CHRISTMAS TREE WORMS: SEASONAL SPIROBRANCHES

December 18, 2017 by Rolling Harbour

CHRISTMAS TREE WORMS: SEASONAL SPIROBRANCHES

“Deck the Reefs with Worms Like Christmas Trees… Fal-La-La-etc-etc ” is a traditional Carol familiar to all. Well, most. Ok, some, then. Oh right – maybe with different words? Anyway, now is the perfect time to take another look at these remarkable subsurface symbols of seasonal good cheer (nb they are animals not plants).

10 CHRISTMAS TREE WORM FACTS TO PONDER

The 2 colourful spirals are not the worm, but complex structures for feeding & respiration
The spirals act as specialised mouth extensions for ‘filter-feeding’
Prey is trapped by the feathery tentacles & guided by cilia (microscopic hairs) to the mouth
The tentacle things are radioles and act as gills for breathing as well as prey traps
It is not believed that prey slide down the spiral to their doom, like on a helter-skelter

Christmas Tree Worm (Melinda Riger / Grand Bahama Scuba)

The actual worm lives in a sort of segmented tube, with extremely limited mobility skills
It contains digestive, circulatory & nervous systems – and a brain in the middle of it all
The worm also has a tiny drainage tube (I think I have this right) for excretion etc
They embed themselves into heads of coral such as brain coral. And stay there
And yes, the Christmas trees are retractable… (see below for some action)

HOW DO THE WORMS… YOU KNOW… ERM… REPRODUCE?

This is a delicate area. They don’t tend to talk about it much, but as far as I can make out they eject gametes from their what-I-said-above. There are mummy and daddy worms, and their respective gametes (eggs and spermatozoa) drift in the current and presumably into each other to complete the union. The fertilised eggs develop into larvae, which settle onto coral and burrow into it, build their protective tubes and the process begins again.

YOU DON’T REALLY UNDERSTAND THESE CREATURES, DO YOU?

I won’t lie. I found it hard to work out how the CTWs function in practice. There are plenty of resources showing them in their full glory, but that only takes one so far. Then I came across a short video that shows it all brilliantly simply (except for the reproduction part).

The worms, in their coral burrows, hoist their pairs of ‘trees’. You can easily see small particles – possibly zooplankton – drifting in the water, and the radioles swaying to catch potential food. Suddenly it all makes sense (except the repro bit – I haven’t found footage of that). Next: the New Year Worm (there is no Easter worm).

A WHOLE FESTIVAL OF CHRISTMAS TREE WORMS

Credits: Melinda Riger (G B Scuba); Nick Hobgood; Betty Wills; Video by ‘Super Sea Monkey’;Reef Collage by RH; MarineBio; Wikibits & Magpie Pickings

Happy Christmas to all those who put up with RH with such fortitude

NASSAU GROUPER: ENDANGERED… AND PROTECTED

December 7, 2017 by Rolling Harbour

NASSAU GROUPER: ENDANGERED… AND PROTECTED

Most creatures need some space for creative activity of one sort or another. Especially one particular sort, namely breeding. And for vulnerable and endangered species, this is especially important in order to maintain a sustainable population, and preferably to increase it year on year. Which is why there are closed seasons for certain fish, ensuring a time when they can be left alone to breed in peace and to perpetuate their species.

The Nassau grouper Epinephelus striatus is just one of a number of grouper species that inhabit Bahamian waters. They are mostly found in the Northern Bahamas but only the Nassau grouper is on the IUCN Red List as an Endangered Species in need of protection.

WHY ARE THESE FINE FISH ENDANGERED?

Sad to say, mankind is the main cause of the population fragility that has led to the official listing, and the imposition of a strict closed season for 3 months between December 1st and February 28th. Scientific studies have shown that commercial overfishing has reduced a thriving population to fewer than 10,000 mature fish. That may sound plenty to be going on with… until you consider that a net annual loss of only 10% would lead to extinction in a decade.

10 CONVENIENTLY COLLECTED NASSAU GROUPER FACTS TO PONDER

An adult can grow to more than a metre long, and weigh 25 kg
They tend to be solitary daytime feeders, eating small fish & crustaceans
Their large mouths are use to ‘inhale’ or suck in prey
The colouring of an individual can vary from red to brown
These fish have little black spots around the eyes (I’ve no idea why).
Their habitat is in the vicinity of coral reefs, from shallows to 100 m deep
Spawning occurs in Dec & Jan during a full moon
Large numbers gather in a single location to mate in a mass spawning
These groupers are slow breeders, which compounds the overfishing problem
They are easy mass targets at spawning time; hence the need for a closed season

Department of Fisheries information sheet (interesting if you have the time)

A Nassau Grouper glumly contemplates the possibility of extinction Nassau Grouper (Melinda Riger / Grand Bahamas Scuba)

RELATED POSTS

Credits: all photos, Melinda Riger; Infographic by Royal Defence Force (tip o’ the hat to Char Albury); Info Sheet, Dept of Fisheries

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.

