JACKKNIFE FISH: BAHAMAS REEF FISH 30


Jackknife Fish ©Melinda Riger @ GB Scuba

JACKKNIFE FISH: BAHAMAS REEF FISH 30

The rather uncomfortably ‘double-k’  Jackknife fish is one of 3 types of similar drumfish subspecies of Equetus found in Bahamas waters. The others are the High Hat and the SPOTTED DRUMFISH – the first fish featured in this series. Each of these drumfish species has juveniles that are elegant and delicate, becoming more conventionally fishlike as they grow to adulthood, as the final image shows.

Jackknife fish (juv) ©Melinda Riger @ G B Scuba copy

I always want to stick a hyphen in to separate each k: jack-knife fish. I think it’s an English thing. I have seen, at the other extreme, ‘jack-knifefish’, which looks most weird of all. Checking online, jackknife fish wins by a distance as the correct spelling. 

Jackknife Fish (juv) ©Melinda Riger @GB Scuba

These little fish, typically between 6 and 9 inches, inhabit the coral reefs of the Caribbean, the Gulf of Mexico, Florida and the Bahamas. Juveniles eat plankton and similar organism, graduating to small crabs and shrimps as adults.

Jackknife Fish ©Melinda Riger @ G B Scuba

A FULLY GROWN JACKKNIFE FISH (NOAA)Jackknife fish adult_NOAA_Photo_Library

Like other drumfishes, the jackknife can produce ‘croaking’ or ‘drumming sounds. This involves the fish beating its abdominal muscles against its swim bladder. There’s a lot more to it than my rather simplistic summary, but it’s probably as much as anyone needs or wants to know… The primary reason is believed to relate to mating. Other reasons include ‘low-level aggression’, and keeping in touch with each other in turbid waters.  I prefer the unscientific theory that sheer happiness makes them croak. Here’s a short video of a happy juvenile Jack knife fish (that’s yet another spelling variant…)

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Credits: Melinda Riger / GrandBahama Scuba; NOAA

WTF? (WHAT’S THAT FISH) 10: FLYING GURNARD


Flying Gurnard (Adam Rees / Scuba Works)

WTF? (WHAT’S THAT FISH) 10: FLYING GURNARD

Imagine that you are swimming along resplendent in your snorkelling gear (me) – or in scuba gear for the advanced swimmer (you). There, below you, camouflaged against the sea bottom is a fish. A strange-shaped brown sort of creature with odd side fins. As it progresses over the gravelly sand, your immediate reaction is ‘what the…?’ Its fins seem to be turning into… wings. Like this:

Flying Gurnard (Adam Rees / Scuba Works)Flying Gurnard (Adam Rees / Scuba Works)Flying Gurnard (Adam Rees / Scuba Works)

Yes, it’s a flying gurnard. Unlike flying fish, it can’t actually fly through the air. But once its wings are fully spread, it certainly looks as though it could.

Flying Gurnard (Adam Rees / Scuba Works)Flying Gurnard (Adam Rees / Scuba Works)

WHAT’S THE POINT OF THE WINGS IF THE THING CAN’T FLY?

This gurnard species usually gets around using its ventral fins as ‘legs’, with the pectoral fins (‘wings’) close to the body. There seem to be several possible reasons for possessing the ‘sudden-deployment-of-flashy-wings’ superpower. 

  • It surprises and deters predators by movement, turning prospective prey into an apparently different creature
  • Bright or lurid colouring may be a deterrent warning of a foul-tasting or poisonous species  (APOSEMATISM)
  • A creature may actually be harmless and even tasty (as here) but may appear to be unpalateable or poisonous (BATESIAN MIMICRY)
  • In any event, the wings enable the fish to take off from the sea bottom and travel faster by ‘flying’ thought the water to escape a predator

Dactylopterus_volitans Flying Gurnard (cralize wiki)

I had a quick look to see how  scientists in history had depicted this extraordinary fish. The earliest illustration I could find was taken from “Allgemeine Naturgeschichte der Fische (General natural history of fishes),” a 12-volume encyclopedia by author/illustrator Marcus Elieser Bloch (1723-1799), which described all fish species then known to science (and 267 previously unknown) (© AMNH\D. Finnin) sourced from ‘Hyperallergic’
Flying Gurnard

Here’s a short video of a flying gurnard on the move, from ‘Sia Big Fish’

Credits: All main images Adam Rees / Scuba Works with many thanks, except final one ‘cralize wiki’; Hyperallergic for the historic image; Sia Big Fish for the video

CONCH QUEST: ABACO’S MOST VERSATILE GASTROPOD


Conch Shells, Sandy Point, Abaco

CONCH QUEST: ABACO’S MOST VERSATILE GASTROPOD

The conch. Such a fascinating gastropod, and with so many uses both culinary and decorative. In certain cultures, religiously significant. A rudimentary musical instrument for a shell.  And did I mention delicious? 

