Abstract
Chaenogobius castanea O'SHAUGHNESSY is a small goby, most common in estuaries and shores of Japan throughout, where it passes the whole period of its life history. The external characters of the fish such as the coloratoin and color-pattern, and the number of the fin-rays, spines, vertebrae, scales and gill-rakers are so variable that many species have been established from the same fish from different localities.
The spawning season extends from January to April in the vicinity of Fukuoka City, Kyushu. The male adult generally attains a smaller size than the female (Fig. 1). Before spawning, the ripe male prepares a room for breeding, usually utilizing the vacant living-hole of a kind of shrimp, Upogebia major DE HAAN, which is common in the shallow sandy bottom of the estuary. Often a couple of parent fish were observed in that hole. The eggs are deposited on the inner wall of the hole, about 1 cm. in diameter and 5-10cm. deep.The female parent lieves the hole soon after spawning, while the male stays there guarding the eggs until they hatch out (Fig. 2). The spawned egg is rather large and club-shaped, about 4.1mm. in length, about 1.3mm. in width (Fig. 3).
The newly hatched living larva is 7.mm in total length. The larvae, 10-16mm. in total length, are found to live a pelagic life in the bay, mainly feeding upon copepods. The juvenile at about 20mm. in total length commences a bottom-life, when the feeding habit changes into an omnivorous one. The formation of the color-pattern on the bodyside is very slow, attaining its completion at the total length over 40mm. (Fig. 4).
Specimens, collected in the vicinity of Fukuoka City show the male to grow to 37-51 mm. in total length in a year, 49-55 mm. in 2 years and over 55 mm. in 3 years, while the female to 40-56 mm. in a year, 56-64 mm. in 2 years and over 64 mm. in 3 years.