RELATED POSTS

REEF BUTTERFLYFISH

SPOTFIN BUTTERFLYFISH

LONGSNOUT BUTTERFLYFISH

Image Credits: 1, 2, 3, 4, 6, Melinda Riger / Grand Bahama Scuba; 5, Lazlo Ilyes

SPERM WHALES – BMMRO FIELD TRIP, BAHAMAS

November 28, 2017 by Rolling Harbour

SPERM WHALES – BMMRO FIELD TRIP, BAHAMAS

I can never quite get my head around the fact that the waters around Abaco are home to the twin leviathans, sperm whales and humpback whales. And before anyone points it out, I realise they can’t actually be twins: sperms whales (cachelots) are TOOTHED WHALES whereas humpback whales are BALEEN WHALES.

During November, the Bahamas Marine Mammal Research Organisation (BMMRO) undertook a rather special field trip. Using sophisticated devices, the scientists first located a group of sperm whales, and then tracked them through the night using the communications between the creatures – ‘vocalisations’ – to follow them. Later analysis of the recordings will have made it possible to identify the individuals through their unique vocal patterns – and so to recognise them again.

The hydrophonic equipment used is extremely sensitive, and can pick up the sounds made by whales and dolphins over a great distance. The box of tricks looks deceptively modest – I took these photos on a previous trip when we were looking for beaked whales and dolphins. Charlotte Dunn holds the microphone submerged on a cable and underwater sounds are amplified so that the slightest chirrup of a dolphin can be heard by everyone on the vessel. The sounds are recorded and locations carefully logged.

Besides the sperm whales, the BMMRO team also had sightings of spotted dolphins, bottlenose dolphins and beaked whales during the field trip. These bonus sightings will also have been logged for future reference. It all adds to the detailed research data that assists the conservation of the prolific marine mammal life in Bahamian waters.

Atlantic Spotted Dolphins Atlantic Spotted Dolphins, Bahamas (BMMRO)

By the time one of the whales decided to breach, it was some distance away, so I’m afraid I can’t bring you a dramatic close-up from the trip. But just to see this view at all is breathtaking.

All photos BMMRO except the 2 hydrophone ones on the research boat (Keith Salvesen)

BAHAMAS REEF FISH (39): YELLOWTAIL DAMSELFISH

October 23, 2017 by Rolling Harbour

BAHAMAS REEF FISH (39): YELLOWTAIL DAMSELFISH

Yellowtails are just one of several damselfish species in Bahamas waters. These small fish are conspicuous not just for the bright tails that give them their name. More striking if anything – especially if seen underwater in sunlight against the coral – are the electric blue spots visible in both adults and juveniles.

The body of adults is dark blue to brownish to almost black

The body of juveniles is blue

Yellowtails are a common and widespread variety of damselfish. They have a limited ability to change colour according to their surroundings, but with their bright tails and luminous blue flecks, it’s hard to see how they can look, to a predator, anything other than a tasty snack.

I have enjoyed seeing these little fish at Fowl Cay Marine Preserve, Abaco. The reef there makes for easy and rewarding snorkelling, with a wide variety of small and medium-size reef fishes to be seen. It’s an expedition I would definitely recommend to anyone wanting to see a healthy and active reef in a completely natural protected area.

I found that a video I took with a tiny camera was sadly of use only to myself. No one else would be able to make anything out due to the marked camera shake. Novices, huh? You are spared that: here’s a brief example of yellowtails swimming instead, showing the difference between juveniles and adults.

Credits: all photos, Melinda Riger / Grand Bahama Scuba; video from Desert Diving

BLAINVILLE’S BEAKED WHALES IN ABACO WATERS

October 16, 2017 by Rolling Harbour

BLAINVILLE’S BEAKED WHALES IN ABACO WATERS

It’s hard to believe that the seas around Abaco and its cays are home to a number of whale species, from huge sperm and humpback whales down to so-called dwarf or pygmy species. In the middle of this range come the beaked whales, the most common being the Blainville’s Beaked Whale. I say ‘most common’, but in fact they are rare in the world, being found in only two other main locations on earth.

These whales are carefully monitored by the Bahamas Marine Mammal Research Organisation (BMMRO), and there is a tagging program to keep track of them. As with dolphins, individuals are identified by markings on the dorsal fin, which vary for each whale. The one above has distinctive scarring at the tip. There are also striations on the body, and conspicuous circular marks that are healed wounds caused by cookie-cutter sharks.

