Squretail Rabbitfish

The dusky spinefoot (Siganus luridus), also known as the squaretail rabbitfish, is a marine ray-finned fish belonging to the family Siganidae. It is native to the undefined and has spread to the Mediterranean Sea through the Suez Canal (🇪🇬 Egypt) (Lessepsian migration). The dusky spinefoot is primarily known as a food fish.

Formally described in 1829 by German naturalist Eduard Rüppell, the dusky spinefoot was given the scientific name Amphacanthus luridus. The species was named for its pale yellowish color, as observed by the type specimen collector Christian Gottfried Ehrenberg. However, Rüppell described the color as bluish black with paler spots and a yellowish ring around the pupil.

The dusky spinefoot has a compressed body and a depth that is 2.1 to 2.8 times its standard length. It possesses a single row of incisor-like teeth in its jaws, with each tooth having 1 or 2 lateral cusps. The dorsal fin contains 13-14 spines and 10 soft rays, while the anal fin has 7 spines and 9 soft rays. The caudal fin is truncate. This species typically reaches a total length of 20 cm (7.9 in), although it can grow up to 30 cm (12 in). Its coloration varies, ranging from olive green to dark brown with a mottled pattern. The pectoral fins are hyaline-yellow, and the caudal fin has dark bars.

The dusky spinefoot is found along the coast of eastern Africa, from 🇲🇿 Mozambique to the 🌊 Red Sea, as well as in the Comoros, 🇲🇬 Madagascar, and the Mascarene Islands. Its presence in the 🌊 Persian Gulf is yet to be confirmed. It first appeared in the Mediterranean Sea in 1955 off 🇮🇱 Israel, after entering through the Suez Canal (🇪🇬 Egypt). Since then, it has rapidly spread across the eastern Mediterranean and now reaches as far west as the French Mediterranean coast and the Adriatic Sea. It is typically found at depths between 2 and 40 m (6 ft 7 in and 131 ft 3 in) in areas with hard substrates like coral and rocky reefs.

The dusky spinefoot spawns between April and August when the seawater temperature ranges from 24 to 29 °C (75 to 84 °F). Its eggs and larvae are planktonic and feed on phytoplankton and zooplankton. The adults are herbivores, active during the day and occasionally hiding in cavities at night. They are often seen in schools but can also be found alone, grazing on algae. Their diet includes larger brown algae species and other macrophytes.

The dusky spinefoot possesses venomous spines in its fins, which it uses for defense against predators. When threatened, it can stop suddenly and erect its dorsal, anal, and pelvic fins, showcasing its venomous spines as a potential threat.

Predators primarily target the planktonic and larval stages of the dusky spinefoot, as these stages experience the highest predation pressure. Known parasites of this species include the monogeneans Glyphidohaptor plectocirra and Tetrancistrum polymorphum, as well as the digeneans Hexangium brayi, Hexangium sigani, and Progyliauchen magnacetabulum.

The dusky spinefoot is caught using set fish traps, gillnets, and beach seines, and it is sold as fresh fish. It has become an important species for fisheries in the Mediterranean. In other areas, such as 🇰🇪 Kenya, it is often caught as bycatch. Consumption of this species has been associated with mild cases of ciguatera-like poisoning.

Here are some additional facts about the squaretail rabbitfish:

• The squaretail rabbitfish is a hermaphroditic fish, meaning that it can change sex from male to female.
• The squaretail rabbitfish is a territorial fish, and will defend its territory against other fish.
• The squaretail rabbitfish is a spawning fish, and lays its eggs in the water.
• The squaretail rabbitfish is a fast-growing fish, and can reach sexual maturity in one year.