Various members of the NORFANZ team kept a diary of their experiences over the four-week voyage. You can read about their experiences below.
Day 15: 24 May 2003
By Mark Norman, Museum Victoria
Smooth seas, low slow swell (1-2 m), no wind, 20 ° C
Busy day yesterday finishing with several very productive trawls in shallower water around the Lord Howe region. Many interesting fish and invertebrate species were collected including some rare species. The most interest was sparked by a small colourful fish, known as the Ballina Angelfish. Other findings included a new species related to nannygai or redfish (genus Centroberyx), many pelagic cowfish (which are rare elsewhere), about twenty Galapagos sharks (returned live to the sea), a large ray (also returned live to the sea), large leatherjackets, a flutemouth and a pipe horse. Reports from divers in this region suggest that it has one of the highest concentrations of Galapagos sharks of any region of the world. Soft and black corals were also collected, as were many sea urchins of several species.
This was followed last night by a very deep trawl around 1900 metres as we steamed away east from Lord Howe Rise (the seamount chain from which Lord Howe Island and Ball’s Pyramid emerge). This trawl used the “ratcatcher” net, a bottom net that samples smaller creatures than the orange roughy net. This depth is at the edge of the “abyssal” zone. The sea is divided into four major depth zones: littoral (0-200 m), bathyal (200m-2km), abyssal (2-6km) and hadal (after hades or hell, >6km). The deepest sea is 11 km deep off the Philippines. Although our catches were not large (usually only 3-5 fish bins) they included many exciting animals. The most dramatic was a large red Stone Crab covered in very sharp spikes . Other invertebrates included a large sea spider, many brittlestars and stalked grazing sea cucumber. Amongst the fishes, the most common were the slickheads (family Alepocephalidae), including one possible new genus. Slickheads are thought to make up most of the fish biomass in these deeper waters. Other fishes included halosaurs, the fangtooth, deep-sea lizardfish, morid cods, a few grenadiers (also known as rattails) and a deep-sea catshark (genus Apristurus). One of the strangest fish was a small blind jelly-like fish called Aphyonus, a rare deep mid-water fish. They are rarely captured because they are so fragile. They are probably so soft and gelatinous to help them stay buoyant in the water and save energy. The bones are reduced and their transparency probably helps them avoid detection by predators. The trawl net also captured some other pelagic fishes on its long trek back to the surface. These included small light fishes and a Gulper Eel.
After every sample, all fish and invertebrates are sorted, identified to lowest level possible, labelled, recorded and preserved in three different ways: in ethanol for DNA studies, in formalin for long term preservation in reference collections (like museums) or frozen for fixation and treatment after the voyage. Any new species or first captures for this voyage are photographed, logged and their images placed in reference folders for the different groups. This speeds identifications in subsequent trawls and provides a constantly updated record of the diversity encountered. For photography, fish specimens need to be carefully prepared. As so many species are identified by fin colour and form, the fins must be flared to show these features. Other structures such as chin barbels or anglerfish lures must also be arranged to show their structure. As a consequence, each fish to be photographed must be carefully pinned out and have formalin brushed on to the fins and other structures. The formalin helps stiffen these up so that they remain flared when the pins are removed. The time consuming task of preparing and pinning out the fish is done by Al Graham and Dan Gledhill, both of CSIRO Marine Research in Hobart. Once set, the fish are photographed on a raised lightbox of glass to prevent loss of detail caused by shadows. This high-resolution digital photography is done by Robin McPhee of Te Papa, New Zealand and Kerryn Parkinson of the Australian Museum, Sydney.
At around 9am this morning we brought up another ratcatcher trawl from 1400 metres. It was a good fish catch for diversity including two large chimaeras (ghost sharks), two small deep-sea catsharks, lots of slickheads, basket eels, halosaurs and rattails. It also included some of the more interesting small fishes such as another fangtooth, another deep sea lizardfish, a slingjaw and viperfish. The chimaeras turned out to be a species described by one of the shark experts on board. Dr Bernard Seret (from the Institute for Research and Development in Paris) described this species from specimens collected on this same ship, the Tangaroa, in a survey near New Caledonia in 1997.
As I send this off, we are about to put down another deep trawl. More tomorrow.
