Ocean Currents » population survey http://blog.oceanconservancy.org News, opinions, photos and facts from Ocean Conservancy Fri, 27 May 2016 15:06:23 +0000 en-US hourly 1 http://wordpress.org/?v=3.4.2 Five Sharks Spotted During My Shark Research Cruise http://blog.oceanconservancy.org/2013/08/09/five-sharks-spotted-during-my-shark-research-cruise/ http://blog.oceanconservancy.org/2013/08/09/five-sharks-spotted-during-my-shark-research-cruise/#comments Fri, 09 Aug 2013 17:15:00 +0000 Claudia Friess http://blog.oceanconservancy.org/?p=6494 measuring a baby tiger shark

A scientist measures a juvenile tiger shark during a population survey. Photo: Claudia Friess / Ocean Conservancy

More than 70 species of shark occur in the Gulf of Mexico and along the U.S. Atlantic coast. Of those, we catch over a dozen large and small coastal species during the bottom longline population survey I’m participating in with the National Oceanic and Atmospheric Administration.

Here are five of the species we commonly spot:

Atlantic Sharpnose Shark
This small shark is the most commonly caught species during our survey because it is ubiquitous in this region. In the right depths, it is not uncommon for us to catch around 50 of these small sharks per set of 100 hooks.

Population status: Due to their abundance in the western North Atlantic, their population status is not considered to be of great concern. Apart from humans, Atlantic sharpnose sharks also have other, larger sharks to fear as predators.

Sandbar Shark
These sharks are often preying on small sharpnoses caught on our hooks. Sandbar sharks are the most abundant large coastal sharks in the western Atlantic, reaching lengths of up to 7.5 feet. They are among the more feisty species we catch; you really have to watch out for those razor-sharp teeth.

After leaving their shallow-water nursery areas, juvenile sandbar sharks spend a few years migrating between nearshore and offshore areas in schools. On this trip, we seemed to have found one of those sandbar schools off the coast of Florida. We had one set with an abnormally large amount of roughly 5-foot sandbar sharks, when normally we only catch a couple of them per set, at most.

Population status: Sandbar sharks are currently classified as overfished by NOAA, and while the population is increasing slowly due to rebuilding measures, it is not expected to be recovered until the year 2070.

Scalloped Hammerhead Shark
One of our favorite species to see is the magnificent scalloped hammerhead. These sharks reach lengths of up to 14 feet. By their physical appearance you would not guess it, but hammerheads are surprisingly fragile when caught on a hook or in a net. They usually don’t fight back much by the time they are brought to the boat, and we know when we catch one, we have to work fast if we want to get it back in the water alive.

Population status: These sharks are highly desired for the shark fin trade and have become quite rare in the western Atlantic and around the world. They are considered overfished by NOAA and were recently included under CITES appendix II, resulting in monitoring and special permitting requirements for international trade.

Tiger Shark
Another one of my favorites is the tiger shark. At lengths of up to 17 feet, tiger sharks are one of the largest shark species in the world. The ones we commonly catch on the bottom longline survey range from pups of just over a foot long to juveniles and young adults up to about 8 feet, but occasionally we do catch bigger specimens. My crew had a particularly large tiger on the hook the other day, but the sea was too rough for us to cradle it, so we had to cut it loose without measuring or tagging it. The tiger shark is a voracious predator that also doesn’t refuse human garbage such as license plates and old tires.

Population status: The status of tiger sharks in U.S. waters is currently unknown because there has not been a scientific assessment of the tiger shark population. The International Union for the Conservation of Nature (IUCN) classifies tiger sharks globally as near threatened.

Smooth-hound Sharks
There is one species of smooth-hound on the Atlantic side, the smooth dogfish, and there are three in the Gulf of Mexico. Two of the three Gulf species, the smooth dogfish and the Gulf smooth-hound, can be identified only by looking at the shape of their denticles, the small, tooth-like scales that cover a shark’s body and give it the feel of sandpaper. We have to take dermal skin plug samples from any smooth-hounds we catch in the Gulf to identify it to the species level later in the lab.

