On the southeast US coast, nearshore bottlenose dolphins migrate 

 seasonally (Kenney 1990). They travel northward in the summer as far as 

 Delaware Bay, New Jersey, and southward in the winter, where they range 

 into Florida (Mead and Potter 1990, Mallon-Day 1993). Seasonal density 

 changes have been found in Texas bays, cis discussed below, but nothing is yet 

 known about the source of the arriving dolphins or the destination of those 

 departing. It is not known whether migration is inshore between bays, 

 coastally longshore, or directly offshore. 



SURFACING PATTERNS 



Mean dive duratiorxs on the order of 20-40 sec, as we have found, are 

 common in coastal bottlenose dolphins (e.g., Shane 1977, 1990, Wiirsig 1978, 

 Ballance 1992). Though occasional radio-telemetered dives may be spuriously 

 long (dolphins were seen to surface for a breath without expxjsing enough 

 antenna for a signal to be received) maximum dive durations of around 3 

 min have also been observed in Sado Estuary, Portugal (dos Santos and 

 Lacerda 1987). Several studies have shown different dive durations and 

 surfacing patterns to correlate with different behaviors (Shane 1977, 1990, 

 Ballance 1992). We hop)e that further analyses of the surfacing interval data by 

 members of the MMRP will provide a link between surface duration and 

 number of respirations, and an eventual ability to ascertain general behavior 

 by a description of remotely-sensed telemetry information when correlated 

 with the behavioral observations made by the tracking vessel. 



We found longer dives during night than in the day. Long night-time 

 dives by dolphirxs living near or beyond continental shelf waters often signify 

 increased feeding (Wiirsig and Wiirsig 1979, 1980; Norris et al. 1985). In the 

 present study, a difference of only a few seconds would seem to be of little 

 biological significemce. However, the data are means of means, which tends to 

 reduce variability; and, taken together with longer surface durations and 

 lower dive rates at night, we believe that longer average nighttime dives may 

 be related to resting. While no evidence of a diurnal difference was reported 

 for radio-tagged dolphins in Sarasota Bay, Florida by Irvine et al. (1981), 

 Rossbach et al. (1993) found longer dives and more time submerged in the 

 afternoon /evening than in early morning for one satellite tagged individual 

 in Tampa Bay, Florida. 



Some long dives were interspersed with protracted surface times (many 

 seconds, to minutes). These tended to occur more frequently at night, but we 

 also have observed protracted surface durations exhibited by dolphins resting, 

 or feeding or traveling in extremely shallow water (< 0.5 m deep) in the 

 daytime. Irvine et al. (1981) also report that dolphins stayed at the surface for 

 minutes at a time in the Sarasota area. We recorded longer mean surface 



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