Day 16: 25 May 2003
By Mark Norman, Museum Victoria
Low swell (~2 m), 18 knot E, 18 ° C
Beautiful unusually calm day yesterday. In the afternoon, the ratcatcher net lived up to its name and caught lots of rattails. The most common fish in the net was the Globe-headed Rattail, Cetonurus globiceps, a distinctive fish with a swollen soggy head and little narrow tail (hence the name). This catch also caught many basketwork eels, Synaphobranchus capensis. They get their name from the criss-cross pattern on their bodies visible when their skin is scraped off. One eel had a squid sticking out its mouth that proved to be as long as its own body. The third common group in this catch was again the slickheads. Amongst this haul was one of the stranger relatives of sharks, a Pacific Spookfish, Rhinochimaera pacifica.
This catch also included a new species of small skate of the genus Notoraja. Skates differ from rays in that they have no barbs on the tail. This new species is dark underneath and light on top. Most fish in shallow ocean waters, such as tuna, have a dark upper surface and a silver reflective underside. This is called “counter-shading” and hides the animal from above by the top matching the dark water below, while the silver underside matches the bright sunlight above. Many creatures that live on the deep-sea floor (including this new skate species) have the opposite colours (dark below and light on top). This is known as “reverse counter shading”. This stops them being obvious when seen from above against the light mud or from below against the dark sea.
We also caught another type of rare jelly-like fish from the family Aphyonidae. This one is a new species in the genus Sciadonus. Like the species caught yesterday, it is virtually blind and would find its prey by feeling vibrations in the water around it. Andrew Stewart of Te Papa, New Zealand found and identified the perfect specimen of this rare fish group which was caught much shallower than is normal for these fishes, 900 m deep when they normally occur >1700 m.
Between trawls we had a safety drill to test our mustering abilities and to test the foam fire hose needed in case of fire in our alcohol stores.
Overnight the rattail theme continued with an exciting catch, a massive 11 kg Giant Rattail, Coryphaenoides rudis, as big as one of our onboard experts on this group. Rattails belong in the family Macrouridae, the biggest and most diverse family of mid- to deep-water fishes. They go under various names including grenadiers and whiptails. The grenadier name comes from one of the first to be described having a peak on its head shaped like the helmet of the grenadier soldiers.
The rattail catch yesterday also included two specimens of the species Coryphaenoides grahami : a special species as it was named by Dr Iwamoto after Ken Graham of NSW Fisheries. Both fish experts are onboard the NORFANZ cruise.
Today we trawled around 850 m deep over soft mud made of the dead bodies of billions of microscopic creatures known as foraminiferans: the mud is called “foram ooze”. The soft seafloor must be good for foraging fish because we caught a large number of bottom-dwelling sharks. Included in this catch were numerous Black Sharks, Centroscymnus owstoni, which typically occur at depths from 600-1200 m deep. This shark is taken in commercial deep-sea trawls off eastern Australia and is sold in Melbourne as “flake” and Sydney as “deep-sea boneless fillet”. Members of this genus are the deepest occurring of the sharks, having been recorded down to 3.6 km deep. Other sharks included lantern sharks (genus Etmopterus) and long-snouted dogfish (genus Deania). This catch also included pretty cup corals, long coiled whip corals and some very snotty slimy sea cucumbers.
A subsequent trawl came up with more sharks and three excellent squid species: a hooked squid (family Onychoteuthidae), a flying squid (family Ommastrephidae) and a jewel squid (family Histioteuthidae).
We are now steaming west towards our next site.
Day 17: 26 May 2003
By Mark Norman, Museum Victoria
Low swell (~2 m), 14 knot SE, 18 ° C
It’s 6.30 am and the Sherman sled is down sampling the top of a small seamount several hundred nautical miles south east of Lord Howe Island (1 nautical mile = 1.85 kilometres). It is an old volcano formed millions of years ago with an obvious crater on top. This follows an earlier orange roughy trawl on the sides of this seamount.
