Rock Cale

Fascinating facts about the Rock Cale

• In 1859 German-born British ichthyologist Albert Günther first described the rock cale, accidentally misspelling its genus as *Haplodactylus*, a slip that would later be corrected after a 2000 review by Barry C. Russell. This taxonomic shuffle shows how even seasoned scientists can rewrite a fish’s family tree centuries later.
• The longest recorded rock cale measured 45 cm (18 in), and its body depth is only a third to a quarter of that length, giving it a sleek, elongated silhouette perfect for slipping through tide-swept crevices.
• Its dorsal fin is almost split in two, boasting 17 spines and up to 20 soft rays, while the anal fin adds 3 spines and up to 7 soft rays.
• From Mudjimba on Queensland’s Sunshine Coast down to Victoria’s Gippsland Lakes and even Babel Island off Tasmania, the rock cale lives exclusively in southeastern Australian waters, never straying beyond a 10 m (33 ft) depth where kelp and seaweed provide both food and shelter.
• A true herbivore, the rock cale munches on a buffet of algae, Corallina pilulifera, Ulva lactuca, Jania, and filamentous Sphacelaria, both floating free and clinging to rocks.

At a glance

About the Rock Cale

The rock cale, Aplodactylus lophodon, presents an elongate silhouette whose depth is roughly a quarter of its length, capped by a rounded head and a small, down-turned mouth framed by fleshy, projecting upper lips. Its jaws are lined with three-rowed tricuspid teeth, the outermost row bearing the largest points, while a pair of nostrils sport fleshy flaps edged with tiny tentacles. The dorsal fin stretches along a long base, seemingly split by a deep incision that separates 17 spines from 18-20 soft rays, and the anal fin follows with three spines and six-seven soft rays. Large pectoral fins, sometimes longer than the head, bear five to six unbranched, fleshy rays at their lower edge. Covered in minute cycloid scales that extend onto the cheeks and operculum, the fish displays a palette ranging from grey to bluish-black, punctuated by whitish mottles, a dark saddle blotch beneath the spiny dorsal portion, and a distinctive row of five evenly spaced white spots along its flanks. Juveniles are marked by a stark black patch on the rear edge of the operculum, and the species can reach a total length of 45 cm (18 in).\nIn the surge-washed reefs of southeastern Australia, from Mudjimba on Queensland’s Sunshine Coast down to Victoria’s Gippsland Lakes and Babel Island off Tasmania, the rock cale makes its home on shallow, exposed rocky shores. It thrives just below the surface to about 10 m (33 ft) where kelp and other seaweeds provide shelter, often schooling in the high-energy zone. A dedicated herbivore, it grazes on a variety of algae, Corallina pilulifera, Ulva lactuca, Jania, and filamentous Sphacelaria, both free-floating and attached, frequently perching on coralline “turf” or wedging into rock crevices during strong wave surges. Its abundance in New South Wales’ surge zones makes it one of the most numerous reef fishes there, a testament to its adaptability and the surprising efficiency with which a fish of modest size can dominate a turbulent niche.

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