A Very Unusual Saturday

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On the morning of Saturday the 4th of August, I had my heart set on a quiet day. There’d be a few late nights recently and I never really sleep well over here so I was loving the idea of a day of laziness. By around 3:30pm that day, this is where I was at. Needless to say my day didn’t go as planned….

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It was an strange day guys

We got notified a bit before midday that a mother and calf cetacean had washed up dead at Kleinbrak, fifteen minutes from Mossel Bay. By midday we were deciding to take the interns over to see it. Things got more interesting when we learnt the species. It was a True’s Beaked Whale, a species so rarely that my reference guide prefaced every section on it with “Little is known…”.

True’s Beaked Whale

These species are super rare because they live in the open ocean. They’re only rarely spotted when they surface to breathe or strand on a beach. They’ve been observed of the east coast of North America, off the coast on the United Kingdom, off the coast of Northern and Southern Africa and off the south coast of Australia but we have no idea if thee are isolated populations or part of a larger group. They’re known to dive to depths of around 3000 meters. Little is known about their population numbers or home range. The guide I read about them says of their diet, “they are presumed to eat squid”.

What did I Learn?

Seeing Cetaceans at a distance or on a documentary doesn’t prepare you for the reality. It was somewhat surreal being able to see one up close and touch it. It was incredible to see how evolution has designed these animals.

When the first cuts were made into the animal, I first noticed the thick while layer of blubber. This layer several centimetres thick and covered the entire body. Clearly it’s adapted for life in extremely cold water, Once we cut past the blubber we could see first hand how powerful these animals are.

whale blubber
Blubber insulates the whale in cold waters

Cutting through to the chest cavity meant going through dense red muscle tissue that was in some places was as thick as my hand is long. This means it had the power to dive deep and swim through the open ocean. There was one surprising aspect of its biology however, it had strangely small lungs for an animal that spends long periods of time underwater

As I learnt later its lungs aren’t so much for holding air as for moving oxygen into their muscles for storage. Their muscle tissue is dark red, almost black because they have extremely high levels of myoglobin, a molecule responsible for storing oxygen.

dark muscle tissue
High levels of myoglobin make the whales muscle look almost black

The Whales store as much oxygen as they can in their huge muscular body while breathing at the surface and then dive for long periods of time where oxygen is released from their muscles slowly. This actually makes a lot of sense for deep dives. Under the crushing pressure of a deep water dive, a gas filled space like a lung would be compressed and potentially damaged, So having smaller lungs that don’t need to be filled to capacity is a massive bonus to these mysterious animals.

So why did it die?

Well I wish I could give you a definitive answer on that one. On the day, we removed its lungs, digestive system and numerous other samples for analysis. The first stomach (cetacea have four) looked extremely full. Later analysis showed that what we thought was a large full stomach was all due to inflammation of the inner lining. There were a few squid beaks in there and some parasites but it was clear this animal hadn’t fed in a long time. I may do a follow up post to this if and when I learn more…

Tomasz Pedlow

 

You made me ink!!

So one of my favourite shifts here in South Africa is taking the interns to survey the tide pools. During these shifts, we head to one of several study sites at low tide. From there we lay out a transect rope that runs from the low tide up to the high tide mark. Every five meters we lay out a 1m by 1m square quadrat and record all the invertebrates we see there. Every shift we get data on how the invertebrate community changes depending on position in the intertidal zone.

Why?

Well the purpose is long-term monitoring. The intertidal zone is a pretty extreme place to live. Animals living here spend half their life living underwater dealing with all the usual difficulties of marine life and then the other half of the day exposed to air, an environment they’re not meant for, a place where they’re exposed to extreme temperature, they risk dying out and they can’t readily get food. Living in an extreme environment means that the ecosystem is likely to respond to additional stressers quickly. Changes in the temperature, water quality and human harvesting of species will show up in the data quickly. Its a great way to monitor the health of the local ocean and presents a great way to teach our interns about evolutionary adaptions in the marine environment. We find a lot of cool stuff on our shifts but by far my favourite is the Tuberculated Cuttlefish.

