Named after the inspirational cubist painter, Pablo Picasso, the Picasso triggerfish (Rhinecanthus assasi) has a beautiful, colourful appearance and strikingly patterned body. Generally tan or yellowish in colour and becoming whiter underneath, the Picasso triggerfish is adorned with vibrant stripes, including a tapered, blue-edged brown bar, yellow band and blue line running from the eye to the gill. Four narrow blue bands, separated by black, run between the eyes and across the top of the head (2). The eyes of the Picasso triggerfish are positioned high on the head, the snout is long and pointed, and the mouth is directed slightly upwards, with short, strong jaws (3). The lips are bright yellow, with a narrow, pale blue line and a dark reddish-brown streak extending from above the upper lip towards the pectoral fin. A broad circle of orange encompasses a large black spot close to the anus, and spines at the back of the body have narrow black stripes with ovals of bluish-white (2). The skin of the Picasso triggerfish is extremely tough, with modified plate-like scales armed with small spines or tubercles on the outer surface, giving it a roughened texture. Three rows of small, forward curved spines are found towards the rear of the body, and the pelvic fins are replaced by spine-like protrusions (2)(3)(4).
Little is known about the biology of the Picasso triggerfish; however, it is thought to feed on small benthic (bottom-dwelling) invertebrates(5). It is also likely that the Picasso triggerfish exhibits similar breeding behaviour to other species of triggerfish, depositing eggs in the water during a spawning period, which attach to coral until they hatch. The young fish float close to the surface as they develop, usually in among seaweeds and around flotsam (3).
The Picasso triggerfish is a member of the Balistidae family (the triggerfish), and like other triggerfish, it is renowned for the unusual locking mechanism of the spines in the first dorsal fin, which allow the fish to lodge itself immovably into crevices between rocks and corals. When the fin is erect, the longest dorsal spine is locked into place by a much shorter, second spine, which slides forwards, holding it in position. The first spine can only be lowered again if the second is slid back out of place; something which can only be achieved by depressing a third spine, known as the ‘trigger’ (3)(6).
Randall, J.E. (1995) Coastal Fishes of Oman. Crawford House Publishing Pty Ltd, Bathurst, Australia.
Aiken, K.A. (1975) Chapter 15: The biology, ecology and bionomics of the triggerfishes, Balistidae. In: Munro, J.L. (Ed.) Caribbean Coral Reef Fishery Resources. International Centre for Living Aquatic Resources Management, Manila, Philippines.
Fischer, W. and Whitehead, P.J.P. (1974) FAO Species Identification Sheets for Fishery Purposes. Eastern Indian Ocean (Fishing Area 57) and Western Central Pacific (Fishing Area 71): Volume 1. Food and Agricultural Organisation of the United Nations, Rome. Available at: ftp://ftp.fao.org/docrep/fao/009/e9163e/E9163e1a.pdf
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