BAHAMAS MASTERS OF UNDERWATER CAMOUFLAGE
This is my last post until next week, when apparently we can expect a snowy welcome. Hmmmm. Plenty of new material for kind followers – both of you..
The Mangrove Jellyfish Cassiopea, also called the ‘upside-down jellyfish’ for reasons I needn’t dwell on, is the only member of its particular jellyfish family. These creatures prefer warm waters, and typically live upside-down on the sea-bottom, which no doubt makes catching prey very simple. They can be found individually, though more likely in large groups, with individuals displaying different shades and colours.
The Mangrove Jellyfish has one of the milder stings of the numerous species, though human reactions to the sting will vary with the individual. A greater problem may come from swimming around or over a mass of these creatures. Their stinging cells are excreted in a transparent mucus which may invisibly cover the unwary swimmer. Apart from skin-irritation and a rash, the stings are apparently very itchy. My guess is that scratching can only make things worse (cf No-see-ums…). The first of the two videos below was taken recently by Sarah Bedard (to whom thanks) who “found a great tidal pool full of them at the end of Rock Point Road, Treasure Cay (Abaco)”. The second is short, but with some amazing footage of the Jellyfish in action.
The term ‘PARROTFISH’ comprises many related species (80) around the world inhabiting shallow tropical and subtropical waters. They are commonly found in coral reefs and seagrass beds, and along rocky coasts. They play a significant role in BIOEROSION. Here are some examples of 5 of this species that inhabit the waters of the Northern Bahamas
PARROTFISH FACTS TO ASTOUND AND IMPRESS YOUR FRIENDS WITH
A. FEEDING HABITS
1. Named for their dental arrangements – a mouthful of teeth, forming the characteristic ‘beak’
2. Primarily herbivore but not above snacking on small creatures / organisms or even molluscs
3. Their teeth grow continuously, replacing ones worn away by feeding on coral
4. As they feed on algae etc, their teeth grind up the coral, which they ingest
5. Then (get this!) they digest it and excrete it as sand… it’s a component of your favourite beach!
6. “One parrotfish can produce 90 kilograms (200 lb) of sand each year”. Wiki says so – it must be true
7. They are a vital species in preventing algae from choking coral
B. PERSONAL INFORMATION (theirs, I mean)
1. Some species secrete a protective mucous cocoon to sleep in or to conceal themselves from predators
2. A mucous substance also helps heal damage, repel parasites, & protect them from UV light
3. As they develop, most species change colour significantly to become vivid adults – “polychromatism”
4. Some juveniles can change colour temporarily to mimic other species as a protection
5. Most are “sequential hermaphrodites”, turning from female to male (a few change vice versa)
6. They tend to hang out in groups of similarly-sized / -developed fish
7. Single males tend to have several lady friends, and aggressively defend their love rights
8. Parrotfish are PELAGIC SPAWNERS. Females release many tiny buoyant eggs into the water, which float freely and settle into the coral until they hatch
9. Unlike other fishes, they use their pectoral fins to propel themselves
10. Their feeding behaviour makes them unsuitable for marine aquariums
Anyone interested in getting more information about Parrotfishes – maybe about that whole female / male transformation thing? – is recommended to look at an article by Tim Smith of Miami University, Ohio entitled THE BAHAMAS: A CLOSER LOOK AT THE COLORFUL AND UNIQUE PARROTFISH Click on the P-word to get to it directly.
