Arno goby
Padogobius nigricans
FAMILY
Gobiidae
TAXONOMY
Gobius fluviatilis var. nigricans Canestrini, 1867, Arno River, Italy.
OTHER COMMON NAMES
Italian: Ghiozzo di ruscello.
PHYSICAL CHARACTERISTICS
Males reach slightly beyond 4.9 in (12.5 cm) total length. Tubular species with a blunt head and terminal mouth. Two dorsal fins, second with 12–14 fin rays. Rounded caudal fin. Pelvic fins form a sucking disc, which does not extend as far as the anus. There are 44–49 ctenoid scales along the midline of the flanks. Brownish or light brown dorsally, and whitish ventrally. Five characteristic brown bands over the back, the first at the base of the pectoral fin and the last at the caudal peduncle. Dorsal fins with alternating light and dark gray bands; the first dorsal fin has a yellowish orange border.
DISTRIBUTION
Formerly widespread through fresh waters of central Italy. Currently found in the Serchio, Arno, Ombrone, and Tiber River basins. Populations have become restricted because of environmental degradation and pollution.
HABITAT
Small to medium-sized streams with moderate current. Usually found in clear waters, over a stony substrate.
BEHAVIOR
Usually stationary, positioned under stones, occasionally moves quickly from one stone to another.
FEEDING ECOLOGY AND DIET
Predaceous; feeds on oligochaetes, crustaceans, and insect larvae.
REPRODUCTIVE BIOLOGY
Probably reaches sexual maturity during the first year, at 1.6–2 in (4–5 cm). Males become very dark during the reproductive period, which usually occurs between May and June. The male is territorial and guards a nesting cavity under a stone, attracting females with a courtship display and making noises as he does. The male carries small stones out from the nest in his mouth and deposits them near the female, and then quickly returns to the nest. He repeats this behavior until the female enters the nest, and then swims several times upside down over the roof of the nest. The female attaches herself to the roof of the nest using the pelvic disk and spawns 100–200 eggs, which are stuck to the roof. Several females can spawn in the same nest, which may hold over 1,500 eggs at various stages of development. The male cares for the eggs until they hatch, after about 17 days.
CONSERVATION STATUS
Listed as Vulnerable by the IUCN, with a suspected population reduction of at least 20% over the last 10 years, or three generations. Populations are threatened by environmental degradation and, in some areas, by the introduction of Padogobius martensii, which probably competes for similar ecological niches.
SIGNIFICANCE TO HUMANS
There is no commercial or sports fishery for this species. However, the flesh tastes good and fishes are collected illegally and eaten fried.