To the untrained eye, there are no noticeable marks on the dorsal fin of the whale above. However, the whale’s back has a prominent pattern of scarring and healed cookie-cutter wounds. The whale below really looks as though it has been in the wars, with long deep healed wounds behind the head.

I can’t tell without seeing the head, but I wonder if it is a male and the scars have been caused in a fight with another male – adult males have prominent tusks with which they do battle. Here is an photo that I took from the research boat on a different occasion. The tusks protrude upwards from the lower jaw, and are often covered in barnacles. They are capable of causing serious injury.

Blainville’s beaked whales are amongst the deepest divers of all whales. But that and other whale topics will have to wait for another day… My computer malware / virus has been removed professionally with no data loss, and I have some catching up to do. Cost in terms of panic and stress: huge. Cost in real terms: $90.

All photos BMMRO except the tusked male, Keith Salvesen

AN ‘EXHILARATION’ OF ABACO DOLPHINS

September 25, 2017 by Rolling Harbour

AN ‘EXHILARATION’ OF ABACO DOLPHINS

Bottlenose dolphins! Tursiops truncatus! These engagingly playful show-offs of the inshore waters round Abaco are 99.99% adorable**. It’s been a harrowing few weeks in the western Atlantic, and everyone is hoping that the 2017 hurricane season has had enough of causing death and destruction over vast swathes of vulnerable islands and on the US mainland. Some cheer is needed.

Dolphins are good for the soul. And if you are out on a boat watching them – and especially tracking them for a whole day – every encounter reinforces the impression that all the leaping, bow-wave riding, boat under-swimming, and general sociability and interaction is often as much for sheer enjoyment as anything else.

Abaco is fortunate in having the HQ of the Bahamas Mammals Research Organisation (BMMRO) based at Sandy Point. That just happens to be an excellent area for bottlenose dolphin spotting in the turquoise shallows. Many sightings are made within clear sight of land. Further south, where the bright blue gives way to darker and deeper water, live the equally frolicsome Atlantic spotted dolphins. The 3 photos above were all taken on the margins of where the colour of the sea changes from light to dark.

I’m a bit of a collector of collective nouns. For dolphins, apart from the matter-of-fact ‘group’ or ‘pod’, there is no exotic word to describe a number of them when they are having fun. No equivalent of ‘exaltation’ (larks), ‘charm’ (goldfinches) or ‘parliament’ (owls). So I’m nominating an ‘exhilaration’ as a candidate to fill the gap…

The photo above shows clearly how individual dolphins can be identified by researchers. All tend to have scars or tears to their dorsal fins that enable them to be distinguished. The closest has distinctive scars near the tip. The furthest has a W-shaped nick at the back. In fact, it could even be Rocky, a well-known dolphin on Abaco that has been sighted over many years. There are regular reports annually. I saw him myself once, in 2012, playing about in Hopetown harbour.

STOP PRESS To demonstrate how the ID methods work, I’ve now cross-checked with the BMMRO photo ID archive. Here is Rocky’s original dorsal fin ID image (“Tt15”) from October 2010. There’s a W-shaped nick, sure, but my speculation above was wrong because overall the two fins are clearly different…

** The 0.01%? Dolphins may, rarely, be alarming for divers in circumstances I won’t repeat here (hint: to do with over-friendliness, ok? Yes, the thing that dogs do)

Credits: all photos BMMRO – and taken in the last 2 months

EYES ON STALKS: CONCH WATCH ON ABACO

August 10, 2017 by Rolling Harbour

EYES ON STALKS: CONCH WATCH ON ABACO

This is not so much about you looking at, and admiring (without salivating too much, I trust) conchs in their natural element. More about them watching you watching them – and focusing on their rather remarkable stalk-based eyes. Take a look at these examples of the ‘watcher in the shallows‘ (to misquote a well-known book title).

