Siganus canaliculatus

Lore & Background

Siganus canaliculatus was first formally described in 1797 as Chaetodon canaliculatus by Scottish explorer Mungo Park, with the type locality given as Bengkulu Province on Sumatra. The specific name canaliculatus means 'grooved', a reference to the grooves in the fin spines; Park did not know that these spines contained venom glands for defence. This taxon is largely sympatric with the mottled spinefoot (Siganus fuscescens) and they are very similar in appearance. Molecular analyses in 2011 found three separate lineages within S. canaliculatus and S. fuscescens that interbred, with each lineage containing specimens referred to either taxon, suggesting S. canaliculatus may be a junior synonym of S. fuscescens—though this is not the position taken by FishBase or Catalog of Fishes.

The colour and pattern of the white-spotted spinefoot is very variable, ranging from greenish grey to yellow brown, marked with 100–200 pearlescent blue to whitish spots on the nape and anterior body. Alarmed or injured fishes adopt a mottled pattern of light and dark brown and cream. There is normally a dark spot similar in size to the eye immediately behind the upper end of the gill opening. The species attains a maximum total length of 40 cm, though 20 cm is more typical. Juveniles form very large schools, which reduce in size as the fish mature; adults occur in groups of around 20 individuals. When spawning, adults gather in much larger aggregations, observed only from April to July, though gonadosomatic indices suggest another less defined spawning period in November. Spawning events are synchronised with the lunar cycle, and a mature female can spawn multiple times in a season, laying up to a million eggs.

Reader's Guide

Siganus canaliculatus is an important quarry species for commercial fisheries. In the Persian Gulf it is considered a good quality food fish, even though it is a rather small species. It is caught using bottom trawls and seine nets in coastal waters, and in the Persian Gulf largely by trapping in intertidal net fences and dome-shaped metal traps called gargoors. The fish landed are sold fresh in large numbers; it is also taken as bycatch. The Teochews of Singapore and Malaysia are particularly fond of this fish, which they refer to as pek tor her (Chinese: 白肚鱼; pinyin: báitùyú; lit. 'white rabbit fish'). It is typically steamed and eaten with rice or as part of the Teochew porridge spread. The white-spotted spinefoot is particularly popular during Chinese New Year, when the fish is heavy with milt and roe and its consumption is considered auspicious; for this reason it is also known as pai ni her (Chinese: 拜年鱼; pinyin: bàiniányú; lit. 'Chinese New Year fish'). The species has been used for mariculture in some areas because it is herbivorous, grows rapidly, and is economically valuable. In some parts of its range the stock has been overfished. The white-spotted spinefoot was also found to be a host of an intestinal acanthocephalan worm, Diplosentis amphacanthi.

Did You Know?

• The specific name canaliculatus means 'grooved', referring to grooves in the fin spines that contain venom glands.
• Molecular analyses in 2011 suggested Siganus canaliculatus may be a junior synonym of Siganus fuscescens, but FishBase and Catalog of Fishes do not accept this.
• The Teochews of Singapore and Malaysia call it pek tor her, meaning 'white rabbit fish', and it is especially popular during Chinese New Year.