Filefish (Family Monacanthidae)

I’d never heard of filefish before I started writing this post. But I was browsing one of the websites I use to get ideas for posts, and the name filefish caught my eye. I always like it when fish are named after other animals or objects because I get to picture a cross between a fish and whatever that fish is named after. Today I thought of a metal file with fins and great big googly eyes, and got a good chuckle out of it. So let’s learn about filefish today, and though you may be disappointed to learn that filefish are not actually a file/fish hybrid, they are pretty cool.

Filefish belong to the family Monacanthidae, which has 27 genera and 102 species. They are fairly widespread, being found in the Atlantic, Pacific and Indian Oceans. Australia is a particularly abundant area for filefish, with over half of all filefish species living in Australian waters. They prefer shallow areas, rarely venturing below depths of 30 meters. Filefish are commonly found in lagoons, reefs, and seagrass beds.


Aluterus scriptus is the biggest species of filefish, and can grow to over 110cm. Image credit: Choo Tee Yong Vincent

Filefish range in size from below 60 cm to 110 cm, depending on the species. They are laterally compressed (meaning their bodies are tall and thin, like they’ve been put in a press and squished), and are shaped a bit like rhomboids. Filefish have two spines on their heads, one of which is much larger than the other. The spines are retractable, and the second, smaller spine holds the bigger spine up when it is erect. Filefish are coloured in a range of hues and patterns, mostly to blend in to their environment.

This type of colouration is vey important to filefish. They have small fins, and so are pretty bad swimmers. This means they can’t easily get away from predators, so camouflaging among corals and sea grass is super important. For filefish that eat invertebrates (some species subsist solely on algae, seagrass, or coral), cryptic colouration also helps hide them from their prey. Some filefish hide out in rock crevices, and use their spines to stay lodged inside if a predator tries to eat them.


Filefish come in such an array of beautiful colours. Image credit: Julian Finn via Wikipedia

Filefish lay eggs on the ocean floor, in nests prepared by the males. Species differ in terms of parental care; in some species both parents guard the nest, while in others that task is left solely to the male. Once the young filefish hatch, they simply drift in the open ocean, often living within Sargassum seaweed species.

I’ve told you a lot about filefish, but I’ve left out the most important fact: why filefish are called filefish. Unfortunately, the reason is fairly mundane. They are thin and have rough skin, which I guess reminded people of files. In fact, it’s said that dried filefish skin was used as a tool to sand wooden boats. In any case, I’m going to leave you with a picture of what a real filefish should look like. Enjoy!


This is what a true filefish should look like. It would use the file part of its body to file open clams and mussels and things. Evolutionarily it is the most perfect of fish. 

Cover image source: Diver Vincent via Wikipedia

Purple Sea Star (Pisaster ochraceus)

One thing I absolutely loved to do as a kid was wander around rocky shores, looking for any form of life. I’d lift up whatever rocks I could to search for crabs, I’d run from tidal pool to tidal pool to peer at starfish and sea anemones. I love living in Ontario, but one thing I desperately miss is the ocean. So today I’m going to going to write about a species of sea star, to fully embrace my nostalgic mood.

Probably the most common starfish I encountered as a child were large purple ones. Unsurprisingly, these are known as purple sea stars, but confusingly are also known as ocher sea stars, since not all of them are purple. They can also be orange, yellow, red or brown. That being said, most of these guys are purple, so I’ll refer to them as purple sea stars. They have five legs, each of which can be from 10 to 25 cm long. Purple sea stars are covered in very small spines, which are no bigger than 2 mm in height.


An example of some colour variants in purple sea stars. Image credit: D. Gordon E. Robertson

Purple sea stars live in the Pacific Ocean, from Alaska to California. Depthwise, they can be found from 90 m to the low-tide zone. They are commonly found along the coast, on mussel beds and rocky shores. Special suckers on their feet allow purple sea stars to cling to rocks with great force, so they can withstand violent waves.

Despite their harmless looks, purple sea stars are quite vicious eaters. They feed mainly on mussels, but will also eat chitons, limpets, snails, barnacles, and sea urchins. They will swallow their prey whole if they can, grabbing their meal with their tubular feet and then everting their stomach onto their prey. The digestive enzymes in the starfish’s stomachs will then liquify the victim, so it can be easily ingested.


