Animalia Life

Repomucenus richardsonii
FAMILY
Callionymidae
TAXONOMY
Repomucenus richardsonii Bleeker, 1854, Nagasaki, Japan.
OTHER COMMON NAMES
Japanese: Nezumi-gochi.
PHYSICAL CHARACTERISTICS
Total length 6.7 (17 cm). Sexually dimorphic in character development. Body elongate and strongly depressed with broad, flattened head. Scales lacking. First dorsal fin with 4 spines; 9–10 soft rays on second, elongated dorsal fin. Anal fin has 9–10 soft rays. Relatively large pectoral and pelvic fins. Caudal fin elongate. Color pattern on body is light to medium brown. Males have three dark blotches on first dorsal fin and oblique dark lines along lower half of flank. Faint dark mottling on anal fin and ventral portion of caudal fin. Females and young males have large black mark on first dorsal fin; females also have three faint white spots on second dorsal fin. May live only as long as two years.
DISTRIBUTION
Northwestern Pacific, from central Japan west into the East China Sea.
HABITAT
Coastal bottoms of sand and mud.
BEHAVIOR

BEHAVIOR
not well known. Species is suited for movement, foraging, and crypsis on sandy or muddy bottoms. Social interactions include aggressive
BEHAVIOR
between rival males, usually during courtship periods, with larger males dominating smaller ones. Aggressive
BEHAVIOR
is characterized by display of erect fins during interactions.
FEEDING ECOLOGY AND DIET
Feeds mainly upon benthic invertebrates.
REPRODUCTIVE BIOLOGY
Pronounced sexual dimorphism in color, body size, and fin development; males have greater body size as well as elongated fin spines and rays. These differences contribute toward reproductive success because of their value in defending against rival males or their signal function in attracting females. Courtship and spawning is paired, and commences with male displays of erect fins and results in pelagic spawning in water column. Eggs produced serially, likely spawned on daily basis with one or two spawning seasons (spring and early autumn). No evidence of hermaphroditism. Recruitment of larvae is also seasonal.
CONSERVATION STATUS
Not listed by the IUCN. May be vulnerable or threatened by overfishing, habitats destruction, and pollution that causes anoxic conditions.
SIGNIFICANCE TO HUMANS
Occurs in both subsistence and commercial fisheries. Flesh favored in Japan. Also collected for the aquarium trade.

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