This article originally appeared in The Shark Tagger-1998 Annual Summary
This was an extremely successful year of biological field studies for the staff of the Apex Predators Program (APP) in conjunction with numerous biologists and fishermen. The research included a longline survey of the Atlantic coast (see page 15) and joint studies such as the Cooperative Shark Tagging Program (CSTP) and a new coast-wide pupping and nursery grounds initiative (see Page 17). Many thanks to all participants whose collaborative efforts led to outstanding results in 1998.
Members of the Cooperative Shark Tagging Program tagged and released 7,411 fish including 38 species of sharks and rays and 13 species of teleosts (Table 1). Ninety-one percent of the releases were accounted for by 11 species of shark: blue (49%); sandbar (21%); tiger (4%), shortfin mako, blacktip, Atlantic sharpnose (3% each); bonnethead, dusky (2% each); porbeagle, spinner, and nurse shark (1% each). This brings the total number of tagged fish to over 155,000 tagged since 1962.
Anglers tagged the majority of fish (62%; 37 species) followed by NMFS and other biologists (32%; 31 species), commercial fishermen (3%; 23 species), and fisheries observers on commercial vessels (3%; 17 species). Fish to be tagged were caught by a variety of capture methods including rod and reel (60%), longline (25%), net (12%), and free swimming (3%) by fishermen representing eight countries: United States, England, Canada, Portugal, Germany, Italy, France, and Mexico.
In 1998, cooperators returned data on a record number 721 tags from 21 species of sharks and 3 species of teleosts (Table 2) bringing the total number of recaptures to 8,218 since 1962. Blue shark (532), sandbar shark (69), shortfin mako (41), tiger shark (21), and porbeagle (10) were the most numerous returns. Commercial fishermen (54%) and recreational anglers (43%) were the primary sources of recapture information. Fish were originally caught on rod and reel (72%), longline (18%), net (4%), handline (2%), and released free swimming (4%). Tags were returned from fishermen and scientists representing the following 18 nationalities: United States, Spain, Venezuela, Canada, Portugal, Japan, Cuba, Mexico, Taiwan, Brazil, Italy, England, Canary Islands, St. Lucia, Trinidad, Tobago, Grenada, and Guadeloupe.
Distances traveled ranged from 1 to 3,438 nautical miles (nm) - A total of 225 (47%) of the blue shark returns showed distances traveled over 1,000 nm. Of these, 38 moved over 2,000 nm, and 1 over 3,000 nm. The latter return is the third longest distance recorded overall for any blue shark recaptured to date. This fish was tagged 13 nm southeast of Portsmouth, NH in September of 1997 and was recaptured off Brazil after only 6 months at liberty. Returns from fish that traveled over 2,000 nm showed movements from the New England and New York coast to: Flemish Cap, Azores, Canary Islands, Western Sahara, Cape Verde Islands, Suriname, and Guyana and from south of the Flemish Cap to: Cape Verde Islands, Senegal, and Venezuela. Additional recapture locations for blue sharks showing movements between 1,000 and 2,000 nm included Tobago, Lesser Antilles, and Cuba (see map).
Many times blue sharks were tagged in the same place and at the same time, and were then recaptured in close proximity to each other. For example, six blue sharks, tagged approximately 100 nm east of Provincetown, MA by NMFS Narragansett biologists on the same day, were all recaptured within 8 months of tagging after travelling directly east for distances ranging from 942 to 1,447 nm. One other blue shark, however, tagged just two days earlier in the same location, was recaptured off Venezuela (1,860 nm S) after 8.5 months at liberty. There are further examples of blue sharks that are tagged on the same date and location that show very diverse recapture locations. Three fish, tagged on the same day in June off Montauk, NY, were all recaptured within two months - one after 12 days 41 nm to the east, one after one month off Cape Sable, NS, Canada (273 nm E), and the third after two months, only 27 nm to the northeast. Two other fish tagged on the same day in September off New Hampshire were recaptured after 7 months at liberty - one south of the Flemish Cap (1,197 nm E) and the other off Brazil (3,438 nm SE). Similar divergent movement patterns exist in the Eastern Atlantic. Two blue sharks tagged in the same area off the southeast coast of Portugal in the summer of 1996 were recaptured within one day of each other hundreds of miles apart - one traveled 183 nm northwest and the other 1,379 nm to the west.
Information on interesting returns received in 1998 include four blue sharks that were recaptured approximately 475 nm northeast of the Flemish Cap within eight days of each other by a Portuguese longline fisherman. All were tagged off the New York and New Jersey coast and were at liberty for between 0.9 and 6.6 years. This is the northernmost recapture location for any blue shark in the history of our program. An example of an unusual tagging location for a blue shark was in mid-ocean approximately 800 nm east of Antigua Island. This fish was tagged by a US high seas fisherman and was recaptured by a Spanish longline fisherman northeast of the Cape Verde Islands (1,300 nm E). Although the straight line distance and direction traveled is known, the true migratory route is unknown during the this shark's 1.8 years at liberty.
Multiple recaptures of the same fish provide detailed information on the migratory routes of individual sharks. One blue shark tagged south of Montauk, NY in June of 1995, was recaptured 2 years later, only 19 miles northeast of its original tagging location. This fish was re-tagged and recaptured again, 10 months later, after traveling almost 1,000 nm the east.