Live conchs enjoy motoring around uninhibitedly on the sea floor, keeping an eye out…Conch on the move ©Melinda Riger @ G B Scuba copy Conch Man-o-War Cay, Abaco (Charmaine Albury) copy Conch in shell ©Melinda Riger @ G B Scuba copy

Conchs also enjoy racing each other…Conch race ©Melinda Riger @ G B Scuba copy

“Eat my dust…”Conch Trail ©Melinda Riger @ G B Scuba copy

Conch Pearl – one of the rarest natural pearls in the worldConch Pearl (Ambergris Caye Beize)

A conch spiral close-up

Conch close-up, Abaco (Rhonda Pearce)

Conch shells just lie around the place at Sandy PointConch Shells, Sandy Point, Abaco (Keith Salvesen) 2Conch Shells, Sandy Point, Abaco (Keith Salvesen) 3

Conchs are widely used for serving cocktails or as ashtrays in the best beach bars*Conch Shells, Abaco (Keith Salvesen) 1

*This is a lie. Sorry about that. I meant to say “make prefect table decorations”

Image credits: Keith Salvesen / RH (1, 9, 10 ,11); Melinda Riger / GB Scuba (2, 4, 5, 6); Charmaine Albury (3); AmbergrisCaye.com (7); Rhonda Pearce (8) 

WHALE-WATCHING: THE APPLIANCE OF SCIENCE


Blainville's Beaked Whale, Sandy Point, Abaco 14 (Keith Salvesen

WHALE-WATCHING: THE APPLIANCE OF SCIENCE

The Bahamas Marine Mammal Research Organisation has just celebrated its 25th year of existence. It was formed in 1991. The omnivorous leviathan Amazonus giganticus emerged in 1994 and the invasive species Megacorpus googleii not until 1998. A full 10 years later the first garbled recordings of Sarahpalinus illogicus were made. And all the while, a watchful eye was being kept on the cetaceans of the Bahamas – researching, counting, measuring, identifying, recording, poop-scooping, analysing samples, tagging, comparing, protecting and conserving. 

Blainville's Beaked Whale, Sandy Point, Abaco 20 (Keith Salvesen

As the years passed, so the science and technology evolved and became more sophisticated. Researching became at the same time easier, yet more complex as the organisation’s remit expanded to accommodate the vast increase in data collection now made possible by refined techniques. Here are two very recent examples – 25th anniversary projects, in fact – with thanks to Charlotte, Diane, their team and their colleagues in linked organisations.

TAGGING BLAINVILLE’S BEAKED WHALES

Last month, a tagging project started, involving suction cups being attached to the backs of BLAINVILLE’S BEAKED WHALES. The purpose of the research is to compare the foraging efficiency of the whales in Abaco waters with those of Andros, the second part of the project. I imagine this will provide valuable insights into the whale movements and behaviours in each location as well as such issues as the comparative availability of the food supply, and other factors that may affect expected foraging patterns. 

The tag is moved towards an adult male. Note the aerial (antenna?) at the back of itTagging a Blainville's beaked whale with a suction cup 1

Planting the tag on the whale’s backTagging a Blainville's beaked whale with a suction cup 2

Successful suction!Tagging a Blainville's beaked whale with a suction cup 3

The tag in placeTagging a Blainville's beaked whale with a suction cup 4

The tag is tracked for 18 hours, after which it is retrieved and the recordings can then be analysed back at BMMRO HQ in Sandy Point. So far, an adult male, a young male and two adult females have been tagged. Each female had a calf, but these were not tagged.

Female beaked whale with her calfBlainville's beaked whale female and calf

AERIAL PHOTOGRAMMETRY USING A HEXACOPTER

Drone technology is rapidly expanding as new uses for them are devised. BMMRO in conjunction with NOAA have used a sophisticated HEXACOPTER to take the first  PHOTOGRAMMETRY images of Blainville’s beaked whales. These aerial photographs were taken from approximately 100ft altitude. But note: not just anyone with a $50 drone can do this: the project required flight clearance from the Bahamas Department of Civil Aviation and a permit for research on marine mammals granted by the Bahamas Department of Marine Resources.

