Balistes capriscus

Family : Balistidae

 

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Text © Giuseppe Mazza

 

 

English translation by Mario Beltramini

 

 

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Balistes capriscus is the only triggerfish present in the Mediterranean © Giuseppe Mazza

The Grey triggerfish ( Balistes capriscus - Gmelin, 1789 ) belongs to the class of the Actinopterygii, the ray-finned fishes, to the order of the Tetraodontiformes and to the family of Balistidae.

The name of the genus “balistes” comes from the Latin “ballista” = crossbow, due to the arcuate shape of the big fins and the presence on the dorsal of a trigger mechanism evoking this weapon of the old times.

The name of the species, “capriscus” should indicate, Latinizing, a “small goat”.

Zoogeography

It is at home in the tropical and temperate waters of the Atlantic Ocean and of the Mediterranean Sea where it is the only one member of the Balistidae.

Just to give an idea about its distribution, we find it along the African coasts from Morocco, Mauritania and Cape Verde up to Angola. Then at Ascension Island and on the other side of the ocean, from Canada, the Gulf of Mexico and the Caribbean up to Brazil.

Carried by the Gulf Stream, it has been fished also along the Belgian, English and Irish coasts, thus marking the conquest of the northern limit for the family of the balistids.

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It’s the Balistid which has gone more north, up to England and Ireland © Giuseppe Mazza

Ecology-Habitat

It swims up to 100 m of depth, but rarely going down under the 50 m, along the coasts but also offshore, behind the schools of oily fishes.

Morpho-physiology

It can reach the 60 cm of length, but rarely exceeds the half metre. The body is oval, tall, very flat, covered by bony scales arranged in lozenge thus to form a cuirass.

On the back we note the trigger, typical of the Balistidae, formed by three spines blockable in erect position. For lowering the first, long and sharp, it is necessary to act on the third, freeing the second, which holds, with an interlocking hole, the base of the spike. This is an important deterrent for the predators because also after the death of the fish, the dagger keeps blocked vertically and it is difficult to swallow the prey without getting injured.

Furthermore, when the Balistes capriscus finds a cavity with a narrow entrance, where it can enter only with lowered fin, it can adopt it as den and sleep peacefully with the trigger erect without the risk of being carried out by the currents or being caught sleeping by big predators such as the Thunnus albacares, the Acanthocybium solandri, or the Coryphaena hippurus.

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For some its flesh is tasty, but with risk of ciguatera, a serious food intoxication © Giuseppe Mazza

The second dorsal fin has 26-29 soft rays and is symmetrical to the anal, which has 23-26 of them. The pectoral ones have 14-15 unarmed rays; the ventral ones, atrophied, have transformed in a mobile wrinkly plate and a dozen of small spines kept united by a membrane; the caudal, rounded in the juveniles, gets truncated in the adults and crescent-shaped in the oldest specimens with two showy filaments.

The eyes and the mouth are decidedly small in comparison to the body, but the sight is excellent and the solid sharp teeth easily break the cuirasses of the sea urchins and the shells of the molluscs.

Compared to the fanciful colours of the other members of the family, the livery of the Balistes capriscus is much sober. Usually, the dominant tint is the lead-grey, paler on the belly, with light blue, greenish or violaceous reflections.

Ethology-Reproductive Biology

The grey triggerfish nourishes of echinoderms, crustaceans, molluscs and fishes. In many zones the main course is in fact formed by the schools of sardines and of silversides or of the small fishes swimming among the corals. It is pointless to say that it has a fondness for the mussels and the oysters and that, in the Mediterranean, is not, and by sure, loved by the oyster farmers.

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The juveniles livery is surely more colourful than the adults’ plumbeous one © Giuseppe Mazza

It lives solitary or in small schools.

During the reproductive period, under the satisfied eyes of the male, the female digs for 2-3 days a deep nest in the sand, blowing it away with water jets from the mouth and carrying away the stones with the teeth.

The fecundated eggs hatch after 50-55 hours and the planktonic larvae measure 1,7 mm. The juveniles have a livery decidedly more coloured than the adults, brown with blue spots, and easily adapt to the aquarium life, passing, in appropriate pools, the 12 years of age.

Not rarely, the adults end up into the trawls and the flesh, appreciated by the locals, is often consumed in the Caribbean and the Central America in spite of the risk of ciguatera, an alimentary intoxication related to the accumulation in their tissues of poisonous substances coming from a diet rich in fishes nourishing of corals or toxic algae. The populations can double n 1,4-4,4 years and with a moderate risk of vulnerability, of 35 per 100, the species is presently not endangered.

Synonyms

Balistes carolinensis - Gmelin, 1789; Balistes forcipatus - Gmelin, 1789; Nematobalistes forcipatus - Gmelin, 1789; Balistes spilotopterygius - Walbaum, 1792; Balistes buniva - Lacepède, 1803; Balistes caprinus - Valenciennes, 1839; Balistes fuliginosus - DeKay, 1842: Balistes taeniopterus - Poey, 1860; Balistes powellii - Cope, 1870; Balistes moribundus - Cope, 1871.

 

→ For general information about fishes please click here.

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The photographic file of Giuseppe Mazza

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