548 



Fishery Bulletin 102(3) 



mid-summer of 2001, from 37.6 r /ic in May to 

 25.7'7< c in June (owing to tropical storm Allison) 

 and rose to 32. 3^ in July. Salinity values were 

 lower and more variable within the inshore zone, 

 ranging from 29 f « to 37^ (33.4%« average) in 

 2000 and from 15%c to 37%o (average 28.87« ) in 

 2001. In contrast, the offshore zone exhibited 

 higher and more stable salinity values, ranging 

 between 337 fc and 38 f ;< (36%< average) in 2000, 

 and between 287« and 36% f (34.97« average) 

 in 2001. Temperature and salinity values are 

 likely to be influenced by variation in precipita- 

 tion between years. Precipitation from January 

 through July of 2000 (14.29 inches) was half that 

 of 2001 (29.92 inches) and well below the 30-year 

 average of 22.17 inches (National Weather Ser- 

 vice, Dickinson, TX). Dissolved oxygen content 

 was similar between years; values decreased 

 throughout the summer months and were higher 

 within the inshore zone. 



Spatial and temporal distribution 



A total of 181 YOY S. dumerili was collected 

 from 42 purse seines over the two-year study 

 period. CPUE values were fourfold higher in 

 2000 than in 2001. averaging 6.38 (±3.0) and 

 1.50 (±0.8) per seine, respectively (Fig. 3A). 

 A significant year effect indicated that rela- 

 tive abundance was higher in 2000 (P= 0.019). 

 Additionally, CPUE values were higher in the 

 offshore zone in both years (Fig. 3, B and C). 

 However, no significant zonal difference existed in abun- 

 dance between the inshore and offshore zones in 2000 

 (P=0.063) or 2001 (P=0.058). Temporal patterns indi- 

 cated S. dumerili was highly abundant in May and June, 

 declining in July in both years (Fig. 3A). A significant 

 seasonal effect occurred for 2000 when highest relative 

 abundance occurred in June with a CPUE of 16.2 (±0.8) 

 (Tukey HSD, P<0.05). 



Size comparison 



Sizes of S. dumerili ranged from 33 to 210 mm SL 

 (mean 125 mm SL ±3.8). Juveniles greater than 100 

 mm accounted for 68% of the total catch, whereas indi- 

 viduals less than 50 mm accounted for only 15%. Size 

 differences of S. dumerili were observed between 2000 

 (average 125.5 mm) and 2001 (average 141.5 mm); sig- 

 nificantly larger S. dumerili were collected from the 

 offshore zone in 2001 (P=0.001). A significant interaction 

 (yearxmonth) occurred that indicated that the magni- 

 tude of size differences was variable over time. Sizes 

 were also significantly different between zones in 2000; 

 larger individuals were collected within the offshore zone 

 (P=0.025). No zonal comparison was performed for 2001 

 because few individuals were collected from the inshore 

 zone. In addition, a trend existed within both years: 

 mean sizes significantly increased from May to June, 

 then decreased in July (Tukey HSD, P<0.05). 



Hatching-date distribution 



Hatching-date distributions for S. dumerili were pro- 

 tracted in both 2000 and 2001. Fishes collected in 2000 

 exhibited hatching-dates from 29 January to 25 May 

 (117 days), whereas those collected in 2001 hatched 

 from 11 January to 30 May (139 days) (Fig. 4). In 2000, 

 over 80% of the fishes appeared to result from spawning 

 events in March and early April. The adjusted distri- 

 butions from the age-specific mortality correction for 

 both 2000 and 2001 were indistinguishable from those 

 without the correction. 



Age and growth 



Results of the age-validation exercise indicated that 

 juvenile S. dumerili deposit otolith increments on a 

 daily basis (Fig. 5). Average increment counts at day 

 5, 10, and 15 were 4.8 (±0.2 SD), 9.2 (±0.4), and 14.0 

 (±0.7), respectively. A relationship between the observed 

 versus expected increments was described by the follow- 

 ing equation: 



Observed increments - 0.92 (expected increments) + 0.14 



(r 2 =0.95) 



where days after staining represent expected increment 

 count. 