The nets that we use sample in different ways. The captain, Andrew Leachman, bosun Mike Steele and crew members Craig Robinson and Barry Fleming helped explain to me how all the nets work and all the terminology. The biggest net is the “orange roughy trawl”, the same as those used by deep-sea commercial trawlers. It has a long conical net with wing-like extensions going out from each side. At the end of the wings there are two large steel plates known as “doors” or “otter boards”. As the net is towed, these doors glide outwards and hold the net mouth open. The mouth of this net is about 16 m across and 7 m high. Along the top of the rectangular net mouth is the “head line”, held up by a row of large floats. Along the bottom edge is the “ground rope” loaded with large steel balls known as “roller bobbins”. The orange roughy net samples along the seafloor, the large bobbin balls rolling over irregular ground. This net has quite a large mesh size and is used to catch larger and faster fish.
The “ratcatcher net” is a slightly smaller modified orange roughy net with two basic changes: a ground rope with small rubber rollers and a finer mesh rear-end of the net (the “cod end”). This net is towed slower and samples more from the seafloor, including smaller fish and more invertebrates. It is used on flat bottom, sand or mud. Sensors on the doors and head line of both these net types send up signals on the depth of the doors and whether the net is trawling in the right way.
The next net is the “beam trawl”. This net has a round pine beam four metres long that joins two steel frame skids together. The net is towed from this frame. The lower edge of the net mouth has a ground rope with small rubber disks. It has two net cones, one inside the other: a fine mesh outer net and a super fine mesh inner liner. This trawl is used to sample seafloor life such as corals and bottom-living invertebrates and fishes. The wooden beam is used to hold the two metal skids apart and keep the net open without needing doors. Wood is used instead of steal because it can break. Under pressure the wood snaps and the net and two steel skids can still be brought to the surface, complete with the fish catch inside. The ship carries replacement beams.
The toughest sampling device on board is the “ Sherman sled”, named after the Sherman tank. This steel-framed sled weighs 1.5 tonnes and is used on especially difficult bottom types. It has thick steel skids to slide over rocks and can sample both ways up. It tows a short net with a fine mesh liner. In case the sled gets stuck, it has four sets of “weak links”. These are chain links of known breaking strain that break when the sled becomes wedged. As they break, it shifts the point of attachment to different corners of the sled to pop it out of any jam. The sled also has “sacrificial chains” in front of the scraping blades, which will break if they hit any rocks or else pulverise the rock.
After catching quite a few sharks yesterday lunchtime, a trawl at similar depths last night got very few sharks. Ken Graham of NSW Fisheries suggested that this made sense as sharks such as brier sharks (genus Deania) feed mainly on lanternfishes (family Myctophidae, see “creature feature”), one of the many groups of fishes and free-swimming invertebrates that rise up into shallower waters at night to feed. It is likely the sharks swim up with their prey. These vertical migrations happen every night in oceans worldwide. Free-swimming creatures move on mass up towards the surface to feed under the cover of darkness. They get so thick that they can be picked up on echo-sounders as a distinct layer in the sea. Dr Malcolm Clark, a fisheries scientist onboard from the National Institute for Water and Atmospheric Research in New Zealand explained that this is known as the “scattering layer”, where high densities of zooplankton and midwater fishes move together in a mass from depths of around 700 metres up towards the surface. Their exact depth each night depends on how much night light there is, on black moonless nights many species come right up to the surface. With a full moon, they may stay several hundred metres down. It’s all about having enough light to see food but not be easily seen by predators. Many of these creatures, particularly the fishes and squids produce light, just enough on their undersides to hide their silhouette from nasties below.
Other creatures collected overnight included lots of small flatfish known as tongue soles (Symphurus sp. B), silver roughies (Hoplostethus intermedius) and some deep-sea batfish (family Ogcocephalidae).
This morning, Sherman brought up a few urchins and anemones while the orange roughy trawl brought up some deep-sea scorpionfishes (genus Helicolenus), more silver roughy, some Ribaldos (Mora moro) and anemone hermit crabs .
An orange roughy trawl just before lunch contained quite a few Alfonsino (Beryx splendens). This brightly coloured fish is an important commercial species elsewhere. Our material will provide important data on distribution of this species while tissue samples will aid population and stock assessment studies. This trawl also contained an especially weird stargazer, Pleuroscopus pseudodorsalis .
As I write this, the NIWA Seabed Mapping team are searching for good ground to put down the orange roughy trawl again.