 Blainville’s beaked whale photogrammetry image – adult male (note ‘erupted’ teeth) Blainville's beaked whale photogrammetry image - adult male (note 'erupted' teeth) BMMRO

 Blainville’s beaked whale photogrammetry image – female and calf Blainville's beaked whale photogrammetry image - female and calf BMMRO

STOP PRESS Two additional images from the latest batch Blainville's beaked whales photogrammetry image - BMMRO  Blainville's beaked whales photogrammetry image - BMMRO

Photogrammetry: the science of making measurements from photographs. Applications include satellite tracking of the relative positioning and alterations in all Earth environments (e.g. tectonic motions etc), research on the swimming of fish, of bird or insect flight, and other relative motion processes. The results are used to guide and match the results of computational models of the natural systems. They help to invalidate or confirm new theories, to design novel vehicles or new methods for predicting or/and controlling the consequences of earthquakes, tsunamis etc, or to understand the flow of fluids next to solid structures, and many other processes. (Wiki-précis)

Hexacopter (6 rotors)Hexacopter_Multicopter_DJI-S800_on-air_credit_Alexander_Glinz

Tag Team: BMMRO, University of St Andrews (Scotland), Woods Hole Oceanographic Institution

Hexacopter: BMMRO, NOAA

Photo Credits: top two, moi (from BMMRO research vessel); remainder except for last, BMMRO; last, Wiki

MAKE FRIENDS WITH ANEMONE (2): SPECTACULAR REEF PLANTS


Corkscrew Anenome = Peterson Cleaner Shrimps ©Melinda Riger @G B Scuba copy

Corkscrew Anemone with Peterson Cleaner Shrimps

MAKE FRIENDS WITH ANEMONE (2):  SPECTACULAR REEF PLANTS

Going snorkelling? Planning a scuba day on the reef? You’ll see wonderful fish and amazing coral for sure. But sometimes the beauty of the plant-life on the reef can be overlooked. Check out the anemone in the header image, with the camouflaged cleaner shrimps playing around it. You wouldn’t want to miss a sight like that. The many and varied forms and colours of anemone on the reefs of the Bahamas make up a vital component of a spectacular underwater world.

Giant Anenome ©Melinda Riger @ G B Scuba copyGiant Anemone ©Melinda Riger @ G B Scuba copy 4Anemone Melinda Riger @ G B ScubaAnemone on Rope ©Melinda Riger @ G B ScubaAnemone ©Melinda Riger @ Grand Bahama ScubaAnemone (Giant) ©Melinda Riger @GBS copyAnemone ©Melinda Riger @ GB Scuba

All photos: Melinda Riger of Grand Bahama Scuba, with thanks

WTF? (WHAT’S THAT FISH) (9): THE HARLEQUIN BASS


Harlequin Bass ©Melinda Riger @ G B Scuba copy

WTF? (WHAT’S THAT FISH) (9): THE HARLEQUIN BASS

I’m conscious of being rather unfair on this pretty dwarf bass species by including it in the WTF? series. The usual denizen of the series is a fish so strange that one’s immediate instinct is to yell into one’s facemask, “WTF?”. BATFISH or FROGFISH or GUITARFISH and their bizarre ilk. So with apologies to this species for its somewhat harsh classification, here are some quite flattering photos of it to make up for any hurt feelings.

Harlequin Bass Fish ©Melinda Riger @ G B Scuba copyHarlequin Bass (jpc what'sthatfish)

The Harlequin Bass Serranus tigrinus has unusually striking body markings and a rather endearing spotty tailfin. They are hardy creatures and I note that they are recommended aquarium fish “and make a great candidate for beginners”, though there are warnings that they are “semi-aggressive”. NB they are only a few inches long, so no need to panic.

Harlequin_Bass_Serranus_tigrinus wikiHarlequin_Bass_(Serranus_tigrinus) wiki

If you are still not confident that you can ID one in the wild, here is a short video… Actually I’m really including it to show how these fish swim around. And next time, I promise a truly eye-watering WTF? fish from Bahamian waters, though its camouflage is so good that you may never notice it…

Credits: Melinda Riger / Grand Bahama Scuba (1, 2); jpc/ what’s that fish; wiki

REMARKABLE REEF CREATURES TO ADMIRE


Octopus (Adam Rees : Scuba Works)

REMARKABLE REEF CREATURES TO ADMIRE

Here is a small collection of recent photographs from Adam Rees of Scuba Works. Three OCTOPUSES, an astounding FROGFISH,  a SEAHORSE, a MANTIS SHRIMP at close quarters, and a wonderful HAWKSBILL TURTLE. Clicking on a link will take you to a post with more photos and information about each creature. If these images don’t make you want to scuba then… what will?

Frogfish Hunting (Adam Rees : Scuba Works)Seahorse (Adam Rees : Scuba Works)Mantis Shrimp (Adam Rees : Scuba Works)Octopus 3 (Adam Rees : Scuba Works)Hawksbill Turtle (Adam Rees : Scuba Works)Octopus 2 (Adam Rees : Scuba Works)

All photos Adam Rees / Scuba Works, with thanks for use permission