FISHERY BULLETIN: VOL, 77. NO, 



we report here on the size and density of the 

 bottlenose dolphin population in the Port Aransas 

 Pass-Matagorda Peninsula region of the Texas 

 coast as observed in late March 1978 and compare 

 the density figures with those obtained in the 

 previous studies. Observations on T. truncatus 

 distribution, behavior, sighting cues, and the per- 

 pendicular distances of the sightings, and alterna- 

 tive procedures and results are also presented and 

 discussed. 



STUDY AREA AND METHODS 



Based on previous research (Leatherwood el al. 

 1978), a strip transect was designed (Eberhardt 

 1978). The dolphin herds were sighted and their 

 numbers estimated within strips theoretically 

 804.5 m wide (0.435 n.mi.). All sightings, regard- 

 less of the numbers of animals, were statistically 

 considered as a herd, and the term is used here in 

 the general sense of a grouping of animals without 

 implying more complex behavior. To achieve pre- 



cision the same area was surveyed during five 

 replicate flights. The extent of the area surveyed 

 was limited to dimensions that could be covered in 

 7-8 h of flying time and that would provide approx- 

 imately 17^Y coverage of the area on any one repli- 

 cate survey. 



The surveyed territory extended along 160 km 

 (86 n.mi.) of the central Texas coast from Port 

 Aransas at the northern end of Corpus Christi Bay 

 to the base of the Matagorda Peninsula (Figures 

 1-3). This terrain is a complex of bays, bayous, 

 lakes, and channels bordered seaward by long, low- 

 barrier islands. Convoluted arms of the larger 

 bays extend inland into river deltas surrounded by 

 agricultural lands. Marshes fringe much of the 

 barrier and outer bay shorelines and numerous 

 sand and shell reefs, small islands, and spoil 

 dumps interrupt the water areas. Extensive 

 shoals are covered by water of < 1 m, and the 

 deeper parts of the bays are limited to about 4 m 

 depths. Oil well platforms and well heads are 

 numerous in some parts of the bays and man-made 



Mission Bay 



I ' ,^ 



Aransas 



SURVEY DATE SYMBOL 



I 3/26/78 O 



n 3/27/78 • 



m 3/28/78 i 



m 3/30/78 A 



I 4/1 /78 D 



I I I I I I I I I I I 



5 10 (km) 



FlIilKE 1,- 



586 



-Distribution of bottlenose dolphin herds and their estimated numbers from Aransas Pass to MesquiteBay (transects l-8l, 



Texas. 



