Showing posts with label sharks. Show all posts
Showing posts with label sharks. Show all posts

Saturday, 23 June 2018

Eye for Adventure

The ocean is there to be discovered and Steve Brady is an intrepid diver who has explored many underwater locations with a salty tale to tell.

“We’ve got it all and there’s just so much diversity of marine life in and around Australia. It’s amazing” Brady says. “This is probably a funny thing to say but if I had gills I’d be a very happy boy.”


With a litany of dive experiences under his belt, Brady wanted others to learn what the ocean has to offer. Informed by research from marine biologists and feedback from pro divers, he developed a calendar featuring marine wildlife events throughout the year, and uses the calendar to schedule dive trips at all levels of experience from beginner to advanced around Australia and beyond.

“Finding where you can go to see certain marine life is a very big thing for people and I’m the same. I want to see mola molas, I want to see mantas, so I want to go to a place that has the best chance at the best time to see them” says Brady.
















Brady has an eye for adventure and despite the unpredictable nature of the sea, he is not deterred from making new discoveries. He recalls an incredible rendezvous with a manta ray after travelling out to an open ocean destination via spotter plane in West Australia.

“In West Australia we went to the township of Coral Bay. We specifically went out on a trip where they have spotter planes, and you aren’t on a reef. You’re in open water. Sandy bottoms, maybe twenty metres of water and you’re snorkeling with them. They’re just down there, just swimming around, very acrobatic, very inquisitive. Just to have one of them come gliding over the top of you, that’s very special” says Brady.

























Australian dive sites are world renowned for their pristine waters, thanks to clean up projects led by conservation organisations and social media groups. Despite awareness campaigns and changes to the community’s attitude toward disposing rubbish, microplastics are severely impacting the health of marine life globally.

When marine organisms filter seawater for their food and to absorb oxygen, they vicariously take in these tiny microplastic pieces. This plastic can become lodged in digestive and respiratory tracts, causing animals to suffer health problems or worse, mortality. In the ocean, it's not just small filter feeding species like corals and clams that are being negatively affected, the larger pelagic animals, whales and sharks, are also being hit hard by this invisible threat. 

“Plastic is everywhere, even in places we can’t see” says Ian Kiernan, founder of Clean Up Australia, an organisation that coordinates community clean up events of the environment every year in Australia and worldwide.























“Even if you aren’t really concerned about the health of marine creatures, you might pause when you know that you cannot escape that easily because they are in our drinking water” Kiernan says.

To decrease the problem of microplastics in our water, Kiernan recommends consumers buy clothes made with natural fabrics instead of synthetic material and avoid purchasing products like cosmetics, soaps, shampoos and detergents that do not clearly state they are free of microplastics.























Another way of overcoming obstacles to the continued health of the marine world is through ecotourism, which is offering coastal communities the benefit of financial return, by showing visitors how beautiful preserved natural environments are.

The Great Barrier Reef along Queensland’s coast and Ningaloo Reef off Exmouth in West Australia, both World Heritage listed areas, are prime examples of ecotourism’s success.























Divers share their once in a lifetime experiences when they dive with whales, sharks and dolphins through social media, attracting a lot of attention which ultimately turns marine species into major tourism draw cards overnight. “People’s expectations are all different and everyone enjoys diving around the coral. But when people are fortunate enough to see species like mantas that would be their trip for the rest of their lives” says Brady.

Spectacular Coral Sea locations lying beyond the Great Barrier Reef are a prize ready for the taking. “You’re talking thousands of metres of water, massive drop offs, just awesome visibility and you will get large pelagic marine life out there. If you like sharks, that’s the place to go” says Brady.

Another exciting dive destination is the S.S. Yongala shipwreck, which sunk in 1911 off Alva Beach, Ayr, in North Queensland. “It’s a feeding station for mantas, bull rays, groupers and sharks. It’s safe to go learning to dive because you don’t have strong currents. You’ve got pristine visibility. You’ve got nice corals. I would promote it as one of the best places to learn to dive” says Brady.























The Ribbon Reefs are part of the Great Barrier Reef, which extend from Port Douglas all the way up passed Lizard Island. 

“In June, July each year, you get the migration of the Minke whale coming through and that’s very special. That’s really a highlight for me in terms of marine species” says Brady.

And for the nouveau diver who stumbles upon a manta ray or a whale shark for the first time? 

“You just let them be in their natural environment, you let them be the inquisitive one and you’re in for a great experience” says Brady.

Report by Gabrielle Ahern

Steve Brady manages ‘Dive In Australia’ located in Cairns (https://diveinaustralia.com.au) a travel agency matching dive companies to divers looking for their ideal wildlife encounter.

All images © Steve Brady - Dive In Australia - www.diveinaustralia.com.au

My interview with Steve Brady will feature in a future podcast episode of the Noisemaker series. So stay tuned.


Sunday, 1 May 2016

LEMON SHARKS

The barrier reef around Heron Island attracts many marine vertebrates, among them various members of the Class Condrichthyes, who hold the mantle of keystone predator.

At birth the lemon shark, Negaprion acutidens (Carcharhinidae), measures 60 – 65 cm in length and can grow to 380 cm TL (male). The average size of a litter is 6 – 12 pups. The lemon shark is an active predator, whose behaviour is affected by the different conditions of its environment, for example, water temperature, currents, prey in the area and time of year, to name but a few. Its habitat includes tropical, shallow inshore and offshore waters in coral reef, lagoon and mangrove estuary environments.

Species within the Carcharhinid family have a complex social and reproductive behavior as compared to other families of shark. Studies have revealed the reef shark is geared to learn about its reef habitat due to a more developed telencephalon in the brain.

With growing maturity the lemon shark’s diet has been observed to change. As juveniles they feed on teleosts, crustaceans and molluscs around shallow waters, but as adults, they switch to teleost and cartilaginous fish in pelagic waters. This may reflect the change in visual pigments, which occurs, rapidly enhancing its ability to hunt prey at night, along with its developing olfactory senses and important electro receptive ability. After hunting for prey all night, sharks seek shelter in the reef during the day.

Adult sharks hunt in pelagic or open ocean environments, while juvenile sharks hunt opportunistically during the day and twilight close to shore in the reef lagoon. Sharks have been observed to work as a group when hunting for food. They herd schools of reef fish toward the shoreline and with nowhere else to go the fish are vulnerable to attack. The sharks complete their hunt by ram feeding on the cornered fish.

Lemon sharks do not feed on a regular basis. They eat on average 2.68 % of their own body weight in short bursts and invest more time in digestion. Their stomachs are usually voided within 25 – 41 hours. The voiding mechanism is executed by the scroll valve, which everts to flush out any parasites.

Studies suggest a combination of factors: the sharks coral reef habitat, competition between different parasite species and the number of parasites living on a shark, contribute to the demise of a shark’s health, leading in some cases to its early death. Despite the sharks efforts to reduce the chance of infection, opportunities for parasites to infect a shark are increased by the shark’s own behavior, for example, its hunting location and the type of fish it consumes.

Lemon sharks remain connected to a specific coral reef habitat throughout their lives. The IUCN Redlist has listed the species as Vulnerable. By nature they are quite a shy animal but dangerous if provoked. Current threats to lemon shark populations include: shark fisheries, dynamite fishing, pollution and mangrove deforestation due to its limited home range.

Lemon sharks are really fascinating animals, and if you would like to know more about their biology and ecology, please refer to the following sources of information, local library or the World Wide Web.

Written by Gabrielle Ahern








Salty Wave Blue – Into all things ecology.

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If you would like to see images of sharks in their marine environment, please take a look at my Pinterest site: https://www.pinterest.com/saltywave

Web Links

IUCN Redlist

Wildscreen Arkive

FishBase

Atlas of Living Australia