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Home , Centrophorus, Hexanchus, Sand tiger shark

THE

I TAGGER 1982 SUMMARY

JOHN CASEY, HAROLD WES PRATT, CHARLES STILLWELL PHOTO BY H. W. PRATT

1982 OVERVIEW In 1982 a total of 4,S-53 and (bony ) were tagged under the NMFS Cooperative Shark Tagging Program. These represented 36 species of sharks and 7 species ofteleosts (Table 1). Of the total • OVER 4500 TAGGED AND 139 RECAPTURED IN number of fish tagged, rod and reel fishermen 1982 accounted for 44%; U.S. longline fishermen, 11 %; U.S. Fishery Observers on foreign vessels, 17%; U.S. • TEN TAGGED BLUE SHARKS TRAVEL OVER 2000 Ml Research Vessel Geronimo, 15%; Polish Research Ves­ (U.S. TO EUROPE, AFRICA, AND SOUTH AMERICA) sel Wieczno, 10%; and the remaining 3% were released • FIRST TAGGED CROSSES EQUATOR by NMFS biologists. (NORTHERN TO SOUTHERN HEMISPHERE) A total of 139 tags from 18 species were returned in 1982. These came from blue (66), mako (15), sandbar • TAGGED SETS NEW RECORD OF 17 (10), tiger (9), lemon (8), dusky (6), other sharks (20), YEARS AT LIBERTY (ANOTHER RECAPTURED AFTER and teleosts (5) (Table 2). The categories of fishermen 16 YEARS) who returned tags in 1982 were: U.S. sportsmen (41 %), U.S. longliners (24%), other U.S. fishermen (5%), for­ • SIX SANDBAR SHARKS TRAVEL IN EXCESS OF 1000 Ml eign longliners (21 %), and other foreign fishermen FROM NORTHEAST COAST OF U.S. INTO GULF OF (9%). In the latter categories, tags were returned by MEXICO fishermen from 15 countries including Japan (11), Mexico (5), Korea (5), Cuba (5), Spain (3), Taiwan (2), • TAGGED TIGER AND BIG EYE THRESHER SHARKS SET Canary Is. (2), Canada (1), West Indies, Bermuda and DISTANCE RECORDS FOR SPECIES Bahama Is. (5), and others (3).

SCALLOPED HAMMERHEAD, Sphyrna lewini

Newsletter of the Distribution of th is newsletter is Cooperative Shark Tagging Program limited to active participants in the U.S. Department of Commerce NMFS Cooperative Shark Tagging National Oceanic and Atmospheric Administration Program. This information is pre­ National Marine Fisheries Service liminary and subject to revision. ~s· .f-" · · Northeast Fisheries Center o,.,,4 ~~'< 'lr""ENr , 0 e,o Narragansett, Rhode Island 02882 Printed compliments of Carl Darenberg, Jr., Montauk Marine Basin, Montauk, N.Y. l

