El Hierro sits on a ridge on the 3’500-metre-deep seabed, making it a dive spot with rich biodiversity. As marine biology is an overwhelming field, I’ve compiled a simplified and incomplete scheme. The abundant marine life in El Hierro can be classified into bony and cartilaginous fish, whales, crustacea, molluscs, Anthozoa (anemones, corals, and gorgonians), and a diverse group of other animals (e.g. Echinodermata, sponges, nudibranchs, and salps).
Most of marine life has been described only from animals already caught dead – certainly a challenge for underwater photographers in times of climate change and species threatened from extinction.
Bony fish (Osteichthyes)
At the southern tip of the island around the fishing village La Restinga is a marine reserve. On every dive in El Hierro, there is a colourful spectrum of fish.
- Tetraodontiformes, such as porcupinefish (Diodontidae), grey triggerfish (Balistes capriscus), pufferfish (Sphoeroides marmoratus), and planehead filefish (Stephanolepis hispidus)
- Eels, e.g. garden eel (Heteroconger longissimus), moray eel (Muraena augusti), brown moray (Gymnothorax unicolor), golden tail moray (Gymnothorax miliaris), and leopard eel (Myrichthys pardalis)
- Perciformes, e.g. the dusky grouper (Epinephelus marginatus), barracuda, greater amberjack (Seriola dumerili), small red scorpionfish (Scorpaena notata), and the endangered island grouper (Mycteroperca fusca)
- Percomorphaceae, such as sergeant-majors (Abudefduf luridus) hiding in small rocky holes, and the wide-eyed flounder (Bothus podas) hiding in the sand of the seabed
- Wrasses (labridae), e.g. the colourful parrotfish (Sparisoma cretense), and ornate wrasse (Thalassoma pavo)
- Sea breams (sparidae), e.g. zebra seabream (Diplodus cervinus), and salema porgy (Sarpa salpa)
- Ray-finned fishes (Syngnathiformes), such as trumpetfish (Aulostomus strigosus), and seahorses
Cartilaginous fish (Elasmobranchii)
Cartilaginous fish contain for example the angel shark (Squatina squatina) visiting in spring. In summer, I’ve seen stingray, eagle ray, and one manta ray (Mobula), and I’ve heard from first hand (and seen on video) of a hammerhead shark sighting.
Although not easily sighted, there are many different kind of whales, for example whale sharks, dolphins, blue and fin whales.
Examples of crustacea seen underwater in El Hierro are:
- Slipper lobster (Scyllarides latus)
- Crabs, such as Stenorhynchus lanceolatus with long spider-like legs
- Shrimps, e.g. Lysmata grabhami cleaning moray eels from parasites
Molluscs come in all kind of shapes.
- Cephalopoda like Octopus and cuttelfish (Sepia officinalis)
- Bivalvia, such as mussels
- Gastropoda contain sea snails, such as nudibranchs
The marine invertebrates Anthozoa include sea anemones (for example the tube-dwelling anemone Ceriantharia), stony corals, soft corals, and gorgonians.
The bearded fireworm (Hermodice carunculata) is a Polychaeta with bristles able to penetrate human skin and inject a painful neurotoxin.
Echinodermata contain sea stars, and sea urchins such as Diadema antillarum with very long black spines, sea lilies and feather stars (Crinoids), and sea cucumbers.
An example for sponges (Porifera) is the Crater sponge (Hemimycale columella).
Salps are fascinating creatures appearing from the deep blue water. The translucent animals are chordates with dorsal nerve cords, and thus related to vertebrates. They have internal organs, eat plancton, and can actively swim.
Two excellently illustrated books about sea animals of the Canaries were published by Sergio Hanquet.