Population status: On the Atlantic side, a considerable fishery for these small sharks has developed over the past two years, and questionable exceptions were made in the fin requirements of the Shark Conservation Act for the smooth dogfish fishery. Even though smooth dogfish mature relatively early and have large litter sizes (between 4 and 20 pups) for shark standards, they are still vulnerable to overexploitation, like all sharks, and must be managed with care.

http://blog.oceanconservancy.org/2013/08/09/five-sharks-spotted-during-my-shark-research-cruise/feed/ 13
Shark Sighting: What It’s Like Cruising for Sharks http://blog.oceanconservancy.org/2013/08/05/shark-sighting-what-its-like-cruising-for-sharks/ http://blog.oceanconservancy.org/2013/08/05/shark-sighting-what-its-like-cruising-for-sharks/#comments Mon, 05 Aug 2013 20:00:07 +0000 Claudia Friess http://blog.oceanconservancy.org/?p=6460 hammerhead shark

Hammerhead shark caught for a population survey. Photo: Claudia Friess / Ocean Conservancy

While most people out on the water are trying to avoid sharks, I’m on a boat that’s looking for them. We’re trying to find out which shark species are doing well and which ones are in trouble.

The answer: it’s complicated. But one important piece of evidence is the information collected on scientific surveys of population abundance, like the one I’m on right now.

It’s my third year as a volunteer on the science crew with the National Oceanic and Atmospheric Administration. I am currently on the NOAA ship OREGON II, a 170-foot research vessel with its home port in Pascagoula, Miss.

This is the first leg of the annual shark and red snapper bottom longline survey. The survey is conducted in the U.S. Gulf of Mexico from South Texas to the Florida Keys and along the East Coast up to Cape Hatteras, N.C. That’s a total of four legs lasting two weeks each.

Our job is to go from station to station deploying a mile-long line (the longline) with 100 baited circle hooks on it, then haul back the line after an hour of soak time and process everything that is caught. We fish in depths between 60 and 240 feet.

But boat time is not cheap, so we fish around the clock to make the most of these valuable days at sea. My crew fishes from midnight to noon, and the day crew fishes from noon to midnight.

When we catch a small shark, we bring it on board, and when we catch a big shark, we use a crane-operated cradle to lift the shark out of the water and line it up alongside the boat. Regardless of the size of the shark, the most important thing is to control the head. If you do that, you won’t get bitten.

We measure and weigh each shark as well as record species and sex. Most species also have genetic samples taken and get tagged. Then we throw them back overboard. Sometimes we also catch non-shark fish, most often the highly sought-after red snapper.

By far the most common shark we catch is the Atlantic sharpnose shark, a small species that only reaches about 43 inches in total length. Other species we see are blacktips, blacknose and sandbar sharks.

Sandbar shark caught with sharpnose shark in its jaws

Photo: Claudia Friess / Ocean Conservancy

Often, the bigger sharks get caught because they have eaten a smaller shark (usually a sharpnose) that had previously been caught on the hook! And then there is the occasional treat: a hammerhead or a tiger shark. Unfortunately, these beautiful fishes have become quite rare.

Aside from collecting biological data on the species we catch, the most valuable part of surveys like these is that it’s designed to track the status of these shark populations over time. Each year, the gear is fished the exact same way, and stations are surveyed randomly, which allows researchers to calculate an annual catch rate for each species.

Over time, if the catch rate increases, that indicates the population is going up. Conversely, if the catch rate decreases, that is evidence that the population is declining.

This research is important to helping increase the knowledge for these vital ocean species. The more we know, the more we can help protect them. So these surveys are much more than a regular fishing trip; they’re generating valuable data for the conservation and management of top ocean predators that are so vital to healthy, functional ocean ecosystems.

Want more updates like this on ocean conservation or opportunities to take action? Join our email list.

http://blog.oceanconservancy.org/2013/08/05/shark-sighting-what-its-like-cruising-for-sharks/feed/ 6