By Ross Daley, Research Project Leader
Harrisson’s Dogfish (Centrophorus harrissoni) is a small shark that occupies a narrow strip of continental slope off eastern Australia and remote seamounts in the Tasman Sea, 300 to 600 metres deep. It grows to about 1.2 metres and has large, iridescent green eyes that locate lantern fish in the near darkness of the seafloor. Males and females of the species mostly live apart, moving together every two to three years to breed.
CSIRO – in association with the fishing industry and supported by fisheries managers – has conducted comprehensive field surveys of this species, and the first electronic tracking surveys of the closely-related Southern Dogfish (Centrophorus zeehaani). The surveys gather information on species distribution and home range to assist their conservation and management.
Dogfish follow schools of prey up the continental slope at night
It has been estimated that Harrisson’s Dogfish populations have declined by more than 90% in key parts of their distribution off southern New South Wales and eastern Victoria. Healthier populations remain off northern New South Wales, eastern Bass Strait and on remote seamounts in the Tasman Sea. In June 2013, the species was listed as Conservation Dependent under the Environmental Protection and Biodiversity Act.
Historically, Harrisson’s Dogfish have been targeted for liver oil in Australian state and Commonwealth fisheries. Targeted fishing was essentially halted by 2005, but with very low breeding rates, even limited incidental fishing mortality can be a problem. Populations can take decades or longer to recover because females don’t breed until they are about 17 years of age and produce only one or two young every three years.
The Upper Slope Dogfish Management Strategy has been implemented by the Australian Fisheries Management Authority to halt decline and support recovery of Harrisson’s Dogfish and Southern Dogfish in offshore waters managed by the Commonwealth. Under the strategy, a network of areas − large enough to ensure males and females can meet to breed − is closed to all fishing.
Electronic tagging at the largest closure off South Australia indicates most Southern Dogfish stay inside the closure. Outside the closures the strategy is complemented by a code of practice for the release of live sharks caught as bycatch. New South Wales restrictions have limited combined catches of Harrisson’s Dogfish to 15kg per day in trawl, trap and line fisheries. A closed area off Sydney helps protect Southern Dogfish.
As the world’s human population escalates, demands for food and energy have seen resource use expand into the deep-sea. Closed areas are a key strategy to maintain biodiversity in the ocean, particularly for species that are largely sedentary. Fishing closures such as those for Harrisson’s and Southern Dogfish can also protect species known to move on a limited scale. But the economic costs of such closures are high and cumulative. For slow-growing, deep-sea sharks such as Harrisson’s Dogfish, recovery is uncertain and a precautionary approach supported by ongoing monitoring and research is warranted.
Meet the sea pig. It’s a little different from the land pig. Actually, other than it’s plump appearance, it has no resemblance.
The sea pig rules the dark and mysterious depths of the sea. They’re typically found at depths of 1000m on the sea floor of the Indian and Pacific Ocean. A type of sea cucumber, they have several large “legs” or tube feet, which are really noodly appendages. While noodly appendages are generally fascinating, these sea pig appendages are particularly monstrous. The sea pig has the ability to inflate and deflate the appendages using water cavities within its skin.
Sea pigs are deposit feeders, meaning that extract their food from particles in the deep sea mud. There are more amazing sea pig facts in this video (accuracy not guaranteed):
Blue Marlin: This week a blue marlin washed up on a suburban Adelaide beach. It is thought this is the first time a marlin has been found in the cool waters of Gulf St Vincent where Adelaide sits.
Scientists from the South Australian Research and Development Institute think the fish took a wrong turn at Kangaroo Island and ended up in the Gulf.
They also think that the 3.2m long, 250kg marlin swan along the WA and SA coasts in the warm Leeuwin Current which at this time of year flows down the WA coast and around into the Great Australian Bight.
Below is a picture of the current (red turning to yellow and green as it cools) whipping around the bottom of WA. The second image shows the SA coast with the relatively warm water flowing around Kangaroo Island.
