Summary The sea gobiid fishes Chasmichthys dolichognathus (Hilgendorf) and C. gulosus (Guichenot), both common tide-pool species ranging from Japan to the southern Korea, were studied on the morphological and ecological specificities including spawning, growth, age, food preference, population density, rate of co-existence, “stay-in” habit, etc. Special attention was called to the problems of interspecies competition in the tide-pool. The studies were conducted selecting about 130 tide-pools located on the tidal zone at Kominato and Banda, Chiba Prefecture in 1966 and 1967, and nearly 2, 000 specimens were collected. These two species of gobies, which have often been treated as a same species due to their closeness in external characters and habitat, were well dis., tinguished by the pectoral ray counts, number of vertebrae and gill-rakers (Table 2), and the color pattern both in the young (Fig. 1) and adult. The age of maturation (full one year), spawning season (January to May with peak in February and March), spawning habit, and eggs were not well specified by the two species, but the egg-mass of C. dolichognathus was found consisting of 300 to 600 ova against 800 to 1, 400 of C. gulosus. The age of these gobies, tested by size frequency (Fig. 2), but not by ill-defined circuli on the scales, was believed to be usually one year in C. dolichognathus, which grows to 75 mm in body length, but, with some reserves, two or more years in C. gulosus, of which the maximum size of 130 mm was noted. The floatup young of the two species were observed in the same waters of lower littoral and sub-littoral zones where the micro-habitat preference was believed working. The young of the two species enter into tide-pool and find their normal habitat there, but food preference developed at this stage. The food items taken by the adult of C. dolichognathus were found nearly identical with those of the young of C. gulosus, but such apparent food competition was thought compensated by the different age (or size) composition in the population of the two species. A significant difference of the two species was found in their food preference when they attained adult size, namely, C. dolichognathus heavily depends on amphipod crustaceans, whereas C. gulosus shows wide range of food items including macruran, anomuran and isopod crustaceans, sea-weed, etc. (Fig. 3). This fact, among others, was believed to be the most significant ecological factor to permit the co-existing of the two species in the same habitat. The ecological specificity demonstrated by the two species was also found, but in lesser extent, in their preference of different tide-pools as the usual habitat. It was observed (Table 3) that the two species usually share the same pool water, but C. dolichognathus outnumbers the other species in the community, regardless of the types of pools which were categorized into four entries (Table 1). The significant fact was that C. dolichognathus preferred the tide-pools of types I and II (90 %) to those of the types III and IV (10%), whereas, C. gulosus inhabited in those of the types I and 11 (60%) and III and IV (40%) (Table 4). The test of“stay-in the pool” habit by marking and recapture of the fishes (Table 5) revealed that only 20% of C. dolichognathus remained in the same pools after the two months, and 60% of C. gulosus after the same period. It is, however, admitted that for both species the “stay-in” habit varied by the types of tide-pools, namely the higher the level of pools located the higher their extent to remain in the same pool. In conclusion, the two species of gobies, which developed in the limited surface of tidal zone, are able to co-exist successfully on rocky shore through ecological isolation particularly ascribed to food and habitat preference (Figs. 4 and 5).
Abstract Tne histopathological effects of the two insecticides, heptachlor and nicotine were studied on the gills of the freshwater catfish, Heteropneustes fossilis. The fishes exposed to 1.0 ppm of the former and 3.2 ppm of the latter at room temperature (18.89-23.89°C), died within 19 to 44 hours. The fishes exhibited acute respiratory distress with both the insecticides. The gills of fishes exposed to heptachlor were found coated with a layer of mucus, but no such covering was found on the gills of those died in nicotine. The surface cells of the gill filaments of fishes killed by heptachlor showed disintegration, rupture, vacuolation, karyorrhexis, and extrusion and degeneration of nuclei and cytoplasm. The number of mucous cells in these gills was increased which resulted in the secretion of mucus over them. With nicotine, only the basal parts of a few gill filaments were damaged. It appears that injury with heptachlor was due to surface irritation rather than absorption of the poison through the gills. The lesions caused by nicotine appear to be the indirect action of the poison. Due to paralytic action induced by this poison, the fishes failed to renew water of their opercular chamber which resulted asphyxiation and finally death. These findings strongly support the hypothesis put forth by Herr, Greselin and Chappel (1967) rejecting the views of Carpenter (1927), Jones (1935), Westfall (1945) and Derse and Strong (1963).
Summary The longtail tuna, Thunnus tonggol (Bleeker) had been known from Japan by a single specimen by the name of T. rarus Kishinouye (1915), which is a synonym of the former. In 1968, some 40 years after the first record, the longtail tuna were found trapped in sardine set-net at Kundatai, Wakasa Bay, Japan Sea, numbering about 1400 and 1000 on the 3rd and 24th respectively, September. The same species of tuna were caught in the set-net at Odashukuno in the same bay on the 4th of the month, which numbered 9 and measured 48.6 to 51.4 cm in fork-length. The nonrecognition of the species in Japanese waters in the past may be ascribed to the misidentification of the young of the species with those of either T. thynnus or T. albacare.