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Seasonal Occurrence of the White Shark, Carcharodon Carcharias, in Waters Off the Florida West Coast, with Notes on Its Life History

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Seasonal Occurrence of the White Shark, Carcharodon Carcharias, in Waters Off the Florida West Coast, with Notes on Its Life History Seasonal Occurrence of the White Shark, Carcharodon carcharias, in Waters off the Florida West Coast, with Notes on its Life History DOUGLAS H. ADAMS, MICHAEL E. MITCHELL, and GLENN R. PARSONS Introduction waters from Cape Cod to Cape Hatteras the occurrence of the white shark off (Casey and Pratt, 1985). The white the west coast of Florida, 2) include re­ The white shark, Carcharodon car­ shark is considered rare south of Cape cent verified records from this area, 3) charias, is typically found in cold and Hatteras and in the Gulf of Mexico present evidence of seasonal (winter/ warm-temperate waters throughout the (Castro, 1983), although the species is spring) occurrence in the region, and 4) world, although occurrences in tropical encountered by both commercial and provide selected life-history data. waters have been documented (Com­ recreational fishermen in these regions. pagno, 1984). In the western North At­ Methods and Materials White sharks caught by commercial lantic Ocean, the species is most com­ longline vessels operating in Florida All white shark specimens examined monly encountered in continental shelf waters are often sold in a small but lu­ were captured by commercial fishermen crative market, primarily for their jaws. with bottom longline gear designed spe­ The high value of white shark jaws and cifically for targeting coastal-pelagic Douglas H. Adams is with the Florida Marine meat has encouraged "erratic spot fish­ sharks or grouper/snapper species. The Research Institute, Florida Department of Envi­ eries" in New York, California, South bottom longline fishing gear used off ronmental Protection, 1220 Prospect Avenue, Suite 285, Melbourne, FL 32901; Michael E. Africa, and South Australia (Com­ Florida's west coast has evolved since Mitchell is with the Florida Marine Research pagno, 1990). Commercial longline the early 1980's. Initially, the bottom Institute, Florida Department of Environmental Protection, 1481-A Market Circle, Port Charlotte, fishermen and seafood dealers on longline fishery in Florida's west coast FL 33953; and Glenn R. Parsons is with the Florida's west coast report that demand waters targeted grouper/snapper species Department of Biology, University of Missis­ for white sharkjaws has increased since and consisted of 4-10 km long stain­ sippi, University, MS 38677. the late 1980's. The jaws from white less steel mainlines with 600-1,500 sharks collected in Florida waters can hooks attached to the mainline with ap­ sell for up to several thousand dollars proximately 2 m long monofilament in unprepared condition for a large, gangions. In the current longline fish­ ABSTRACT-The white shark, Carcharo­ high-quality set, while fully prepared ery targeting sharks off the west coast don carcharias, is considered rare in the jaws may yield double that price '. A of Florida, longline gear typically con­ Gulf of Mexico; however, recent longline similar market for targeted and inciden­ sists of 8-24 km monofilament (or to a captures coupled with historical landings information suggest that the species occurs tally caught white sharks in California lesser degree, stainless steel) mainlines seasonally (winter-spring) within this re­ waters prompted recent legislation with approximately 2 m long monofila­ gion. We examined a total ofseven adult and (California Assembly Bill 522, effective ment gangions. juvenile white sharks (185-472 em total I January 1994) which restricts land­ Total length (TL), fork length (FL), length) captured in waters offthe west coast of Florida. Commercial longline fisheries ings to prevent white sharks from be­ and precaudal length (PCL) of each were monitoredfor white sharks during all coming overfished by commercial and specimen were recorded according to months (1981-94), but this species was cap­ recreational fisheries. Compagno (1984). In this paper, total tured only from January to April. All white Due to its apparent rarity or low en­ lengths are used unless otherwise speci­ sharks were captured in continental shelf counter rate in the Gulf of Mexico, very fied. Total weights were taken when waters from 37 to 222 km offthe west coast of Florida when sea surface temperatures little biological data has been published possible or were estimated according to rangedfrom 18.7° to 21.6°C. Depths atcap­ on the white shark from this region, and Mollet and Cailliet (1993). State of ture locations ranged from 20 to 164 m. verified records are scarce. In this study maturity was determined by macro­ Fishing gear typically used in Gulf of we will I) review historical reports of scopic examination of the reproductive Mexico offshore fisheries may not be effec­ tive at capturing this species, and the ap­ tract, clasper condition, or by published parent rarity of white