If you are pressed for time, here is the article conveniently digested into bullet points:
Some more bullet points from Tim Smith’s article:
STOPLIGHT PARROTFISH (adult and, below, juvenile form)Thanks to Melinda of Grand Bahama Scuba for her fantastic illustrative pics; the header is mine own
It’s possible that I won’t be quite as attentive with posts / replies to comments etc over the next couple of weeks or so. I’ve a few things in the pipeline, but it may depend on wifi access… I’m giving up trying to use an iPhone to post while on the move – fine for snaps, but not for anything more complicated. So apologies in advance, and like Arnie, I’m afraid I’ll be back…
SHARK FINS – OOOP! A MODEL USE OF HUMOUR
TO CONVEY A SERIOUS MESSAGE
The CAPE ELEUTHERA FOUNDATION has produced a short video about sharks and shark fins that manages to be both amusing and to carry a powerful conservation message. It’s a hard trick to pull off successfully. Attempts to use humour to leaven a serious message or to modify earnestness in presentation so often trespass into the no-man’s land known as ‘Meh’ (twinned with ‘Wotevah’). I’m grateful to the always-interesting ABACO SCIENTIST for sharing this item. Photo credit: Melinda Riger, with thanks for use permission [I am posting this from NYC via iPhone, so any weird formatting or typos will have to be dealt with next week]
I recently posted about the highly coloured QUEEN ANGELFISH, a striking coral reef resident glowing with fluorescent blues and yellows. It’s the Angelfish that went into showbiz and succeeded. Its close cousin the Gray Angelfish is a more sedate creature, with the appearance of a professional – law, possibly, or medicine. That thin blue fin-edging suggests a flamboyant streak. Slightly mean mouth? Lawyer.**
This species is found in the warm waters of Florida, and south through the Bahamas and Caribbean as far as Brazil. They are found at depths from 2 m. down to 30 m. You are most likely to encounter one on a coral reef feeding on sponges, its main diet. The fish below with the bluer face is a teenager, in transition between juvenile and adult.
It’s clear from side on that Gray Angelfish are ‘upright flat’, but it’s surprising just how slim they actually are. Photographer Melinda Riger has captured this front view against a stunning red backdrop. Disappointingly, these fish seem to lead blameless and anodyne lives as reef-foragers, and I’ve been unable to turn up a single interesting fact about them. That’s lawyers for you.**Photo Credits: main images ©Melinda Riger, Grand Bahama Scuba; Header – Wikipix
** I can say this – I am one…
This post is the first of a planned series on Bahamian reef fish. Those who follow this blog (I thank you both) may recall with horror (or worse, pity) my own efforts with reef fish, using a tiny cellphone-sized video camera. Misty stills culled from video footage. Enthusiastically wobbly movies as I struggle to swim and breathe simultaneously in an alien element. I am more underwater CLOUSEAU than COUSTEAU. However, thanks to Melinda Riger, who with husband Fred runs GRAND BAHAMA SCUBA, I have kind permission to borrow and display images from her stock of wonderful reef fish photographs.
The spotted drum fish (or Jack-knife fish) belongs to a large worldwide family, the Sciaenidae. Besides other drum varieties, the family includes ‘croakers’. These species are all named for the repetitive throbbing or drumming sounds they make. This involves the fish beating its abdominal muscles against its swim bladder. If I find out the reason for this (Species communication? Food call? Alarm? Warning? A piscine ‘advance’? Happiness?) I will add it here in due course. Here an example of an atlantic croaker from the excellent DOSITS site (Discovery of Sounds in the Sea)
The spotted drum is one of the few fish of the species to inhabit coral reefs – most are bottom-dwellers (often in estuaries), avoiding clear water. These fish tend to be nocturnal feeders, feeding on small crabs, shrimp and small invertebrates. As far as I can make out they are solely (or primarily) carnivore, and do not graze on algae of other reef plant life.
The photos above are of adult spotted drums. The ones below are of juveniles, and show the remarkable growth-pattern of these fish, from the fragile slender creature in the top image, through the intermediate phase of the one below it (with the amazing brain coral), to the striking adult versions above. People like to keep these pretty fish in aquariums; fine, I’m sure there are plenty to go round, but these ones look pretty happy to me in their natural reef environment…
Juvenile drum fish (school-age)
Finally, I’ve just come across this short video from a “Florida Aquarium”, showing how these fish swim. It rather looks as though it has been fin-clipped for some reason… or just damaged, maybe