Enclosure traps that quickly surround well-defined areas of habitat are perhaps the most widely used method for sampling fishes in vegetated habitats. However, relatively few data are available to evaluate the effects of habitat structure on sampling characteristics of enclosure traps. In this study, we determined how clearing efficiency and accuracy of 1-m 2 throw traps varied across a range of environmental conditions in the Florida Everglades by sampling within enclosed areas of marsh habitat. Throw trap clearing efficiency and sampling accuracy did not differ among two widely separated locations and appeared to be unaffected by variation in water depth, canopy height, plant cover, plant stem density, and periphyton volume. Sampling accuracy averaged 63% of fishes present after correcting for clearing efficiencies. On average, 83% of the fishes present in a throw trap were recovered. Therefore, it appeared that about 17% of the missing fishes may have burrowed into the substrate or been discarded with sorted detritus. In contrast, the remaining 20% of fishes probably avoided the throw trap. This is the first study to differentiate between potential sources of throw trap sampling errors. Importantly, density estimates obtained by throw traps were positively correlated (r = 0.82) with actual population densities. Mean fish lengths and fish size distributions obtained by throw trapping usually did not differ from actual mean lengths or fish size distributions. Finally, high concordance of fish species ranks indicated that throw traps accurately described fish community structure. Throw traps appeared to provide relatively accurate estimates of fish density, fish size, and community structure across a range of environmental conditions.

We evaluated the effectiveness of airboat electrofishing for sampling large fishes (standard length, SL ≥8 cm) in shallow, vegetated habitats. Concurrent block‐netting (0.1 ha) and airboat electrofishing were conducted at 11 sites in freshwater marshes of the Florida Everglades. We found significant positive relationships between log‐transformed electrofishing catch per unit effort (CPUE) and both fish density (number/0.1 ha) and biomass (grams dry weight/0.1 ha) estimates from block nets. Analysis of covariance revealed that estimates of species richness were similar for electrofishing and block‐net samples after accounting for differences in the total number of individuals sampled. Nevertheless, length‐frequency and species‐composition data differed between airboat electrofishing and block‐net samples. Relative abundance of yellow bullheads Ameiurus natalis, Seminole killifish Fundulus seminolis, sunfishes (Lepomis spp.), and small size‐classes of all species, were lower for electrofishing than for block‐net samples. Florida gars Lepisosteus platyrhincus, largemouth bass Micropterus salmoides, and large size‐classes of all species, had greater relative abundances in the electrofishing samples than in the block‐net samples. Despite these differences, CPUE from airboat electrofishing was positively related to fish density in block nets for two size‐classes (from 8 to <12 cm SL and ≥12 cm SL). Residuals from the CPUE–fish density regression were unpatterned with respect to water depth, conductivity, and floating‐mat volume but were positively related to emergent‐stem density. This suggests that electrofishing was less effective in sparsely vegetated habitats, possibly because fish were better able to detect and flee from the airboat. Our study suggests that airboat‐electrofishing (log10CPUE) provides a useful index of the abundance of large fishes in shallow, vegetated habitats, but length‐frequency and species‐composition data should be interpreted with caution. Additionally, emergent‐stem density should be included as a covariate in statistical analyses of airboat electrofishing CPUE.