Marine Life & Conservation Blogs
Shark Personalities of the Month
It has been a wonderful two weeks at Seal Island with such settled weather recently. We have been fortunate to have a number of days at the island with stunningly clear blue water – which has given us visibility of up to 15m at times! I have really enjoyed being able to see the reef below us and watch the behaviours of the white sharks as they have interacted with one another around the boat.
Interestingly this month we have been seeing not just two sharks at a time by the boat but up to FOUR individuals swimming together. It is very rare to see such interactions here, as usually these sharks go to great lengths to avoid each other around the bait. During one trip last week I was thrilled to witness a number of occasions with three sharks swimming around the boat, almost snout to tail and calmly swimming along as a procession of beautiful sharks. On the occasion that we saw four sharks together we really couldn’t believe our luck and both the guests and crew alike knew it was something very special to see. Two of the sharks were so close to each other that their pectoral fins were overlapping at times as they swam along together. It was magical to witness and a moment I will never forget.
The clear water has also given me the opportunity to experience the unique behaviours and personalities of the different sharks we have come to know well so far this season. Each shark has such a distinct personality and exhibits very specific behaviours around the boat. This month we have continued to see Zamalek and he is still being adorable and melting everyone’s hearts with his continual right turns close to the cage. He is such a relaxed shark and still spends the majority of his time calmly circling the cage closely and occasionally veering off course to examine the baits. He is such a joy for our divers to see and is one of those sharks that remain with us for a long time when he visits. Having said how calm he is we have however also discovered his livelier side and his interest in our decoy seal. As kitnip is to a cat, the decoy seal is to Zamalek! He absolutely adores our fake seal and we have to be very careful putting the decoy in the water when he is with us. It really switches him on to pursuit mode and he chases it constantly until he manages to get hold of it. Even then he tries repeatedly to grasp it. I have not seen a shark that keen on our decoy for a long time indeed and it certainly demonstrates a different side to Zamalek’s personality.
Another shark that is also very unique in his behaviour this month is Pinkie, the 3.1m male shark. This shark is so named because of a pink rosette on his dorsal fin and he is one of our more dominant sharks. White shark dominance is based on hierarchy and it is normal for us to see that the smaller sharks give way immediately to the larger sharks around the boat. Pinkie however appears to be unaware of his small size and is very dominant around both the smaller and larger sharks. On a number of occasions I have seen him wait until the very last moment to give way to our larger female sharks in the 3.7-3.9m size range. On more than one occasion I have expected him to receive a warning bite from these females as he refuses to give way and is positioned right in front of their mouths. They are extremely tolerant however, and let Pinkie get away with behaving so brazenly. He is going to be quite formidable when he is larger if he remains so dominant and confident. In contrast to Pinkie’s lack of submissive behaviour we have seen a gorgeous 2.0m white shark at the island last week that had quite the surprise and was understandably very submissive. This shark was approaching the top bait one day, which consisted of a tuna head that was quite frankly larger than the shark’s entire head and he followed it closely with his snout. I assume he couldn’t see around the bait as on the other side was our large 3.7m female Magnoona, who is very dominant and was also approaching the bait. The little shark had the shock of his life as he rounded the bait and was faced with swimming unknowingly into Magnoona’s face. Magnoona was calm and tolerant as always and the small shark practically leapt out of the water and swam incredibly fast to remove himself from the situation. I was delighted to see he made a cautious return later.
Magnoona has also captured me with her behaviour this month as she can be very relaxed or very lively. She veers from one extreme to the other within and between trips and when she is lively she keeps us on our toes. She is quick to approach the bait and often from depth to gain more speed. She is also very agile and executes tight turns close to the boat as she pursues her bait of choice. She mostly focuses on the top bait and is a shark that both our divers and boat-based guests enjoy because of the time she spends up at the surface with us. When she is feeling calm she is quite the opposite and cruises extremely slowly around the boat at the surface. She literally brought a tear to my eye the other day with the behaviour I describe below and because of that moment I am just a little bit in love with this lady. When Magnoona was approaching the bottom bait recently she took hold of it gently and as she then moved forwards the top bait rope drifted into her mouth. From previous observations of sharks when they take hold of the bait I would have expected a fairly strong reaction to finding a rope in her mouth. However… in Magnoona’s surprise she spat the bottom bait out and remained calm. She ever so slowly and gently twisted her head from side to side to remove the top bait rope from her mouth. Unfortunately all she managed to do was flip the top bait over her head and so had the rope around her snout. Magnoona was utterly unfazed by this and just calmly hung there as she assessed her situation and slowly tilted her head to the side as Poenas removed the rope and she went on her way. We were mesmerized by her behaviour and just how gentle she was in her approach. These animals really are incredible and continue to surprise me daily with their intelligence and gentle nature.
It has been an experience of a lifetime observing another side to the sharks’ behaviour recently; their incredible predatory activity. The best is yet to come!
To find out more about the sharks of False Bay, visit www.apexpredators.com.
In this series, the Shark Trust will be sharing amazing facts about different species of sharks and what you can do to help protect them.
This month we’re taking a look at the Dusky Shark, a highly migratory species with a particularly slow growth rate and late age at maturity.
Dusky sharks are one of the largest species within the Carcharhinus genus, generally measuring 3 metres total length but able to reach up to 4.2 metres. They are grey to grey-brown on their dorsal side and their fins usually have dusky margins, with the darkest tips on the caudal fin.
Dusky Sharks can often be confused with other species of the Carcharhinus genus, particularly the Galapagos Shark (Carcharhinus galapagensis). They have very similar external morphology, so it can be easier to ID to species level by taking location into account as the two species occupy very different ecological niches – Galapagos Sharks prefer offshore seamounts and islets, whilst duskies prefer continental margins.
Hybridisation:
A 2019 study found that Dusky Sharks are hybridising with Galapagos Sharks on the Eastern Tropical Pacific (Pazmiño et al., 2019). Hybridisation is when an animal breeds with an individual of another species to produce offspring (a hybrid). Hybrids are often infertile, but this study found that the hybrids were able to produce second generation hybrids!
Long distance swimmers:
Dusky sharks are highly mobile species, undertaking long migrations to stay in warm waters throughout the winter. In the Northern Hemisphere, they head towards the poles in the summer and return southwards towards the equator in winter. The longest distance recorded was 2000 nautical miles!
Very slow to mature and reproduce:
The Dusky Shark are both targeted and caught as bycatch globally. We already know that elasmobranchs are inherently slow reproducers which means that they are heavily impacted by overfishing; it takes them so long to recover that they cannot keep up with the rate at which they are being fished. Dusky Sharks are particularly slow to reproduce – females are only ready to start breeding at roughly 20 years old, their gestation periods can last up to 22 months, and they only give birth every two to three years. This makes duskies one of the most vulnerable of all shark species.
The Dusky Shark is now listed on Appendix II of the Convention on the Conservation of Migratory Species (CMS), but further action is required to protect this important species.
Scientific Name: Carcharhinus obscurus
Family: Carcharhinidae
Maximum Size: 420cm (Total Length)
Diet: Bony fishes, cephalopods, can also eat crustaceans, and small sharks, skates and rays
Distribution: Patchy distribution in tropical and warm temperate seas; Atlantic, Indo-Pacific and Mediterranean.
Habitat: Ranges from inshore waters out to the edge of the continental shelf.
Conservation status: Endangered.
For more great shark information and conservation visit the Shark Trust Website
Images: Andy Murch
Diana A. Pazmiño, Lynne van Herderden, Colin A. Simpfendorfer, Claudia Junge, Stephen C. Donnellan, E. Mauricio Hoyos-Padilla, Clinton A.J. Duffy, Charlie Huveneers, Bronwyn M. Gillanders, Paul A. Butcher, Gregory E. Maes. (2019). Introgressive hybridisation between two widespread sharks in the east Pacific region, Molecular Phylogenetics and Evolution 136(119-127), https://doi.org/10.1016/j.ympev.2019.04.013.
In this series, the Shark Trust will be sharing amazing facts about different species of sharks and what you can do to help protect them.
This month we’re looking at the Undulate Ray. Easily identified by its beautiful, ornate pattern, the Undulate Ray gets its name from the undulating patterns of lines and spots on its dorsal side.
This skate is usually found on sandy or muddy sea floors, down to about 200 m deep, although it is more commonly found shallower. They can grow up to 90 cm total length. Depending on the size of the individual, their diet can range from shrimps to crabs.
Although sometimes called the Undulate Ray, this is actually a species of skate, meaning that, as all true skates do, they lay eggs. The eggs are contained in keratin eggcases – the same material that our hair and nails are made up of! These eggcases are also commonly called mermaid’s purses and can be found washed up on beaches all around the UK. If you find one, be sure to take a picture and upload your find to the Great Eggcase Hunt – the Shark Trust’s flagship citizen science project.
It is worth noting that on the south coasts, these eggcases can be confused with those of the Spotted Ray, especially as they look very similar and the ranges overlap, so we sometimes informally refer to them as ‘Spundulates’.
Scientific Name: Raja undulata
Family: Rajidae
Maximum Size: 90cm (total length)
Diet: shrimps and crabs
Distribution: found around the eastern Atlantic and in the Mediterranean Sea.
Habitat: shelf waters down to 200m deep.
Conservation Status : As a commercially exploited species, the Undulate Ray is a recovering species in some areas. The good thing is that they have some of the most comprehensive management measures of almost any elasmobranch species, with both minimum and maximum landing sizes as well as a closed season. Additionally, targeting is entirely prohibited in some areas. They are also often caught as bycatch in various fisheries – in some areas they can be landed whilst in others they must be discarded.
IUCN Red List Status: Endangered
For more great shark information and conservation visit the Shark Trust Website
Image Credits: Banner – Sheila Openshaw; Illustration – Marc Dando
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