Table 1. SUMMARY OF SHARKS ANO TELEOSTS TAGGED, January--December 1982 Blue sharks were recaptured after a maximum of 4 years at liberty and over distances of nearly 3,000 miles. Several blue sharks made transatlantic migrations from North America TAGGED SY to the offings of the Azores, Canary, Madeira, and Cape COOPERATIVE NARRAGANSETT SPECIES TAGGERS BIOLOGISTS TOTALS Verde Islands. Others tagged off the northeastern U.S. were recaptured off Cuba, Barbados, Trinidad, French Guiana, Sharks and Colombia, South America. Recapture distances for blues included 10 over 2,000 miles, 5 over 1;000 miles, 4 over 500 Slue shark 2,268 135 2,403 Sandbar shark 464 0 464 miles, 10 over 200 miles, 10 over 100 miles and 27 "local" Ousky shark 440 0 440 returns (less than 100 miles). 24 0 24 Blacktip shark 68 0 68 The blue shark is a wide-ranging species in which some Spinner shark 5 0 5 mixing occurs between populations in the eastern and west­ 45 0 45 Si l ky shark 52 0 52 ern Atlantic. Until this year, however, we have not seen evi­ White shark 6 0 6 Shortfin mako 1hark 236 0 236 dence that blue sharks cross the equator. In April and May of Lon gfin mako shark 3 0 3 1982, cooperating Polish scientists.aboard the RIV Wieczno Porbeagle shark 10 0 10 Sand 9 0 9 tagged 450 blue sharks off the north coast of Africa. This is an Smooth dogfish shark 11 0 11 area where we have had several recaptures from blues tagged 8onnethead shark 17 0 17 Great 16 0 16 off North America. Two months later one of the Wieczno's Sea 11 oped hammerhead shark 65 0 65 blue sharks was recaptured in the southern hemisphere, hav­ Smooth hammerhead shark 6 0 6 145 0 145 ing travelled from approximately 600 miles north to 600 miles Blacknose shark 7 0 7 Tiger shark 122 0 122 south of the equator. This recapture may be an example of an Finetooth shark 2 0 2 individual straying away from its normal range. However, 109 0 109 47 0 47 the movement appears quite direct since the shark averaged Bi geye 17 0 17 19.0 miles per day. This rate is near the maximum daily rate Co1M1on thresher shark I 0 I Night shark 36 0 36 we have observed in blue sharks from tracking experiments 8ignose shark I 0 I and otper tagging data. Angel shark 6 0 6 Sa ski ng shark 4 0 4 Additional tagging off the European, African, and South Reef shark 32 0 32 American coasts would certainly add to a clearer understand­ Leopard shark 2 0 2 Florida smoothhound shark 2 0 2 ing of the relationships between populations of blue sharks in I 0 I different parts of the Atlantic. granulosus 3 0 3 .I vi tul us 5 0 5 Hammerhead unspecified 29 0 29 Shortfin makos were recaptured after 4.6 years at liberty Thresher unspecified 3 0 3 Sand unspecified 5 0 5 and over distances of 1,500 miles. The longest distance Blacktip unspecified 3 0 3 recorded came from a mako tagged off Oregon Inlet, N.C., Brown/Dusky unspecified 2 0 2 Unknown* 3 0 3 that was recaptured off Barbados, British West Indies (1,534 miles, 56 months). Another return came from a mako tagged Total sharks 4,332 135 4,467 off Texas that was recaptured off the east coast of Florida. Teleosts This is the third mako to demonstrate movement from the Swordfi s h 59 0 59 Gulf of Mexico into the Atlantic. The remaining mako recap­ White marl in 9 0 9 Blue marlin 3 0 3 tures in 1982 generally showed movements of less than 300 Bluefin tuna 7 0 7 miles along the east coast, although some individuals were at Miscellaneous teleosts 8 0 8 liberty for two or three years. Total tel eosts 86 0 86 In 1981 the mako that covered the longest distance was also tagged off Oregon Inlet, N.C., and recaptured off the British Grand Total 4 ,418 135 4,553 West Indies (1,592 miles, 46 months). Although mako sharks tagged off the northeastern U.S. have in the past been recap­ *Includes species reported as "shark". tured in the Sargasso Sea, the West Indies, and in the Caribbean, their overall migration patterns are difficult to describe. So little is known about the makos' life history, OVERVIEW (Continued from page 1) particularly with respect to the distribution of large females The 139 fish that were recaptured in 1982 were originally and their breeding grounds, that it is only from observations tagged by: U.S. sportsmen (52%), U.S. longliners (9%), U.S. covering a wide geographic range that knowledge of this fishery observers aboard foreign longliners (11 %), RIV Gero­ species will advance. For example, makos occur in the Gulf nimo (17%), RIV Wieczno (9%), NMFS biologists and others Stream off Cape Hatteras, N.C., in all months of the year. Yet, (2%). some members of the population undertake the long distance Long lists of statistical information can be a bit indigesti­ movements we mentioned. Unfortunately, it is almost com­ ble for even the strongest of stomachs. Nevertheless the pletely by chance that extremely large specimens have ever above fi~ures reflect the diversity of people who participate in been taken. We would appreciate a telephone call (401-789- the taggmg program. They also show the types of fisheries 9326) from anyone who learns about the capture of a pregnant that are (or can be) directed toward sharks. Any attempt to mako or any mako in excess of 1,000 lb. manage sharks as a resource will, depending on the species, have to consider several different international and U.S. Sandbar sharks were recaptured after up to 17 years at interests. (See article on Recreational Catches in this issue). liberty and over distances of 1,948 miles. With respect to the In 1982, both the number offish tagged and recaptured was tagging program, 1982 was indeed the "year of the sandbar shark." Six of the ten recaptures showed movement from slightly lower .than in 1~81 (826 fewer tagged, 14 fewer recap­ northeastern U.S. into the Gulf of Mexico, and of these, three tures). The difference is largely explained by fewer blue were taken off Mexico. Two of the three returns from Mexico sharks being tagged and recaptured in June of 1982. Poor were tagged off Long Island, N.Y., by the same fisherman weather conditions last spring resulted in reduced fishing and were recaptured 37 miles apart on consecutive days. Her­ effort when blue sharks are normally most abundant off New man Kornaherns tagged a young sandbar shark on June 27, York and New Jersey. Our data from tournaments and results 1976, off Long Island, that was recaptured off Tampico Mex­ of t~ggi.ng efforts later in the summer did not indicate any ico, on September 24, 1982 (6 years at liberty). The foll~wing declme m the shark population. year, on July 8, 1977, he tagged another sandbar shark near 2 the same Long Island location that north coast of Cuba and into the Gulf of swordfish at liberty