Diver Matt Incursions in Melbourne, Victoria, Australia | Educational consultant

Diver Matt Incursions

Locality: Melbourne, Victoria, Australia

Phone: +61 435 910 003

Address: 16 Lugg St 3018 Melbourne, VIC, Australia

Website: http://www.divermatt.com.au

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25.01.2022 After a cracker of a first outing we're going live for our second digital snorkeling session. If you know someone between the ages of twelve and twenty-five who's missing their underwater time please let them know about the digital marine science party that is the Port Phillip EcoCentre staff's Online Snorkeling session.

23.01.2022 Yesterday's snorkeling highlights.

21.01.2022 Diver Matt's Daily Discovery Date: 20/7/20 Location: Altona Description: Polola sayin' YOLO. These strands of protein are the posterior halves of worms in the order Eunicida that live in burrows in the shallows. In the lead up to the winter spawn the posterior end differentiates into a seething mass of eggs or sperm or eggs and sperm and the lateral parapodia grow large and paddle shaped. ... When the moon phase is just right the posterior ends break off and start swimming, departing the burrow and reaching the surface waters all at the same time, at which point the skin ruptures and the water fills with eggs and the sperm necessary to fertilise them. Messy but more efficient than throwing your gametes into the water and hoping they can find their counterpart from the correct species. These things were wriggling about in large numbers this evening and if you get your skates on you can likely witness this annual event in the next few hours but don't go looking for it tomorrow night as the species has likely shot its bolt. In some tropical nations the density of worm hinds in the water prompt an annual feast but I wasn't hungry, myself, and left the wrigglers to get on with their final twitching release. See more

21.01.2022 Winston Cowie posted this footage of a whale shark swimming in a marina in Abu Dahbi. I've wanted to see a whale shark since I can remember and even after a quarter century in marine science they remain elusive to me. What a beautiful animal and what an amazing encounter for Winston and co.

20.01.2022 What I've been getting up to with my mornings of late. Data collection thrills me, whether we're accumulating multibeam swath pings over previously unmapped seafloors or measuring how long my boots last in an experiment testing the efficacy of boot polish. So satisfying to be contributing reliable data to a fish stock management programme. And John's nice to work with, too, but the data's the exciting bit.

20.01.2022 Diver Matt's Daily Discovery Date: 7/6/20 Location: Surf Beach, Phillip Island Description: A picture of a place with a smell. I rate myself as a worderer but I struggle when I attempt describing scents. There's a wondrous earthy smell in the heathland of coastal sand dunes and I love it.

19.01.2022 Marine mammals in the Yarra. Always keep eye out for rakali in the margins. They aren't as graceful as seals and they aren't as beautiful as dolphins but they are our native neigbours and make good company above and below the water. The webbed toes and white tail tip tell the observer that this is no introduced pest species rat and their fishing and foraging over the nearshore benthos is worth watching, bordering on the mesmerising. Thanks for spotting, documenting and sharing this furry wonder, Jackie.

19.01.2022 June 19 will be the very first World Albatross Day. As part of the lead up there will be a Albaicake Bake Off!! All entrants will receive a prize!... What a fun & delicious way to spend time while in isolation and get us thinking about some of the threats facing albatross species and seabirds in general. For more information: https://www.acap.aq//3655-announcing-a-world-albatross-day

19.01.2022 John Kean's been out bird spotting once more and coming up with the goods and the story behind the goods.

19.01.2022 Diver Matt's Daily Discovery Date: 23/6/20 Location: Rye Description: Whelk, Dicathais orbita.

18.01.2022 Diver Matt's Daily Discovery Date: 13/05/20 Location: Portsea Description: A school of globefish as seen from below. Globefish are ponderous, cowardly, cartoonish looking and entirely endearing fish. At low speeds they swim with their pectoral fins, rowing them through the water in a manner referred to as labriform. When they need to put on some pace they switch to ostraciiform swimming with rapid oscillations of the caudal fin at the tail end, and even that doesn't offer a...n especially impressive turn of speed. I've never bothered one enough to make it puff up underwater but I've brought thousands up in trawl nets and they immediately inflated themselves with air, covering the deck with spiky beachballs with ridiculously bugged out eyes. We got them over the side after weighing them in the fish bin and they deflated and swam back to the depths. I saw this school of globos while swimming under the pier at Portsea. They were hanging out just outside the pier shadow and moved away anytime I tried getting near enough to take a picture. I set my camera down on the benthos and departed far enough to let the school relax. It still took seven minutes for them to return to the site of their previous greatest density but I'm glad I waited as the resulting two minutes of globefish drifting about in the surge is now my favourite footage ever. https://youtu.be/jOKpNDLEtfU