HALF A DOZEN CONCH EYE FACTS TO PONDER

The eyestalks are attached to an extendable ‘snout’
The two eyestalks (ommatophores) are retractable within the shell
Their purpose is to provide a wider field of vision around the shell
The eyes at the tip of each eyestalk have ‘proper’ lenses, pupils and irises
Amazingly, amputated eyes normally regenerate completely
The small projection below the eye is a ‘sensory tentacle’ or feeler

CAUTIONARY WARNING

For a rather depressing view of the current state of conch populations, check out this recent article in the MIAMI HERALD. Not a great deal to be optimistic about…

I’M WATCHING YOU…

CREDITS: All remarkable ‘conch watching’ photos by Melinda Riger / Grand Bahama Scuba – except for the wonderful header image by Charmaine Albury (contributor the The Birds of Abaco), taken on Man-o-War Cay; Cindy James Pinder for the heads-up for the Miami Herald article

DOLPHINS DISPORTING IN THE BAHAMAS

August 3, 2017 by Rolling Harbour

DOLPHINS DISPORTING IN THE BAHAMAS

‘Disporting’. Not a word I’ve used very often. Or possibly ever. It looks a bit like ‘unsporting’, which is emphatically what dolphins are not. Basically, it just describes what dolphins are doing when you see them on the surface: amusing themselves, frolicking around in the waves, and simply enjoying themselves.

True, they are probably keeping an eye out for food… But when you have a group sociably following alongside the boat your are in, moving in front, dropping behind, diving under, and generally playing around, it’s quite hard to believe that these are completely wild creatures. They seem to be performing just for you, simply because they want to. You don’t even have to throw fish at them to earn this free display.

As is well-known, the BAHAMAS MARINE MAMMAL RESEARCH ORGANISATION (BMMRO) is the custodian for the welfare of these beautiful creatures for the entire Bahamas. However, being based on Abaco and carrying out the majority of the research from the HQ at Sandy Point means that many of the great images that get taken are from Abaco waters. Indeed some are taken within swimming distance (not mine) of the shore.

The photographs featured here were taken during the last few weeks. Some are of the familiar bottlenose dolphins. The others – with speckled undersides clearly visible in the header image & below – are of Atlantic spotted dolphins. There’s even one of my own taken from the research vessel.

For the researchers, the most important part of an individual dolphin is its dorsal fin. Unique patterns of cuts and scars mean that each dolphin sighted can be logged and their profiles built up. Some have been found in the same area for many years. They are not usually given jocular names – ‘Davy Jones’, ‘Finny Phil’ or whatever. The first time we went out on the research vessel we were slightly surprised by the practical, scientific calls during a sighting of a dolphin group: “there’s B4 again” and “over there – D5 is back”. All said fondly however – many of the dolphins are old friends.

This dolphin has a notable notch on the dorsal fin with a nick below, & a scar line – with a prominent white scar on the lower front edge

Notice how these 3 dolphins all have quite different fin profiles. The nearest one’s fin looks unblemished, but has a paler tip. Powerful binoculars and a serious camera can pick out small differences at a distance that the eye could not Bottlenose Dolphin, Bahamas - Dorsal Fin Damage (BMMRO)

Coming soon: Manatees & Man in the Bahamas

All photos (bar one by me) BMMRO, with thanks to Diane & Charlotte, and a tip of the hat to the current interns involved in the research projects (Hi, UK Thomas!)

ONE GOOD INTERN DESERVES ANOTHER (Part 1)

June 1, 2017 by Rolling Harbour

ONE GOOD INTERN DESERVES ANOTHER (Part 1)

Four years ago a young English friend of ours, Oscar Ward, was lucky enough to be offered an internship with the Bahamas Marine Mammal Research Organisation (BMMRO). At the time, he was post-school, and waiting to start a degree course in marine biology at university. He had no practical experience at all, so he had to progress from the menial tasks (scraping barnacles off the bottom of the research boat) to the more adventurous (whale poop-scooping) to the scholarly (collection and analysis of samples and data, including audio file matching of whale calls for identification). The need for hard work, concentration and accuracy were made clear from the outset… and as you will see, Oscar’s short internship has stood him in very good stead during his university course.

Oscar weekending at Gilpin Point – self-sufficient

From a promising start on Abaco, and with 2 year’s study behind him, Oscar is currently spending the 3rd year of his 4-year course in Australia, working with The Australian Institute of Marine Science. He has been involved in a number of complex projects focussed on corals and reef life – as we all know, a matter of huge concern – and the projections for the future of the reef systems in a time of warming seas and raised acid levels. Oscar also assists PhD students, for example examining the damaging effects of parasitic worms on coral; and the effect of changing light conditions on corals.

Much of Oscar’s time has been spent doing fieldwork. Often he is at sea, monitoring and collecting samples in the Southern Great Barrier Reef, diving two or three times a day. This work is often carried out in restricted or preservation zones, and with ever-present manta rays, sharks and sea turtles around him.

Right now Oscar is involved with the investigations into the recent bleaching events, work that is at the forefront of serious concern for the GBR and far beyond. I have recently corresponded with him – he has definitely not forgotten that his grounding for the fieldwork and studies that he is engaged in – and very likely his career – came from his time on Abaco and the lessons he learned during his time with the BMMRO at Sandy Point. (In part 2: another good intern, currently at Sandy Point)

All photos: Oscar Ward (the header image is taken from a research vessel – no idea how, maybe a drone with fish-eye lens?)