for up to 2 years. was subsequently recaptured off Tam­ Mexico. Until recently it was consi­ The longest distance covered by a pico on September 23, 1982 (5 years at dered rare north of Florida and its dis­ swordfish was 561 miles from North liberty). Size data from these and sev­ tribution and abundance in the Gulf of Carolina into the Florida Straits off eral other recaptures that were at lib­ Mexico is still not well known. The West Palm Beach. Information on the erty from 3 to 1 7 year· 1 provided longfin mako was also considered a recaptures from other sharks are valuable supporting evidence for our strictly tropical offshore species until included in Table 2. Although we have age analysis from rings in vertebrae recently. It has been reliably (but not mentioned them in this brief over­ (related article in the Newsletter). uncommonly) reported from the outer view we acknowledge the importance The higher percentage of recaptures edge of the as far of these returns in providing informa­ from the Gulf of Mexico in recent years north as Georges Bank. The recapture tion on local movements, growth, and is interesting because it indicates that of an individual that travelled 859 other aspects of our studies. Moreover, sandbar sharks from the Atlantic and miles from the Gulf of Mexico into the your release records include unique Gulf are very likely members of the Florida Straits in 1982 is the longest observations and provide valuable same population. This is not a new distance recorded for a tagged longfin information on distributions, sizes, sex idea, although previous information mako. The 1982 recapture of a bigeye ratios, and species composition for a suggested that sandbar sharks taken thresher that travelled 1,048 miles is variety of sharks. Thanks to all of you in the western Gulf were probably also a new long-distance record for that for making 1982 a successful year. strays from the Atlantic population. species. The was That could still be the case, but recent tagged by a U.S. fishery observer tag returns indicate a higher degree of aboard a Japanese longliner 150 miles mixing between the stocks in the southeast of Cape Cod. It was recap­ Atlantic and Gulf than had been tured by a longliner from Taiwan in the proposed. mid-Atlantic 855 miles east of Ber­ An important aspect of some of the muda. Recaptures were made from four long-term recaptures was that the addresses on the fin tags were com­ pletely worn away. We are fortunate that the tags found their way back to us and that the numbers were still legible. AGE AND GROWTH OF THE SANDBAR SHARK If you hear of anyone who has a tag from a shark, please have him send it to our laboratory. Tiger sharks were recaptured after up Biological information on the age, Age and growth of the sandbar to 2 years at liberty and over distances size at maturity, and rates of growth is shark was estimated from rings in the of 1,500 miles. The longest return came essential for the successful manage­ vertebrae, tagging data, and size­ from a 9'6" (fork length) individual ment of any fishery resource. Our age frequency distributions. Vertebrae measured and released by a U.S. for­ studies are directed toward providing were prepared for age analysis by cut­ eign fisheries observer after it was this information on some of the impor­ ting thin sections (z-z' in Fig. 1 on page 8) caught by fishermen on an Italian tant species of large Atlantic sharks. from the center of each vertebrae after trawler off North Carolina. The Traditional techniques for determin­ which they were stained and mounted shark was tagged in October 1980 and ing age and growth in fishes utilize on glass slides. The "rings" (0-4, Fig. 1) recaptured in January 1982 off Marti­ marks ("rings") on scales, otoliths (ear were then measured with the aid of a nique, West Indies. This is a new long stones), vertebrae, gill covers and fin microscope. Growth zones on vertebrae distance record for a tagged tiger spines. Other methods, such as analy­ from 475 sandbars, including samples shark. Another tiger shark tagged off sis of size-frequency information, tag­ from full term embryos and adults were the west coast of Florida was recap­ recapture data and studies of captive "read" and the measurements used to tured 8 months later on the north coast fish are often used to validate ring back calculate the size of each shark at of Cuba. studies. previous ages. From average back­ Although tagged tiger sharks have As cartilaginous fishes, the elasmo­ calculated lengths at each ring we con­ travelled several hundred miles from branchs (sharks, skates, rays) present structed the growth curves shown in Bermuda into the Gulf of Mexico, and special problems in ageing because Figure 2. The open circles in this figure from Florida to the Bahamas and West they either lack the hard parts used in are mathematical predictions based on Indies, the details of their migrations ageing bony fishes, or, ifthe structures the measured data. The oldest male are largely incomplete. Since the tiger are present, rings are often confused or aged from the vertebrae was 15 years shark is one of the largest sharks, and lacking. However, rings do appear on (154 cm fork length) and the oldest quite easy to identify, a more intensive the densely calcified vertebrae of some female was 21 years (204 cm fork tagging effort in southern areas where sharks which, when compared with length). The estimated age to maturity it is most abundant (i.e., Florida, the size frequency data and tag-recapture was 13 years for males and 12 years for Bahamas, the Gulf of Mexico, and the information, can provide estimates of females. Annual growth averaged 7.5 Caribbean) would be particularly use­ age. cm in males and 7.1 cm a year in ful to understanding their movements. In the past two years we have been females. successful in determining the age and Evidence from 220 tag-recaptured Other species. Returns from other growth of the shortfin mako and the sharks at liberty for up to 17 years also species showed movements of night sandbar shark. A summary report of showed the slow growth rate seen in sharks from the east coast of Florida work on the mako was presented in our the vertebral data. Although many of southward into the Gulf of Mexico and 1981 Newsletter. We present here a these returns came from sharks that northward to Georgia. This species summary of our findings for the sand­ had estimated lengths, 22 sharks that appears to be quite abundant along the bar shark. were measured at tagging and recap- outer edges of the continential shelf from the Middle Atlantic Bight to the Continued on Page 8. 3 Table 2. Tag recoveries : January-December 19B2