17.01.2022 Diver Matt's Daily Discovery Date: 17/05/20 Location: Point Gellibrand Description: Grapsid crab. Grapsidae are classic crab shaped crabs that you find in the sort of rock pools you expect to find crabs in. Squared off carapaces, strong chelae (nippers) on the front pair of pereopods (walking legs) and a sore finger for anyone silly enough to try handling them, though that last isn't a diagnostic feature. I don't know which species this one is because I'm smart enough not t...o handle them while they're alive and so I only got this picture and can't examine the hairs on the limbs and other such diagnostic features. About twenty millimeters across the carapace and too quick on the move to allow much examination beyond that. See more

15.01.2022 Diver Matt's Daily Discovery Date: 8/6/20 Location: Surf Beach, Phillip Island Description: Sea tulip in the genus Pyura. Sea tulips look like the dutch flower but are animals in the phylum chordata and the class Ascidiacea, placing them closer on the family tree than all the other invertebrate species I bang on about. ... They are chordates because they have a dorsal nerve chord when they are in their planktonic larval stage. Every other invertebrate I post about has its nerves running along the ventral side of their body. I call sea tulips and all similar sea squirts and tunicates invertebrates because while they do share our dorsal nerve chord at one point in their life cycle they lack the vertebrae we wrap around and provide support and articulation for our precious central nervous system. Invertebrate and vertebrate aren't categories within the Linnaean hierarchy but they are handy shorthand labels to bung on animals with and without our handy internal skeleton backbone. Sea tulips, sea squirts, ascidians, tunicates and their free swimming associates the salps, feed on zooplankton, drawing water in through one siphon, passing it over a basket like gill structure and blowing the newly plankton free water out through the other siphon, the plankton staying behind on the gills and being passed into the digestive tract. The free swimming larval stage eventually settles on a hard substrate, gluing itself head first on the benthos. The bulk of the nervous system dissolves and the nutrients are incorporated into other structures as the adult form takes shape, because you don't need a nerve chord or brain or ganglial cluster to suck and blow water all day, every day. I don't know what species this one is. I have some ideas but you have to cut a specimen open and examine its gills to be certain. Australia's sole ascidian taxonomy expert is deeply unpleasant to deal with, and even moreso since they died, so I never bothered seeking their aid in identifying specimens or their mentoriship in learning how to use their arcane literature on the topic. Pyura onnastick is as far as I've ever needed to classify the stalked ascidians for incorporation in ecological models of a system so it's largely moot what this thing is actually called as far as my interest and research is concerned. See more

14.01.2022 Diver Matt's Daily Discovery Date: Two weeks ago Location: Ricketts Point Description: Rock flathead, Platycephalus laevigatus. Rounder in cross section than sand flatheads and tastier than yank flatheads, rock flatheads live in rocky habitats and have flat heads. They lie still until you're almost on top of them, apparently confident of their camouflage, then they're off into the middle distance with some quick flicks of the tail.

