Sandbar, dusky and tiger sharks are among dozens of shark species living in the coastal waters off the U.S. East Coast. Little is known about many of the species, but a survey begun nearly 25 years ago is helping scientists and fishery resource managers to monitor shark populations and their role in marine ecosystems.
NOAA scientists from the Northeast Fisheries Science Center (NEFSC) lab in Narragansett, R.I., recently conducted their ninth coastal shark survey from Florida to Delaware. The survey, conducted every two to three years, is the longest survey independent of the fishing industry of large coastal sharks in the U.S. Atlantic Ocean.
Using commercial Florida-style longline fishing methods to standardize results from survey to survey, researchers caught 1,675 sharks from 19 different species and tagged 1,352 individuals during the 2009 survey in April and May. Most of the animals caught and tagged were sandbar sharks, a common species in the western Atlantic. Longline fishing is a type of fishing that uses a long or main line with baited hooks spaced out at certain intervals along the line.
“During the survey, we often catch 19 or more species, many of which are highly migratory, and we still have a lot to learn about them,” said Nancy Kohler, who heads the Apex Predators Program at the Narragansett Lab and has been on every survey. “We do not know how large certain species are when they mature, for example. It is important that we obtain basic biological information from the fish we catch so that we can learn as much as possible about their life histories, or the changes that the animals undergo from birth to death.”
Researchers record the length, sex and location of each animal caught before the fish is tagged and released. The sharks can range from 1 foot to 15 feet; they are not weighed. Any dead fish are carefully dissected at sea, with researchers looking for parasites, collecting DNA and blood samples, and obtaining samples for studies of age and growth, reproductive biology and food habits.
The first systematic survey of Atlantic sharks was conducted by the Apex Predators Program in 1986 between Florida and southern New England waters from 5 to 200 meters deep (about 16 to 660 feet). In addition to basic biological information, researchers gather data on shark abundance and distribution and migration patterns.
Kohler said the survey is conducted in the spring because coastal shark species distributions are concentrated during this time of year since the waters north of Delaware are too cold, thus making it easier to survey the whole population. Nearly all of the surveys have been conducted from the NOAA ship Delaware II, based at the NEFSC’s Woods Hole Laboratory.
“We caught more fish and tagged more fish on this survey than any other,” said Lisa Natanson, who heads the coastal survey effort and has been on all but one of the surveys. “The previous high total was in 1998, when we caught 917 sharks and tagged 859. Some years we catch very few, so it really varies." In addition to numerous sandbar sharks, the researchers also caught one great white, many tiger and dusky sharks, and some Atlantic sharpnose. The current data are part of just one of several long-term data sets that are used to determine the health of shark populations.
The survey takes six weeks to complete and is divided into three legs, each approximately two weeks long. Eight scientists are on board for each leg, and fishing is conducted around the clock. Environmental information, such as water temperature and ocean chemistry, is obtained at each station.
Survey data are provided to the fishery managers who monitor populations in the Atlantic and Gulf of Mexico. NOAA Fisheries Service manages the commercial and recreational shark fisheries in U.S. waters, including the Caribbean Sea and the Gulf of Mexico. The United States began regulating shark fisheries in 1993 and currently manages 39 species. A fishery management plan that includes sharks, swordfish, and tunas went into effect in 1999, regulating sharks under a catch limit and quota system.
In addition to the coastal shark survey, Kohler, Natanson and colleagues in the Apex Predators Program work with thousands of volunteers throughout the Atlantic Ocean, Gulf of Mexico and the Mediterranean Sea through the Cooperative Shark Tagging Program. The lab also manages and coordinates the Cooperative Atlantic States Pupping and Nursery Survey, collaborating with researchers in coastal states from Rhode Island to Florida to conduct a comprehensive and standardized investigation of shark nursery areas.
Scientists in the program conduct life history studies of commercially and recreationally important shark species, participate in and conduct a variety of research cruises, and often go aboard commercial vessels to obtain biological samples from the catch as well as to tag sharks. Biological samples are also collected from recreational fishing tournaments in the Northeast U.S.
NOAA Fisheries Service is dedicated to protecting and preserving our nation’s living marine resources and their habitat through scientific research, management and enforcement. NOAA Fisheries Service provides effective stewardship of these resources for the benefit of the nation, supporting coastal communities that depend upon them, and helping to provide safe and healthy seafood to consumers and recreational opportunities for the American public.
NOAA understands and predicts changes in the Earth's environment, from the depths of the ocean to the surface of the sun, and conserves and manages our coastal and marine resources.
Shelley Dawicki | EurekAlert!
Further reports about: > Atlantic > Atlantic sharpnose > Fisheries > Gulf of Maine region > NOAA > Pacific Ocean > SEA > Shark > basic biological information > blood sample > coastal waters > marine ecosystem > marine ecosystems > marine resources > reproductive biology > sandbar sharks > shark biology > shark populations > tiger sharks
Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel
Removing fossil fuel subsidies will not reduce CO2 emissions as much as hoped
08.02.2018 | International Institute for Applied Systems Analysis (IIASA)
At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.
At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...
There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?
At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...
A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.
The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...
02.05.2018 | Event News
13.04.2018 | Event News
12.04.2018 | Event News
23.05.2018 | Life Sciences
23.05.2018 | Life Sciences
23.05.2018 | Physics and Astronomy