日本海南西海域におけるドスイカについて

Abstract

In order to obtain information on the biology of Berryteuthis magister in the southwestern Japan Sea, a total of 1484 specimens sampled from midwater (at 35-180m) and bottom trawl (at 287-665m) catches were investigated. The results obtained aze summarized as follows. 1. Most of the females of Berryteuthis magister attain sexual maturity at about 180mm in mantle length and the males at about 130mm. 2. Spawning season was confirmed to be from December to May with a peak between Febru-ary and March. 3. The total production of eggs larger than 0.5mm considerably varied from about 6000 to 10000. It may be that female spawn a few times, and number of eggs in a single spawning perfemale is about 400. 4. In these waters, perhaps Berryteuthis magister spend their early life (smaller than about 50-60mm in mantle length) at surface layers, and adults live near the bottom. 5. Most of the females attain sexual matulity at about 2 years and the males about 1.5 years. The lifetime of females is around 2 years or more, and of the males is same as the females or less than that. 6. The growth of Berryteuthis magister from these waters can be expressed by the following equations.Female: MLt=206.9(1-e-0.186(t-0.070))Male: MLt=179.5(1-e-0.120(t-5.570))(ML mm: Mantle length, t: Number of months) 7. The main diet species of Berryteuthis magister varied considerably with the growth. That is to say, they are Crustacea, Maurolicus muelleri, Watasenia scintillans and Enoploteuthis chunii, and other fishes.