Day 18: 27 May 2003
By Mark Norman, Museum Victoria
Low swell (~2.5 m), 20 knot SE wind, 16 ° C
Today is less frantic as we steam for 16 hours to our next site, site 11, on the south side of Wanganella Bank (also known as West Norfolk Ridge). So people are catching up on notes, databases, organization, gear, specimen storage, cruise T-shirt design and sleep.
We are cruising at around 13 knots. The “Tangaroa” is a very stable ship. This stability is maintained by an “anti-roll system”. This consists of a long rectangular water tank under the floor of the bridge. It is 1.5 m high and the full width of the ship (16 m across). Inside this tank at either end are fixed steel plates in pairs with a narrow opening aimed at an angle towards the centre of the tank. Up to 20 tonnes of water can be held in this tank. When the ship rolls one way the water moves slower and counters the rolling action. By the time it leaks through to the other end it is in time to counter the roll the other way. It ends up giving a very smooth ride. The “Tangaroa” has travelled widely including cruises throughout the subantarctic islands and SWATH mapping in Antarctica. It is capable of rolling from side to side to a 60 degree angle without capsizing. As the captain Andrew Leachman says, “At this angle it is easier to walk on the walls than on the floor!” As the ship is only 70 metres long it can be a lumpy ride directly into big swell as the ship is not long enough to ride across several wave peaks at once, so that it can fall into the troughs in big seas. The bends in the plates above the bow show the landing can be rough, these bends coming from surviving an 18 m swell.
After leaving our small seamount yesterday, we moved out to do some sampling in deeper waters. At around 3 am last night we did the last of these deep sites at around 1100 m deep. The catch included some large black chimaeras, a different species of spookfish (long-nosed chimaeras), a rare eelpout, a Rudderfish (Centrolophus niger) and a perfect Giant Hatchetfish. The invertebrates included some glass squids (family Cranchiidae), large anemones, a muscular bottom-dwelling octopus (genus Benthoctopus) and an excellent jelly-like finned octopus.
As we steam east, the crew are preparing the nets for sampling at around 8 pm tonight. Bruce Barker, Senior Technical Officer from CSIRO Marine Research is also preparing the headline still camera that is attached to the net. Bruce is onboard to oversee the operation of a Photosea camera, a modified Nikon in a special underwater housing that allows it to be sent down to 6 kilometres deep. This camera is on a timer so that it starts photographing once the net has reached the seafloor. It can then take 250 high resolution images at 12 second intervals. The other camera system is a drop frame containing a Benthos camera (also based on a modified Nikon 35 mm camera) operated by Miles Dunkin and Richard Garlick of NIWA. It is lowered vertically, with a weighted line beneath it. When the line hits the seafloor, the camera takes an image. As the ship drifts and the cage bobs up and down it takes photos along the seafloor. It can take up to 800 images in one go. Both cameras use wide angle, 28 mm lenses. Bruce can process all images onboard and give direct feedback on seafloor types.
As I send this everybody is getting ready again. It will be a busy night ahead.
Day 19: 28 May 2003
By Mark Norman, Museum Victoria
Slightly larger swell (3+ m), 25 knot SE wind, 16 ° C
It’s around 3 am and we’re groggily doing the changeover of shifts. I’m still not used to the starting time of these 12 hour shifts. Some of us stumble round bumping into each other during the changeovers. The crew seem more used to it.
A ratcatcher has just gone down so we’re about an hour off it coming onboard. Last night an orange roughy trawl to around 800 m brought up 10 species of chondricthyans (the scientific name for the group containing sharks and rays, all of which have a skeleton of cartilage): the tally was 9 shark species and one skate species. Yesterday the head of a mako shark was found in one catch. By the clean knife cuts on it, it must have been discarded by a fishing boat. Bernard Seret of IRD in Paris has spent the last day preparing the skull and jaws to be kept as a reference specimen. He has been carefully scraping away the skin and flesh with a scalpel. The soft cartilage skull is then “fixed” in a chemical known as formalin, the same embalming fluid that funeral directors use. It stops muscle and cartilage from decaying. This chemical is used to “fix” many of the reference specimens collected in this voyage. Others are fixed in alcohol so that DNA can be extracted for studies of fish stocks, populations and the evolutionary origins of different groups.