A purple sea star. Image credit: D. Gordon E. Robertson via Wikipedia

Mussels try and defend against starfish by clamping their shells together very tightly, but sea stars are patient hunters. Mussels need to open their shells slightly, both to breathe and to feed. The starfish then use their strong feet to pull the mussel shell further open, and insert part of their stomach into the shell, digesting the poor mussel inside. Purple sea stars have quite large appetites, with one sea star being able to eat eighty Californian mussels a year (a California mussel can reach lengths of 20 cm, so they aren’t small).

Purple sea stars breeding from May to July, with both sexes releasing gametes into the water. If all goes well, sperm and eggs meet in the ocean,  and the fertilized eggs can drift around until they hatch. Sea stars progress through a number of larval stages, and at this stage of their life the little starfish are filter feeders, relying on plankton to sustain them. Purple sea stars live to be at least four years of age, and may live much longer.

purple sea star 1

I decided to try something a bit more abstract for this week’s drawing. I had fun with all the shapes!

Purple sea stars aren’t just pretty; they are an extremely important species. Thanks to their diet, purple sea stars help keep mussel populations under control. A loss of only a few purple sea stars leads to a drastic increase in mussel populations. When sea stars are present, the intertidal ecosystem is diverse, instead of becoming dominated by mussels. So next time you see a sea star, remember that they help keep our oceans wonderfully diverse!

Cover image source

Spotted Ratfish (Hydrolagus colliei)

A lot of fish are named after land animals — catfish, dogfish, rabbitfish, porcupine fish, kangaroo fish (that last one does’t actually exist, but I wish it did).  Today’s animal, the ratfish, seems to have gotten the short end of the naming stick. I like rats, but I don’t think I’d want to be named after them.

Ratfish belong to the family Chimaeridae, otherwise known as shortnose chimaeras. Chimaeras are an odd group of fish that have cartilaginous skeletons like those of sharks and rays. In fact, their closest relatives are sharks. Almost all chimaeras are deep water fish, and are therefore difficult to find and to study. So today I’m going to focus on one of the few chimaera species that hangs around in shallow waters, the spotted ratfish.

Spotted ratfish live in the Pacific Ocean, from Alaska to Baja California. They have been found at depths of up to 913 m, but are much more common in areas between 50 and 400 m deep. In the spring and autumn spotted ratfish tend to hang out in shallower waters, moving to deeper areas in the summer and winter. They prefer to live on the ocean floor, particularly on sandy, muddy or rocky reefs.


These guys are a little strange looking…     Image source

Spotted ratfish are named for their spots, and for their long, ratlike tails. They can grow to be up to a meter in length, and females are much larger than males. Ratfish tails can make up almost half of the fish’s length, and are long and thin. Spotted ratfish have silvery-bronze skin, and are covered in fun white spots. They have big huge adorable eyes, which reflect light like those of a cat or dog.

Spotted ratfish hunt during the night, using their sense of smell to locate prey. They swim slowly above the ocean floor, looking for shrimp, worms, fish, crustaceans and sea stars. Ratfish particularly enjoy foods with some crunch to them, such as crabs and clams. They have incisor like teeth that act as grinders to help break up their yummy diet.

Spotted ratfish may be hunters, but they themselves fall victim to predators. Sharks, halibut, pinnipeds and pigeon guillemots are all known to consume spotted ratfish. Eating a ratfish is not always a pleasant experience, however. They are equipped with a venomous spine on their dorsal fin, which can cause painful wounds. The spine can also be deadly if ingested: harbour seals have died after a ratfish spine penetrated the stomach or esophagus. The lesson here: don’t eat ratfish, unless you posses spine-removal tools.


A spotted ratfish egg sack. Image source

Breeding season in spotted ratfish occurs from spring to autumn. Female ratfish lay one or two fertilized eggs into sandy or muddy areas every two weeks or so. Egg laying can last for four to six days, which is a long time, but is necessary, considering the size of the egg sacks. Each sack is twelve centimetres long, and is basically a leather pouch. The eggs take a long time to develop and hatch, sometimes staying inside the egg case for up to a year.

