天草周邊に於ける重要生物の資源學的研究III.天草沿岸のマイワシに就いて

Abstract

Though the Japanese sardine, Sardinia melanosticta (Temminck & Schlegel), has been closely reserched by several authors, that of the west coast of Kyusyu has not yet been dealt with satisfactority. Therefore, we observed this fish at Tomioka, Amakusa, from September in 1946 to February in 1948, to make clear its some biological characteristics. The fishing season of the said fish is extending from April or May to November at the mentioned districts. It measures from 60mm to over 160mm in total length, most of the catch belonging to O-age group. The average number of vertebrae for each group ranges from 50.29±0.0580 (S. E.) to 50.65±0.0348 (containing a urostyle). Comparing it with those of the other districts in Japan, it is a rather low in value. The coefficient of variability of total length, C (=σ×100/M; M, average, to ?? al length in mm; σ, standard deviation), lies from 3.36 to 17.45. We can not recognize a clear relation between total length and C, but the seasonal variation of C is rather distinct, showing a minimum from the latter part of July to the middle of August. The yalues of k and n in a formula, W=kLn (W, body weight in g; L, total length in mm), are 1.97×10-6 and 3.269 respectively. When n is made equal to 3.269, the value of k for each group lies from 1.71×10-6 to 2.44×10-6. Such a value of k bears a close relation to the total length as far as we observed, being maximum at 100mm in total length. Further it varies according to the advancement of the season, showing a minimum in the latter part of July. We consider that its seasonal variation is strongly affected by that of total length.