Fish fauna in the Zostera zone in Shimoda Bay and Nabeta Cove was studied by monthly sampling with a small beam trawl during March 1973 to March 1974.Sampling was made also in the sandy bottom of Nabeta Cove.A total of 135 species (13 orders, 58 families) were collected, i.e., 106 species (11 orders, 50 families) in the Zostera zone of Shimoda Bay, 84 species (10 orders, 39 families) in the Zostera zone of Nabeta Cove, and 60 species (10 orders, 34 families) in the sandy bottom of Nabeta Cove.Analysis of species composition revealed a slight difference between the Zostera zone of Shimoda Bay and that of Nabeta Cove, and a considerable difference between the Zostera zone and the sandy bottom in Nabeta Cove.The significant effect of Kuroshio Current on the fish fauna and the abundant appearance of rocky shore fishes were also noticed in these areas The percentage of both the number of species and that of individuals among yearround resident, seasonal resident, seasonal transient, and casual species was nearly the same between the Zostera zone of Shimoda Bay and that of Nabeta Cove, but it was fairly different between the Zostera zone and the sandy bottom in Nabeta Cove. The number of species and the total number of individuals collected in the Zostera zone showed a different seasonal change between Shimoda Bay and Nabeta Cove.This seems due to the difference of embayment degree between the two bays.The number of individuals obtained suggested that the Zostera zone has a higher population density than the sandy bottom.
There are many problems to be solved for establishment of more reasonable and simplified method of fry production in the marine fish culture.One of the most important subject is to clarify the feeding ecology of larvae and juveniles under rearing condition.In the former works, times required for satiation and digestion in the larvae of Oplegnathus fasciatus (Temminck and Schlegel) were tested.The present paper deals with those examinations in the juveniles with a fairly developed stomach. The copepod Tigriopus japonicus Mori was used as food.Degrees of satiation and digestion were estimated by counting the number of food organisms in 5 portions of the digestive tract: mouth cavity, stomach, anterior intestine, posterior intestine, and rectum. Time required for satiation in the juveniles (19.3-20.2 mm in T.L., 36 days after hatching), which were starved for 15 hours, was nearly one hour after the food organisms were supplied at density of 10 individuals/ml.Content of digestive tract amounted 15.8% of body weight when satiated.At that time the stomach contained 80% of the total food. Times required for digestion (remained content less than 10% of satiation amount) in stomach and digestive tract of the juveniles (19.4-22.8 mm, 37 and 38 days after hatching) were 3 to 4 and 5 to 6 hours, respectively. The feeding behavior of juveniles seems to show the transitional pattern from that of larvae to that of adults with a full-developed stomach.
The present report deals with a study of the age and growth estimations based on the ring marks of scales for each of three subspecies of Carassius auratus: ginbuna, Carassius auratus langsdor fi Temminck et Schlegel, gengorobuna, C.a.cuvieri T.et S., and nagabuna, C.a.buergeri T.et S.The materials used in this study consist of 463 individuals of ginbuna, 270 individuals of gengorobuna, and 175 individuals of nagabuna.They were collected in the lower reaches of the Nagara River, central Japan, during one year from May 1976.For examination of the scales, six scales, from 8th to 13th, of the row just above the lateral line of the left side of the fish were taken, and three scales among them which are revealed to be subject to regular in shape were employed for measurement.
Forty-two specimens of a gohy hitherto unrecorded from Japan were recently collected from Ishigakijima, one of the southern islands of Okinawa Prefecture.These specimens were identified as Mangarinus waterousi Herre after comparison with the type specimens. Herre (1943) reported that this species has “two large flat incisor-like teeth on the vomer”.However, after our examination of Japanese specimens, the so-called teeth of the original description.were found to be not teeth, but slight downward projections of the anterior lateral sides of the vomer.