Research Cruises

Members of the Apex Predators Program (APP) participate in and conduct a variety of research cruises. Additionally they often have the opportunity to go on board commercial vessels to obtain biological samples from the catch as well as tag sharks. Currently, the bi-annual survey is the most prominent and consistent of the APP cruises.

Apex Predators Program Large Coastal Shark Survey

The fishery independent survey of Atlantic large and small coastal sharks is conducted bi-annually in U.S. waters. Its primary objective is to conduct a standardized, systematic survey of the shark populations off the U.S. Atlantic coast to provide unbiased indices of relative abundance for species inhabiting the waters from Florida to the Mid-Atlantic. This survey also provides an opportunity to tag sharks with conventional and electronic tags as part of the NEFSC Cooperative Shark Tagging Program, inject with OTC for age validation studies, and to collect biological samples and data used in analyses of life history characteristics (age, growth, reproductive biology, trophic ecology, etc.) and other research of sharks in U.S. coastal waters including the collection of morphometric data for size conversions. The time series of abundance indices from this survey is critical to the evaluation of coastal Atlantic shark species. The next survey is scheduled for Spring of 2012.

History

In 1986, the APP conducted a longline cruise which represented the first systematic survey of sharks covering most of the US Atlantic coast from Southern New England to mid-Florida in depths of 5 to 200 m. Pre-determined stations were positioned roughly 30 nautical miles (nmi) apart, with additional (tagging only) stations in regions of high shark abundance. The cruise was designed to obtain baseline information on the abundance and distribution of large pelagic fishes, primarily sharks, using standard pelagic longline gear. By 1989, the objectives of the survey shifted from pelagic fish to large coastal sharks and this survey covered the waters from Tampa, FL to Southern New England (SNE). The gear was weighted and the bottom longline survey was initiated. Survey procedures and gear were standardized between the NEFSC and Southeast Fisheries Science Center (SEFSC) in 1995 to make the surveys comparable and to mimic the gear used in the commercial large coastal shark fishery. Changes to the NEFSC survey were: 1) gear changed from New England pelagic (rope mainline, rope and wire gangions) to Florida bottom (monofilament mainline and gangions), 2) soak time increased from 1 to 3 hrs, 3) bait changed from mackerel to spiny dogfish, 4) stations limited to depths between 5 and 40 fms, and 5) longline fished entirely on the bottom, eliminating the pelagic sets of the previous surveys, 6) 300 hooks fished rather than 100.

Gear

Currently the standard sampling gear consists of a 300 hook 'Florida' commercial style bottom longline. This gear consists of a 940 lb test monofilament mainline with 12 foot (3.6 m) gangions composed of 730 lb test monofilament with a longline clip at one end and a 3/0 shark hook at the other. Gangions (referred to hereafter simply as 'hooks') baited with chunks of spiny dogfish are attached to the mainline at 60-70 ft intervals; 5 lb (2.3 kg) weights are attached every 15 hooks and a bullet float and 15 lb (6.8 kg) weights are placed at 50 hook intervals. A 20 ft (6 m) staff buoy ('high flyer') equipped with radar reflectors and flashers (at night) is attached to a poly ('tag') buoy by a 12 ft line. The poly buoy is then attached to the mainline and there is a set of these to mark each end of the mainline. To ensure that the gear fishes on the bottom, 20 lb (9.1 kg) weights are placed at the beginning and end of the mainline after a length of line 2-3 times the water depth is let out.

Once set, the gear is fished for three hours with a approximately 6 hours from start of setting to completion of haulback. The mainline covers from 2.0 to 5.5 nm with an average of 3.7 nm. Fishing takes place at all times of the day. Number of sets completed per day varies from one to three with an average of 2.5.

The number of sets is dependent on distance between stations, weather conditions, and the length of time to complete previous sets during the day.

Life on Board

The survey has been conducted primarily on the NOAA Ship Delaware II, although it has also been conducted on the R/V Wieczno out of Gdynia Poland and the UNOLS vessels Pelican out of Cocodrie, LA and Longhorn out of Port Aransas,TX.

The survey is divided into 3 parts, or legs, each of which is approximately two weeks long. Generally eight scientists are on board for each leg. Fishing is conducted around the clock and there are two 12 hour watches of four persons. Duties are primarily directed towards fishing, such as cutting bait, baiting hooks and helping deploy and haul the gear.

Commercial Longline Fleet Cruises

An investigation of pelagic nursery grounds in conjunction with the high seas commercial longline fleet was initiated in 2007 as part of pelagic shark biology, movements, and abundance studies. This collaborative work offers a unique opportunity to sample and tag blue sharks (Prionace glauca) and shortfin makos (Isurus oxyrinchus) in a potential nursery area on the Grand Banks, to collect length-frequency data and biological samples, and to conduct conventional and electronic tagging of these species.

Recaptures were primarily blue sharks that were recovered by commercial fishermen working in the mid-Atlantic Ocean. In addition, 500 blue sharks have been double tagged using 2 tag types to help evaluate tag-shedding rates used in sensitivity analyses for population estimates and to calculate fishing mortality and movement rates for this pelagic shark species. This research is being filmed by Original Productions as part of a television series called 'Swords: Life on the Line' which first aired on the Discovery Channel in 2009. In 2007 and 2008, two real-time satellite (SPOT) tags and five PSAT tags were deployed on shortfin makos and one PSAT tag was deployed on a blue shark.

www.nefsc.noaa.gov

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(File Modified Sep. 14 2011)