More images of the ocean currents around Australia can be found at the Bureau of Meteorology site which gets the information through the Bluelink program run by CSIRO’s Wealth from Oceans Flagship in collaboration with the Bureau of Meteorology and the Royal Australian Navy.
Anyway, back to the blue marlin. There is a debate going on about the classification of the Atlantic blue marlin and the
Indo-Pacific blue marlin (Makaira mazara) as separate species. Genetic data seems to show that although the two groups are isolated from each other they are both the same.
The blue marlin spends most of its life in the open sea far from land and preys on a wide variety of marine life and often uses its long bill to stun or injure its prey.
Females can grow up to four times the weight of males and the maximum published weight is 818kg and 5m long.
Blue marlin, like other billfish can rapidly change color, an effect created by pigment-containing iridophores and light-reflecting skin cells. Mostly they have a blue-black body on top with a silvery white underside.
Females can spawn up to four times in one season and release over seven million eggs at once. Males may live for 18 years, and females up to 27.
Here’s a fun fact: the words “sarcastic” and “sarcasm” come from the Greek word sarkasmos, meaning “to tear or rend flesh”.
And so I introduce to you the Sarcastic fringehead – a ferociously fierce and territorial fish.
The ‘fringehead’ part of the name comes from the little fringe-like appendages above their eyes. And of course, the ‘sarcastic’ bit relates to their highly aggressive nature. I’m sure if they could talk, they would be nastily witty too.
Fringeheads are found in the Pacific Ocean off North America and tend to hide inside shells or crevices. They have also been known to live inside cans and bottles. Whatever the shelter used, they will fearlessly defend their home territory against any unwanted intruders.
When two fringeheads have a territorial battle, they wrestle with their mouths as if they are aggressively kissing…how romantic (and yes, I’m being sarcastic).
This is how they interact:
Dark Smiling Whiptail: I was trying to be smart and find a fish with some sort of connection to the Winter Solstice (today) to try and make the shortest day of the year bearable. So I started to search the ScienceImage database using words like solstice, daylight, night etc etc and came across the Dark Smiling Whiptail.
I have got to tell you there is very little of interest about this fish. It lives down to about 850m of water which is something, but apart from that, not much.
Then I started to have a look at the scientists who described the fish and named it in 1999 – T. Iwamoto & A. Williams. As it turned out Dr Tomio Iwamoto has been the Curator of Ichthyology for 37 years at the California Academy of Sciences.
Then I found a connection to CSIRO. Dr Iwamoto is named as one a number of scientists who have made a major contribution to the fishmap interactive database which is a part of the Atlas of Living Australia. Dr Iwamoto has done a lot of work in Australian waters and contributed an enormous amount of information and experience to marine science.
There is always something interesting about everything.
So, hopefully this has helped get you through the day. For those in the Southern Hemisphere, from now on things are looking brighter!
Also known as the toothpick fish or vampire fish, the Candiru is a slender, translucent parasite. These creepy critters are native to the Amazon Basin and live in the gills of larger fish, feasting on their blood.
While some Candiru species can grow up to 40 centimetres long, the majority are quite small. It’s these smaller species that are famous for their alleged tendency to invade and parasitise the human urethra, although the truth to this story remains unknown.
Nonetheless, if you plan to swim in the Amazon, it might be a good idea to go to the bathroom first.
Mackerel Icefish: Right. It is starting to get a bit cold around the countryside so I thought this may be of interest.
It is a fish found only in the Southern Ocean and are mainly Heard and McDonald Islands, and islands in the south Atlantic such as South Georgia.
They are found in depths up to 700m with older juveniles and adults forming large schools at or near the sea bottom or mid-water range of the water column, feeding on krill and small fish.
They grow quite quickly and mature at a length of between 22cm to 26cm after about three or four years. They grown to about 35cm.
Apparently the flesh is white and firm like the King George Whiting but with a higher oil content. They are good for grilling, baking or steaming.