Other fish catches overnight included orange roughy, silver roughy, oreo dories, halosaurs, spineback eels, more rattails, slickheads, lanternfish, viperfish and several deep-water conger eels. The invertebrates included jewel squids, brittle stars, sponges and small urchins.
Each 12 hour shift of researchers has a fish team and an invertebrate team. The catch is quickly sorted into these major groups on deck and then tubs of animals are taken to the different labs for sorting, identification, photography and labelling. The invertebrate team is co-ordinated by Karen Gowlett-Holmes from CSIRO Marine Research in Hobart. Karen has a wide knowledge of marine invertebrates and is joined on the night shift by experts in particular groups: Rick Webber, Te Papa (prawns, shrimps and other crustaceans), Matilde Richer de Forges, Queensland Museum (sponges) and Tim O’Hara, Museum Victoria (brittle stars and other echinoderms). The day shift consists of Penny Berents, Australian Museum, Sydney (amphipods and other crustaceans); Peter Davie, Queensland Museum (crabs and other crustaceans); Don McKnight (seastars, urchins and other echinoderms) and myself, Mark Norman, Museum Victoria (octopuses, squids and other cephalopods).
For each new species found or for species that are captured for the first time on this voyage, digital photographs are taken for placement into photo reference folders. These folders are constantly updated by Karen and Penny for the invertebrates and their data entered into the trip database. These folders are very useful for checking identifications against species already encountered. The fish teams use the same process. Brent Wood and Neil Bagley co-ordinate input of all the data onto the ship’s computer systems with input from shift leaders Malcolm Clark (day) and Peter MacMillan (night). At the end of the trip the resulting large databases of information and images, combined with getting the unidentified material to experts around the world, allows the results of the voyage to be quickly worked up and the information rapidly disseminated. At this stage of the voyage, around 1000 species of invertebrates have already been recorded.
I can hear the winches starting up which means it will be half an hour to go before the 3 kilometres of “warp” (the steel cable connected to the trawl) will be brought up. For each kilometre of depth, you need about 1.7-2.0 kilometres of steel cable to tow the net at a low enough angle so that it sits flat on the seafloor but not so low that it digs in. The ideal speed is around 3 to 3.5 knots. The captain, Andrew Leachman, describes it as being like landing a plane, you adjust the speeds and angles according to the conditions. The “Tangaroa” carries 4 km of cable on each of the two major winches, enough to trawl down to 2.7 km deep.
The last trawl from 1500 m deep brought up a lot of ox-eyed dories, some prawns, collapsible sea urchins, basketwork eels, some sharks, more orange roughy, one of the deeper hatchetfishes with eyes on the side of its head, more rattails, a snailfish (probably Psednos sp.) and a blobfish (Psychrolutes sp.).
This afternoon we snagged the orange roughy net on rough ground once and then got tangled doors in the next trawl. The second trawl went to 250 m and did catch some shallower colourful sea perches and some pieces of black coral carrying serpent stars and barnacles. While repairs are made to the orange roughy gear the Sherman sled has been sent down. More tomorrow.
Day 20: 29 May 2003
By Mark Norman, Museum Victoria
Slightly larger swell (3 m), 18 knot SE wind, 17 ° C
It’s now 8 am and we’re currently choosing a suitable location to send down the nets on a shallow seamount on the Wanganella Bank. Trawl sites are chosen according to the scan images and information generated onboard by the NIWA seabed mapping team: Richard Garlick, Kevin Mackay and Miles Dunkin.
It is important to remember that very little of the world’s seafloor has been mapped. In the past our knowledge of the bottom of the oceans has come from individual depth measurements by ships in their narrow tracks across the sea. In the early days even the ship’s location at each depth station was not accurate. This gave a very weak picture of the seafloor and even with the development of echo sounders there were still many errors caused by things such as large fish schools or backscatter layers in the water. This situation is now starting to change with the development of some very fancy technology.