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A tuberculated cuttlefish

Tuberculated Cuttlefish

These little guys grow to about eight centimetres long. They spend their entire lives living in the intertidal zone and are believed to feed on shrimp although their precise diet isn’t fully understood. They’re very clearly adapted to the intertidal zone too. Their eight arms are short and stubby with a slight webbing in-between. This is much better for moving around all the small rock-pools and maneuvering your way through tight gaps between rocks. They still have longer tentacles that they use for hunting. But whats really cool is that their skin.

Camoflage

Its been a fairly regular occurrence on tide shifts that we’ll be counting the species we see and all of a sudden realize there has been a cuttlefish right next to one of us that has gone unnoticed for ten or so minutes. This is because cuttlefish, like most cephalopods have very special skin. Their skin contains special cells called chromatophores, iridophores and leucophores that the cuttlefish can use for camoflage. Chromatophores are little pigment sacs with muscle around the rim, by contracting or relaxing the muscle, more or less pigment is seen. The Cuttlefish’s skin is covered in millions of these cells. that are controlled directly by the nervous system. This means that a cuttlefish can change colour at the speed of thought!!!

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Like this. but cooler 😛 

Iridophores and More

These are where it gets really cool. Chromatophores are typically red, yellow or brown. While they can combine these, that still doesnt let them mimic all colours. Iridophores are what cover the rest. Iridophores are stacks of really thin cells that can reflect light at different wave-lengths. This means if viewed from one angle they might appear blue, from another they might appear red.

Leucophores are the last piece of the puzzle. These cells scatter light and therefore appear white. Just like the others, the cephalopod has control over these cells and its thought they use them to increase or decrease the intensity of the colour they’re trying to display. Its the combination of these cells that allow cuttlefish and other cephalopods to camoflage so well.

I’m trying to think of an eloquent way to wrap this post up but honestly, I just wanted to share how flippen cool these animals and their weird skin are. I hope you all found it as fascinating as I do. Here is a videos of a tuberculated cuttlefish to finish on 😀

 

Catchya next time 🙂

Tomasz Pedlow

 

The ROV in action

We’ve been doing surveys of a near-shore reef to test out the Trident ROV’s new potential as a research tool. Heres an example of what we see. The big schools of fish you’re seeing are Blacktail (with a black dot near the tail) and Strepie.

Whats Shark Research? Part Two

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A chum trip in full swing (photo courtesy of the Oceans Research media interns)

Hi Everyone.

So last time I went into more detail then I initially planned explaining the ethics of chumming and bait roping. Today I wanted to explain the adrenaline rush that is a chum trip. Chum trip is the term for our boat shifts assessing the shark population. I’ll set the scene.

It’s a quiet morning, the wind is down, the sky is covered in a smattering of grey clouds with random patches of blue sky. You can hear the calls of the seals sounding something like a mix between a goat and Chewbacca, the repetitive lapping of the water against the boat, the random conversation of the interns. It seems like a calm relaxing day, but you’re intensely focused. The noise is all background chatter to you as you watch the Tuna head at the end of your bait rope bobbing in the water. You know at any second, the calm could be shattered. You’re standing on a little platform on the side of the boat with a metal railing against your legs holding the bait rope in two hands.

Suddenly you notice a change in the water. It’s bordering on imperceptible, you don’t even really have time to fully realize whats changed. But in an instant, you know whats coming. In that fraction of a second you yank hard on the rope as the water in front of you explodes. The tuna head leaves the water just as a great white shark bursts from the water a meter or so from you. In under a second you can go from staring at calm flat water to staring one on of the oceans top predators with its body from a half out of the water as it launches for your bait.

Its not always this intense, but this is a recount of one particularly memorable encounter I had with a white shark on a chum trips was like with Oceans Research. What I’m doing with the bait rope is a key part of our white shark population monitoring. It lures nearby sharks to the surface and hopefully close enough to record data on them. My goal is to make sure the sharks don’t get the baits.