GENERAL LOCATIONS DIST, & DIR. CAPTURE METHOD TAGGED BY MONTHS/ TRAVELLED SPECIES TAGGED RECAPTURED LIBERTY N. Ml , TAGGING RECAPT . TAGGER RESIDENCE

Blue shark NE Oregon Inlet , NC E Jekyll Is ., GA 4 364 s LL LL John Bazuin NMFS Obs. II II MS S Block Is. , RI E Jacksonville, FL 5 443 s LL LL RV WIECZNO Pol and ESE Block Is ., RI ESE Trinidad 7 2310 SE FS LL Al Anderson RI SE Mont auk, NY SE Ocean City, MO 1 202 SW RR LL Jim Humphrey .CT S Block Is., RI SE Block Is. , RI 2 30 NE RR RR Lou Rosado NY SW Nantucket, MA E Barbados, W Indies 7 2362 SE LL LL Stephen Connett RI S Mori ches, NY SE Nantucket, MA 22 3B7 NW LL LL Biologist RI S Montauk, NY E French Guiana, s. America 19 217B SE LL LL Stephen Connett RI S Block Is. , RI E Sao Miguel , Azores 31 2357 E RR LL Walter Kapriel ian NY SE Block Is., RI ESE Trinidad 30 2697 SE LL LL Stephen Connett RI S Moriches, NY SSE Block Is., RI 1 73 NE RR RR Frank Signorello NY SE Fi re Is . , NY E Block Is., RI 1 310 E RR LL Ray Wittman NY S Montauk, NY SSE Cape Hatteras, NC 21 390 s RR LL Zac Grossman NY SE Block Is., RI SE Oregon In l • , NC 6 325 SW LL LL Alan Criss NMFS Obs . MS S Shinnecock , NY NE Oregon Inl ., NC 7 271 SW RR LL William Williams NY SE Mont auk, NY E of Cape Cod, MA 10 4B5 E LL LL Stephen Connett RI S Mont auk, NY SE Nantucket, MA 22 1B7 E RR LL Frank Mundus NY S Mont auk, NY S Manasquan, NJ 9 93 SW RR RR Frank Mundus NY SSE Block Is., RI S 34 2BB1 E LL LL Stephen Connett RI SE Shinnecock , NY SE Shinnecock, NY

