Tuckey and Dehaven: Fish assemblages found in tidal-creek and seagrass habitats in the Suwannee River estuary 



105 



-1 — I — I — I — I — I — I — I — I — I — I — I — I — I — I — I — I — I — I — 1— 

 Jan Mar May Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May Jul Sep Nov 



1997 1998 1999 



Figure 2 



Monthly mean values (± standard error) for water temperature, dissolved oxygen, and 

 salinity from January 1997 to December 1999. Circles represent values measured in 

 seagrass habitats; triangles represent values measured in tidal-creek habitats. 



in the number of larger fish. The mean length of each 

 species in each sample was calculated by habitat, and 

 differences in mean length were tested by using fish 

 assemblages as the main factor in a one-way ANOVA. 

 Multiple comparisons tests (Tukey's test) were then 

 conducted to examine significant ANOVA results and 

 these tests determined which assemblages contained 

 fishes with significantly different lengths. 



Results 



Environmental conditions 



The combination of water temperature, salinity, and 

 water depth had the highest correlation (p,^=0.659) 

 with the fish assemblages of any possible combination 

 of measured abiotic variables. Seasonal patterns were 

 observed for water temperature and dissolved oxygen, 



whereas salinity fluctuated in seagrass habitats and 

 generally increased during 1999 in tidal-creek habitats 

 (Fig. 2). Water temperatures ranged from 7.5° to 32.5°C 

 (mean=23.0°C, SE = 0.99) in the seagrass habitats and 

 ranged from 10.3° to 33.3°C (mean=23.1°C, SE = 0.91) in 

 the tidal-creek habitats. Minimum values of dissolved 

 oxygen coincided with the highest water temperatures 

 in each habitat and ranged from 2.9 to 12.7 mg/L in the 

 seagrass habitats and from 2.9 to 13.6 mg/L in the tidal- 

 creek habitats. Salinity, however, was lower during all 

 seasons in the tidal-creek habitats than in the seagrass 

 habitats (Fig. 2). Mean salinity in the seagrass habitats 

 was 27.1%f (SE = 0.91) and ranged from nearly fresh 

 (1.3^?^) to marine (34.8%f ) depending on river discharge, 

 whereas in the tidal creeks, mean salinity was 9.5%c 

 (SE = 0.81) and ranged from 0.0%t. to 29. 0%^. An unusu- 

 ally high period of rain during February and March of 

 1998 decreased salinity values in the tidal-creek and 

 seagrass habitats. 