What Happens When the Sharks Arrive?

When the first shark comes to the surface the first job falls to an intern working the camera. They’re job is to get a clear photo of the sharks fin for later identification. There are certain types of pigmentation on the sharks fin that persist throughout its life making them a useful method for identification. You can see what I’m talking about below.

Shark fins
On the left you can see an example of white pigmentation, on the right you can see black pigmentation spots (image courtesy of Oceans Research

We never officially record a shark on our data sheets until we get the first photo of it. We always aim to get the best fin shots possible, but sharks don’t always play ball. So we end up taking a lot of photos.

Before we even get the photo, my minds already working. This is likely to be our first recorded shark so I need to be recognize it. In those flashes of time I look first for identifying markers. Scratches, scars, hooks in the mouth and  strange coloration are all things I need to be able to recognize a shark long term.

This helps when you’re up to shark eleven or twelve for a shift and suddenly, your spotters call out “shark threes back, and shark seven”. As you can imagine, it gets pretty fast paced at times.

What happens when we get a photo?

Thats when the shouting starts and the intern recording data gets anxious.

“175-224”,

“absent all fin deformities and amputations”,

“Photos one to five are shark one”

“Video one is shark one”,

The person on data likely gets this yelled at them all at once from three different people. The first parts come from the field specialist on shift, its size class information and whether or not the shark has any significant damage to the fins. It’ll change depending on the shark. The third bit comes from the camera person at the front of the boat, so we know later which photos are of which shark. The last bit comes from the person manning the GoPro pole. What this is a long metal pole with a platform at the bottom and a gopro attached to the platform. We use this to work out a white sharks gender.

The only way to tell a white sharks gender is to look for the presence or absence of claspers on the sharks underside near the caudal fin. Claspers means it s a male, no claspers mean its a female. The Gopro pole lets us film the underside of the shark.

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Male Shark                                                                       Female Shark

Sometimes these shifts can be incredibly fast paced, sometimes not, it depends on the sharks. But one thing that stays constant is the need for spotters. This is a job for two people who stand up on the observation platform and watch for sharks. As the bait roper, I rely heavily on these two. When I have the bait in the water, my focus narrows to about a meter square patch of water with the bait in the middle. I need the spotters calling out to me where sharks are, if they’re coming at the bait, what direction they’re coming from and how far out they are. Depending on the weather conditions, water visibility can range anywhere from one meter to six meters, So the spotters can definitely have a tough job.

The last job was touched on in the previous post, the chummer.  The intern on chum is mixing a block of mashed up pilchard parts with sea water and pouring scoops into the water, its not glamorous but its important to attract sharks. It creates a scent trail (roughly 150m) as its carried away by the water that nearby sharks will be curious about it and come to investigate.

These shifts run in four hour blocks, twice a day (if the weathers right). The data from this trip has been the backbone of a PhD thesis and has lead several interesting discoveries.

What have we Learnt?

There has been a lot of really interesting science to come out of the chum trip data from Mossel Bay. Almost nothing was known about the sharks that lived there before this research. Now we know that the population is exclusively juvenile sharks and that they must leave the bay when they’re past a certain age. We now know the population is largely female with an increase in males during the winter. This seems to concur with other research around the world that suggests great white shark populations usually display strong gender segregation. In my opinion, one of the more interesting finds is that they utilize different habitats at different times of the year. In Summer and Autumn, they tend to congregate in coastal waters off the coast of Grootbrak and Kleinbrak, two rivers that enter Mossel Bay. In winter they congregate at Seal Island and in Spring they congregate at at Seal Island and another coastal site called Hartenbos. This seems to be likely due to changes in prey abundance throughout the year.

Its the habitat usage patterns like this that make me wonder whether similar research could be useful in Western Australia.

 

Tomasz Pedlow