GENERAL LOCATIONS DI ST. & DIR. CAPTURE METHOD TAGGED BY MONTHS/ TRAVELLED SPECIES TAGGED RECAPTURED LIBERTY N. Ml. TAGGING RECAPT. TAGGER RESIOENCE

W Charlotte Hbr., FL N Cayo Coco, Cuba 8 428 SSE FS LL Clark Balsinger FL E Oregon Inl ., NC N Martinique 15 1556 SSE TN LL Brad Haskell NMFS Obs. MA E May port , FL Ponte Verde Beach, FL 25 21 s RR RR Cathi Frascella FL S Shinnecock, NY SE Ocean City, NJ 12 123 SW RR RR Floyd Carrington NY SE Mori ch es, NY E Barnegat Inl., NJ 1 83 SW RR RR Vin Pascale NY S Shinnecock, NY SSE Atlantic City, NJ

NOTE: BS = Beach Seine; EMB=Embryo; FS= Free Swimming; GN=Gi 11 Net; HL=Hand Line; HP= Harpoon; LL=Longl i ne; NR=Not Reported; Obs . = Foreign Fisheries Observer ; RR=Rod & Reel; SG=Speargun; and TN=Trawl Net.

ESTIMATES OF THE U.S. RECREATIONAL CATCH OF SHARKS IN THE ATLANTIC

The primary consideration of the the east coast of the U.S., including the catch was in the northeast between Fishery Conservation and Manage­ Gulf of Mexico. Maine and Cape Hatteras, N.C. (54%), ment Act (FCMA) is to provide for the We examined several past national followed by the southeast from Cape needs of U.S. interests through the surveys and decided that the most Hatteras to the Florida Keys (26%) and development of. fishery management recent survey, directed specifically at the Gulf of Mexico (20%). Blue sharks plans (FMP's). These FMP's provide sport fishing for billfish and sharks, dominated the overall catch (98,000 estimates of the optimum sustainable provided the "best available data" on sharks, 8.4 million pounds), followed yield for each species (or species the numbers of sharks caught (dogfish by hammerheads (23,503 sharks, 2.6 group), how much is needed by U.S. were excluded). We compared our tag­ million pounds), and mako sharks (17, fishermen, and whether or not any sur­ ging data for 1963 through 1982 to the 973 sharks, 2. 7 million pounds). As a plus is available for foreign nations. number and species composition data species complex, blacktip, dusky, bull, Although tuna are excluded from the in that survey, (Hamm and Slater, sandbar, and other carcharhinid FCMA, the by-catch of sharks and bill­ 1979, NOAA Tech. Memo SEFC-5, 169 sharks were important (76,000 sharks, fish is within the jurisdiction of the pp). Average weights for each species, 7.0 million pounds), particularly in the law. In the Western North Atlantic, from measurements obtained aboard southeast and Gulf of Mexico. Addi­ several nations including Canada, research vessels and from your catches tional species, including tiger, Cuba, Denmark, Japan, Korea, Nor­ at tournaments, were then applied to thresher, and nurse sharks, repres­ way, and the United States participate the numerical estimates from the sur­ ented 6% of the total catch (approxi­ in pelagic longline fisheries primarily vey. Results of our analysis showed mately 14,600 sharks, 2.0 million directed at tuna and swordfish. During recreational fishermen caught 230,000 pounds). These results generally agree the preparation of the preliminary sharks weighing 22. 7 million pounds with our tagging records that show the management plan (PMP) for sharks (overall average 98.1 lb per shark, recreational shark fishery has been I :!',~ ';,°'° a.ked to pwvide e'timatea of although average size differed slightly most intensive in the Middle Atlantic L__ecreational catch of ,h.,ka along in different regions). Most of the shark Bight (Cape Cod, Mass. to Cape Hatte- 5 ESTIMATES (Continued from page 5) ras, N.C.). Since the completion of the sharks to U.S. fisheries has been Islanders have requested and received survey in 1978, however, we have clearly recognized in the fishery man­ an allocation of 500 metric tons (1.1 noticed a marked increase in the agement plan for sharks. Our calcula­ million pounds) of porbeagles and to recreational shark fishery in the Gulf tions and estimates were described in a date that allocation has not been of Mexico and along the east coast laboratory report that was submitted reached in any year since 1978. All south of Virginia. The number of to the Management Councils together other sharks taken by foreign fisher­ taggers and shark tournaments has with information from other sources on men must be returned to the sea. also increased in other areas. This con­ commercial shark catches in the We provided this update in answer to tinued expansion of the recreational Fishery Conservation and Manage­ questions about catches and regula­ fishery generally indicates that our ment zone. Partially due to the size and tions relating to sharks. There are no 22. 7 million pound estimate may be economic value of the recreational regulations on sharks that apply to conservative, and in fact, well below fishery, the current management plan U.S. fishermen. Whether there ever the current actual catch. Although allows for a total foreign allocation of will be, will depend on the future some large sharks are released, catches only 1,150 metric tons (2.5 million demands for sharks in our domestic of young sharks from inshore waters pounds) of sharks. In terms of commer­ fisheries. are not included in any survey. These cial fisheries this is an insignificant catches may be considerable in some amount which seems to have discour­ areas. aged foreign nations from requesting In any event, the importance of an allocation of sharks. Only the Faroe

AN ACOUSTIC TELEMETRY EXPERIMENT WITH SWORDFISH

Partial support for research on large which allowed us to visualize the pres­ of the day. The echo sounder showed apex predators by Dr. Frank Carey ence of some of the other organisms in an aggregation of small fish or squid (WHO!) has been provided by NMFS. the water with our experimental fish. within 10 meters of the bottom. The The following is his report of a recent swordfish stayed in the vicinity of experiment. these echo returns and ignored the abundance of organisms that the echo · As part of our research on large sounder detected in overlying waters. · pelagic fishes we have conducted a In the late afternoon the swordfish number of experiments in which trans­ reached the edge of Corsair Canyon at mitters are attached to billfish, sharks 300 m. It rose up from the bottom and in or tunas, allowing us to follow them in less than 3 minutes lept out of the water course and depth as they swim free in right in front of our bow. We burned our the open ocean. From such experi­ supper. as we all crowded forward to ments we learned that swordfish make watch it breech about 8 times in 10 a regular daily migration between the minutes. surface at night and depths as great as The swordfish again spent.the night 600 m during the day. In the open near the surface over deep water. As ocean these vertical movements are the sky began to lighten, it turned related to light. The swordfish leaves toward the bank again and before the surface at first light just before dawn, it was swimming down with the dawn and comes back up just after of the main sound scattering sunset. In a number of places in the layer which we could follow with the world, however, swordfish may be echo sounder. The swordfish and the found basking or finning on the sur­ sound scattering layer had reached a face during the day. These fish may be 30' depth of 350 meters by 9 AM when we approached by a boat and harpooned. abandoned it to head home to Narra­ This behavior is quite different from On 29 August we were working with gansett. We had followed the fish for 42 the daily v:ertical migration and we the fishing vessel Gale out of New Bed­ hours over a distance of 105 miles. wondered how the two activities were ford. At 2 PM the pilot of the Gale's The muscle temperature record dur­ related. spotting plane found a 250 lb swordfish ing the experiment showed that the Last summer we had an opportunity on the surface on the northeast peak of swordfish cooled slowly when it swam to work with swordfish in the harpoon Georges Bank. Captain William Gell through the thermocline into cold fishery on Georges Bank. NOAA­ harpooned our depth and temperature water, but warmed rapidly when it NMFS provided us with a research ves­ transmitters into the fish and we returned to warm surface water. The sel, the Gloria Michelle, which we returned to the Gloria Michelle to fol­ "basking" behavior of swordfish may equipped for following swordfish. We low it for two days. be related to such changes in body were using transmitters which told the The swordfish swam near the sur­ temperature. We hope to continue these depth of the fish and its muscle temper­ face in the upper 20 meters and left experiments next year and would wel­ ature from a thermistor in the harpoon Georges Bank by the Northeast Chan­ come assistance from interested dart. During such an experiment we nel (Figure 1). It spent the night on the fishermen. measure daily changes in environmen­ surface and moved at a steady speed of tal features such as light intensity and 3 knots to the southwest. At dawn the water temperature structure with next morning, it turned toward the depth, using instruments lowered from bank and when over the 300 fathom the research vessel. On this cruise we curve, dove and swam along the bot­ also had a powerful echo sounder tom on the edge of the bank for the rest 6 THE TEMPERATE HAMMERHEADS

FAMILY SPHYRNIDAE 1 FT 30°5 CM

SCALLOPED HAMMERHEAD Sphyrna Lewini * Head indented at midline * Corners of mouth behind head *Teeth smooth * Maximum size 13 ft.

SMOOTH HAMMERHEAD Sphyrna Zygaena

* Margin of head smooth

* Corners of mouth even with head * Teeth of adults saw-edged * Rear tip of second dorsal closer to tail than scalloped * Maximum size 14 ft.

THE TEMPERATE HAMMERHEADS The scalloped hammerhead hammerhead (Sphyrna mokarran) than 6 ft) inshore species with a (Sphyrna lewini) and the smooth ham­ also has an indented head but adults "shovel" head; and two South Ameri­ merhead (Sphyrna zygaena) are the are distinctive in having a "hammer" can species Sphyrna media and S. two species of hammerhead sharks at right angles to the midline instead of tudes which venture into the Southern that commonly migrate north of Cape swept back as in the scalloped and Caribbean but do not overlap the Hatteras, N.C. They are separated by smooth hammerheads. Both the upper ranges of the scalloped and smooth the presence or absence of a distinct and lower teeth of the great hammer­ hammerheads and are not likely to be indentation in the midline of the head head are serrated (saw-edged). The taken by U.S. anglers. Casey's of the scalloped hammerhead; the great hammerhead is tropical in distri­ "Angler's Guide to Sharks ... " provides smooth hammerhead has only a slight bution and has not been reported north details of the first four species. Our indentation. The teeth of the scalloped of Cape Hatteras. There are three addi­ supplies of this guide are depleted. hammerhead are smooth-edged and tional species of hammerheads that Copies are available for $1.50, from: the corners of the mouth are behind the occur in the western Atlantic: the bon­ The American Littoral Society, High­ rear margin of the head. The great nethead (Sphyrna tiburo ), a small (less lands, NJ 07732.

7 AGE AND GROWTH OF THE SANDBAR SHARK Continued from Page 3. ture grew an average of 5.2 cm a year (1 large sandbar sharks also show to 10 years at liberty). Six of these extremely slow growth. In September sharks measured at tagging and recap­ 1966 an adult male was caught from ture by the authors (after 1 to 5 years) shore at Edisto Beach, S.C. The shark z grew an average of 4.1 cm a year. The was hauled to the beach, measured, following recaptures are examples that tagged, photographed and released. illustrate growth rates for different Ten years later when it was recaptured sizes and time at liberty. A 4 7 cm sand­ and measured at Jacksonville, Fla., it bar which we carefully measured at tag showed little, if any, growth. The pho­ and recovery showed less than 3 cm tograph confirmed it was a large male growth between mid-July and mid­ at tagging and its total length at recap­ September. Another shark, a 99 cm ture (223 cm) was only 2.5 cm less than male we tagged in Virginia was recap­ the maximum reported size for males. tured 15 years later by a gillnet fisher­ Assuming males mature at about 15 man off Rhode Island. Although the years this individual was at least 25 fisherman did not measure the length years old. This recapture and others of the shark, it was one of 26 juvenile suggest that this species may live for sandbar sharks he caught and sold on 30 years or more. the same day. The weights of the Manuscripts for the mako and sand­ sharks and discussions with the fisher­ bar sharks were presented at an Inter­ man established the best fork length national Age and Growth Workshop estimate for the tagged shark was held in Miami, Fla., during February between 130 and 148 cm. Since the min­ 1982. Much of the material for these imum fork length at maturity in male studies was collected during the past sandbar sharks is about 150 cm, and several years on research and commer­ mature male sandbar sharks are usu­ cial vessels and at shark fishing tour­ ally found segregated from juveniles, naments from Massachusetts to New this individual could have been imma­ Jersey. We are grateful to those of you ture at an estimated age of 23 years. A who allowed us to collect samples from recent return came from a 92 cm female your shark catches and particularly to we measured in Virginia in 1965 that you taggers who have contributed so was recaptured 17 years later near much to our research. Campeche, Mexico. The reported length of 125 cm at recapture appears z1 underestimated (1.9 cm/ yr) but assum­ ing the shark had reached an average FIGURE 1 adult size ofl 75 cm it would still show a 1 relatively slow growth rate of 4.8 cm/yr. Individual recaptures from

FEMALES N = 299

/

BACK CALCULATED MEANS o---o VON BERTALANHY

6 8 10 12 14 16 18 20 22 24 BO 1 2 4 6 8 10 12 14 16 18 20 22 24 I R T H AGE {YRS) 8