Sampling Fishes in Vegetated Habitats: Effects of Habitat Structure on Sampling Characteristics of the 1-m²Throw Trap

Abstract

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.

A Comparison of Macroepifauna Among Vegetated and Unvegetated Habitats in a South Florida Estuary Using a Passive Sampling Gear

“…Our findings that seagrasses support greater overall abundance, richness, and diversity relative to unve- getated substrate are consistent with earlier reports that structurally complex habitats support more individuals and species (Lewis, 1984;Jordan et al, 1997a). The basket shell, pinfish, and rainwater killifish (Lucania parva), for example, displayed dramatic preferences for seagrass over unvegetated substrate, and this contributed to these differences.…”

“…Comparisons of epifauna found in seagrass meadows and adjacent bare substrates have shown that diversity and abundance is higher (Thayer et al, 1975;Orth, 1977;Virnstein et al, 1983;Bell et al, 1984;Lewis, 1984;Orth et al, 1984;Sogard, 1992;Jordan et al, 1997a;Arrivillaga and Baltz, 1999) and predation lower (Virnstein et al, 1983;Summerson and Peterson, 1984) in vegetated habitats. Arrivillaga and Baltz ( 1999), for example, found that crustacean and fish abundances were 7 and 20 times higher, respectively, in meadows of turtle grass ( Thalassia testudinmn) than over sand.…”

Spatial pattern of a fish assemblage in a seasonal tropical wetland: effects of habitat, herbaceous plant biomass, water depth, and distance from species sources

“…Fish were collected using two methods: throw trap -(consisting of a cubic metal structure (1m³) with the four sides covered by a nylon 1.5 mm mesh) -that is efficient for the collection of individuals up to 100 mm in length (Jordan et al, 1997;Baber et al, 2002, Pelicice et al, 2005, and gill netefficient for different size classes. These fishing techniques were used on different days, so that one method did not interfere with the efficiency of the other.…”

“…These temporary water bodies are formed by the expansion of the littoral zone of the permanent water bodies during each new flood cycle (Junk et al, 1989;Ward et al, 2002). The high availability of nutrients in the system during flooding stimulates the rapid growth of microorganisms, invertebrates and aquatic macrophytes, providing food and shelter for species that exploit this environment (Jordan, et al, 1997;Lowe-McConnell, 1999;Penha et al, 1999;Saint-Paul et al, 2000;Agostinho et al, 2001;Li & Gelwick, 2005). The magnitude and duration of the flood may act in a different way on species that use temporary habitats to complete their life cycle, thus affecting the species composition of aquatic communities that use the river-plain system Petry et al, 2003;Thomaz et al, 2007).…”

Salinity Tolerance of Two Gobies (Microgobius gulosus, Gobiosoma robustum) from Florida Bay (USA)

“…In this study, I was particularly interested in the ability of these fish to survive rapid shifts in salinity because freshwater is presently being diverted via canals, and this will directly affect salinities in the northeastern Florida Bay. It is unlikely that the overall (chronic) level of salinity affects distribution of these fish because they occur over a wide range of salinities (Table 1) Fish were collected with a 1-m 2 throw trap (Kushlan, 1981), which is the most effective gear available for sampling demersal organisms on the shallow, soft mud banks of Florida Bay (Powell et al, 1986;Jordan et al, 1997 Three replicates were completed for each treatment; therefore, a total of 108 individuals were tested for each species (nine treatments X four fish per aquaria X three replicates). Filtered seawater (30 ppt) was diluted with deionized water for salinities of 5-30 ppt.…”