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Fishery Bulletin 93(1), 1995 



in observer effort, mortality factors, and whale dis- 

 tribution. That increased observer effort could ac- 

 count for the increase seems unlikely. The size of 

 stranded humpback whales and both the public and 

 media interest in such events results in few carcasses 

 escaping notice. Additionally, strandings of finback 

 whales, Balaenoptera physalus, over the same time 

 period have remained relatively constant (1985 to 

 1988, n=10; 1989 to 1992, n=9)) (calculated from 

 MMEP, Smithsonian Institution). An increase for this 

 large baleen species might also be expected if the 

 reported humpback change were due solely to in- 

 creased observer effort. 



If the reported increase in strandings is not an 

 artifact of observer effort, it may be due to an in- 

 crease in factors resulting in mortality, an increase 

 in the number of animals inhabiting the study area, 

 or both. While the tonnage of cargo moving through 

 Atlantic ports in 1989 showed a 9% increase over 

 the mean of the previous four years (calculated from 

 Anon., 1991), the number of vessels using the Chesa- 

 peake Bay area, and probably the rest of the Atlan- 

 tic coast, has decreased because ships capable of car- 

 rying greater tonnage are being used (Pringer 3 ). 

 While a decline in vessel traffic may result in a de- 

 creased risk to whales, it is possible that these larger, 

 faster, deeper draft vessels pose a greater danger 

 than the slower, shallower draft vessels of the past. 

 In addition to commercial shipping, some areas, such 

 as near Chesapeake Bay and northern Florida, are 

 subject to substantial use by military vessels. How- 

 ever, data pertaining to trends in military vessel traf- 

 fic were not available. 



Evidence also indicates that as much as 25% of 

 the reported mortality may be attributable to inter- 



action with commercial fishing activ- 

 ity, such as gill netting. North 

 Carolina's coastal sink gillnet fishery 

 expanded dramatically during the 

 1980's (Ross 4 ). South Carolina, the 

 state with the lowest SIR, banned the 

 commercial use of gill nets in 1987 

 (with the exception of a tended shad 

 net fishery) (Moran 5 ). However, fish- 

 ing effort in the entire study area is 

 inadequately monitored to determine 

 trends (Read, in press; Bisack 6 ). 



While changes in shipping and 

 commercial fishing activity may rep- 

 resent increased hazards to animals 

 inhabiting the study area, they seem 

 inadequate to account for the dra- 

 matic change in stranding levels reported. Each of 

 these hazards existed prior to 1989, the period when 

 strandings began to increase. The most likely expla- 

 nation for the reported increase in mortality appears 

 to be increased use of this area by juvenile hump- 

 back whales that are then exposed to such hazards. 

 Although few standardized marine mammal sur- 

 veys consistently cover the study area, anecdotal and 

 published observations point to a recent increase in 

 live sightings of humpback whales in coastal waters 

 of Florida and Georgia (Kraus 7 ), North Carolina 

 (Barrington 8 ), Virginia (Swingle et al., 1993), and 

 Maryland (Driscoll 9 ). Although reliable estimation 

 of the length of free-swimming whales is difficult, 

 there is general agreement among observers that 

 most, if not all, of the animals frequenting the area 

 are small. 



Changes in humpback whale distribution in rela- 

 tion to changes in prey composition and abundance 

 have been demonstrated elsewhere (Payne et al., 

 1986; Piatt et al., 1989; Payne et al., 1990), and such 

 a prey shift may account for or be an important fac- 



3 Pringer, Captain M. Association of Maryland Pilots, Baltimore, 

 MD 21228. Personal commun., January 1993. 



4 Ross, J. L. 1989. Assessment of the sink net fishery along North 

 Carolina's Outer Banks, fall 1982 through spring 1987, with 

 notes on other coastal gill net fisheries. Special Sci. Rep. 50, 

 North Carolina Dep. of Environ., Health and Nat. Resour., 

 Moorehead City, NC, 54 p. 



5 Moran, J. South Carolina Wildlife and Marine Resource De- 

 partment, Charleston, SC 29422. Personal commun., Septem- 

 ber 1993. 



6 Bisack, K. 1992. Sink gill net fishing activity in the North At- 

 lantic as reflected in the NEFSC weightout database: 1982- 

 1991. U.S Dep. Commer, NOAA, Natl. Mar. Fish.Serv. North- 

 east Fish. Sci Cent., Woods Hole, MA 02543. Unpubl. manuscr., 

 4 p. 



7 Kraus, S. New England Aquarium, Boston, MA 02 110. Personal 

 commun., March 1993. 



8 Barrington, P. North Carolina Aquarium, Fort Fisher, Kuri 

 Beach, NC 28449. Personal commun., April, 1993. 



9 Driscoll, C. NMFS, Office of Protected Resources, Silver Spring, 

 MD 20910. Personal commun., March 1993. 



