The Life History of the Gobiid Fish, Inu koma

The gobiid fish, Inu koma Snyder is a small eel-shaped fish and grows to 45 mm. in total length in full grown size (Fig. 1). The specimens had been collected from some localities in the central and southern parts of Japan and Pusan, Korea. The authors newly collected over 50 specimens from Kominato, Chiba Pref., Misaki, Kanagawa Pref., Tsuyazaki, Fukuoka Pref., and Kawara and Nomo, both near Nagasaki City. From the close examination of the stained specimens collected from Kawara, it was found that the squamation of the fish is different from that described by Snyder (1909) in his original paper, but rather similar to that of the relative fish, Inu ama also reported in the same paper (Fig. 2). Snyder detected in the paper that the difference of squamation between Inu koma and Inu ama is one of the most important characters to differentiate the two species. During the ebb tide, the fish was found among pebbles exposed in the air in the intertidal zone of the coast of Kawara staying with some small eel-shaped relative gobies. It feeds on small gammarids. An egg mass of the fish was collected from the habitat on the coast of Kawara on October 23, 1972. The eggs were attached to the underside of a stone embedded in pebbles. They were rather dense in one layer being comprised of 72 eggs in the early embryonic developmental stage. The eggs are club-shaped ranging from 2.71 to 2.89 mm. in long axis and from 0.77 to 0.85 mm. in short axis and each one is provided with an orange yellow yolk. The incubation of the eggs took over 128 hours until hatching at the temperature varying from 18.5 to 20.5℃ (Figs. 3 and 4). Twenty individuals of the newly hatched larvae being from. 3.55 to 3.90 mm. in total length were reared in a 30 liter plastic container for 26 days. They were fed first with the rotifer, Brachionus plicatilis and then with the nauplii of the brine shrimp, Artemia salina. One of the larvae grew to a 8.1 mm. postlarva (Fig. 5)