Abstract
AbstractWe conducted hydroacoustic, gill‐net, and push trawl surveys to quantify changes in habitat‐specific fish size and biomass in shallow (<2‐m) estuarine waters of Barataria Bay, Louisiana, in order to evaluate essential fish habitat. Surveys were conducted monthly between June 2003 and May 2004 among regions located along a north—south salinity gradient. The fish length distributions derived from the gill‐net and push trawl catches showed moderate concordance with the measured target strength distributions, indicating that our integrated approach more effectively characterized the fish community than using only a single gear type would have. Acoustic estimates showed that biomass was highest during fall (mean ± SE; 2.30 ± 0.27 g/m3) and next highest in spring (1.49 ± 0.20 g/m3), with relatively low biomass during summer (0.70 ± 0.14 g/m3) and winter (0.86 ± 0.14 g/m3); pelagic fish biomass from nets was low during winter (53.9 ± 14.9 grams per unit effort [gpue]) but relatively high in fall (846.1 ± 207.2 gpue), spring (774.3 ± 175.5 gpue), and summer (620.3 ± 140.7 gpue). Oyster habitat supported a greater biomass of pelagic fish (acoustic survey: 1.54 ± 0.15 g/m3; gill‐net survey: 467.3 ± 81.0 gpue) than soft‐bottom habitat (acoustic: 0.94 ± 0.11 g/m3; gill‐net: 315.2 ± 54.8 gpue). Among regions, the greatest biomass of pelagic fish was observed at polyhaline stations (acoustic: 1.78 ± 0.19 g/m3; gill‐net: 654.3 ± 136.5 gpue), followed by mesohaline (acoustic: 1.18 ± 0.15 g/m3; gill‐net: 378.5 ± 79.1 gpue) and oligohaline stations (acoustic: 0.82 ± 0.12 g/m3; gill‐net: 228.3 ± 50.2 gpue). Gill‐net biomass was linearly related to the acoustic biomass estimates of small pelagic fish. The complementary, multigear approach proved to be useful in evaluating habitat use and may be particularly helpful in identifying and monitoring ecosystem reference points to evaluate change and in standardizing ecosystem‐based assessment approaches.
Highlights
Links between estuarine ecosystems and fishery production have been inferred by many studies
Aside from marshes, two habitats dominate the estuaries in Louisiana: soft-bottom and subtidal oyster reef–shell; softbottom habitats are predominant in Barataria Bay
Target strength estimates were variable across seasons (P, 0.05) and habitats (P, 0.001), generally decreasing with increasing salinity, not Downloaded From: https://bioone.org/journals/Marine-and-Coastal-Fisheries:-Dynamics,Management,and-Ecosystem-Science on 02 Nov 2021 Terms of Use: https://bioone.org/terms-of-use
Summary
Links between estuarine ecosystems and fishery production have been inferred by many studies Estuarine systems have been shown to serve as nursery habitat for many transient and resident fishes, including important commercial and recreational species (Rozas and Minello 1998; Dahlgren et al 2006). In 2006, marine recreational and commercial fisheries in Louisiana accounted for US$2.3 billion in retail sales, 36,700 jobs, $598 million in salaries and wages, and $146 million in federal income tax revenue (LDWF 2006), highlighting their economic importance in addition to their ecological importance; estuaries are important given the proportion of the harvest comprised of estuarine-dependent species (75–85%; NOAA 2009). Biases in the fishing gears used to collect samples can affect the observed trends in catch (Hayes et al 1996; Hubert 1996; Jackson and Harvey 1997)
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