略论武昌东湖鲢鳙鱼种的年轮形成及湖泊放养的规格问题

本文对武昌东湖鲢鳙鱼种的年轮形成和放养规格问题进行了研究。东湖幼龄鲢、鳙的年轮形成时期是四月份,环片有规则的由稀疏转向紧密排列,同时伴随切割相是年轮形成的主要标志。Ⅰ和Ⅱ龄鲢、鱅,从4月份开始新的一年长度和重量增长,8月份为高峰期,10月份以后生长速度明显下降,冬季停滞生长。三种不同大小的鲢、鳙鱼种放养结果表明,它们的生长率和回捕率都是不同的,越大的鱼种,生长越快,回捕率也越高。为了提高东湖鲢、鳙放养的效益,建议提高放养鱼种的规格。

ON THE SCALES ANNULI FORMATION OF SILVER AND BIGHEAD CARPS IN LAKE DONG HU, WITH SPECIAL REFERENCE TO THE PROBLEM OF RATIONAL SIZE OF "SEEDLINGS" AT THE TIME OF STOCKING

The problem of rational size of "seedling" at the time of stocking is of growingimportance as lake fisheries develop. During 1973-1978,more than fifteen million fishof different sizes were stocked into lake Dong Hu, in which 86% were silver (Hypo-phthalmichthys molitrix) and bighead carps (Aristichthys nobilis). Studies have beencarried out on the growth and rate of recapture of those fish stocked in 1973. Observa-tions were also made on the characteristics and the time of formation of annuli on thescales so as to obtain scientific basis for determining the rational size of "Seedling" atthe time of stocking. The fingerlings or yearlings on which the growth estimatim are in three differentsizes, namely 11. 5-13. 0 cm (from Zhejiang province), 13. 3-16. 3 cm (fingerlings,reared locally) and 16.6-23.1 cm (yearlings, and locally). 482 individuals weresampled. Distinctions were drawn from the continuation and discontinuation of circuliand by the number of radii of apical part of the scales. The results obtained are asfollows: 1) Annuli formation on scales of silver and bighead carps fingerlings begin inApril. The main charateristics of annuli are the arrangement of circuli from dense tosparse and their continuation and discontinuation. 2) The annuli growth in body length and weight of the fingerlings take placefrom April to late October, the growing season lasts for seven months, with the peakin August. 3) Within the same length group, the growth of bighead carp is more rapid thanthat of silver carp. 4) The growth rate and recapture rate of fingerlings of the three size groups areentirely different. The larger the size at the time of stocking the higher the growthrate and recapture rate. In view of the above results, it is recommended that the rational size of fish atthe time of stocking should be raised to 16.5-23.1cm.