WTF? (WHAT’S THAT FISH?) 15 PORCUPINEFISH

April 12, 2018 by Rolling Harbour

WTF? (WHAT’S THAT FISH?) 15 PORCUPINEFISH

The porcupinefish Diodon hystrix falls into the general category ‘pufferfish’, though the particular species named PUFFERFISH are distinct in their own right. There are other similar species – e.g. balloonfish, blowfish and burrfish – with which there is scope for confusion. The relationship is something like this: all porcupinefish are pufferfish (in a broad sense); but not all pufferfish (in its species sense) are porcupinefish.

Porcupinefish are slow-moving reef dwellers and like their puffer cousins, they can inflate themselves by ingesting water, turning them into spiny balloons. This defence mechanism is a response to threat and works in two way: only predators with large mouths would consider them a meal; and even then they have to deal with the spines that become prominent when the fish is bloated.

I’VE HEARD PUFFERFISH ARE POISONOUS? WHAT ABOUT THIS GUY?

Good question. Checking it out, I’ve found some contrary statements about this. The truth seems to be that unlike pufferfish, they do not produce toxic secretions from their skins, so are not poisonous to touch (if you must**).

However porcupinefish do contain powerful (neuro)toxins in their internal organs and are best not eaten – though in some parts of the world they are considered a minor delicacy. They may also suffer the ignominy of being dried in their inflated state and sold to tourists as novelties – with lightbulbs inside for added amusement value.

ARE PORCUPINEFISH FAMOUS IN ANY RESPECT?

Indeed they are. They had the honour of being recorded by Charles Darwin. He gives a surprisingly long account of this creature, encountered during his renowned voyage on the Beagle. It clearly fascinated him. I’ve ‘ripped’ the relevant passage (open source – it’s ok) and turned it into an eezi-reed pdf if you want to check out Darwin’s careful observations in more detail:

THE VOYAGE OF THE BEAGLE – CHARLES DARWIN

WAIT! ISN’T THERE A MORE RECENT CLAIM TO FAME?

Yes! In ‘Finding Nemo’, Bloat the Porcupinefish was part of the ‘Tank Gang’ in a dentist’s office. He had an encore in the closing credits of ‘Finding Dory’. Enough of fame already. Here’s a 50 second video demonstrating the puffer / porcupine distinction.

PUFFERFISH

WTF? SERIES PAGE

MONSTERS OF THE DEEP

Photo Credits: Melinda Riger (1, 2); George Parilla (3); Virgini Cooper (4); Bernard Dupont (5); Adam Rees (6, 7); Video, ‘AquariumKids’ (I do high-powered research, see?)

**Incidentally, it’s apparently not considered an act of animal kindness to catch them / scare them so you can have the pleasure of watching them blow up

SHARKS! APEX PREDATORS IN THE BAHAMAS

March 29, 2018 by Rolling Harbour

SHARKS! APEX PREDATORS IN THE BAHAMAS

Immersion in current affairs these days brings inevitable acquaintance with sharks of various kinds, and all best avoided. Let’s have a look the real thing, the apex marine predators that in the Bahamas are all around you once you leave the safety of the shore. I haven’t featured them for ages, and it’s always a pleasure – a slight thrill, even.

I don’t do scuba, indeed my swimming would easily be outclassed by a competent four-year old. But I see these creatures when I’m out fishing; or as they hang in the breaking waves off the Delphi beach, watching intently for a meal.

We watch them (and stingrays) from the balcony as they lazily make their way round the margins of the wide bay, from little ‘uns to (recently) a huge bull shark. We watch as, when someone is in the water, they change course slightly to pass by them. So far, anyway…

Feeding sharks

The one that got away… (a sad sight)

I once took a rather primitive underwater camera with me while snorkelling in Fowl Cays National Park. This was several years ago, when I believed a cheap 2mb camera might turn me into one of the Blue Planet team. I was wrong. The shark I saw, apparently some 20 miles away (when I examined the image) – well, that’s its tail, top left…

Just to look at these images is to understand that when you are in the sea, you are in the sharks’ environment. They are the masters of it. They have their rules, and they are not much interested in you… unless you break them. Or so the theory goes.

This fine shark below exemplifies the power and the menace of the shark. A creature to be admired, but also to be respected.

All fantastic photos: Melinda Riger / Grand Bahama Scuba

BAHAMAS REEF FISH (44): PORKFISH

March 1, 2018 by Rolling Harbour

BAHAMAS REEF FISH (44): PORKFISH

Behold the porkfish Anisotremus virginicus, the slightly unattractively named representative of the (arguably) even less attractively named grunt species. These small, bright-coloured reef dwellers are rarely more than 12 inches long. They are mainly nocturnal fish, feeding on small crustaceans, mollusks and so on. Juveniles have been observed acting as cleaners to larger species, feeding on parasites – an example of mutualism between species, in which both sides benefit from the arrangement.

WHY IS A ‘PORKFISH’ A ‘GRUNT’

The terminology seems to be somewhat confused by local usages, but in general terms all porkfish are grunts; but not vice versa. Yet I notice that the term ‘porkfish’ is used to describe other types of grunt. A good rule of thumb is the the Atlantic Porkfish is the only grunt with two black vertical bars and yellow stripes… Note that grunts differ from their cousins the snappers by having a different dental arrangement – no canine teeth.

AND WHY ‘GRUNT’ ANYWAY? DO THEY SOUND LIKE PIGS?

Well, perhaps a bit. All grunts, including porkfish, are capable of producing grunt-like sounds from some kind of grinding of their back teeth that is too technical to go into here**. The sound is associated with ‘situations of duress and danger’ – such as being caught and unhooked…

DO YOU HAPPEN TO HAVE A RECORDING?

As it so happens I do. This is taken from a rather longer Youtube video in which a grunt was caught, unhooked and returned.You’ll hear a couple of grunts as the fish was unhooked, and some (perhaps understandable) hilarity on the boat. I guess you had to be there.

Porkfish are gregarious, and also mix with other species Porkfish (Grunt), Bahamas - Melinda Riger / Grand Bahama Scuba

ARE PORKFISH EDIBLE?

Like most if not all grunts, they are, with the proviso that there is some association with ciguatera. I’ve never knowingly eaten one myself, but I gather that “grits and grunts” is a popular culinary combo in some places. For those that might want to know more, a quick look at a couple of threads reveals the following:

They taste great, a bit like ham
Their white meat cooks very well
They taste better than black margates (another grunt species)
Eat them in enchilado or breaded fillets
‘Big-ass head’ on them so not much if you filet
If you scale and cook whole you get a better yield on them
When fishing for supper, ‘shoot ’em up and hold off for the bigger ones’

Credits: all great photos by Melinda Riger / Grand Bahama Scuba, except the last by Brian Gratwicke (wiki); soundbite from Youtube video 2010 by peachyree; research from seaworld.org; britannica.com and the usual suspects…

** Subtle code for “I haven’t really understood it…”

GRAYSBY (GROUPER): BAHAMAS REEF FISH (42)

February 1, 2018 by Rolling Harbour

GRAYSBY (GROUPER): BAHAMAS REEF FISH (42)

The Graysby Cephalopholis cruentata is a small, spotty grouper, which grows to a maximum of around 16 inches. These rather unassuming and solitary fish have a preference for coral reefs, where they can blend in with their surroundings on ledges and in caves and crevices during the day. At night, they become active – that’s when they feed on feed on small fish, crabs and shrimps.

The graysby has variable colouring in a range from light brown to pale gray, with all-over spots that may be red, orange or brownish. Often, they have 3 to 5 contrasting spots on their backs, along the base of the dorsal fin, as below:

The long erectile dorsal fin comprises both spines and ‘rays’ – spines at the front, rays at the back. Like this:

The spots of a graysby can change in colour (at least to a limited extent), becoming either paler or darker. I imagine this is a protective feature to enable the fish to blend in more easily with its reef surroundings.