13.01.2022 Diver Matt's Daily Discovery Date: 23/05/20 Location: Blairgowrie Description: Purple sausage worm, which sounds like an end result of a game of "Telephone" in an episode of "The Simpsons," which is why latin binomials are so handy in ecology. Myxicola infundibulum is a species of sabellid fan worm and no-one's sure if it's an exotic species in Port Phillip waters because no-one's sure if it's the species we're seeing in the soft sediments. Certainly it looks and acts like ...Myxicola infundibulum and the spread through Port Phillip sediments follows the pattern we expect to see from an exotic species that turned up on a ship from overseas but the money isn't available to study the matter in depth and the story pretty much lies where we left it twenty years ago when the Centre for Research on Introduced Marine Pests fell through. Unlike the other common large sabellids in Port Phillip, which make leathery protective tubes extending beyond the substrate, Myxicola live in a burrow lined with a thick, soft mucous lining. They extend their feeding crown above the sediment surface to catch the hyperbenthic plankton. The radioles of the feeding crown are connected by a palmate membrane absent from most other local feather duster worm species and I suspect this mechanism prevents the animal ingesting sand drawn clear from the sediment/water interface by waves and currents in nearshore environments, but without experimental evidence that's a conjecture on my part based on the coincident structure and habitat. The specimen in the image, and most other specimens encountered nearby, sat proud of the sediment surface in a manner I'd not seen before and while I didn't see it occur I suspect this was caused by the nearby congregation of spider crabs. Certainly the footprints indicated they'd passed through this area and that Myxicola in a nearby area without crab footprints sat in the usual posture with their mucous tube mouth flush to the sediment surface supports this idea. I think the crabs tried to pry the worm out of the burrow by the mucous tube but gave up when the worm kept pushing deeper. With the mucous tube offering little nutritional reward the crabs gave up, moved off and the worms returned to feeding from their newly elevated mucous tube appertures. I have some time lapse footage of the crabs to watch through and I'll be keeping an eye out for exactly that phenomenon to see if I can better support this "just so" explanation for the observation made in this image. Science is a tough task master but by sticking to what you can reliably support it prevents you from cantilevering your ideas out into the unsupportable nonsense so popular among the anti-vax, Plandemic, chemtrails cohorts of our community. See more

13.01.2022 Moar crab action

13.01.2022 Diver Matt's Daily Discovery Date: 9/5/20 Location: Secret spot because I don't want people finding my protostomic friends and catching them at the rate of thirty per person, per day, and eating them, because that's bad for the crab's health and disappointing for the humans because these... Oops. Said too much. Don't want to give away the surprise. Description: Watch and wait for it. Worth your time, I swear.

12.01.2022 Diver Matt's Daily Discovery Date: 16/05/20 Location: Williamstown bassalt shelves Description: Pebble crab, Bellidilia laevis. This wee crab is likely struggling to feed as its first pair of pereopoda, wallking legs, are missing. In crabs the first pereopods are usually chelate, armed with a nipper comprising the dactylus and propodus articles of the articulated limb. Without the dexterity afforded by this pincer structure this crab will struggle to lift food to its mouthparts. It might replace the missing limbs if it has enough reserves to moult but I wouldn't bet on its survival even if I were the betting kind, which I'm not.

12.01.2022 Diver Matt's Daily Discovery Date: Early last year Location: Altona Description: This is the test of a heart urchin. Heart urchins burrow beneath the sediment surface, eating sand and gaining nutrition from the bacteria and fungi adsorbed thereon. Being largely unseen, few people realise how common these echinoderms are but there's I'd put my money on this particular heart urchin, Echinocardium chordatum, as making the single largest contribution to Port Phillip biomass. ... This example is large for the species but heart urchins can get much larger, their size being limited by their ability to move through the sediment rather than structural or predation limitations. They use short, paddle shaped spines on the outside of their test to "row" through the sand and mud, excavating a space in front of them and pushing the sediment behind themselves. And that leads me to a significant difference between the hear urchins and their kina kin. Heart urchins are bilaterally symmetrical, like us. You can only divide them down one axis and come up with roughly equal parts on both sides. Most urchins are radially symmetrical and so long as you divide them in half through the vertical centre you'll end up with the same organs and structures on both sides. Most urchins have no defined front or back but heart urchins do. Even though they lack a head or even a concentration of sense organs where a head would go if they had one, they only ever move in one direction through the sediment and the shape and size of the spins varies from one end of the test to the other, the spines in each area optimised to their role. The test is thin and frangible because the heart urchins are kept safe from most predators through their behaviour. Eagle rays eat lots of them but given their teeth even a test wall as thick as that of urchins on the surface wouldn't save a heart urchin from that crushing fate. Heart urchins, by pushing the sediment around as they travel through it and eat it, provide significant eco-system services for other species, bioturbating the sediment, oxygenating muds and sands to a deeper extent than occurs in their absence. This specimen washed up on Altona beach after a storm and I was lucky to find it intact. I'm more accustomed to finding them while working underwater and the fragile tests rarely make it back to shore intact. The only specimens I have in my collection of marine stuff came ashore when I found them at the very end of a task and had a hand free to keep the test safe from impacts. Those times they've come ashore in a bag or a pocket I ended up with a pile of calcite gravel for my troubles. See more

