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広島大学水畜産学部紀要 6 巻 2 号
1966-12-20 発行
マサバの摂餌生態に関する研究Ⅰ : 食性と摂餌の選択性
Studis on the ecology of feeding of the mackerel, Pneumatophorus japonicus I : On the food habit and the selective feeding,
高橋 正雄
Abstract
The ecology of feeding of the mackerel, Pneumatophorus japonicus HOUTTUYN, was studied both through the observations of the stomach contents under the natural conditions and feeding experiments in the aquarium, for the purpose of analysing the angling-technique for the school of the pelagic fishes including the important fish species for the commercial fisheries in Japan. The present paper is concerning with the results on the kinds of prey taken by the mackerel and the selective feeding of these preys in the mackerel.
The observations on the stomach contents of I ,310 mackerel, caught by trap-net settled in the surrounding wates of Oshika Peninsula and their adjacent waters, Miyagi, during the period from April to October of I 954, revealed the following facts;
(1) While prior to the mid July the number of mackerel feeding on Euphausia pacifica was larger than the number of those feeding on the anchovy, Engraulis japonica, the former was smaller than the latter posterior to the mid July.
(2) In the period of feeding on Euphausia, there were more individuals with empty stomach than in the period of feeding on the anchovy. Although the sardine, Sardinops melanosticta, and the horse mackerel, Trachurus japonicus, also were found out in the stomachs of the mackerel, the number of individuals having them in the stomach was very much smaller than the number of those having the anchovy in the stomach.
(3) The body length of the anchovy taken most abundantly by the mackerel was 26 to 36% of the body length of the mackerel and the body length of the largest one taken by the mackerel was about 50%. The same relations were observed between the body sizes of the mackerel and of the sardine taken by the mackerel. However, the body length of the horse mackerel taken most abundantly by the mackerel was 18% of the body length of the mackerel and the body length of the largest one was smaller than 30%.
(4) The largest amount of the stomach contens observed was 16.3% of the body weight of the mackerel. The results of the feeding experiments performed in August indicated that;
(1) The mackerel have taken the anchovy and the Euphausia with almost the same intensity of feeding in spite of the period of feeding on the anchovy.
(2) The anchovy was taken with very much higher intensity than the horse mackerel by the mackerel.
The observations on the stomach contents of I ,310 mackerel, caught by trap-net settled in the surrounding wates of Oshika Peninsula and their adjacent waters, Miyagi, during the period from April to October of I 954, revealed the following facts;
(1) While prior to the mid July the number of mackerel feeding on Euphausia pacifica was larger than the number of those feeding on the anchovy, Engraulis japonica, the former was smaller than the latter posterior to the mid July.
(2) In the period of feeding on Euphausia, there were more individuals with empty stomach than in the period of feeding on the anchovy. Although the sardine, Sardinops melanosticta, and the horse mackerel, Trachurus japonicus, also were found out in the stomachs of the mackerel, the number of individuals having them in the stomach was very much smaller than the number of those having the anchovy in the stomach.
(3) The body length of the anchovy taken most abundantly by the mackerel was 26 to 36% of the body length of the mackerel and the body length of the largest one taken by the mackerel was about 50%. The same relations were observed between the body sizes of the mackerel and of the sardine taken by the mackerel. However, the body length of the horse mackerel taken most abundantly by the mackerel was 18% of the body length of the mackerel and the body length of the largest one was smaller than 30%.
(4) The largest amount of the stomach contens observed was 16.3% of the body weight of the mackerel. The results of the feeding experiments performed in August indicated that;
(1) The mackerel have taken the anchovy and the Euphausia with almost the same intensity of feeding in spite of the period of feeding on the anchovy.
(2) The anchovy was taken with very much higher intensity than the horse mackerel by the mackerel.
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