MEPS 213:253-271 (2001) - doi:10.3354/meps213253
Spatially explicit analysis of estuarine habitat for juvenile winter flounder: combining generalized additive models and geographic information systems
Allan W. Stoner*, John P. Manderson, Jeffrey P. Pessutti
ABSTRACT: Quasisynoptic seasonal beam trawl surveys for age-0 winter flounder Pseudopleuronectes americanus were conducted in the Navesink River/Sandy Hook Bay estuarine system (NSHES), New Jersey, from 1996 to 1998, to develop spatially explicit models of habitat association. Relationships between environmental parameters and fish distribution were distinctly nonlinear and multivariate. Logistic generalized additive models (GAMs) revealed that the distribution of newly settled flounder (<25 mm total length) in spring collections was associated with low temperature and high sediment organic content, placing them in deep, depositional environments. Fish 25 to 55 mm total length were associated with high sediment organics, shallow depth (<3 m), and salinity near 20 ppt. The largest age-0 fish (56 to 138 mm) were associated with shallow depths (<2 m), temperature near 22°C, and presence of macroalgae. Abundance of prey organisms contributed significantly to the GAM for fish 25 to 55 mm total length, but not for fish >55 mm. Independent test collections and environmental measurements made at 12 new sites in NSHES during 1999 showed that the GAMs had good predictive capability for juvenile flounder, and new GAMs developed for the test set demonstrated the robustness of the original models. Maps for the probability of capturing fish of particular sizes were produced by integrating GAMs with maps of environmental data in a geographic information system (GIS). These plots revealed 2 important centers of settlement in the system, probably related to hydrographic conditions, and the fact that nursery locations shift rapidly with fish size during the first year of life. It was also apparent that nursery habitats are dynamic ‹ expanding, contracting, and shifting position with changes in key environmental variables.
KEY WORDS: Habitat · Nursery · Spatial analysis · Generalized additive model · Estuary · Flounder
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