Blenny

Blennies are generally secretive and depend on cryptic colouration to blend into their surroundings. To spot them, divers should move slowly over shallow reef structures, boulder fields, and tide pools, scanning small holes, barnacle clusters, empty mollusc shells, and rocky ledges. Look for their distinct blunt heads and large, expressive eyes protruding from narrow crevices, as well as the tiny whisker-like cirri decorating their foreheads.

Approaching blennies requires patience and neutral buoyancy. Avoid sudden hand movements or leaning directly against the substrate, as startling them will cause them to retreat deep inside their burrows. If approached calmly, blennies often remain motionless, allowing macro photographers an ideal opportunity to capture close-up shots of their facial structures and vivid body patterns. However, divers must exercise caution around members of the genus Meiacanthus, as these species possess hollow fangs capable of delivering a venomous bite containing enkephalin toxins. Additionally, watch for mimic species like the false cleanerfish, which may approach divers or other marine life expecting a cleaning session only to nip at fins or skin.

Blennies can be observed year-round in tropical, subtropical, and temperate coastal waters across the Atlantic, Pacific, and Indian Oceans. Because their distribution spans global marine habitats—ranging from temperate European waters to tropical Indo-Pacific coral reefs—optimal diving conditions depend heavily on the specific geographic region.

In temperate areas such as the north-eastern Atlantic and the Mediterranean, species like the common blenny (Lipophrys pholis) undergo active spawning during the warmer months from April to August. During this period, males display intensified colouration, such as darkening to an all-black body with a contrasting white mouth, and actively guard egg nests inside intertidal rock crevices. By autumn, juvenile blennies become notably abundant along shallow rocky shorelines and in littoral pools. In tropical Indo-Pacific and Atlantic regions, blennies remain active and accessible to divers throughout the year, with continuous breeding cycles reported in many warmer-water species.

Blennies are primarily marine, benthic fish occupying coastal and shallow inshore waters, including shallow intertidal zones, tide pools, grass beds, and coral or rocky reefs. A few species venture into estuaries, brackish river stretches, or even inland fresh waters such as Italian lakes. Geographically, true blennies occur worldwide in tropical, subtropical, and temperate regions across the Atlantic, Indian, and Pacific Oceans, as well as the Mediterranean Sea. While families like the Blenniidae and Tripterygiidae are globally distributed, Clinidae are mostly temperate, and other families are largely Neotropical.

In shallow marine environments, blennies inhabit crevices, burrows in sandy or muddy substrates, empty mollusc shells, and spaces under seaweeds or boulders. Intertidal species demonstrate homing behaviour and air-breathing capabilities, enabling them to survive low-tide exposure by sheltering in rock pools or beneath damp rocks. Although most blennies remain anchored to the sea floor or substrate, free-swimming sabre-toothed blennies maintain swim bladders and hover above the bottom.

Most blenny species feed primarily on small benthic invertebrates, algae, or plankton. Their diet commonly includes small crustaceans such as amphipods, isopods, copepods, barnacles, and small crabs, along with benthic molluscs like snails, limpets, and mussels, as well as polychaete worms. Combtooth blennies possess specialized close-set, comb-like teeth arranged in a single row along their jaws, allowing them to efficiently scrape algae or scrape sessile invertebrates from hard rock and coral substrates.

Feeding activity varies across species and light conditions; many intertidal and shallow-water blennies are strictly diurnal, foraging actively during high tide when water covers their feeding grounds. Certain specialized sabre-toothed blennies employ parasitic or aggressive feeding strategies. Genera such as Aspidontus and Plagiotremus use cleaner wrasse mimicry to approach host fish close enough to bite off pieces of fins, scales, or skin. Other predatory blennies rely on hollow venomous fangs or enlarged lower canine teeth to secure prey or deter rivals during territorial feeding bouts.