Moon Jellyfish: It is rare for these to live more than six months in the wild but they are really interesting.
All species in the genus are closely related and is hard to pick them apart except by genetic sampling.
They grow to about 25–40cm in diameter and can be recognized by its four horseshoe-shaped gonads, easily seen through the top.
It is not really a strong swimmer and it mainly drifts with the current feeding on plankton, fish eggs, small organisms and molluscs. It captures food with its tentacles and scoops it into its body for digestion.
Moon Jellyfish are found throughout most of the world’s oceans, from the tropics to as far north as latitude 70°N (runs through the middle of the US and Spain) and as far south as 40°S (runs through Tasmania).
It has also been found in waters as cool as 6C to as warm as 31C.
They do not have any respiratory parts such as gills, lungs, or trachea so it respires by diffusing oxygen from water through the thin membrane covering its body.
Today we’re crossing the Tasman for a mystery of the deep. Fishy remains became famous last week when a strange carcass washed up on a New Zealand beach and made it big on YouTube under the guise of a “sea monster”.
Speculation about the prehistoric origin of the “monster” was atwitter until one of New Zealand’s marine mammal experts stepped in (cue the Get Smart theme song). New Zealand Museum’s Anton van Helden told NZ TV that it could be identified as an Orca (a.k.a. killer whale), due to a distinctive flipper. Killer whales are found in all oceans and it’s estimated that the largest population lives in Antarctic waters. New Zealand’s Bay of Plenty was certainly full of surprises, as this YouTube clip shows:
It’s unknown why the killer whale died or washed up on shore. I imagine if it could talk, it would probably say something like this…
The photo above was sent in by a friend of a friend who came across the dead fish at Goolwa in South Australia this week and was unsure what it was.
I sent it to Alastair Graham who is the Fish Collection Manager at the Australian National Fish Collection in Hobart. As expected Alastair was a font of fishy knowledge.
“The photo does not show all the diagnostic characters, however I would say that it is most probably a Shaw’s Cowfish (Aracana aurita). They are normally found on coastal rocky reefs and seagrass areas at 10-160 metres. Not being strong swimmers, they are often found washed-up after storms.”
I had to laugh when Alastair said it was was not a good swimmer – seems pretty important to a fish…
Anyway, they are found around southern coastal waters of Australia from central New South Wales to south west Western Australia.
Nananananananana batfish! Pancake batfish that is.
The Louisiana pancake batfish is a newly discovered species native to the Gulf of Mexico. It was only just before the big oil spill in 2010 when these cool critters were first found. Unfortunately the fate of their population following the disaster is not yet known.
It’s no surprise where the name pancake batfish comes from. These funny looking fish have flat bodies with an enlarged head and trunk which form a round disc shape. They are small enough to fit in the palm of your hand and are about as thick as a fluffy pancake (probably not as tasty though).
And if you thought turtles were awkward, you haven’t seen these guys move. Pancake batfish have small foot-like fins, complete with elbows, which are used to ‘walk’ along the ocean floor in a bizarre motion – kind of like a crawling bat. Needless to say, they aren’t the most graceful swimmers.
Luckily they are well camouflaged, so it isn’t too hard to get some grub. Being a member of the anglerfish family, a simple wiggle of their dangling ‘lure’ is enough to capture unsuspecting prey without having to clumsily flounce around the sea bed.
While they might not be the prettiest or most elegant fish, they are quite popular. In fact, the Louisiana pancake fish was recently named as one of the Top 10 New Species of 2011, right after being described as “remarkably hideous (in a good way)”. I’d take that as a compliment…
TGIFFT! (Thank God It’s Friday Fish Time!) Here’s a riddle to get you in the fishy spirit:
Q: What do you call a fish with clear blood?
A: An Ocellated Icefish.
Okay, so that was pretty lame. But how cool does that fish look? Cool enough to distract you from my poor attempt at a riddle…right?