TURTLE BREEDING SEASON & A SMALL POEM TO PONDER

May 1, 2017 by Rolling Harbour

TURTLE BREEDING SEASON & A SMALL POEM TO PONDER

The turtle lives ‘twixt plated decks
Which practically conceal its sex.
I think it clever of the turtle
In such a fix, to be so fertile.

Anyone unfamiliar with the works of OGDEN NASH (1902 – 1971) would do well the check out his inimitable poetry, in which he takes extreme liberties with both rhyme and scansion to great comic effect. The poem above is a good example of Nash’s neat way with words. It always makes me laugh, anyway. So simple, looks so easy, but a very difficult trick to pull off consistently as Nash effortlessly does.

As the turtle breeding season moves forward, I though this would be a good time to show a few of the great turtle photos taken by Adam Rees of ‘Scuba Works’.

All photos: Adam Rees / Scuba Works

ATLANTIC SPOTTED DOLPHINS OFF ROCKY POINT, ABACO

March 23, 2017 by Rolling Harbour

This pair was in a group of 8 Atlantic Spotted Dolphins that we encountered yesterday during a day’s expedition on the Bahamas Marine Mammal Research Organisation (BMMRO) research boat. We spent nearly an hour with them, and there will be a longer post about these magnificent creatures in due course. But right now, I’m still in single image posting mode while “on-island”…

Photo: Keith Salvesen / BMMRO

FORAYS WITH MORAYS (4): EXPRESSIVE FEATURES

March 10, 2017 by Rolling Harbour

FORAYS WITH MORAYS (4): EXPRESSIVE FEATURES

Time to return to those extremely expressive characters of the coral reefs, moray eels. Specifically, some green morays. One hesitates to anthropomorphise or ‘project’ human emotions onto creatures but with some species it’s hard not to do so. Following Mr Grumpy (or perhaps Mr Sad) in the header image, here are some close-ups of morays appearing to express their emotions, from happy to downright furious… Eels featured here include Judy and Wasabi, and I remind myself that the human habit of naming familiar wild creatures is itself a (perfectly harmless) form of benign animism. Exactly as with the regular banded piping plovers featured elsewhere in this blog that overwinter on Abaco’s beaches, such as Harry Potter, Bahama Mama and the delightfully-named Felicia Fancybottom…

Happy and contented?

Something on my mind…

Slightly amused?

Pretty funny, actually

Ha ha…! Hilair!

Watch it. You are beginning to bug us, Mr Harbour, with your stupid captions

ANGRY. BACK OFF… NOW!!!

THE NEXT POST WILL BE FROM ABACO HQ NEXT WEEK

Credits: All morayvellous photos, Melinda Riger / Grand Bahama Scuba except 6, Virginia Cooper / Grand Bahama Scuba

SAWFISH: UNIQUE LIVE BIRTH FOOTAGE ON ANDROS

February 22, 2017 by Rolling Harbour

SAWFISH: UNIQUE LIVE BIRTH FOOTAGE ON ANDROS

The word ‘awesome’ – a word of Biblical origin and medieval usage connoting an experience of wonderment with an element of dread* – lost its power once it became the common verbal currency for describing the offer of a beer, a photograph of a sulky cat, or a so-so pub band. Where to turn for something truly momentous? Oh, actually that might do nicely. Breathtaking, astounding, astonishing, awe-inspiring, staggering, extraordinary, stupendous, and spectacular are examples of synonyms that have retained at least some of their power. And perhaps ‘mind-blowing’, though it’s a bit substance-tinged. ‘Amazing’ has pretty much gone the way of awesome. Amazeballs and badass? Let’s not!

Ok. Having got that linguistic grump out of the way (index under ‘English Language, debasement of, modern usage in), here’s the real deal: a truly phenomenal short video of a smalltooth sawfish Pristis pectinata safely giving live birth in the wild to her 5 babies (which are called pups) on Andros during a FSU research trip. The pups emerge as small replicas of their parent, complete with their hedgetrimmer-style rostrums, ready to swim away. Fishes that carry their young and give birth to one or more developed juveniles in this way are called ovoviviparous.

The commentary is clear and informative, the research potential for this vulnerable species is considerable, and if you have a soul and a spare 3 minutes, you really should watch this!

