Nomeus gronovii family
Gobius gronovii Gmelin, 1788, eastern Atlantic. other common names
English: Bluebottle fish, shepherd fish; Spanish: Pastorcillo, Pez azul.
Standard length 13.7 in (35 cm). Head somewhat tall, body tallest at level of pelvic fins, tapering posteriorly; dorsal fin continuous, originating at midbody length, with 9-12 spines and 25-27 rays (IX-XII, 24-28); pectoral fins elongate, with 21-23 rays; caudal fin forked, with some 15 rays; anal fin with two spines and 24-29 rays (I—II, 24-26); pelvic fins very long and prominent, reaching posteriorly to level of pectoral fin extremities, with one spine and five rays (I, 5); eyes large; no teeth on tongue. Juveniles have vertical, dark blue and broad bands, with blue blotches on head and fins; adults have irregular blue blotches on body, head, and fins; background color silvery, pelvic and dorsal fins black. Larger adults more uniformly dark in color.
Tropical and warm temperate waters of Atlantic, Pacific, and Indian Oceans.
Pelagic offshore, usually warm waters, commonly found in association with the siphonophore Portuguese man-of-war (Physalia), but larger adults may live independently in deeper waters. Juveniles may be found pelagically in waters 98 ft (30 m) deep.
Usually found in large numbers living underneath the bell of the Portuguese man-of-war, swimming in and out among its tentacles. The mottled color pattern mimics the tentacles of Physalia. It lives commensally by being resistant to the venom of the siphonophore.
feeding ecology and diet
Feeds on the tentacles and gonads of the Portuguese man-of-war, zooplankton, and other soft-bodied jellyfishes. Sometimes eaten by its host.
Eggs and preflexion larvae are unknown; postflexion larvae as small as 0.27 in (0.7 cm) have been recorded, and adult form is mostly attained by 0.9 in (2.5 cm). Other aspects of its reproduction are unknown, but as with other stromateoids, eggs and larvae are pelagic and they are probably broadcast spawners. Small individuals of 0.39 in (1 cm) have been found in association with the Portuguese man-of-war, indicating that this association forms early in life.
conservation status Not threatened.
significance to humans
Of minor commercial importance, due to infrequent fishing. ♦
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