10.01.2022 A big fish encounter from PT. These sharks always look like they're smiling.

10.01.2022 Diver Matt's Daily Discovery Date: 27/05/20 Location: Beaumaris Description: Nudibranch. I don't know what species. While they're more colourful than terrestrial slugs I don't hold them in much higher regard than those slimy smears of protein.... Nudibranchs do some neat tricks in terms of capturing and using the stinging cells of other organisms but I barely cared enough to snap a picture of this one to share with you. Tambja is pretty enough to warrant some attention and there's a genus called Discodoris, which is awesome on its face for conjuring the image of a funky char-lady but sea-slugs just don't do it for me in the same way most molluscs and any crustacean can. Maybe it's a colour vision thing. See more

09.01.2022 Diver Matt's Daily Discovery Date: 23/05/20 Location: Blairgowrie Description: Colour variant specimen of the sparsely spotted stingaree. When I first saw this animal I thought it was Urolophus cruciatus, the banded stingaree, but close examination showed up the telltale white spots and the characteristic tail length and cross section of Urolophus paucimaculatus, the sparsely spotted stingaree. ... I'd never seen this colour form before but I saw other examples that day, and more standard colour form examples nearby. I've no idea what's going on, here. Is it pigment? Is it abrasion? Only a specimen collected for close examination could yield further information and as I've no intention of getting a barb through the hand and no way to preserve the specimen on the day even if I did have a way of collecting it safely, it will remain a mystery to me. Unless someone reading this can shed some light on the matter or share this post with someone who might. See more

09.01.2022 My take on finding, appreciating and protecting our arthropod overlords.

09.01.2022 Jackie Kerin coming through with more Kororoit goodness.

08.01.2022 Diver Matt's Daily Discovery Date: 15/05/20 Location: Mornington Description: The frilled venus shell, Circomphalus disjecta. This is the most striking bivalve found in local waters. The delicate lamellae often don't remain intact if the dead shell washes up on a beach but this is as near to complete as any speciment I've found. ... The species belongs to the family Veneridae, one of the largest groups of the largest animals among the bivalves. This species lives in coarse sand sediments fed by strong currents. I would need to run some experiments to confirm the hypothesis but I think the lamellae act as an anchoring mechanism when the animal is feeding just below the sediment surface, a situation where the large surface area of the animal's shell could potentially see it sucked out of the sand by the same current that's bringing the plankton it needs to feed on. I knew this species as Callanaitis disjecta in my youth and I'm reminded how many Australian benthic taxa have jumped from one genus to another or become the basis for a new genus in my lifetime. The Australian fauna are highly endemic and we're likely still a long way from finding something approaching taxanomic equilibrium. My books fall out of date regularly but I try to keep up as best I can.

08.01.2022 Repeat performance for the Port Phillip EcoCentre, keeping me in some coin through online marine science content delivery. This time on Zoom and featuring moderated Q & A. Thursday the 23rd April, 0800 GMT