The first stage starts with satellites. Exact location information is now provided by “GPS” (Global Positioning Systems), able to separate location a metre apart. Another satellite system provides “satellite altimetry data” which can generate a rough map of the seafloor for all the earth’s oceans. It does this by measuring the height of the sea surface. No, the sea is not evenly curved all over the earth (even if you take out the influences of tides, currents and swell). In spots it bulges up, elsewhere it is lower. This corresponds to the depth and type of the seafloor directly underneath. It is all about gravity: the pull of gravity on the seawater depends on the size and composition of underwater features. Large underwater mountain ranges of dense rock have higher gravity pull than trenches full of mud. By measuring the sea surface heights, this system can generate a rough map of the seafloor and can pick up large underwater features like the Lord Howe Rise. Errors can occur where different rock densities can give false readings of shallower or deeper depths. For more detail, like defining individual seamounts, the mapping must be done more directly. This is where our ship comes in.
The Tangaroa is specially fitted for “multibeam mapping”. It works like the echo sounders used on small boats, but on a much larger scale. The keel of the ship has had a special structure added called the “pod” or the “gondola” that carries two large arrays of transducers (large plates that send and receive pulses of sound). The transmitter series is 8 metres long in line with the ship’s hull while the receiver series is 4 metres wide across the ship. This system, known as the Kongsberg Simrad EM300, sends out a thin fan of 30 kHz sound waves with an angle of up to 150 ° wide. The receivers receive the bounce-back signal. It is the equivalent of 135 single echo sounders all sending and receiving at once. The width of the seafloor scanned depends on the depth, if the sea is one kilometre wide, then it can scan up to 4 km wide beams across the seafloor. When you get a lot shallower, the beam narrows, so more passes are required.
To make the multibeam system as accurate as possible, the speed of the sound transmissions through the water needs to be considered. Seawater is not just seawater. It varies in temperature, salinity, pressure, particles and marine life. There are layers in the sea of temperature changes (thermoclines), salinity changes, density changes or dense bands of animals (the “scattering layer” mentioned already in the NORFANZ diary). These factors can bend (refract) or change the scanner beam, just like light through prisms. To compensate for these layers, an “SV probe” (Sound Velocity probe) is lowered to measure the speed of sound through the water at the different levels in different layers. The results improve the accuracy of the data and images generated. Another factor to be considered is the motion of the ship. How can the signal be held steady by a rocking and rolling ship? The job of taking motion into account is done by a little orange box known as the “inertial motion sensor”; it contains spinning wheels and disks that sense ship motion and instantly controls the direction of the scanner beam to keep it steady.
There’s one more thing that this system does. It can measure the hardness of the seafloor. It does this by measuring the strength of the returning signal, if it is weak, the sediment is soft, and if it is very strong it is bouncing back from hard rock. This information can be draped over the resulting maps to show the rock types. You can even see the lava flows that ran down the sides of extinct volcanoes millions of years ago.
The result of all this technology is spectacular maps, like moonscapes. The three images shown are: 1) the seafloor at site 7 north of Lord Howe Island, 2) the passes of the ship that allowed this map to be generated, and 3) the overlay of rock density, showing the ridges of hard lava down the sides.
On a side note, “Side-scan Sonar” is a different system that the Tangaroa uses in some surveys. It is a towed unit (called a “towfish”), pulled behind the ship that can get closer to the bottom. It sends out the beam to the side so that it is effectively looking for shadows, like shining a torch across a night landscape. It has much higher resolution but is more appropriate for mapping small areas in high detail, i.e. marine farm sites or sewerage outfalls. It can resolve objects down to less than a metre, handy for finding lost wrecks.
Enough technology. Back to the critters. Last night we trawled to around 1400 m deep. This morning, crewmember Barry Fleming made a discovery when preparing the nets for the day: a missed specimen of one of the more dramatic toothy creatures of the deep, a Humpback Anglerfish.
Shallower trawls today (140 m) brought up large numbers of porcupine fish (returned spiky and flapping overboard), slender bellowsfish, a few flying gurnards and leatherjackets.
We are now waiting for the mapping team to tell us the best place to set down the next beam trawl. You know how they do it now.