This unique recorded event took place last December. The joint research trip to Andros by the FSU Coastal and Marine Lab and NOAA was led by Dr. Dean Grubbs. The purpose of the research was to discover evidence of any exchange between the sawfish population in the U.S. and Bahamas. You can find out more about the research and scientists at the FSUCML website. And if you want to get involved and take part in an expedition, click GET INTO THE FIELD

RELATED POSTS

RH SAWFISH PAGE – pics, facts and vids, including how the rostrum is used in feeding

GUITARFISH (WTF? 8)

* ‘Awful’ had the same meaning as awesome, historically – cf dreadful. It did not mean a bad film or a lousy restaurant.This recent photograph by Adam Rees of Scuba Works was taken in Florida waters. It is one of an astonishing school of 8 smalltooth sawfish, the largest group Adam has ever encountered.

Credits: Header, Grant Johnson @60poundbullet (Bimini), with many thanks; BNT / Buzz Cox (Grand Bahama); Adam Rees / Scuba Works

BLUEHEAD WRASSE: PRIVATE LIFE LAID BARE

February 14, 2017 by Rolling Harbour

BLUEHEAD WRASSE: PRIVATE LIFE LAID BARE

The bluehead wrasse (or blue-headed wrasse) Thalassoma bifasciatum is a denizen of the coral reefs of the tropical waters of the western Atlantic Ocean. This bright little 4-inch fish is… a wrasse with a blue head. No more and no less. Unless it’s a juvenile. Then it is mainly bright yellow. It’s similar to BLUE TANG (aka ‘the Disney Dory’), which starts life bright yellow and grows up to be blue.

The species may be found singly, in pairs or small groups, or in schools. They have an important role to play in the life of the reef. They are CLEANER FISH, vital to the health and wellbeing of the larger species they attend to, and thus of the reef itself. This is ‘cleaning symbiosis’, a relationship of mutual benefit. The big fish get cleaned; the little fish have a useful function and – importantly for them – therefore don’t get eaten.

Having said that, blueheads are of course fair game as a snack for species that aren’t in the market for their cleaning services. And, unfairly, some species that are content to let cleaner gobies runtle around their gills and mouths are not so considerate of the wrasse. Some types of grouper and moray eel, for example.

TELL US EXACTLY SEVEN BLUEHEAD WRASSE FACTS

Juveniles can alter the intensity of their colour, stripes & bars
The bluehead wrasse is a ‘protogynous sequential hermaphrodite’
All are born female**. Some change sex to male during maturation (see below)
Food includes zooplankton, small molluscs and small crustaceans…
…and parasites / other juicy bits (fungal growths, anyone?) from bigger fish
The main threat to the species is coral reef degradation or destruction
The bright colours invite aquarium use, but the trade is not a significant one

** Some sources suggest some are born male and remain male. I’m not sure which is right

A juvenile bluehead (with feather-duster worms) – mostly yellow, with a pale underside

THE REMARKABLE SEX LIFE OF THE BLUEHEAD WRASSE

This is an unavoidable topic, I’m afraid. The bluehead’s sex life is the most interesting thing about them, and this is no time to be prudish. It is the subject of extensive scientific research, not all of which I have read since I decided to write about the species last night. Like many human relationships, “it’s complicated”, but in a conch shell it boils down to this:

To recap, BWs are born female and as they mature, some become male.
Males reach an ‘initial phase’ when they can breed in groups with females
Some males grow even larger & reach full colouration. This is the ‘terminal phase’
These large males aggressively chase away smaller ones & seek females to pair with
Their state of readiness (as it were) is signalled by colour changes
This behaviour is similar to that seen in many city centres in a Saturday night
The smaller fish have one bonus – their sperm count is higher than a dominant male
Prozac tests have shown that the drug reduces a dominant male’s aggression

As the excellent organisation OCEANA puts it: Bluehead Wrasses may reproduce in four different ways throughout their lifetime: 1) as a female in a group spawning event; 2) as a female in a pair spawning event within the territory of a large male; 3) as a small male in a group spawning event; and 4) as a dominant, terminal male in a pair spawning event within its own territory.

A cropped still from a video I took at Fowl Cay marine reserve. I’ve looked at dozens of images online and not found one that was all blue with a yellow end to its tail fin. Maybe it’s not a BW at all. Or it’s a different type of fish completely. Or perhaps it is just an all-blue alpha male.

Credits & Sources: Melinda Riger; Adam Rees; James St John; Oregon State edu / Pinterest; Wiki images; self; Oceana; IUCN; magpie pickings

A bluehead wrasse passes the time of day with a grunt

ABSORBING SPONGES ON THE BAHAMAS REEFS…

February 6, 2017 by Rolling Harbour

ABSORBING SPONGES ON THE BAHAMAS REEFS…

A while back I showed a collection of colourful sponges – one that you might come across with minimum equipment. Snorkel, mask, flippers. Oh, and a coral reef, if you happen to have one handy. I suspect that to quite a few people the word ‘sponge’ means soggy yellow thing, as found in the proximity of a bath. Or a scratchy nylon-based equivalent. Well, here are a few more sponges to enjoy. Some I can give you the names of, some I don’t know and am too idle busy to look up… Sorry.

