Fishery Bulletin 100(1) 



Results 



Rainfall patterns 



In 1993 and 1994, mean annual rainfall at 

 Coro was 228.4 and 58.7 mm, respectively. 

 Precipitation, which was below the histori- 

 cal yearly average (403.5 mm; 1921-87), was 

 distributed irregularly. Wet and dry seasons 

 did not show any evident pattern (Fig. 2). In 

 1993, rains peaked in April and May, and sec- 

 ondary peaks occurred in July and Novem- 

 ber, whereas in 1994, precipitation reached a 

 maximum during July-August and there was 

 a lesser amount in January. During the latter 

 year, four months were entirely deprived of 

 rain (Fig. 2). 



Physicochemical variables 



Water temperature means and ranges from 



two-year monthly measurements at the estu- 



arine and three foreshore stations are shown in Figure 



3A. Temperature did not differ significantly among marine 



sites. However, mean water temperature was higher in the 



estuarine site (Table 1), with an average of 29°C, and so 



was the range, 25-34°C (Fig. 3A). 



Mean salinity and its range varied slightly between ma- 

 rine stations (Fig. 3 1. The highest value was reached at 

 station 1 and the lowest at stations 1 and 2. Salinity was 

 significantly lower in the estuarine site (Table 1), but its 

 range was much wider than at any other site (Fig. 3). Sa- 

 linity varied very little over time at the marine stations, 

 with the exceptions of the beginning of 1993, when salin- 

 ity dropped to nearly 30%(r, and November-December 1994 

 and the onset of 1994, when the water reached hypersa- 

 line levels (Fig. 3). Salinity at the estuarine site varied 

 widely through time, peaking in February 1993, January 

 1994, and August 1994. Minima were registered in Sep- 

 tember 1993 and July 1994 (Fig. 3). 



Mean dissolved oxygen was highest at station 2 and 

 lowest at the estuarine site, where similarly the lowest 

 absolute value obser\'ed throughout the study was re- 

 corded (Fig. 3). At the marine stations, dissolved oxygen 

 had a smaller range than at the estuarine site, whereas 

 the range was shifted to lower values. Oxygen increased 

 steadily from the end of 1993 until the end of 1994, 

 when concentrations plunged at stations 3 and 4, and less 

 abruptly at station 1. At station 2, the oxygen concentra- 

 tion increased to a maximum value at the end of the year 

 (Fig. 3). However, no significant differences in dissolved 

 oxygen were found between stations (Table 1). 



Distribution, abundance and diversity 



Surf zone A total of 478 swimming crabs were collected 

 during the first stage of our study in the surf and at the 

 estuarine pond (Table 2). Overall, A. cribrarius and C. dauae 

 dominated. They were followed by C. bocourti. C. sapidus, 

 C. exasperatus, C. maracaibocnsis. and C. larvatiis. At the 



marine biotope, where five species of portunids were caught 

 throughout our study, A. cribrcD-ius was the prevailing spe- 

 cies, with shares of 77.5%, 73.7<X and 86.5%, at stations 1, 

 2, and 4, respectively. The second most abundant species 