By Mark Norman, Museum Victoria
Low swell (<2 m), 11 knot SW wind, 16 ° C
It’s early morning and the ratcatcher is down. Last night was a mix of beam trawls and ratcatchers and one trawl with badly tangled doors. The crew efficiently untangled the knot and trawling continued. One catch brought in many redbait (Emmelichthys nitidis), a small fish in the bonnetmouth family (Emmelichthyidae). The bonnet name refers to their expandable jaws. These fish feed in large schools like anchovies.
Everybody is working very hard. It is 12 hour shifts, seven days a week. The crew work from 12 to 12 and have all the work associated with running and maintaining the ship, deploying nets and changing between sampling gear types. They also have nets to prepare, gear repairs and modifications. The researchers work from 3am to 3pm (or vice versa). There is always a lot to do: making sure that all specimens are identified correctly, collection data is logged, animals are preserved in the right manner, computers are functioning properly, photo reference folders are kept up to date, tissue samples are taken, alcohol and formalin supplies are maintained, full drums of specimens are correctly stowed or backlogs of specimens are not left for the next shift. For some researchers, they are the only expert in their group so they also try to help out the alternate shifts. Bed is a very welcome location at the end of each shift and a long steam between sites is always a welcome catch-up.
Included in one of yesterday’s trawls was another toothy deep-sea fish, a Scaleless Dragonfish (Opostomias micripnus). Another trawl contained a chimaera egg case, complete with developing baby chimaera.
Cartilaginous fishes (sharks, rays and chimaeras) have three different ways of having their young. The first is by laying eggs (known as “ovipary”). Chimaeras (all 3 families), skates (family Rajidae), catsharks (family Scyliorhinidae) and bullhead sharks (family Heterodontidae) all lay horny (keratin) egg cases. These sometimes wash up on shore and get called “mermaid’s purses”. The eggs are laid on the seafloor and are left for the young to develop on their own (taking 3 to 9 months). Different shape egg cases are laid in different places, the spiral cases of bullhead sharks (like the Port Jackson Shark) are wedged into crevices, those of catsharks have long threads and are tangled around algae or corals, while the flat egg cases of skates and chimaeras probably lie on the seafloor or are “posted” into crevices.
The second sort of reproduction is used by stingrays and most sharks. It is called “ovovivipary”, which means “egg-laying and live-bearing”. This means that there is an egg enclosed in a membrane that develops and hatches inside the oviducts of the female, so that the young are free-swimming when they hatch. This is a good strategy compared to egg cases in that the young start life well developed and can immediately fend for themselves.
The third strategy is true live bearing of young (known as “vivipary”), where direct internal development occurs. Only one group of sharks uses this strategy: members of the family Lamnidae that includes the Mako, Porbeagle and White Pointer sharks. Very weird behaviour occurs in some (or possibly all) of these sorts of sharks. The young start to eat each other, while still inside the mother! This is called “uterine cannibalism”. The developing shark pups first grow off their own yolk sac. They then develop functional mouths and stomachs. The strongest pup starts by eating unfertilised eggs that are also in the ovary and oviduct. Once they’ve run out, it starts to eat its brothers and sisters! In the end only one very strong pup survives, coming out into the world snapping. There is a story of an ichthyologist (the official name for a fish expert) opening the belly of a dead female Porbeagle shark to be attacked and bitten by the ferocious pup inside.
In general sharks and rays produce few young. Some sharks and rays produce only one pup at a time. The record is held by one whale shark from Japan that had 302 pups inside it. This is not many compared with some fish species that can produce millions of eggs.
A number of the attributes of sharks, rays and chimaeras make them vulnerable to overfishing: they produce few young, gestation can be up to 2 years, they are slow growing (some don’t mature until 12 years old) and the largest produce the most young (and are often the first to go in a fishery). Many shark species have shown rapid declines from overfishing. This includes many deep-sea shark species around the world. Shark research on the NORFANZ cruise provides critical information on identification, diversity and distributions of sharks and rays in this region, important information for appropriate management and protection of these animals.
We’ve just brought up a “pipe dredge”, a steel tube on a chain used to sample seafloor sediment. It came up packed with fine white sand and Penny and Don are now sieving it to see what small animals it contains.
We have had a lone Wandering Albatross behind the ship all day, along with Cape Petrels (a bird more typical of subantarctic waters) and Short-tail Shearwaters. More tomorrow.
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