Scientific Name:

Siganus rivulatus

Common Name:

Marbled spinefoot

Taxonomic Group:

Fishes

Add Report

Information

Key Identifying Features

This medium-sized fish has an ellipsoidal, compressed body covered with small scales embedded within the skin. It grows to a length of up to 27 cm, commonly 5–25 cm.

The dorsal fin, with 13–14 spines and 10 soft rays, begins above the pectoral fin base, and the first dorsal spine points forward. Key taxonomical features for this species’ identification are pelvic fins with two stout spines connected by a membrane to the abdomen, and the forked tail fin. There are 7 spines in the anal fin with 8–10 soft rays. The anterior spines of the median fins are slender, whilst the posterior spines are stout, all of the spines being venomous. The mouth is small with distinct lips.

Body colour is brown to grey green, and light-brown to yellow on the belly. There are fine, often faint, yellow-gold stripes on the lower half of body. At night or when frightened, the colour is very mottled, withsix diagonal bars across the flank.

Identification and Habitat

The marbled spinefoot lives in shallow waters, preferring hard bottoms of compacted sand with rock, usually covered with vegetation. Adults live in small groups of 50 to several hundred individuals, feeding mainly green and red algae, such as Ulva spp. and Hypnea spp., and seagrasses (Posidonia oceanica).

Reproduction

The spawning season lasts from May to September.

Similar Species Description

Two non-indigenous species of Siganidae are now present in the Mediterranean: the marbled spinefoot, Siganus rivulatus, and the dusky spinefoot, Siganus luridus. The native salema, Sarpa salpa, also shares the same habitat and diet. The salema has characteristic horizontal yellow lines along its body; its eyes are ringed with yellow, and it has a black dot at the base of the pectoral fins. The tail fin shape distinguishes between the two Siganus species: Siganus rivulatus has a forked tail fin with narrow, translucent yellow stripes, whereas Siganus luridus has a straight or slightly concave tail fin and a uniform body colour.

Siganus rivulatus Similar Species (0010) EN — **Siganus luridus**

Similar Species

Scientific Name: Siganus luridus

Common Name: Dusky spinefoot

Taxonomic Group: Fishes

History and Route of Introduction

The marbled spinefoot is a species usually found in the western Indian Ocean and Red Sea. It was first recorded in the Mediterranean in 1927 along the Palestinian coast and spread progressively through the eastern Mediterranean: Syria, Cyprus, the Aegean Sea, Libya, Tunisia, the Ionian Sea and the southern Adriatic (Croatia). S. rivulatus has not yet been reported from the western Mediterranean; however, its presence has been suspected in Corsica since 2010.

Ecological Impacts

The two herbivorous fish species belonging to the Siganidae family, Siganus luridus and S. rivulatus, have become very common in most parts of the eastern Mediterranean and strongly interact with the native herbivorous fish Sarpa salpa through competition for food resources and habitat. The spread of these two alien herbivorous species can result in a drastic decrease in algal biomass, locally eradicating certain algae such as Cystoseira spp. forests, and reducing important nursery habitats for many species.

Economic Impacts

Due to its great abundance in the eastern Mediterranean, the dusky spinefoot is regularly caught by professional small-scale fisheries and nonprofessional fishermen. However, its commercial value is low. The venomous spines can cause painful injuries to bathers and fishers and the damage it may do to diving tourism and the local fishing industry still needs to be assessed.

Some fish farming trials have also been conducted in countries such as Cyprus, Israel and Egypt.

Management Options

These include a) early eradication of new populations by MPA technicians through spear fishing, and b) maintenance of healthy and abundant assemblages of top predators to encourage natural control through predation.