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 semiannual survey is the most prominent and consistent of the APP cruises. In the past few years, there have also been shorter cruises directed towards porbeagle shark tagging and biology. Additionally, personnel participated in two bluefin tuna research cruises and have joined the NMFS SEFSC for their annual shark survey in the Gulf of Mexico.
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 was 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. A brief description of the changes in survey procedures and design are given in the table below.
| Year | Gear | Area | Hooks | Soak Time | Bait | Dates |
|---|---|---|---|---|---|---|
| 1986 | Pelagic LL | Miami, FL - SNE | 100 | 1hr | Mackerel | Jul-Sep |
| 1989 | Pelagic LL | Tampa, FL - SNE | 100 | 1hr | Mackerel | Apr-May |
| 1991 | Pelagic LL | Miami, FL - SNE | 100 | 1hr | Mackerel | Apr-Jun |
| 1996 | Bottom LL | Miami, FL - SNE | 300 | 3hr | Sp Dogfish | Apr-May |
| 1998 | Bottom LL | Key West, FL - DE | 300 | 3hr | Sp Dogfish | Apr-May |
| 2001 | Bottom LL | Key West, FL - DE | 300 | 3hr | Sp. Dogfish | Apr-May |
| 2004 | Bottom LL | Key West, FL - DE | 300 | 3hr | Sp. Dogfish | Apr-May |
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.
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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.
As part of a directed study of porbeagle shark (Lamna nasus) life history several cruises were conducted to: 1) tag and inject with tetracycline porbeagle sharks for migration and age and growth studies; 4) collect biological samples from sharks for age studies; 5) collect food and feeding information from sharks; 6) collect reproductive data from sharks. The 2000 cruise also incorporated acoustic tracking. All of the cruises took place on shelf and slope waters along the east coast of the U.S. and Canada from the Cape Cod, MA to St. Pierre Bank, Canada. All available information on water temperature, satellite imagery and historical knowledge of where porbeagles have been found was used to help catch as many sharks as possible. Generally these trips were 2 weeks in duration. Pelagic longline gear was used for this project which consisted of 100 to 400 gangions and allowed to fish for an average of five hours with repetitive fishing in subsequent 24-hour periods (approx. 2 sets daily). Pelagic gear differs from bottom gear in that it is not weighted and the gangions are substantially longer (approx. 24 ft for this project) with a 6 ft wire leader attached to an 18 ft monofilament or rope portion. The hook size also differs from the bottom gear.
Five directed porbeagle cruises (1997 cruise, 1998 cruise) were conducted between 1996 and 2000 on 3 vessels: NOAA Ship Delaware II, F/V Panther, and the Isabel S. Additionally, members of the APP went on two commercial trips on the F/V Panther and multiple trips on a Canadian commercial vessel the F/V Bakur, which targets porbeagle sharks.
Data collected and analyzed from these cruises has resulted in the publication of research papers on porbeagle age and growth, food habits and population dynamics. Other studies on migrations and acoustic tracking are ongoing.