Habitat dynamics of summer flounder Paralichthys dentatus within a shallow USA estuary, based on multiple approaches using acoustic telemetry

Abstract

A comprehensive understanding of habitat use for economically and ecologically impor- tant species in estuaries is lacking. This research, based on passive and active ultrasonic telemetry, fo- cuses on temporal and spatial patterns of juvenile and adult (length = 268 to 535 mm) summer flounder Paralichthys dentatus habitat use during years, seasons, tides, and diel periods from 2003 to 2005 in the Mullica River-Great Bay estuary in southern New Jersey, USA. Annual site fidelity was demon- strated by tagged fish that returned to the study estuary and frequented locales within 550 m or less of the sites where they were located in previous year(s). Fish resided within the estuary for a mean of 86 d (range: 1 to 217 d) during summer 2004, the year of the most comprehensive tracking. Fish primarily utilized the lower bay, close to the ocean inlet. Several more mobile individuals moved along the chan- nel of the Intracoastal Waterway in Great Bay numerous times in a single season, while others moved up the bay and into the river in a year when salinity was higher than average. Tagged fish typically used deeper areas of the estuary correlated with high, stable levels of dissolved oxygen (DO) and tem- perature. Over diel and tidal periods, fish resided within small (0.18 km 2 ) areas for 3 to 6 h but were in motion 74% of that time. Together, these observations indicate habitat-use patterns that are stable over long periods (years) but dynamic within shorter time periods (seasons, hours).