Graysby (grouper) - Melinda Riger / Grand Bahama Scuba

Signalling to turn right…

I wondered if they are edible. I believe so – but then I also read that the larger adults carry the risk of ciguatera and raised mercury levels. So I’ll give it a miss thanks.

Photo & other credits: all photographs by Melinda Riger / Grand Bahama Scuba; aqua.org; SAMFC (drawing)

WTF? (WHAT’S THAT FISH?) 14: ARROW CRABS

January 16, 2018 by Rolling Harbour

WTF? (WHAT’S THAT FISH?) 14: ARROW CRABS

It’s been a while since the last in the WTF? series, which is dedicated to the wilder, less conventionally fish-shaped side of reef life – those creatures that you may come across, blink into your face-mask, and silently mouth the words ‘What’s That Fish?’ (that’s what it looks like you are saying, anyway).

Let’s meet some Arrow Crabs Stenorhynchus seticornis, one of the very few creatures surely to have a triangular body plus a huge pointy nose (rostrum), supported on long skinny legs. To which add, they wear tiny blue gloves on their two front claws.

These crabs are coral reef dwellers and mostly stay concealed during the day. Their body is protected by a carapace, and the rostrum has serrated edges like a tiny rasp or file. I haven’t found a definitive reason for this gadget, but I suspect it is more for probing than for piercing or fighting.

There’s a considerable colour variation among these crabs, as these images show. The body may even have blue iridescent lines (#2, above). And those claws may be any of 50 shades of blue…

Arrow crabs are most active at night. They eat feather-duster worms (illus.) and similar invertebrates such as bristle worms.

Feather-duster worm (Melinda Riger / G B Scuba)

Arrow Crab Meal

Like certain types of shrimp, they also have a symbiotic relationship with anemones, whereby they make use of an anemone to benefit from the food it captures – and possibly for cover too. They are protected from anemone stings, whereas some of their predators are not.

This was the place where I was going to tell you about the arrow crab’s private life, but, well… “it’s complicated”. Briefly it is: male passes sperm-filled capsule to female; she uses it in some way whereby it fertilises her eggs; she then ‘broods’ the eggs in one of her ‘swimming legs’; the eggs hatch into larvae and swim off to eat plankton; each one then grows & moults, repeating the process until it has reached adult form. On balance, humans have arguably perfected a preferable method.

Arrow Crabs are apparently popular aquarium creatures, although they sound to me rather a disagreeable challenge. They can move quickly on those long legs, and it seems as if they inclined to be aggressive to other inhabitants of the tank. As far as I can make out, it’s best not to put 2 of them together: they certainly won’t be doing the sperm capsule thing described earlier…

Master of Disguise

Photo credits: Melinda Riger / G B Scuba (1, 3, 4, 5, 6); Adam Rees / Scuba Works (2, 8, 9); Nick Hopgood,Wiki (7); Chuck Elliot – video

SOUTHERN STINGRAYS: BAHAMAS REEF FISH (41)

January 9, 2018 by Rolling Harbour

SOUTHERN STINGRAYS: BAHAMAS REEF FISH (41)

Anyone who has scuba-dived or snorkelled around the bright coral reefs of the Bahamas, or hunted bonefish out on the Abaco Marls will have come across Southern Stingrays Dasyatis americana. And there are certain places (eg Manjack Cay) where you can actually feed them – and not come to any harm…

FEED THEM? AREN’T THESE GUYS LETHALLY DANGEROUS CREATURES?

The name that always comes to mind in connection with stingrays is poor Steve Irwin, the charismatic Australian wildlife expert who was tragically ‘stung’ over his heart as he swam close over a ray while filming underwater. But this was, it would appear, a dreadful combination of circumstances with a terrible outcome.

