闽南—台湾浅滩二长棘鲷年龄和生长研究

AGE AND GROWTH OF RED-FIN PARGO, PARARGY ROPS EDITA,IN SOUTH FUJIAN AND TAIWAN BANK FISHING GROUND

本文根据闽南—台湾浅滩1019尾二长棘鲷年龄和生长的周年资料,阐明年轮特征及其形成时期、生长发育阶段和参数,并探讨种群结构的资源特点。其鳞片可作为年龄鉴定依据,从鳞片边缘增长率和体长分布频率,表明年轮每年形成一次,3—4 月为年轮主要形成时期。逆算体长不存在 Rosa Lee现象,各年龄组平均体长的实测值,以定差法所求得的生长参数为最佳值。衰老拐点(相当于Ⅳ龄组)正处于成鱼强壮期转入老年鱼生长衰老期。拖网周年渔获中0龄组最多,Ⅰ龄组次之。应严格限制拖捕当年生的0龄组幼鱼。

The samples of 1019 young and adult red-fin pargo, Parargyrops edita Tanaka, caught by double draggers in the South Fujian and Taiwan Bank fishing ground werecollected monthly from December 1978 to November 1979. Scales are taken from themiddle between the 5-10th dorsal spines and the left lateral line used to determine theage and the growth rates of the fish. The true annuli of the scales ase shown as disco-ntinuous or bsoken circuli on the scales and are formed annually. The age groups arenormally distinguishable in length-frequency distribution. Data on the rates of marginalincrement of the scales show that the time of annulus formation relating to its reprodutiveactivity occurs chiefly during March to April. The relationship between the body lengthL (mm) and the scale radius R (mm) is expressed to be R=0.12229+0.02108L, thelength-weight relationship formulas are calculated to be W=3.2851×10^(-5)L^(3.0299), W'=4.5821×10~5L^(2.5723), where W and W' represent net body weight (g) and total bodyweight (g) respectively. The result of length back-calculation indicates the absence ofthe Rosa Lee phenomenon. According to the mean observed body lengths for each agegroup, Walford's plot method is used to compute the optimal parameter L_∞. Thegrowth parameters are: L_∞=248mm, W_∞= 592g, k=0.17, t_0=-1.24, and the senileinflection point t_r= 5.08 years (approximate to Ⅳ age group). The growth curvesdrawn by von Bertalanffy growth equation show no significant difference between themean calculated lengths (or weights) and the mean observed lengths (or weights).Red-fin pargo matures at one year old and the growth rates decrease after the end ofadult stage. Age groups 0 and I are predominant in commercial catches, the fish olderthan Ⅳ group are not common in catches. The minimum catchable age group and sizeof this fish may be suggested to be I age group, 110 mm in length and 50 grams inweight.