Creature Feature: Whitetip Reef Shark

Our shark adventure continues in Australia as we learn about the Whitetip Reef Shark (Triaenadon obesus). As you might guess, Whitetip Reef Sharks have distinct white coloration on the tips of many of their fins. Whitetips have slender bodies that help them move swiftly throughout reef structures. These sharks are 5.3 feet long on average, but have been reported as large as 7 feet.

You will find these sharks during the day lounging around in caves and on sandy bottoms throughout coral reef habitats. They are known to stay close to home and come back to the same resting area each day. They don’t mind sharing their space with other Whitetips and you can even see masses of these reef sharks lying on top of each other.

Whitetips are most active and feed at night. They eat octopus and crustaceans and some bony fishes that you would find close to coral structures. They search for their prey along the benthos (bottom). Once Whitetips find their prey they will chase it until caught, even pursuing prey into small crevices throughout the coral. The slender body, tough skin, and eye ridges help protect this shark while hunting in tight places.

Join us next week as we look at sharks who live in colder waters.

Edited by Felicia Van Stolk

Photography:  Jeff Rotman and Ron and Valerie Taylor courtesy of ARKIVE

Creature Feature: Bronze Whaler

Today’s featured creature is a neat shark that you might not have heard of before. The Bronze Whaler Shark (Carcharhinus brachyurus) is found worldwide in warm, temperate, and subtropical waters. Although this species is found worldwide and are considered to be relatively common, their populations numbers are often misreported. Researched chalk this up to a case of mistaken identity. Bronze Whalers are frequently misidentified as Dusky Sharks (C. obscurus). Though they are very similar in appearance, there are a few subtle features that can help to differentiate between these two species. One distinction to look out for is the finely serrated, and slanted upper teeth of the Dusky Shark. In case you don’t want to get close enough to a shark to examine the teeth (understandable!) the Dusky Shark is also different from the Bronze Whaler in its lack of any distinctive markings on the body as well as the lack of a dorsal ridge. To learn more about Dusky Sharks click here.

The Bronze Whaler Shark typically inhabits shallow waters like those found in estuaries. The maximum depth at which these sharks have been recorded is 328 feet, though they could possibly be deeper. While swimming around as individuals or in larger aggregating groups, they will feed on squid, octopus, fish like sardines, and even rays.

This species is considered Near Threatened on the IUCN Red List. These sharks are usually caught in long lines, and gill nets as bycatch – in some areas, they are even fished specifically for their meat. Bronze Whaler Shark nurseries can be highly influenced by coastal development and run-off pollution. Like with most young animals, their growth and development can be impacted by disturbances to their habitats and dangerous pollution, which is why it is always important for us to do our parts to reduce our waste and our footprint as much as we can!

References:
Edited by KC O’Shea
Photography: David Fleetham and Doug Perrine courtesy of ARKIVE 
Duffy, C. & Gordon, I. (SSG Australia & Oceania Regional Workshop, March 2003) 2003.Carcharhinus brachyurus. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 25 August 2015
http://www.flmnh.ufl.edu/fish/gallery/Descript/narrowtoothshark/narrowtoothshark.html

Creature Feature: Hooded Carpet Shark

Throughout the year we have discussed a variety of interesting shark species and some of the positive and negative impacts of human activity on sharks. Today we are going to focus on a shark that is located off the coast of Papua New Guinea. The Hooded Carpet Shark (Hemiscyllium strahani) is a really small shark, reaching just over 2.5 feet in length.

You can find this species hanging out in coral beds up to 60 feet deep. L ittle is known about population dynamics and the biology of this shark. What is known is that they are nocturnal, so they spend their days safely snuggled in crevices of the coral and at night they come out to feed. With a species that we know so little about, we may have important questions. What are some of the issues that face this species? How can we help?

This is a beautiful shark that is pretty hardy and is a popular specimen in both private and public aquariums. Aquariums are a great way for people around the world to learn about different organisms but if you have a home aquarium, it is important to make sure you know where your fish came from. Were they caught in the wild or breed in captivity? This article may provide some helpful information about sustainable aquariums and best practices. http://www.alive.com/lifestyle/eco-friendly-aquariums/

One of the most pressing issues that faces the Hooded Carpet Shark is habitat destruction through high pollutants in the water, but there are ways that you can help. Just because the impacted habitat is as far away as New Guinea doesn’t mean that we can’t have an impact on the health of the water. You don’t even need to buy a plane ticket! In your own home, you can make a difference by using phosphate-free soaps and detergents. Phosphates and nitrates are nutrients that are naturally found in the environment, which is good, but it is possible to have too much of a good thing. At high levels, these nutrients turn into pollutants, causing algae blooms and other chemical imbalances within the water. By reducing the amount of phosphates coming into the water from non-natural sources, we can help protect the Hooded Carpet Shark’s unique habitat.

Do you have a great way to reduce pollutants? Leave a comment below to let us know!

References:

Edited by KC O’Shea

Photography: Andre Seale courtesy of ARKIVE

Heupel, M.R. & Kyne, P.M. (SSG Australia & Oceania Regional Workshop, March 2003) 2003. Hemiscyllium strahani. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 30 July 2015.

http://www.fishbase.se/summary/Hemiscyllium-strahani.html

Creature Feature: Coral Catshark

When discussing deep sea sharks in previous posts, we acknowledge that little is known about them. The deep, dark, and hard to reach places of the ocean present a challenge to researchers that wish to observe and study them in their natural habitats. However, even sharks that live closer to the surface can be difficult to research! Habitats within the photic zone have their own set of challenges to contend with. Scientists are constantly innovating and refining techniques to study these fascinating creatures in their natural habitat. This week’s featured creature is yet another hard-to-study shark, the Coral Catshark (Atelomycterus marmoratus).

What we do know is that it is a common and abundant shark that lives in the shallows and within crevices of coral reefs in the Indo-Western Pacific. Like most catsharks, it has elongated and cat-like eyes. It has a slender body only reaching about 2.3 feet long. A beautiful coloration on this shark with saddle markings that have black spots which forms bar marks that bonds the saddles and large white spots. This shark is oviparous (egg laying) and lays pairs of egg-cases, once or twice per month. During the breeding season, 44-52 baby Coral Catsharks can be hatched. They are also harvested, though not for food. Because the Coral Catshark is so visually appealing and can adapt and hatch well in captivity, they are very popular home aquarium sharks.

Join us next week as we look at a shark that we can find right here in the San Francisco Bay.

References:
Edited by KC O’Shea
Photography: Pictures from ARKIVE  Steve Drogin and Wolfgang Polzer 
White, W.T. (SSG Australia & Oceania Regional Workshop, March 2003) 2003. Atelomycterus marmoratus. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 08 July 2015.
http://species-identification.org/species.php?species_group=sharks&id=325&menuentry=soorten

Creature Feature: Frilled Shark

For those of us that dwell above the surf, deep sea creatures can appear truly bizarre and other-worldly – some have even served as inspirations for creatures in science-fiction films! Which makes me think that perhaps no one has told Mr. Spielberg about the Frilled Shark (Chlamydoselachus anguineus). This rare shark’s serpentine body has been known to reach a maximum length of 6.4ft. Even with its snakey body, the creep-factor doesn’t stop there. It has a lizard-like face, behind which it has 6 frilly-edged gills. Unlike most fish, the first gill slit opens continuously across the throat. As if that wasn’t freaky enough, it has around 3 hundred trident shaped teeth arranged in 25 clustered rows.  Check out the video and try to contain your heebie-jeebies.

In the deep sea there are many stresses on the organisms that live there. First, it is hard work to swim at depth with the pressure of all that water pushing against the body. Then there is the difficulty of finding food, due to sparseness and lack of light. How does this strange shark cope?

While it is difficult to know all of the habits and adaptations of deep sea creatures, scientists have made very helpful observations and are always learning more. By looking inside the body of the frilled shark, we know that special oils inside the liver help it to maintain neutral buoyancy at great depths. This allows them to hover and to use their back fins for propulsion and even possibly for striking, much like a snake. Frilled Sharks eat primarily squid, though they have been known to eat other types of deep sea fish and even not-so-deep-sea sharks. It seems to have a number of adaptations for dealing with hard to find food in the Deep. Based on the stomach contents, scientists have determined that these sharks will venture well above the bottom of the sea to find food. They also have an especially sensitive lateral line, allowing them to pick up on even the tiniest vibrations made by prey.

One of the most amazing aspects of this shark is it’s unbelievably long gestation period. If you ask your parents, you’ll find out that your own gestation period (which is the amount of time you spent growing inside your mother) was around 9 months. That’s three quarters of a year, which is a very long time to carry a growing person. It doesn’t seem so long though, when you compare that to the whopping 42 month gestation period of the Frilled Shark. That is 3.5 YEARS! It seems that things move a lot slower at great depths, with low temperatures and high pressure. Growing little sharks is no different!

Join us next week as we talk about another deep sea shark.