The exotic Ocellated Icefish lurks about in the chilly depths of the Antarctic Ocean, and as you’ll soon find out, it’s certainly one of a kind.
Aside from being able to survive in such an extreme environment, these fascinating aquatic vertebrates also lack haemoglobin. This could explain why their blood is clear, since haemoglobin gives most blood its red colour. You’d think the fish would have a hard time getting by without this essential protein, but amazingly their circulatory system does fine without it. In fact, these guys have super strong hearts that are larger and pump blood five times faster than most other fish.
And it gets weirder. The Icefish also lack scales, which some say makes them sort of like the Sphinx cat among fish.
To this day, nobody knows how these fish evolved in such a strange way.
If you want to see them in person, you’ll have to take a trip to Tokyo Sea Life Park – the only place in the world where a male and a female specimen are living in captivity. Otherwise you could go for a casual dive in the Antarctic Ocean.
Just recently, the two lovebirds in Tokyo successfully spawned – which was a world first for this species. Scientists are hoping this might help unlock some of the fish’s deep, dark secrets.
I’ve got to say though, for an unusual fish they sure are boring! Take a look at this video and see if you agree.
Humpback Anglerfish: Ah, the anglerfish. Such a fascinating and (let’s face it) unfortunate looking creature.
Also known as the ‘black seadevil’, the Humpback Anglerfish lives among the darkest depths of the Atlantic and Antarctic oceans. Interestingly, male and female anglers are completely different in their characteristics.
Only the female fish has the distinctive ‘fishing rod’ style dorsal spine hanging above its head, complete with a fabulous bio-luminescent tip that acts as a lure to attract prey. The glow is made possible by the millions of bacteria that live inside the spine – how very hygienic. With a simple wiggle of this glowing outgrowth, the anglerfish can draw her prey close enough to devour them in one bite. Her expandable stomach and jaws means she can swallow prey up to twice her own size.
Male anglers, on the other hand, aren’t so special. They are about ten times smaller than females and lack the specky fishing rod spine. Without this asset, they have a pretty hard time salvaging food. To make matters worse, when the male angler matures, its digestive system degenerates making it impossible to feed on its own. This means it has no choice but to become a permanent parasite.
The male uses its small hook-shaped teeth to attach itself to any female it can find. Once he bites into her skin, he releases an enzyme that dissolves the skin of his mouth and the female’s body. The two become fused together and their blood vessels combine as one (aww, how romantic). The male will spend the rest of his life joined to the female, getting all of his nourishment from her body. Talk about clingy…am I right ladies?
The female can carry up to six males on her body at one time – so when she’s ready to spawn she can easily take her pick of the lot. Looks like they’ve got it pretty easy unlike the poor blokes!
Here’s what this would look like if the fish were human:
Red-bellied piranha: Don’t let their glittery scales fool you – piranhas are one school of fish you don’t want to mess with…or so we’ve been led to believe.
There are over 20 different species of piranha, most of which live in the Amazon River Basin. Surprisingly though, the majority pose no real threat.
Red-bellied piranhas are possibly the most misunderstood fish in the world. Despite their fierce and aggressive reputation (thanks to popular culture), these little critters feed mainly on fish, insects, plants, fruits and small aquatic invertebrates.
As you might have presumed from the name, the fish have a reddish tinge on their bellies, while the rest of the body is grey with silver flecked scales. The male belly tends to be a deeper, more intense red while female bellies appear more yellow. They generally grow up to 33cm in length and weigh a tiny 3.5kg.
But don’t be fooled by their size. Their powerful jaws and sharp, triangular teeth allow the fish to bite through food with incredible force and ease. It’s no surprise why the name ‘piranha’ literally means “cuts the skin” in the native South American language Tupi-guarani.
Occasionally, the fish can go into a ‘feeding frenzy’, where they hunt large groups of prey and strip them clean within a matter of minutes. These frenzies don’t tend to be random attacks though – they are often the result of aggravation or starvation when food is scarce. Long story short, if you ever come across a piranha, don’t do this: