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Blog Tags: Hammerhead Sharks

Hammerheads under Siege: Human Pressure Threatening an Iconic Species

Scalloped hammerheads received protected under the ESA

A school of scalloped hammerhead sharks (Sphyrna lewini). (Photo: Oceana / Rob Stewart)

Sharks have existed for roughly 450 million years—even before the dinosaurs. But, the very adaptations that have allowed sharks to survive for so many millions of years may now be working against them in the face of a relatively new threat: fishing. Under modern fishing pressure, are certain sharks “evolved for extinction”?


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Hammerhead Shark Management Should Reflect Unique Evolutionary Traits, Scientists Say

A school of scalloped hammerhead sharks (Sphyrna lewini)

A school of scalloped hammerhead sharks (Sphyrna lewini). (Photo: Oceana / Rob Stewart)

Known for their mallet-shaped heads, hammerhead sharks are one of the most easily recognized—and favored—shark species. Their “hammers” give them a widened-view to scan for food, and they have enhanced sensory organs that can detect electrical fields from their prey. If that doesn’t make hammerheads cool enough, they can grow to incredible sizes—reaching 20 feet in length and weighing up to 1,000 pounds.


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U.S. Coast Guard Captures Illegal Fishermen in Texas

Source: U.S. Coast Guard Visual Information Gallery

Following Oceana’s newly released report on the harmful impacts of illegal fishing, one of the questions that I as Oceana's Northeast representative was asked most often was, “Where is this happening?”  The short answer: Illegal fishing happens everywhere, from the most distant waters near Antarctica to just off the U.S. coast.


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Breaking: FL Protects Tiger and Hammerhead Sharks

hammerhead shark

Hammerhead shark. [Image via Wikimedia Commons]

I’m sitting in the meeting of the Florida Fish and Wildlife Conservation Commission down in Key Largo, and I have great news: A decision has just been made to protect tiger sharks and three species of hammerhead sharks in state waters.

The new rules go into effect January 1, 2012 and prohibit the commercial harvest, possession and landing of tiger and hammerhead sharks (scalloped, smooth and great hammerheads) in state waters -- that’s three miles off the Atlantic coast and nine miles off the Gulf coast. Recreational fisheries for these species could continue, as long as they’re “catch and release."

We really like this new regulation. Tiger sharks have declined drastically in recent decades -- up to 97% in US Atlantic waters. And these three species of hammerhead sharks have declined about 70% in northwest Atlantic waters. Sharks are often caught for their fins that eventually end up in shark fin soup.

There are some other shark species that still would benefit from this same protection in Florida’s waters, but for now we’re pleased to see the state make positive changes to these shark fisheries. Florida’s waters provide essential habitat for these species; their babies (called pups) use these waters as nursery grounds.

Protected sharks = more shark babies = healthier oceans. Thanks to everyone who helped with this huge victory for sharks!


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2,000 Sharks Massacred in Colombian Sanctuary

shark fins

Shark fins drying in the sun. © Oceana/LX

Just a few weeks after we celebrated a soaring victory for sharks on the U.S. West Coast, Colombian authorities have reported that as many as 2,000 hammerhead, Galápagos and silky sharks may have been slaughtered in Colombia's Pacific waters.  

According to the Colombian president’s top environmental adviser, divers saw 10 Costa Rican trawlers illegally entering the Malpelo wildlife sanctuary.  When the divers swam down to the ocean floor, they found a shocking amount of sharks without their fins.

The Malpelo sanctuary, a UNESCO World Heritage site, provides an ideal habitat for threatened sharks. Unfortunately, the high concentration of sharks in the sanctuary draws illegal fishing boats from nearby nations.

It’s sad day for sharks, but we'll continue working to stop illegal fishing and shark finning. You can help by supporting our campaign to protect our ocean’s top predators from extinction.


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55 Baby Hammerheads Killed for Sport

© Mote Marine

Yesterday’s esquire.com mako shark recipes were pretty outrageous, but it reminded us of another shocking shark story that's worth remembering this shark week. A few years ago, a 1,280-pound pregnant hammerhead shark was killed in Florida in the name of “sport fishing”, with 55 mini-hammerheads still in her womb.

This record-breaking hammerhead was caught off Boca Grande, FL, after struggling for hours. Female sharks are often caught as record-breakers in sport fisheries; they are often so heavy precisely because they are pregnant! This not-so-little lady was 40 or 50 years old and due to give birth any day, with the largest number of shark pups scientists have ever seen.

Killing sharks to win a spot in a record book is unfortunate, as these slow growers can’t sustain their populations against high fishing pressure. We like catch and release models much better, like the Guy Harvey Ultimate Shark Challenge in Florida, in which scientists tag all sharks caught and fishermen release them back into the water.  

In good news for these sharks in Florida, a proposal is moving forward to prohibit killing hammerheads (and tiger sharks) in state waters. Staff of the Florida Fish and Wildlife Conservation Commission will present this recommendation to the state wildlife commission next month.

Kudos to our devoted Florida Wavemakers who helped make this key step a reality! We’ll keep you posted on the outcomes; with a victory, any record-breaking pregnant sharks and her babies will remain in the oceans where they belong, and not on a lab table.

Take action to protect hammmerheads if you haven't already!


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Fact of the Day: Scalloped Hammerhead Shark

Scalloped Hammerhead Shark (credit: Barry Peters)

Shark Week started last night! (And how great was ‘Ultimate Air Jaws?!”)

Oceana is a partner in Shark Week this year, and it’s my favorite week of the year, so I’m going to keep the celebration going with daily shark facts!

The scalloped hammerhead shark is just one of the many species of hammerhead shark, all of which have the characteristic t-shaped head.


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Sights on CITES: Shark Showdown

This is the eighth in a series of dispatches from the CITES conference in Doha, Qatar.

More difficult news out of Doha today.

While seven of the eight proposed shark species (including several species of hammerheads, oceanic whitetip and spiny dogfish) were not included in Appendix II, the one bright spot was for the porbeagle shark, which is threatened by widespread consumption in Europe.

The porbeagle’s Appendix II listing is a huge improvement because it requires the use of export permits to ensure that the species are caught by a legal and sustainably managed fishery.

And there is a slight chance that the other shark decisions could be reversed during the plenary session in the final two days.

Here are Oceana scientists Elizabeth Griffin and Rebecca Greenberg reflecting on the shark decisions:


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Sights on CITES: Hope for Sharks

This is the seventh in a series of posts from CITES. Check out the rest of the dispatches from Doha here.

While CITES has disappointed so far on bluefin tuna and corals, there's hope yet for sharks

Eight shark species have been proposed for listing to Appendix II of CITES, including the oceanic whitetip, scalloped hammerhead, dusky, sandbar, smooth hammerhead, great hammerhead, porbeagle and spiny dogfish.

Listing these species, which are threatened by shark finning, is necessary to ensure international trade does not drive these shark species to extinction.

Here's Oceana's Ann Schroeer from our Brussels office with an optimistic outlook on the upcoming shark proposals at CITES.

 


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Q&A with Shark Biologist Michelle McComb

michelle mccomb

Michelle McComb with juvenile scalloped hammerhead sharks at the Hawaiian Institute of Maine Biology at Coconut Island. © Dr. Stephen Kajiura.

A study in the Journal of Experimental Biology made big news late last year by beginning to answer a fundamental, fable-like question: why are hammerhead sharks shaped the way they are? The answer, as it turns out? The better to see their prey with, my dear.

The researchers found some surprising results about hammerhead vision. One of those researchers, Michelle "Mikki" McComb of Florida Atlantic University, happens to also be an enthusiastic Oceana supporter. Mikki was kind enough to answer some questions about the research:

Can you summarize the conclusions you and your colleagues reached about hammerhead vision? 

The popular literature is filled with claims that hammerheads have better vision, but this was never tested.  Our goal was to quantify the extent of the visual fields of hammerhead sharks in contrast to more typical head shaped sharks, in order to determine if they possessed binocular vision.

The visual field is the entire expanse of space visible around the head and can be described by one eyes field of view (monocular field), two eyes field (cyclopean) and the overlap of the two monocular fields (binocular overlap). We determined the horizontal and vertical visual fields of three hammerhead shark species as well two closely related “typical” shaped sharks. 

What we found was a surprise!  Hammerhead sharks do have binocular vision, and even more surprising, the extent of binocular overlaps was greater than found in the “typical” shaped sharks.  The largest binocular overlap was found in the winghead shark, the hammerhead with the widest head, and is a result of the positioning of the eyes on the end of the head. 


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