Spotted Seatrout Distribution in Four Coastal Louisiana Estuaries

Abstract

We analyzed experimental gill-net catches of spotted seatrout Cynoscion nebulosus at 28 stations in various estuarine habitats over 3 years (1988–1990). Cluster analysis indicated that the 28 stations reduced to three “natural” groupings representing salinity zones that correspond to upper (oligohaline, 0–9‰), intermediate (mesohaline, 10–14‰), and lower (polyhaline, 15–30‰) estuarine zones. Principal components analysis applied to log-transformed gill-net catches yielded a two-factor model that explained 78% of the variation in the data; factors were interpreted as recruit size (females smaller than 31 cm in total length and males smaller than 26 cm) and spawner size (females larger than 31 cm and males larger than 26 cm). Both recruit and spawner models were highly significant (P < 0.0001), and the zone-by-season interaction accounted for the greatest proportion of the variation in the models (P < 0.0001). Abundances of recruit and spawner spotted seatrout were greatest in the lower estuarine zone (15–30‰) during the spawning season (May–August), when both recruit and spawner abundances had high positive correlations with salinity (P < 0.01). After the spawning season (September–December), spawners were uniformly distributed over all estuarine zones, whereas recruits were significantly more abundant (P < 0.01) in the upper estuarine zone (0–9‰). During this time, recruit spotted seatrout abundance showed a high negative correlation with salinity (P < 0.01).