Overall, times at liberty for blue sharks ranged from 1 day to 7.4 years, with the majority at liberty for less than 2 years. Twenty-eight percent of the blue sharks for which recapture information was received are still at liberty, having been either re-tagged, released with the same tag, or released untagged.
Distances traveled ranged from 0 to 1,437 nm. The majority (36) of sharks traveled less than 100 nm; 24 traveled between 100 and 1,000 nm; and 8 traveled greater than 1,000 nm. These long distance returns were all recaptured along the west coast of Florida after being at liberty from 5.6 to 13.6 years with fork lengths at tagging between 35" and 50". An additional Gulf of Mexico recapture traveled 705 nm from Cape Fear, NC to Seminole Pt., FL after 8.6 years at liberty.
One sandbar shark tagged southwest of Apalachicola, FL was recovered off the Virginia coast after 9 months. This fish represents only the third tagged sandbar shark that moved outside the Gulf of Mexico. Another interesting return this year shows local movement off Cuba. Originally tagged by NMFS biologists in September of 1998, off Cairbarien, Cuba, this fish was recaptured 11 nm away after 26 days at liberty and is only the eighth sandbar shark returned from this region. Both of these recoveries underscore the need for additional tagging efforts in these areas.
Times at liberty ranged from 3 days to 13.6 years. Most (44) were returned after less than one year. Of these, 35 were tagged as young of the year sandbar sharks (<24" FL) in Delaware Bay as part of a comprehensive coastal shark pupping and nursery study (see Page 17). The majority of these fish (22) showed mostly local movements inside Delaware Bay (<8 nm) and were recaptured within 2 months of tagging. Three local recaptures, however, were recovered after 2 years at liberty. Ten additional Delaware Bay neonate (newborn) tags were recaptured this year: 5 off North Carolina, 3 off Virginia, and 1 each off Maryland and South Carolina after up to 1.2 years at liberty. Recoveries from neonates tagged outside of Delaware Bay include 4 fish tagged off North Carolina in 1996, 3 of which were returned within 57 nm of their tagging location after up to 2.2 years at liberty. The fourth return was recovered in Chesapeake Bay, Virginia (another significant sandbar shark pupping area). An additional young of the year was tagged and recaptured off New Jersey after traveling 8 nm in 25 days.
Shortfin makos were recaptured after traveling distances of 1,923 nm and times at liberty of up to 5.6 years. This is the second highest number of mako returns to date and highlights the cooperative efforts between biologists and recreational, commercial, and foreign fishermen. The longest distance return was from a fish tagged southeast of Saco River, ME and recaptured northwest of Venezuela after approximately 1.8 years at liberty. This is the fifth longest distance traveled for any shortfin mako previously reported to the CSTP; only the fourth recapture off Venezuela; and the first to be recaptured after being tagged in the Gulf of Maine. The 5.6 years at liberty is the sixth longest to date (current record of 12.8 years). Other interesting returns include two makos released SW of the Flemish Cap at the same time by an observer on a commercial vessel that were returned within 4 days of each other one year later. Both were recaptured near the Flemish Cap within 400 nm of each other. Another mako tagged in this vicinity 1 month earlier, was recaptured southeast of Block Island, RI 998 nm to the west after 1.1 years at liberty. A shortfin mako that was tagged for the first time off Montauk, NY and recovered 4 nm away 1 year later, was re-tagged, re-released and then recaptured again 6 months later south of the Flemish Cap approximately 1200 nm away. Three fish were tagged and recaptured with in a period of 4 months off Spain after traveling distances of up to 71 nm. One was originally tagged east of Gibraltar and recovered south of Cadiz, Spain.
Distances traveled ranged from 4 to 3,128 nm. The majority (13) showed movements of over 500 nm with five traveling more than 1,000 nm from their original tagging location. These fish showed movements from North Carolina to south and east of the Flemish Cap, and west of the Spanish Sahara; from Georgia to the Cape Verde Islands; and from Bimini to New York. Of these, the 3 furthest returns represent the second, fourth, and eighth longest distances traveled for any tiger shark previously reported to the CSTP. Other interesting returns include 3 fish recaptured off Cuba, and 3 fish tagged in U.S. waters that were recovered off Mexico (two in the Gulf and one in the Caribbean Sea). These 1998 trans-Atlantic and long distance recaptures for the tiger shark significantly enhance the information on the migratory habits of this coastal pelagic shark species (see map). Overall, times at liberty for tiger sharks ranged from 64 days to 6.0 years with the majority (12) out for less than two years.
Recaptures of other species included some long distance and maximum time at liberty records for the CSTP. A Caribbean reef shark, was recaptured, re-tagged and re-released within 2 nm of its release location after 9.2 years (record time at liberty). A blacknose shark, tagged and recaptured off Florida after 9.5 years, had traveled a distance of 196 nm, a distance and time at liberty record for this species. In addition, important return information was obtained on species of sharks with fewer than ten recaptures. The first two finetooth shark recaptures were made in 1998. Both were tagged in Bulls Bay, SC and were recaptured and re-released in less than 1 month, after traveling up to 12 nm. A smooth hammerhead shark, at liberty for 1 year, was recaptured 3 nm from its original tagging location off Ocean City, MD. This is one of only seven recaptures reported to date. A time at liberty record of 9.5 years and distance record of 2,067 nm was established for the bigeye thresher shark. This shark was tagged southwest of the Cape Verde Islands by Polish research scientists and recaptured off Venezuela and brings the total number of returns for this little known species to nine.