Coastal trevally
Coastal trevally, Turrum coeruleopinnatum (formerly Carangoides): a yellow-spotted reef jack, with notes on the juvenile met on blackwater dives.
The coastal trevally is a small, deep-bodied jack of Indo-West Pacific coastal reefs, reaching about 41 cm but more often met at 25 to 30 cm. The body is nearly oval and strongly compressed, bluish green above and silvery grey below, with many small yellow spots scattered over the flanks and a small dark blotch at the upper edge of the gill cover. The tail is often washed with yellow and the pectoral fins are pale yellow. The name coeruleopinnatum means blue-finned, although the fins show no blue; Rüppell described the species in 1830 from the Red Sea.
Adults tend to keep to deeper coastal reefs, moving in small groups over sand near the reef, and are recorded from 1 to 60 m, entering shallow water less often than many trevallies. The mouth is soft and the teeth weak, so the diet runs to small midwater prey such as krill, larval mantis shrimps, small fish and squid. The range extends from South Africa and the Red Sea east to Japan, Samoa and Tonga, and south to northern Australia and New Caledonia. Nothing is known of its breeding.
Juveniles look noticeably different from adults, with dark vertical bands on the body that fade with growth and a filament on the second dorsal fin that shortens as the fish matures. Young fish have been recorded in estuaries in Natal and in shallow bays in northern Australia, and the species is drawn to floating objects and fish-aggregating devices. A juvenile photographed on a blackwater dive in the Lembeh Strait in October 2018 was identified as this species. Many young carangids shelter under jellyfish and drifting debris at night, as described on the larval jack page, and the young of related trevallies look alike, so a name given from a photograph is provisional.
A juvenile described in 1924 as Caranx uii, long called the Japanese trevally, was shown in 1986 to be this species. The 2022 revision of Carangoides by Kimura, Takeuchi and Yadome moved it to Turrum, the name WoRMS and FishBase now use. The shadow trevally, another former Carangoides whose young ride jellyfish at night, grows larger and has a row of dark blotches along the back instead of yellow spots.
Where to find:
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