07.01.2022 Diver Matt's Daily Discovery Date: Saturday Location: Super Secret Spot Description: Three of the five rays of the day. While out scouting for the crabregation I saw five species of ray. The short tail stingray and the sparsely spotted stingaree only showed up in the video footage but you can see the other three here.... A common stingaree, a spotted stingaree and a fidler ray. Sharks and rays, also called elasmobranchs because of their slatted gills, hold my attention because of the beautiful range of forms and their unique biology. Living near a waterway where I can see five species in a day (my record is seven) gives me a buzz and I'm always excited to see an example of these cartilaginous species. Sparsely spotted stingarees are the most common elasmobranchs in Port Phillip. Smooth rays are the largest rays, full stop. Spotted stingarees are, for my money, the prettiest rays in Port Phillip and eagle rays are the most elegant and fastest rays in our local waters. Other rays you might encounter in our bay include masked stingarees, circular stingarees, and common skates. I know of two records of manta rays in port phillip waters, one about two weeks ago on the eastern shore and one at Safety Beach in 1990, seen by my friend James. I missed it, that day. In fact, I've yet to see a manta ray anywhere, but the fact that I might see one anytime I duck my head under the sea surface is one of the things I find so fascinating about marine systems. They aren't bordered by intractable barriers the way terrestrial systems are and species sometimes turn up in unusual places simply because nothing got in their way. Sometimes those species are unwell because they're out of their accustomed temperature range, as was the case with an olive Ridley turtle that turned up in my lab at Queenscliff one day, but the fact that we might see a lost yellow eye penguin or a leopard seal with wanderlust swim through the heads at any moment adds an element of potential I find absent when contemplating lakes, rivers, mountains and forests. See more

06.01.2022 Diver Matt's Daily Discovery Date: 2/5/20 Location: St Kilda Description: Dredge spoil. Large numbers of live Fulvia tenuicostata writhe among anoxic mud and shell grit where they've been deposited in the shallows from the output pipe from the dredge working to clear the mouth of the marina. There's no way to dredge a channel without displacing large numbers of benthic organisms and few people care enough about molluscs to try to save their lives once they're cast ashore.... One person who does is Neil Blake, who returned to the site after we'd finished our sampling and attended a virtual meeting about the shell survey we were adding data to. Neil collected a bucket load of the bivalves and returned them to the water and I applaud his efforts. Lovely to work with and make music with you, Neil. See more

05.01.2022 Jackie Kerin, coming through with the local goodness once more. Gulls aren't choosy and gulls are gutsy. Not everyone's idea of breakfast includes the stringy meat and veneomous barb of a stingray but this Pacific gull doesn't care what you think. Gulls aren't the honey badgers of the sea but they aren't softcore, either.

05.01.2022 Diver Matt's Daily Discovery Date: Tomorrow Location: 500m east of Super Secret Spot Description: Because I have an early start and a long day planned for tomorrow here's tomorrow's daily discovery today, or yesterday, or the day before that, depending on when you read this. This is a sea cucumber. I don't know the species because I've never encountered this one before and because I'm not Mark O'Laughlin, Victoria's leading holothurian taxonomist. Successful identificatio...n of previously unseen sea cucumbers requires placing a skin sample under a compound microscope to examine the calcerous spicules found there. The shape of the spicules is usually species specific and the taxonomic literature features pictures of these structures more often than it does of the whole animal because one sea cucumeber looks like any other sea cucumber once you're representing them in black and white line drawings. More accurately, successful identification of a previously unseen sea cucumber requires handing it to Mark O'Laughlin, a volunteer taxonomy specialist I met through the Museum of Victoria. This looks to be a burrowing species as its tube feet were very small and the body tapers, so. I have found specimens of Paracaudina australis in this area in the past but they are, in my experience, fatter and browner than this, but that's where the spicules are so helpful. It doesn't matter if the specimen you're looking at is well fed or starving, recently metamorphosed into the adult form or about to fall off the twig, the spicules offer a consistent marker. I don't know why this specimen appeared on the surface but if I had to bet I'd put my money on it getting dug up by spider crabs that then realised it was a sea cucumber and too tough for them to eat. My son pointed out this one looks like a penis, and that's true enough, but lots of biological structures feature this shape because a tube is an economical use of tissue for housing a gut and some organs or for transporting material from one part of an organism to another. It's probably more apt to state that a penis looks like any other efficient tubular biological structure. See more

04.01.2022 PT found this lovely example of decoration among the decorator crabs. So much camouflage the surge is making walking difficult. I can't be sure but I think there's a crab of the genus Naxia under there, somewhere.

