Crenidens crenidens

Crenidens crenidens has an oblong to ovoid shaped body which is slightly compressed. Smaller adults, less than 19.7 cm in length, show a nose like bump in front of the eye. The mouth extends back to the anterior nostril and there are three rows of teeth in each jaw, the upper front jaw has 8-9 brown-tipped incisor like teeth, each bearing five denticulations which give the edge of the teeth a wavy appearance. The inner rows have a few teeth of similar form but the other teeth are granular. The scales finely ctenoid, the scaly cheeks contrasting with the scaleless interorbital region. The dorsal fin has eleven each of spiny and soft rays, while the anal fin has three spiny and ten soft rays. The caudal fin is forked. There are 52-60 scales making up the lateral line.[3][4]

C. crenidens is silvery greenish-blue or olive in colour with darker narrow longitudinal stripes created by dark spots on the scales which are above the level of pectoral fins; the fins are coloured dull yellowish or olive with a dark margin on the dorsal fin and infrequently the axil pectoral fin shows darkish axils. They can grow to 30 cm in length in their native range, although the maximum in the Mediterranean is 20 cm, the more usual measurement is between 10 and 16 cm in length.[3]

Crenidens crenidens is indigenous to the western Indian Ocean from the Red Sea south along the coast of eastern Africa South Africa and has been also reported from southern Madagascar.[5] In 1970 it was recorded for the first time in the Mediterranean in the Bardawil Lagoon (northern Egypt) and has since spread to Israel and to Libya. The most likely route for this species to have followed to colonise the Mediterranean is through the Suez Canal.[3]

Crenidens crenidens is found in shallow coastal water, over sandy substrates which are frequently covered with sea grass.[3] Its main food is algae but it also feeds on smaller invertebrates, such as crustaceans and worms.[5] The eggs and larvae are planktonic.[3] Off the Libyan coast C. crenidens has developed a distinct breeding season from November to February and the fish move away from the coast to spawn elsewhere in March and April. The males attain sexual maturity at 14 cm length and some females reach maturity at around 13 cm to 13.9 cm but for 50% of females maturity occurs at around 15.4 cm length. Fecundity is dependent on the weight of the female and varies from 678 eggs in smaller females to 9,888 eggs.[1]

There were two generally recognised subspecies:

• C. c. crenidens (Forsskål, 1775) which occurs in the Red Sea and southwards along the eastern African coast;
• C. c. indicus Day 1873 which extends from the Red Sea to the Persian Gulf and Nicobar Islands.

The two taxa occur sympatrically in the Red Sea.[3][6] Recent work has supported the raising of C.c. indicus to species level once more and that a third species which is currently regarded as a junior synonym of C.c. indicus, Crenidens macracanthus, known from only two specimens from the Arabian Sea, is a separate valid species.[7]

Crenidens crenidens is caught all year round in the northern Indian Ocean using trammel nets and beach seines and is consumed fresh, however, in the southern part of that Ocean it is fished mainly for bait.[5]