.

Key words： medaka; Oryzias latipes; endangered fish; habitat; ecology

Acknowledgements

We are grateful to Prof. Yanzhen Zhao (associate professor in aquaculture department of the college) for her help in zooplankton identification, and to Jian Zhao, Tongguang Shen and Liang Fu (students in the department of ocean science of the college) for their participations in wild investigations. We thank Prof. Hui Wang and Dr. Zhongli Yao (East China Sea Fishery Research Institute, Chinese Academy of Fishery Sciences) for their trials in the use of this wild medaka in their research work.

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