Unfortunately for spotted ratfish, the appearance of their eggs, and the extensive time it takes for the eggs to hatch means that the eggs are sometimes mistaken as inanimate objects by divers. But the news isn’t all bad: the overall population of spotted ratfish is doing just fine, in part because they don’t taste that good. I guess the key to surviving in the modern world is to taste bad, and not look too pretty.

spotted ratfsih

A quick sketch of a spotted ratfish, emphasizing its big cute eye. 

Cover image credit: Clark Anderson via Wikipedia

Japanese Flying Squid (Todarodes pacificus)

Hi everyone, due to poor planning and the fact that I am helping at a conference all day, we’ll have a guest post for today. Enjoy!

The greatest challenge in writing for “OUR WILD WORLD”, especially as a guest contributor, is to find a good animal to blog about. I am confident that the Japanese Flying Squid meets the lofty standards to which this blog’s readers have rightly become accustomed.

The Japanese Flying Squid has three factors in its favour. First of all, it’s a squid, and squid are funny. Even the word “squid” is funny. Secondly, it’s Japanese. It’s not that Japanese are funny (don’t get me wrong, I’m not saying Japanese are not funny either) – it’s that most animals don’t get citizenship in any country. Finally, it flies. There’s a strong “WTF?” (“what, they fly?”) aspect to the Japanese Flying Squid. So let’s take a closer look at them.


An awesome picture of a flying squid doing what it does best. Image source

As you will have guessed from the name, Japanese Flying Squid live in the northern Pacific Ocean, and in fact are sometimes more mundanely called the “Pacific flying squid”, which just doesn’t cut it as far as I’m concerned. Japan is a relatively small country, and the Pacific is a big ocean, so it isn’t surprising to learn that Japanese Flying Squid are found not only near Japan, but also along the Chinese and Russian (Siberian) coasts, and then down the other side of the Pacific Ocean along the Alaskan and Canadian coasts. And off Vietnam too – that’s a lot of Air Miles.

Japanese Flying Squid live in the upper layers of the ocean, in water up to 27 oC in temperature. They tend to live only about a year, but they pack a lot into this year.

Once the female squid matures, having been fertilized by a thoughtful male in advance, it lays between several hundred and several thousand eggs, which hatch into larvae within a week. The little critters then eat, get bigger and migrate to their mating grounds, where the cycle starts anew. Then they die.

Japanese Flying Squid get bigger as they eat, but they level off around 0.5 kg, and can be half a metre long. Admittedly, that’s not very large compared to the giant squid, much less the colossal squid, which is even bigger. But the giant and colossal squid are too big to fly, so score one for the Japanese Flying Squid. There is even speculation that the legendary kraken, as pictured, was in fact a Japanese Flying Squid, rather than a giant squid as commonly believed.

Screenshot 2016-05-11 08.10.57

Non-flying giant squid – or possibly a kraken – from an old drawing.

Japanese Flying Squid have all the usual interesting accoutrements of squid: eight arms and two tentacles, with suction cups familiar to science fiction movie buffs; obligatory ink sacs, used to defend against predators; a beak; and of course three hearts. But what makes the Japanese Flying Squid truly impressive is that to get around it eschews the two fins on its body in favor of a powerful muscle which takes water in and expels it a high velocity, giving it a form of jet propulsion. The Animal Research Department of the Imperial Japanese Navy would have been happy to have perfected echolocation from bats, but surely jet propulsion was high on its wish list.

Japanese Flying Squid have been observed flying (and “flying” is surely an appropriate description, as opposed to “gliding”) for up to 30 metres. They are thought to use their airborne capability to save energy while migrating (someone can work out the physics of this) and to evade predators. This latter argument sounds more logical, since most of the Japanese Flying Squid’s predators are confined to water – some birds prey on the Japanese Flying Squid, but mainly it has to worry about sperm and baleen whales, dolphins, seals and rays. Since Japanese Flying Squid larvae eat plankton, then graduate to small fish and crustaceans, with occasional bouts of cannibalism when stressed, you can see it is tricky being in the middle of the food chain.