The ray’s stinger is in fact an erectile venomous barbed spine near the base of the tail and not on the end of it (as one might expect). But these creatures are not out to harm you – though of course when you are in their environment you should accord them the respect that they merit.

If you are walking / wading in the water, avoid the risk of accidentally treading on a ray. Best to shuffle your feet forward in the sand; if there’s a half-concealed ray feeding or resting on the bottom nearby, it will swim away peacefully. I took the photo below while bonefishing on the Marls; the ray directly ahead slowly makes off as the skiff drifts closer. The next one is of a ray with its young – completely aware of us as we glide past to one side, but not especially bothered.

If you are swimming, snorkelling or diving, don’t get too close – especially by swimming directly over a ray (apparently Steve Irwin’s mistake, so that he was struck right in the chest by the stinger when the ray reacted).

Enough of the potential dangers. The southern stingray is a magnificent creature, as Melinda’s wonderful photographs show. She spends half her life underwater and I’m not aware that she has had a problem with a ray.

Like many larger sea creatures, stingrays need help with their personal care – the removal of parasites, dead skin and so forth. And so they make use of the services offered by small fish like gobies, wrasses and shrimps at a CLEANING STATION. Here are 2 photos of rays doing just that. You can see the tiny fish by the reef, going about their work. There’s a mutual benefit in this symbiotic relationship, in which it is understood that the cleaners are unharmed. Indeed, they will often enter the mouths and gills of a fish to clean… including the teeth. So there’s dental hygiene on offer too…

RELATED POSTS

YELLOW STINGRAY

GRACE WITH ATTITUDE

TAKEN TO THE CLEANERS

Photo Credits: Melinda Riger / Grand Bahama Scuba, except for the feeding photo (cheers, Samantha Regan), the ‘specimen’ from Tomas Willems (Wiki) and my two noted above

BAHAMAS REEF FISH (40): FOUR-EYED BUTTERFLYFISH

December 1, 2017 by Rolling Harbour

BAHAMAS REEF FISH (40): FOUR-EYED BUTTERFLYFISH

Four-eyed (or foureye) butterflyfish (Chaetodon capistratus) are small, somewhat circular fish with an endearingly pointy little snout. They are one of several butterflyfish species found in Bahamian waters. On their sides are smart ‘go-faster’ chevrons, with the unmistakeable white-circled black ‘eye’ at the back. The real eyes, in the conventional position, are small and far less noticeable, not least because of the stripe that passes right through them.

WHY THIS EXOTIC PATTERNING?

This type of misleading pattern is not uncommon in fishes and indeed in terrestrial creatures. It creates confusion in predators – and when this little fish is threatened it swims away with its large ‘eye’ prominent to the pursuer. It acts as a warning and an off-putting feature that suggests ‘don’t eat me’. If you half-close your eyes and look at the image below, the large eyes stand out against the reef background and hint at a creature not to be tangled with. Why reef predators don’t rumble this ruse within minutes, I have no idea.

WHAT IF THE RUSE FAILS?

Foureyes are very agile swimmers and can take advantage of narrow gaps and clefts in the reef by swimming sideways or even upside-down to manoeuvre away from danger and to safety where the predator cannot reach it.

AND IF THAT DOESN’T WORK?

If the foureye is in deep trouble, it has an alternative cunning plan. It will turn and face the pursuer, head down and dorsal spines erect. This posture says both ‘I’m very spiny – watch out’ and ‘I’m coming atcher’.

AND IF THAT DOESN’T WORK? I’M WORRIED FOR IT NOW…

Curtains. It’s lunchtime, I’m afraid.

♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦

Foureyes are far from the only reef dwellers that have predator-confusing markings. In the image below, the foureye at the top is swimming with a larger BUTTER HAMLET, a species that also relies on an abnormal spot pattern to put off predators. This is a great capture, and it also illustrates how the smaller reef fishes can hang out together amicably.