Candelabra Songe (with brittle stars attached)

Black Ball Sponges

One for Valentine’s Day

Vase Sponges

Spawning Brown Encrusting Sponge

All photos: Melinda Riger, Grand Bahama Scuba

PIP THE PLOVER VARIES HER DIET…

January 26, 2017 by Rolling Harbour

PIP THE PLOVER VARIES HER DIET…

Hi guys, that’s me, Pip, in the picture above. I live in North America in the summer. That’s where I was born. I fly down south to somewhere warm for the winter. Like many migratory humans, my chosen place is the Bahamas. It’s got some great empty, safe beaches and the weather is (mostly) lovely. Unless a Big Wind happens. The tide-line is cram-full of meat-strings (these would be worms. Ed). There are great patches of weed larder to work through. It suits me very well, just like lots of other shore birds. It’s why some of us return every year.

I’ve just got one point to raise, if you wouldn’t mind. There’s a mass of plastic (and other) crap out there on the beaches. It washes in on every tide. I know it isn’t Bahamian crap, but has come from many miles away. But Mr Harbour has done some work with my portrait to identify what’s in the seaweed I’m feeding on that might be harmful. He enhanced it and picked out just the things he’s certain shouldn’t be there. All the blue bits, for a start. And who knows what else is under the weed that I can’t even see to avoid. The shoreline and the wrack line is my dining area. I might easily eat some of the small bits by mistake. I think I must do that quite often. That would be bad – too much plastic crap and I’ll be ill. Or die. There are only about 8000 of us in the whole big wide world. If 80 of us die from plastic ingestion, that’s one per cent. The loss has to be made up next breeding season before we can even begin to increase our population.

Just sayin!

♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦

Photo: Chris Jordan, who studies birds killed by trash

HUMPBACK WHALE SEEN OFF SANDY POINT, ABACO

January 24, 2017 by Rolling Harbour

HUMPBACK WHALE SEEN OFF SANDY POINT, ABACO

Dolphins are regularly seen around the coast and in the fishing grounds of Abaco. Sometimes, they make it easy by nosing into harbours and being generally adorable for a while, to the delight of onlookers. Hope Town can be a good place for this. Those aboard the “Donnies” – the ferries that criss-cross the Sea of Abaco from the main island to the various Cays – may be in luck too. However, it is perhaps less well known that Abaco waters provide a home or a migratory passage for gigantic whales. Beside these mighty creatures, the several other whale species of the Bahamas seem relatively small. Yes it’s true: there are huge whales – humpbacks and sperm whales (cachalots) – to be found in Abaco waters, and not so very far from land either.

The humpback whale Megaptera novaeangliae above, with its characteristic white pectoral fins, was seen about a week ago off Sandy Point (southwest Abaco). You’ll get an idea of its immense size from the photo. An adult of this BALEEN WHALE species can reach 50 feet in length and weigh 35 tons or more. Imagine watching one slipping silently past your boat… and then consider that even larger sperm whales are seen in the same area.

For the link to report a Bahamas whale sighting, please see either link provided below

Humpback whale / adult male human in scuba gear comparison

Humpbacks are found in oceans throughout the world. They migrate huge distances each year, from polar regions to the tropical and sub-tropical waters where they breed. These are the whales beloved of wildlife film producers and whale-watching trips, with their spectacular arched breaching in which half their length or more may emerge from the water before smashing back into the waves.

A humpback breaches on the Stellwagen Bank (about 50 miles offshore of Boston)

Like other large whale species, humpbacks were unsurprisingly prime targets for the whaling industry in a melancholy era of marine history that took them to the edge of extinction until a moratorium was declared in 1966. Since then the population has recovered significantly. They remain vulnerable, however: in some locations, to killing; to entanglement in heavy-duty fishing gear; to ship collisions; and to noise pollution that affects their ability to communicate long-distances underwater, as they need to do.