sharks in this area IG. Hubbell, 150 Buttonwood Dr., Key Biscayne, size-at-maturity estimates (Bigelow and may be, in part, afunction ofgear bias. FL 33149. Personal commun. Schroeder, 1953; Casey and Pratt, 1985; 24 Marine Fisheries Review Pratt, 1993). Testes from one specimen coast of Florida from 1986 through clasper index (clasper length/total were examined histologically, and clasper 1994 (Table 1). Although we solicited length x 100) of 3.5, 14.4, and 10.4%, length was measured on all males. specimens during all seasons between respectively. We histologically sec­ For age determination, vertebrae late 1981 and early 1994, white sharks tioned the testes of the 275 cm shark were removed from the area below the were collected only during winter and and observed fully developed sperma­ origin of the first dorsal fin on several spring months (February and March tozoa. Additionally, a large quantity of of the specimens, and vertebral centrum 1986, April 1987, April 1993, January spermatophores were collected from the diameters were measured to the near­ and February 1994). Mean monthly seminal vesicles, sectioned, and found est millimeter. Determination of verte­ SST of continental shelf waters off the to contain low densities of mature sper­ bral growth bands and age were esti­ west coast of Florida from January 1984 matozoa. The claspers of the largest mated according to Cailliet et al. (1985) to April 1994 ranged from 15.7" to (472 cm) shark were 49 cm long and and Parsons (1985). Sea surface tem­ 31.0°C, although white sharks were were fully calcified. The smallest speci­ perature (SST) data for continental shelf only collected in this region during pe­ men (185 cm) had undeveloped testes, waters off the west coast of Florida were riods when water temperatures were uncalcified claspers, and was immature. obtained from the National Oceanic and 18.7" to 21.6°C (Fig. 1). Locations of The four female sharks were 267, Atmospheric Administration (NOAA) capture extended from waters off 277, 359, and 391 cm long. The ovary Oceanographic Monthly Summary se­ Clearwater, Fla. (lat. 27°58'N), south­ of the immature 277 cm shark contained ries from January 1984 to April 1994. ward to Cape Sable, Fla. (lat. 25°00'N), developing ova. Prominent, partially and ranged from 37 to 222 km offshore. healed scars were observed above the Results Depths at capture locations ranged from insertion of the left pectoral fin of the We examined seven white sharks 20 to 164 m. 391 cm female (Fig. 2). These scars cut (three males and four females) captured The three male sharks collected were through the dermal layer and slightly by commercial fishermen off the west 185, 275, and 472 cm long and had a into the muscle tissue. The wound J N, J N. J N, J N, J J N. J N, J J N, J N, 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 Figure 1. - Mean monthly sea-surface temperatures (SST) for shelf waters off the central west coast of Florida for January 1984 through April 1994 (from NOAA's Oceanographic Monthly Summary series). Vertical lines designate the month of January in each year. Arrows indicate months when white sharks were captured in the study area. 56(4), 1994 25 no validation information is available to determine th.e periodicity of these growth zones. The stomach of the 472 cm male shark contained the remains of a re­ quiem shark, Carcharhinus sp. (prob­ ably C. plumbeus), estimated to be 180 cm long. The stomach of the 391 cm female contained the entire remains (in two sections) ofa dolphin (Delphinidae) estimated at 150 cm long. Two of the white shark specimens were eviscerated at sea, so their stomachs could not be examined. The three other stomachs that could be examined were empty, but not everted. We collected three species of para­ sitic copepods from the 275 cm male shark and the 391 cm female shark. Pandarus smithii and P satyrus were present in the mouth of the male shark, and Dinamoura latifolia specimens were attached to the trailing edge of its Figure 2. - Lateral view of the partially healed scars above the insertion of the left pectoral fin caudal fin. Pandarus satyrus was also of the 391 em TL female white shark. The left edge of the photo shows two posterior gill slits. collected from the mouth and left pec­ toral fin of the female. shape, orientation, and spacing between observed on both immature and mature Discussion parallel punctures, as well as the verti­ individuals in the area, they could not cally orientated lacerations, suggested be confirmed as evidence of mating ac­ The earliest documented white shark that the wound was caused by a con­ tivity (Bruce, 1992). report from the west coast of Florida specific. The placement of these scars Vertebrae were removed from the 277 was a female, estimated to be 457 cm, and the similarity to mating scars found cm and 391 cm specimens. Six growth collected with a set line during the win­ on females of other shark species sug­ bands were counted on vertebrae from ter of 1937-38 off Sarasota (Springer, gest they may have occurred during the smaller shark (centrum diameter = 1939).
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