262 



Fishery Bulletin 100(2) 



dominated (83.3'7f ). Females were more prevalent in class 

 rV {GG.T^'i). Males showed the lowest numbers of strand- 

 ings in class III (n=5) and highest numbers in class V 

 (/(=20). 



Neonates Neonates represented 19.6^/(- (;(=27) of the total 

 number (;) = 138) of strandings of dolphins with known 

 length, ranging from 13.3'^^ in 1993 to 24,1'f in 1994 and 

 were found in every month of the year, except March (Fig. 

 4). Twenty (74.1%) neonates stranded during the spring 

 (« = 14) and summer (n=6) months. June had the greatest 

 number of strandings in=7), followed by May («=4) and 

 November (;? =4). Thirteen of the 27 neonates {48.19i ) were 

 <100 cm. Twelve of these stranded during the spring and 

 fall months. More female neonates (1.3:1.0) stranded in 

 South Carolina than males, though this difference was not 

 significant (X" test of association; P=781). 



Twenty-four (88.9'7t) of the neonates stranded in zones 2 

 (?! = 13) and 3 (n=ll). Neonates were found dead in the in- 

 ner waterways (?! = 18) and along the outer beaches (;?=9). 

 Twelve of the dead neonates found in the inner watei-ways 

 were retrieved while they were floating. 



Females ^220 cm Females found at a length that showed 

 them capable of being reproductively mature (i.e. >220 cm) 

 (Odell, 1975; Mead and Potter, 1990) represented approxi- 

 mately 507( (?i=30) of the total number (/!=61i of females 

 stranded. The proportions of females >220 cm stranded 

 each year were similar, with the exception of those for 

 1992. where only one out of seven females was this length. 

 However, this finding may be biased, except for 1994, 

 because of the number of animals >220 cm that were 

 of unknown sex. The proportion of strandings of females 

 >220 cm in each season was statistically significant (X" 

 goodness-of-fit; P=0.011). A large proportion of the lengths 

 of female bottlenose dolphin stranded during winter (40'~( i 

 and spring (40%) were >220 cm compared with lengths for 

 summer (6.7%) and fall (13.3%). 



Human interaction 



The total number of stranded bottlenose dolphins where 

 either human interaction or no human interaction could 

 be determined was 108. Twenty-five bottlenose dolphin 

 strandings, averaging five per year, showed evidence of 

 human interaction. Eighty-three showed no signs of human 

 interaction and 45 could not be determined (Table 1). Inci- 

 dents of net entanglements, made evident by rope or line 

 marks, net (mesh) marks, and mutilations, accounted for 

 16 of the human interaction cases. Incidence of confirmed 

 human interaction on bottlenose dolphins was highest 

 from March to July (/? = 18). Rope or line marks were more 

 prevalent from February through May (n=8). The ratio of 

 males (?i = 10) to females (/; = 11) was 1:1 in the number of 

 positive human interactions, but there were differences in 

 the length class and types of interaction between the sexes. 

 Of the five males that were involved with net entangle- 

 ments, four were less than 218 cm. Of the eight females 

 associated with entanglements, seven were greater than 

 210 cm and six of these were >220 cm. Eighty-eight percent 



Jan Feb Mar I Apr May Jun I Jul Aug Sep I Oct Nov Dec 

 Winter I Spring I Summer I Fall 



Months 



Figure 4 



Total number of strandings of neonatal bottlenose dol- 

 phins in each month froml992 tol996 1/1=27). Diagonally 

 lined bo.\es represent those neonates <100 cm in length. 



of reported human interactions occurred in zones 2 (/) = 10) 

 and 3 (n=12). Preliminary analysis of stomach contents 

 from bottlenose dolphins stranded on account of human 

 interaction in our study showed that the majority of ani- 

 mals had full stomachs with shrimp or fish remains (or 

 both)(McFee, personal obs.). 



Discussion 



Despite the establishment of an organized marine mammal 

 stranding network in the southeastern United States since 

 1990, there has been little published on basic data from 

 stranded bottlenose dolphuis other than from reports that 

 can be found as "gray literature." Results from our study 

 indicated the value of analyses of strandings and produced 

 three main findings: 1) the northern portion (zone 1) of 

 the state reported significantly more bottlenose dolphin 

 strandings between November and March 2 ) neonatal bot- 

 tlenose dolphin strandings occurred with more frequency 

 between May and July and 3) evidence of human interac- 

 tion as the cause, or contributing factor, in the deaths of 

 some bottlenose dolphins. 



Several hypotheses regarding stock structure of Atlan- 

 tic bottlenose dolphins have been proposed (Hohn, 1997). 

 One hypothesis is that a single coastal migi'atory stock mi- 

 grates seasonally from Long Island, New York, to the cen- 

 tral east coast of Florida (Scott et alM. The other hypoth- 

 esis is that multiple bottlenose dolphin stocks exist that 

 include 1) year-round residents with small home ranges, 

 2 ) seasonal residents with large home ranges, or 3 ) migra- 

 tory groups with long-range movements (Hohn, 1997). 



Bottlenose dolphins begin to leave Virginia in mid-Oc- 

 tober and are mostly absent by mid-November (Swingle, 



^ Scott, G. P., D. M. Burn, and L. J. Hansen. 1988. The dolphin 

 die-off: long-term effects and recovery of the population. Proc. 

 of the Oceans '88 Conf. m; p. 819-823. Unpubl, manu.scnpt. 

 Southeast Fisheries Science Center, 75 Virginia Beach Dr, 

 Miami, Florida 33149. 