Finally, the Sandy Point humpback makes a last dive and, with a wave of its fluke, disappears

Do you have a Bahamas whale or dolphin sighting to report? Please use this link, giving as many of the details as you can. Each report makes a valuable contribution to the BMMRO’s research.

http://www.bahamaswhales.org/sightings.aspx

As a footnote, my first whale encounter was on the Stellwagen Bank mentioned above, when I went on a whale-watching trip from Boston. We encountered a mother humpback with her calf and spent about 1/2 hour watching them interacting. I have the memories luckily – my photos were rubbish, using a very early digital camera that these days would be less effective and well-spec’d that a luminous pink plastic child’s camera now…

HUMPBACK HOPE TOWN ABACO

BLAINVILLE’S BEAKED WHALES

BMMRO

SIGHTING REPORTS

Credits: Brad & his crew, and the BMMRO; Whit Wells / Wiki for the breaching whale; moi for the rotten but quite interesting archive photos from the same place; the whale for being awesome in the true sense of the word

WATCHING NURSE SHARKS: BE PATIENT…

January 12, 2017 by Rolling Harbour

WATCHING NURSE SHARKS: BE PATIENT…

I last took a look at nurse sharks nearly 3 years ago HERE. Time to revisit these creatures. Indeed, time for a close-up look. If you want to know more about this fascinating species, just click the link above.

The two strange items hanging down from the upper lip are sensory barbels

This side-view shows the shark’s relatively small mouth (for a shark anyway)

Admire the extraordinary texture of the the skin; and the tiny evil eye. Click or – better – double click on the image and you will see that the skin is in fact tessellated, made up of a mosaic of tiny squares and near-squares**

This one is a baby nurse shark

A juvenile nurse shark with a couple of grunts. Note the youngster’s paddle-like fin

Head, mouth, jaws and teeth

SO, THEY ARE SHARKS – ARE THESE GUYS DANGEROUS?

Not really, no. They aren’t looking to pick a fight; and they are not as territorially aggressive as the ‘bitey’ sharks are (or can be). These slow-moving bottom-dwellers are generally harmless to humans. However, they can be huge—up to 4 metres —and have very strong jaws filled with thousands of tiny, serrated teeth. They will bite defensively if stepped on or bothered by divers who assume they’re docile. [As I said previously, “there are recorded instances of injuries caused to divers who have tried to pull nurse sharks by the tail. And serve them right, I say. Treat them with patience and respect!”]

**FUN FACT

M.C. ESCHER (the inspiration for Mr Hammer) was the master of tessellation in art. Click the link to explore the dedicated website. Maybe, sensationally, one day a shark will be found with skin like this… (Alert reader: “Actually, I think it most unlikely…”)

Credits: field photos by Melinda Riger, Grand Bahama Scuba; Wiki for the 4 mouth images & the Escher

CHRISTMAS TREE WORMS: FABULOUSLY FESTIVE

December 27, 2016 by Rolling Harbour

CHRISTMAS TREE WORMS: FABULOUSLY FESTIVE

“Deck the Reefs with Worms Like Christmas Trees… Fal-La-La-etc-etc ” is a traditional Carol familiar to all. Well, most. Ok, some, then. Oh right – maybe with different words. Anyway, now is as good time as any to take a look at these remarkable ~~plants~~ creatures and subsurface symbols of good cheer.

10 CHRISTMAS TREE WORM FACTS TO PONDER

The 2 colourful spirals are not the worm, but complex structures for feeding & respiration
The spirals act as specialised mouth extensions for ‘filter-feeding’
Prey is trapped by the feathery tentacles & guided by cilia (microscopic hairs) to the mouth
The tentacle things are radioles and act as gills for breathing as well as prey traps
It is not believed that prey slide down the spiral to their doom, like on a helter-skelter

The actual worm lives in a sort of segmented tube, with extremely limited mobility skills
It contains digestive, circulatory & nervous systems – and a brain in the middle of it all
The worm also has a tiny drainage tube (I think I have this right) for excretion etc
They embed themselves into heads of coral such as brain coral. And stay there
And yes, the Christmas trees are retractable…

HOW DO THE WORMS… YOU KNOW… ER… REPRODUCE?

This is a delicate area. They don’t tend to talk about it much, but as far as I can make out they eject gametes from their what-I-said-above. There are mummy and daddy CTWs, and their respective gametes (eggs and spermatozoa) drift in the current and presumably into each other to complete the union. The fertilised eggs develop into larvae, which settle onto coral and burrow into it, build their protective tubes and the process begins again.

LOOK, YOU DON’T REALLY UNDERSTAND THESE CREATURES, DO YOU?

The worm, invisible in its coral burrow, hoists its pair of trees. You can easily see small particles – possibly zooplankton – drifting in the water, and the radioles swaying to catch potential food. Bingo. It all makes sense! Next: the New Year Worm

Credits: Melinda Riger (G B Scuba); Adam Rees (Scuba Works); Nick Hobgood; Betty Wills; Absolutely Wild Visuals; MarineBio; Wikibits & Magpie Pickings