References:

Edited by KC O’Shea

Photography Kelvin Aitken 

http://www.iucnredlist.org/details/41794/0

http://www.elasmo-research.org/education/ecology/deepsea-frilled_shark.htm

http://www.discovery.com/tv-shows/shark-week/videos/alien-sharks-the-frilled-shark/

http://www.animalplanet.com/tv-shows/weird-true-and-freaky/videos/frilled-shark-prehistoric-animal-f/

Creature Feature: Blue Shark

Today we are going to discuss one of the many species of pelagic shark. First you may ask, what does pelagic mean? Simply put, pelagic just means that the organism in question lives in open water, not too close to shore. But the ocean is a big and varied habitat, so scientists decided to distinguish between two different categories of pelagic fish. There are coastal pelagic fish which tend to live in sunlit waters above the area surrounding large landmasses where the sea is shallow compared to the open ocean – an area known as the continental shelf. Then there are oceanic pelagic fish which prefer to live in waters below the continental shelf. Some species can inhabit both the oceanic and coastal pelagic zones because of the changing stages of their life cycles. Today’s Featured Creature, the Blue Shark, Prionace glauca, is typically oceanic pelagic and can be found at the surface to about 1150 feet below temperate and cooler tropical waters.

The Blue Shark is recognizable by its slender body and long pointed pectoral fin. The snout is also long and conical. As highly observant and sharp witted scientists, you readers have probably guessed the Blue Shark is named for the dark blue coloration on the upper part of the shark. However, this shark isn’t blue all over. The underside is white, which may bring back to your mind an adaptation we’ve discussed in a previous post known as counter shading. (Give yourself a high-five if you remembered counter shading!

A counter shaded coloration pattern helps the Blue Shark blend in the water as they hunt. Their prey includes pelagic octopus, cuttlefish, squid, other invertebrates and bony fish. Even though this species usually hunts for food, these sharks are often opportunistic. Opportunistic feeders will eat whatever they find that can fit in their mouth. They have been witness feeding on dead marine mammals and plucking fish from gill nets. Gill nets hang vertically in the water so that fish get trapped in it by their gills. This is one of the major issues that threatens Blue Shark populations.

Some of the causes for decline in Blue Shark populations are bycatch, recreational fishing, and commercial fishing. There currently exist regulations on the amount of shark meat that can be caught on commercial longlines on the east coast of the United States. Blue shark meat does not keep very long, and so to circumnavigate the regulations, unscrupulous fishermen will cut the fins off and throw the shark back. Thankfully, citizens have rallied, especially in California, and have taken great steps to help further protect sharks like the Blue Shark by outlawing finning and Shark Fin Soup and promoting sustainable seafood awareness. Talk to your family about ways you can get involved locally with ocean and shark protection projects!

Join us next week as we look at a shark with a highly unique shape.

References:
Edited by KC O’Shea
Photography:  Doug Perrine and AndyMurch  
http://www.flmnh.ufl.edu/fish/gallery/descript/blueshark/blueshark.html
http://oceanservice.noaa.gov/facts/pelagic.html
http://www.iucnredlist.org/details/39381/0

Creature Feature: Lemon Shark

Lemon Shark (Negaprion brevirostris) is a blunt-nosed and powerful shark reaching up to 11 feet in length. While their color is yellowish to greyish and lacks any distinct markings, they do have two large, almost equal size, dorsal fins which distinguish them from other sharks. The coloring of this predator helps it live in coastal tropical habitats along the Western Atlantic from New Jersey, USA to southern Brazil as well as the west coast of Africa and eastern Pacific, from Baja California to the equator. They have a high tolerance for shallow areas with low oxygen levels, such as those with sea grass, mangroves, and bays.

Young Lemon Sharks have a tendency to stay close to their habitat but adults will often travel to deeper waters. It is thought that they have seasonal migration due to their feeding habits. Lemon sharks love to feed on a variety of osteichthyes (remember the science word for bony fish?), rays, guitar fish, crustaceans and mollusks.

These are common sharks and are fished for both commercially and recreationally. Their meat is often dried, salted and smoked like jerky, while their fins are also a popular commodity. They are known to be a great “aquarium shark,” meaning they do well in aquarium habitats, and are often used in research.

For some reason, the population of lemon sharks in the Florida region has been depleting. Scientists have not isolated a specific cause and as of now there is no management plan. However, collecting knowledge about the species through research is always helpful, should the time ever come to create such a plan.

Check in next week to start our month on sharks that are found in the East Coast of South America.

References:
Edited by KC O’Shea
Photography: Andy Murch and Tomas Kotouc. Courtesy of ARKIVE
http://www.iucnredlist.org/details/39380/0
http://www.elasmo-research.org/education/ecology/estuaries-lemon.htm
Tricas, Timothy C., Kevin Deacon, Peter Last, John E. McCosker, Terence I. Walker, Leighton Taylr. A Guide to Sharks & Rays. San Francisco: Fog City Press, 2002. Print
http://video.nationalgeographic.com/video/shark_lemon