603 



Abstract— The U.S. Marine Mammal 

 Protection Act requires that the abun- 

 dance of marine mammals in U.S. waters 

 be assessed. Because this requirement 

 had not been met for a large portion of 

 the North Atlantic Ocean (U.S. waters 

 south of Maryland), a ship-based, line- 

 transect survey was conducted with a 

 68 m research ship between Maryland 

 (38.00°N) and central Florida (28.00°N) 

 from the 10-m isobath to the boundary 

 of the U.S. Exclusive Economic Zone. 

 The study area (573,000 km-) was sur- 

 veyed between 8 July and 17 August 

 1998. Minimum abundance estimates 

 were based on 4163 km of effort and 217 

 sightings of at least 13 cetacean species 

 and other taxonomic categories. The 

 most commonly sighted species ( number 

 of groups) were bottlenose dolphins, 

 Tiirsiops truncatus (38); sperm whales, 

 Physeter macrocephalus (29); Atlantic 

 spotted dolphins, Stenella frontalis 

 (28); and Risso's dolphins. Grampus 

 griseus (22). The most abundant spe- 

 cies ( abundance; coefficient of variation ) 

 were Atlantic spotted dolphins ( 14,438; 

 0.63 ); bottlenose dolphins ( 13,085; 0.40 ); 

 pantropical spotted dolphins, S. attenu- 

 ata (12,747; 0.56); striped dolphms, S. 

 coeriileoalba (10,225; 0.91); and Risso's 

 dolphins (9533; 0.50). The abundance 

 estimate for the Clymene dolphin, S. 

 clymene (6086; 0.93). is the first for the 

 U.S. Atlantic Ocean. Sperm whales were 

 the most abundant large whale (1181; 

 0.51). Abundances for other species or 

 taxonomic categories ranged from 20 to 

 5109. There were an estimated 77,139 

 (0.23) cetaceans in the study area. 

 Bottlenose dolphins and Atlantic spot- 

 ted dolphins were encountered primar- 

 ily in continental shelf (<200 m) and 

 continental slope waters ( 200-2000 m ). 

 All other species were generally sighted 

 in oceanic waters (>200 m). The distri- 

 bution of some species varied north to 

 south. Striped dolphins, Clymene dol- 

 phins, and sperm whales were sighted 

 primarily in the northern part of the 

 study area; whereas pantropical spot- 

 ted dolphins were sighted primarily in 

 the southern portion. 



Abundance of cetaceans in the southern 



U.S. North Atlantic Ocean during summer 1998 



Keith D. Mullin 



Gregory L. Fulling 



Southeast Fisheries Science Center 



National Marine Fisheries Service, NOAA 



3209 Frederic Street 



Pascagoula, Mississippi 39567 



E-mail (for K. D Mullin); Keith DMullin(a'noaa-gov 



Manuscript approved for publication 

 11 February 2003 by Scientific Editor 



Manuscript received 4 April 2003 at 

 NMFS Scientific Publications Office. 



Fish Bull. 101:603-613 (2003). 



The U.S. Marine Mammal Protection 

 Act (MMPA) requires that stocks of 

 marine mammal species in U.S. waters 

 be maintained at or above their opti- 

 mum sustainable population (OSP) 

 level, defined as the number of animals 

 that will result in maximum productiv- 

 ity. The MMPA, as amended in 1994, 

 requires that the U.S. National Marine 

 Fisheries Service (NMFS) determine 

 the potential biological removal (PBR) 

 of each stock for management pur- 

 poses. PBR is an estimate of the maxi- 

 mum number of animals that may be 

 removed from a stock due to human 

 activities (e.g. fisheries bycatch) while 

 allowing the stock to reach or maintain 

 its OSP. The PBR is calculated by using 

 the estimated minimum abundance of a 

 stock, half its maximum net productiv- 

 ity rate (theoretical; or estimated), and 

 a recovery factor (Barlow et al., 1995). 

 For the U.S. Exclusive Economic Zone 

 (EEZ) adjacent to the Atlantic coast of 

 the continental U.S., the NMFS cur- 

 rently defines 27 taxa of cetaceans 

 as stocks (Waring et al., 2001). These 

 stocks include 24 one-stock species, 

 bottlenose dolphins (Tursiops trunca- 

 tus) that are divided into two stocks, 

 and one mesoplodont beaked whale 

 stock. Abundance estimates are avail- 

 able for most of these stocks from U.S. 

 waters north of the Virginia-Maryland 

 border (38.00°N). In 1998, except for 

 three stocks, abundance estimates 

 were not available for Atlantic ceta- 

 cean stocks from U.S. waters south of 

 Maryland (Waring et al., 1997). Abun- 

 dance estimates for these three stocks 

 were based on a small amount of effort 

 from a 1992 winter ship survey south 



of Cape Hatteras (Mullin and Ford'). 

 Other cetacean abundance estimates 

 from U.S. waters south of Maryland are 

 for portions of the continental shelf or 

 continental slope (Blaylock and Hog- 

 gard, 1994; Blaylock, 1995; CeTAP2; 

 Fritts et al.-'). 



To estimate the abundance of ceta- 

 ceans in U.S. Atlantic waters south of 

 Maryland, a ship survey was conducted 

 during summer 1998 and the results are 

 reported in this study. Abundance esti- 

 mates from this area are combined with 

 abundance estimates from surveys of 

 U.S. waters north of the Virginia-Mary- 

 land border conducted by the NMFS 

 Northeast Fisheries Science Center to 

 obtain overall abundance estimates for 

 western North Atlantic cetacean stocks 

 (e.g. Waring et al., 2001). 



'Mullin, K.D., and R.Ford. 1992. Report 

 of NOAA ship Oregon II cruise 92-01 

 (198) (a cetacean survey of U.S. Atlantic 

 waters south of Cape Hatteras, winter 

 1992). Southeast Fisheries Science 

 Center, P.O. Drawer 1207, Pascagoula, 

 Mississippi 39568. 



- CeTAP (Cetacean and Turtle Assessment 

 Program). 1982. A characterization of 

 marine mammals and turtles in the mid- 

 and north-Atlantic areas of the U.S. outer 

 continental shelf Final Report of the 

 Cetacean and Turtle Assessment Program 

 Bureau of Land Management, contract no. 

 AA551-CT8-48, 450 p. U.S. Dep. Interior, 

 Washington DC. 



i Fntts, T. H., A. B. Irvine, R. D. Jennings, 

 L. A. Collum, W. Hoffman, and M. A. 

 McGehee. 1983. Turtles, birds, and 

 mammals in the northern Gulf of Mexico 

 and nearby Atlantic waters. Rep. FWS/ 

 OBS-82/65, 455 p. U.S. Fish and Wildlife 

 Service, Office of Biological Services, Wash- 

 ington. D.C. 