It is difficult to study the Japanese Flying Squid in captivity, because they don’t like being penned up, get stressed and act unnaturally. That sounds natural to me. But, as you now know, we actually know a fair amount about them – especially that they fly!

Asian Sheepshead Wrasse (Semicossyphus reticulatus)

I know I’ve written about a lot of weird looking fish, but the Asian sheepshead wrasse is a strong contender for the number one strange-looking fish. With a great bulbous chin and an amazing forehead, these fish definitely make you look twice. Unfortunately, not a lot is known about this marvellous species, but they are too bizarre not to write about.

Asian sheepshead wrasses occur in the waters around Asia, particularly around Japan, Korea, and south China. They prefer cooler waters to warmer ones, and Hong  Kong is likely the species’ southern limit. Sheepshead wrasses live in and around rocky reefs.

These guys are some of the largest known wrasses; they can reach lengths of a meter, and weigh up to 14.7 kg. Young wrasses are remarkably different from the adults, being bright orange in colour and lacking the beautifying facial adornments of adults.

The only observation of mating behaviour in an Asian sheepshead wrasse occurred in an aquarium, where the largest male fish chased away all the other males, and then proceeded to mate with the female at the surface. They are assumed to be long lived and reach sexual maturity late, like other species of wrasse. A closely related species, the California sheepshead wrasse, is a sequential hermaphrodite, changing sex from female to male as they mature. We don’t know whether the Asian wrasses experience similar sexual development, but it’s an interesting possibility.

The lack of information on such a strange fish is sad, and also quite worrying. Fish that are slow to mature are often vulnerable to over fishing, but we have so little data on the Asian wrasse we have no idea how stable the population is. So I hope we go do some research on the Asian sheepshead wrasse, and figure out what this fish is all about!

Cover image source:

Goatfish (family Mullidae)

Goats are funny creatures. So any fish named after our silly ruminant friends automatically gains some of that hilarity. That’s why when I was browsing through the endless realm of the internet this morning, looking for a fish to write about, the goatfish leapt out at me.

Goatfish comprise the family Mullidae, which contains six genera and fifty-five species. They are found in tropical waters, usually around reefy areas. Goatfish can live in the Atlantic, Pacific, and Indian Oceans, as well as in the Mediterranean and Red Seas. They are benthic fish, meaning they tend to stay on the ocean floor, but prefer shallow areas where they don’t have to venture deeper than 100 m.

A bluestriped goatfish sporting some nice barbels.  Image credit: Graham Short via

A bluestriped goatfish sporting some nice barbels.
Image credit: Graham Short via

Like goats, goatfish come in a wide variety of colours. Unlike goats, goatfish can rapidly change their colour (side note: how cool would it be to have a colour-changing goat?!). The fish will change their colour depending on what they are doing; a fish resting on the bottom will have a different colour than a highly active fish. Goatfish sometimes swim with other species of fish, and will change their colour to match that of the schools they swim with.

Goatfish are bottom feeders, using two barbels that protrude from their chin to sweep the ocean floor for any edible meals. They will eat pretty much anything, which is where the ‘goat’ part of their name comes from. Once they’ve found a tasty animal, goatfish dig their heads into the sand, ingesting both the prey and a ton of sand. The food is swallowed while the sand is expelled through the fish’s gill covers.

A whitesaddle goatfish foraging for some food.  Image credit: Divervincent via Wikipedia

A whitesaddle goatfish foraging for some food.
Image credit: Divervincent via Wikipedia

Goatfish don’t just use their funny barbels for foraging; they are also involved in courtship behaviour. Male goatfish will waggle their barbels at females to attract their interest. Females lay eggs in the open water, where they float until hatching. Their behaviour doesn’t change much after hatching, with the little goatfish simply dancing with the currents until they reach 5 cm in length, when they go to the bottom and start acting like real goatfish should.

In many countries, goatfish are caught for human consumption, and have been for quite some time. In ancient Rome goatfish were highly valued thanks to their colour-changing abilities: fish would be served still alive, and as they died the poor goatfish would go through a number of colour changes. I think I’d be put off by food that changed colours before my eyes, but the Romans loved it.

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