When we talk about blennies, we are referring to approximately 900 species of fishes in the order Blenniiformes, which is comprised of six families. The official number of blennies changes every year as scientists and naturalists find new species, and DNA analysis reveals new relationships.
Blennies come in an assortment of shapes and sizes; so what makes a blenny a blenny? I put the question to Dr. Bill Smith-Vaniz, an ichthyologist who has formally described many blennies, to sum up what constitutes a blenny. Paraphrasing: ”Blennies all have a bean shaped pelvis, unlike other fishes that have flat to concave pelvic bones, their anal fins differ from other fishes in the number of spines and types of fin rays, and the first vertebra is different in blennies.” Unfortunately, these characteristics are internal or too subtle for fish watchers to easily see.
Blennies are found worldwide in tropical and temperate waters in many habitats, including tide pools, in, on and around coral reefs, grass beds, rubble and sand flats, kelp, and rocky shores. Most lack a swim bladder, which is why we see many species perched on the bottom, skittering around. Of course there are exceptions, which is what makes blenny watching so much fun.
Why blennies? OK…we love the big animals too - the big guys with teeth, charismatic megafauna that get a whole week on TV every year …well, we get a much bigger kick watching the little fish - because we see a lot more of them when we’re diving and snorkeling. Wherever we are - in almost every habitat - we are almost guaranteed to see a blenny. And blennies have it all - color, style, drama, and even fangs!
For years, we’ve taught a Blenny Bootcamp. It's all you need to know to get started hunting for blennies, and then some. We cover the basics about each family and include a little about their reproduction, where and how to find them. Our BlennyWatcher Blog also contains many of our images and observations from our diving and snorkeling trips. Here is an overview of the contents of our Blenny Bootcamp:
Blenny 101: The Six families of the Order Blenniiformes
Getting Started: Beginning Blenny Watching
Blenny vs. Goby
Hopefully some of the basic pointers below will help you distinguish blennies from other fishes, in particular similar-appearing gobies that often share the same habitats. Most blennies are small, typically one to three-inch bottom-dwellers with a single continuous dorsal fin. Gobies have two-part dorsal fins - one of the identification tips we use is when you see a goby, you can 'GO BEtween the two fins". Corny, but it works!
While perched or swimming, blennies tend to curve and flex; gobies are mainly stiff and straight.
But most crucial for us, blennies are packed with personality, often curious, entertainingly animated and oh so cute, (even with all their delicate beauty, gobies are ho-hum by nature, couldn’t care a whiff about divers and are forever preoccupied with their hiding holes).
Many blennies have fleshy, single or multi-branched filaments, known as cirri, crowning their heads, and to a lesser extent their snouts, (gobies lack cirri altogether). The purpose of cirri is not clearly understood - they might be sensory organs. It has been suggested that they might also aid in camouflage.
Reproduction and Life Cycle
Unlike some reef fishes, like parrotfishes and wrasses, blennies are not hermaphroditic - they don’t change sex - however some males make dramatic, colorful transformations during courtship.
Blennies are egg-layers. Nests sites are usually located in secluded locations where they’re often difficult to find and observe. The sites are selected by males, who sometimes make elaborate jumps and moves to attract females. The females lay adhesive eggs that are guarded and tended by males until they hatch.
Multiple females usually contribute eggs to the nest of a single male. After hatching during the early evening, the larvae move into the open ocean where the offspring mature for three or four weeks before settling back onto the reef or sand habitats where they spend the remainder of their lives. The life span of many of the smallest blennies may be as short as a month or for larger species as long as three or four years. We will use images of the Redlip Blenny, a common species in the Caribbean, to portray the potential phases of a blenny’s life cycle:
Blenny Watching: Where and When?
Blennies live in every habitat available to snorkelers and divers. Most are very site attached, meaning you’ll find them where they eat and guard their eggs. Many blennies are algae eaters, so you’ll find them on the reef or algae-covered rocks, grazing away. If you spot a blenny that is not a tube dweller, say the Redlip Blenny in the Atlantic or the Jeweled Blenny in the Pacific, back off a bit and have the patience to just watch. They have several favorite perches in a small territory, that they return to over and over.
Pikeblennies may be found in sand and grassbeds, pretty much anywhere with abandoned worm tubes. The various species of sailfin blennies are often in rubble and sand, where they use holes in low-lying rocks, and dead or living coral to guard eggs. For something like the Secretary Blenny, look in the sides of rocks in shallow surge zones. Arrow Blennies, a Caribbean species, are often in overhangs, sometimes mixed in with glass/masked gobies. The juvenile Wrasse Blenny, a tube blenny in the tropical western Atlantic is sometimes found up in the water column mixing with juvenile Blueheads which are wrasse. In the Indo-Pacific, the Midas Blenny is often found mixed in with clouds of anthias, picking plankton. There are some blennies, the rockskippers and lipsuckers, that have adapted to spend extended time out of the water - you can see them on rocks, just above the water line. You get the idea...blennies can be found almost everywhere you dive or snorkel!
A good time to see blennies is early morning, when they are often courting and spawning. Blennies that are normally shy and retreating, lose their heads when its time to reproduce. You can observe males “dancing” and jumping to attract females. Occasionally a fight between males will break out. Once the female lays her eggs, the male is very site-attached and will not leave the eggs he is guarding.
Blenny 101: When is a Blenny Not a Blenny?
A Scooter Blenny is Not a Blenny
Although blennydom should be happy to count such a lovely little fish among its members, the Scooter Blenny is not a blenny – it is a dragonet.
It's Blenny, not Blemmye...
A Blemmye is a mythological headless creature with face in its chest.
A Convict Blenny is Not a Blenny
Even we are guilty of perpetuating this name. Pholidichthys leucotaenia is not a blenny (nor a goby); it is in fact in its own family. The correct common name is Convict Fish. I am obsessed with this fish and will write a complete post about them later. There are lots of photos of the adult on the internet – taken mostly in aquariums. I understand from my aquarist friends that they are much more colorful and not as cryptic as the adults in the wild. Here are photos of the juveniles and the very much larger (and dark) adult:
More Blenny Fun
You would be right if you think this Southern Smoothhead Glass Blenny (Emblemariopsis bottomei) looks a little odd. Ned was trying to capture a portrait of this tiny fish, when it flipped around quickly and faced the other way. But it rotated its eyes backward to keep an eye on him!
Read about it in Double Take.
What do the Sailfin Blenny and the Osprey (bird) have in common?
The first specimen of the Sailfin Blenny was collected in 1899 during an expedition aboard the steamer Fish Hawk. Another common name for the Osprey is fish hawk. The scientific name for the Osprey is Pandion haliaetus carolinensis. The scientific name for the Sailfin Blenny is Emblemaria pandionis.
“Investigations of the Aquatic Resources and Fisheries of Porto Rico by the United States Fish Commission Steamer Fish Hawk in 1899” was published in 1900. Evermann and Marsh, authors of the fishes section, described E. pandionis, saying “Named for the U.S. Fish Commission steamer Fish Hawk, Pandion being the generic name of the fish-hawk or osprey, Pandion carolinensis.”
A Very Unusual Blenny
This one really is a blenny! Xiphasia setifer, a.k.a., Eel Blenny, Hairtail Blenny or Snake Eel Blenny, this Indo-Pacific species is one of my favorites because it is so unusual. We encounter them occasionally, because we frequent their turf - mucky or sandy bottoms. It is difficult to get good footage because they are either entrenched in their burrows or swimming back really fast to escape from us!
I shot this video (below) years ago in North Sulawesi, when I found one out feeding: