Marine Life & Conservation Blogs
Creature Feature: The Houndsharks
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 a few of the species from the houndshark family. The houndsharks, a.k.a. Triakidae, are a family of around 45 species. In this Creature Feature we’ll be looking at the Leopard Shark and Common Smoothhound.
Houndsharks are known for having two large, spineless dorsal fins, an anal fin and oval-shaped eyes with nictating eyelids. Animals with nictating eyelids have a third, clear, eyelid. This protects the eye whilst still allowing the houndsharks to be able to see. Houndsharks are small to medium in size, with adults ranging from around 37cm to 220cm. They’re one of the largest families of sharks. They are distributed throughout the world in warm and temperate waters. They predominantly feed on fish and invertebrates on the seafloor and in midwater.
Leopard Shark
Confusingly named after a feline species, the Leopard Shark does indeed belong to the houndshark family. Its name comes from the unique saddle marks and spots that cover the species, resembling those of a leopard (as seen in the banner image).
It is one of the most common sharks found along the Pacific coast of North America. They are active, strong-swimming sharks. Sometimes spotted resting on sand among rocks. Leopard Sharks form large, nomadic schools with different species (such as the North Pacific Spiny Dogfish and Bat Rays.
The species is classified as Least Concern on the IUCN Red List of Threatened Species. Leopard Sharks are primarily caught by recreational anglers. But they are also taken as incidental catch in commercial fisheries. They are generally well managed by commercial fisheries. They are also popular in aquariums due to their distinctive markings and hardiness. The poaching of pups for the aquarium trade has been a significant problem.
SCIENTIFIC NAME: Triakis semifasciata
FAMILY: Triakidae (Houndsharks)
MAXIMUM SIZE: 180cm
DIET: Small sharks eat crabs, the siphons off clams and worms from the seafloor. Large sharks may eat fishes and even other smaller sharks.
DISTRIBUTION: Northeast Pacific – west coast of the United States from southern Washington to the Gulf of California (Mexico).
HABITAT: Cool to warm waters. Most common on or near the seabed in bays and estuaries. Females give birth in water less than 1m deep.
CONSERVATION STATUS:
Common Smoothhound
A medium-sized, unspotted houndshark. The Common Smoothhound is often confused with the Starry Smoothhound which usually has white spots along its back. It’s also often confused with the Tope Shark. Smoothounds are so called because they will gather in large numbers, like a pack of dogs.
The Common Smoothhound is classified as globally Endangered on the IUCN Red List of Threatened Species. The species is classed as Vulnerable in Europe. It is targeted by fisheries across its range, both for sport and in commercial fisheries. The species is caught for food across the Mediterranean, European and West African fisheries. There is often confusion between the Common Smoothhound and Starry Smoothhound. Starry Smoothounds often doesn’t have any stars/spots. So they are very similar in appearance. Genetic analysis is the most reliable way to distinguish smoothhounds.
SCIENTIFIC NAME: Mustelus mustelus
FAMILY: Triakidae (Houndsharks)
MAXIMUM SIZE: 175cm
DIET: Mainly crustaceans. Also cephalopods and bony fishes.
DISTRIBUTION: Temperate east Atlantic. UK to the Mediterranean, Morocco down to South Africa and the Indian Ocean coast.
HABITAT: Continental shelves and upper slopes. Usually 5-50m, but occasionally down to at least 800m.
CONSERVATION STATUS:
For more amazing facts about sharks and what you can do to help the Shark Trust protect them visit the Shark Trust website by clicking here.
Banner Image – ©Barbar Ash via Shutterstock
Image of Leopard Shark – ©ScubaZoo
Maps – ©Chris_huh, via Wikimedia Commons
Smoothound Illustration – ©Marc Dando
Marine Life & Conservation Blogs
Creature Feature: Dusky Shark
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.
Marine Life & Conservation Blogs
Creature Feature: Undulate Ray
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
-
News3 months ago
Hone your underwater photography skills with Alphamarine Photography at Red Sea Diving Safari in March
-
News3 months ago
Capturing Critters in Lembeh Underwater Photography Workshop 2024: Event Roundup
-
Marine Life & Conservation Blogs2 months ago
Creature Feature: Swell Sharks
-
Blogs2 months ago
Murex Resorts: Passport to Paradise!
-
Blogs2 months ago
Diver Discovering Whale Skeletons Beneath Ice Judged World’s Best Underwater Photograph
-
Marine Life & Conservation2 months ago
Save the Manatee Club launches brand new webcams at Silver Springs State Park, Florida
-
Gear Reviews3 months ago
Gear Review: Oceanic+ Dive Housing for iPhone
-
Gear Reviews2 weeks ago
GEAR REVIEW – Revolutionising Diving Comfort: The Sharkskin T2 Chillproof Suit