04.01.2022 Matt's Daily Discovery Date: 13/05/20 Location: Portsea Description: A boofa big smooth ray with the biggest barb I've ever seen on its tail. Large Dasyatis brevicaudata usually have two or three barbs on their tail, assuming they still have their tail. About a third of those we brought aboard during the Port Phillip demersal trawl survey in the late 1990s were missing their tail and while some might have lost theirs to orca or other large and fast predators with a taste f...or stingray flesh, I suspect it's more likely they'd been caught by trawlers and returned to the water short their tail due to the sharp knives the deck crew applied to keep themselves safe from the thrashing of a large and distressed animal on a slippery back deck. Because that's what happened to the large specimens that came on board during that survey, further skewing the ratio toward the tailless variety. The barbs of a stingray's tail are serrated (see second image of one I found on a dead ray on the shore in my teens) and the ray applies a sawing motion once the tail contacts whatever's posing the threat they've applied their tail to, maximising the cutting damage and spreading the venom impregnated flesh that covers the barbs through the resulting wound. This leave the threat bleeding and in tremendous pain as the crystalline venom fires the nerve cells in the newly open wound. The violence of this defensive effort often leaves the barb in the wound. The barbs are attached to the tail sufficiently well to allow good stabbage but not so well that the animal is left attached to the attacker if it gets stuck in the wound and they need to get away, so it's common to see a stingray with barbs at various stages of replacement. In this instance, the spines appear to have never been used in defence and the longest of the three I could see without getting too close easily out-spanned my hand. Lovely to see such a large wild animal so close to shore but ample evidence that you shouldn't try to hug one. See more

04.01.2022 Diver Matt's Daily Discovery Date: 1/06/20 Location: Melbourne Seafood Centre Description: A frilled shark. I normally stick to posting about stuff people might stumble across at the beach or while snorkeling in the shallows along our coast but this was too cool not to bring to your attention. ... Frilled sharks are a deep water species of elasmobranch in the order Hexanchiformes, along with all the other sharks with only a single dorsal finb, the six and seven gill sharks. This small specimen turned up in a bin of fish I was processing for the South East Trawl Fishery and was in such good nick that I passed it along to a guy at the MSC who puts aside oddities for the Melbourne Museum ichthyologists. I've never seen a frilled shark in the flesh before and given their deep and dark water habits I'm never likely to see one in the wild. Dead and awaiting preservation in formaldehyde, I was still excited to see this one as I've been reading books about sharks for as long as I've been reading books about Antarctica and every encounter with a new taxa brings about a mental note like a tick in a twitcher's spotting diary. I hope to visit this specimen in the museum collections, one day. See more

02.01.2022 Diver Matt's Daily Discovery Date: 13/05/20 Location: Portsea Description: A honkin' big Whitley's skate, Dipturus whitleyi. This is only the second live specimen of this species I've seen while underwater and it's definitely the largest, somewhere up at the upper end of the size range, listed in the books as around 1.7m nose to tail tip. ... Skates are different to stingrays and stingarees in the absence of a sting, the flatness of the tail, which is mostly caudal keel, the two dorsal fins on the tail, and they're spelt differently. While they have rough skin and spiny tubercles on their tails they don't have much going on in the way of obvious defensive mechanisms, they swim slowly and unless they're on their accustomed muddy habitat they aren't well camouflaged. As I suspect is also the case with fiddler rays, I think most skates must taste pretty bad, though they are offered for sale in British chip shops. I spent a while observing this one and was tickled to see it "walking" on its ventral fins. When the skate moved at slow speeds across the benthos the ventral fins curled underneath the disc formed by the pectoral fins and pushed the ray forward. Sometimes this continued for several "steps," moving the animal a body length or so forward. Other times it acted as a prelude to the animal flapping its pectoral fins and swimming just clear of the sediment. I suspect this speciment came into the brightly lit, yellow sand shallows to take advantage of the annual spider crab moult and that it will return to deeper waters and muddier sediments once the banquet comes to an end. See more

01.01.2022 Weeeeeeee! Time lapse crabs, going about their crabby business at super-speed.

01.01.2022 Diver Matt's Daily Discovery Date: Yesterday Location: Super Secret Spot Description: The pros and cons of moulting. Arthropods rely on their jointed exoskeleton for protection and support. The hard outer layer protects them from predators that would readily munch them if they were as soft bodied as a worm, and offer anchor points and insertion points against which their muscles can leverage their limbs....Continue reading