Date of Graduation

2003

Document Type

Thesis

Abstract

We used hydroacoustics to seasonally estimate regional density and combined river region total abundance of larvae, juvenile, and adult bay anchovy in the Hudson River Estuary from May 1996 through September 1998. During the fine scale power plant study, pelagic fish abundance and distribution was determined acoustically in the vicinity of Bowline and Indian Point power plants on the Hudson River, New York during July, August, and September 1996, in a study designed to determine size specific spatial and temporal fish abundance and distribution with respect to environmental classifications in the vicinity of the two power plants. August yielded the greatest (p < 0.05) mean density of fish at both power plants. Fish abundance in the 22.00–39.99 and 40.00–89.99 mm TL size ranges was greater than in the 10.00–21.99 and 90.00–1000.00 mm TL during July and August at both power plants. During September, mean density of 10.00–21.99 mm TL fish increased relative to other sizes, at both power plants. Fish were concentrated in Bowline's near field region, thus increasing the potential for deleterious impingement and entrainment effects there. Over all size classes, mean fish density was significantly greater during darkness at both power plants. During July and August mean fish density was significantly higher between l.5 and 4.5 m (depth strata one) of depth at both power plants. During September there was no statistical difference between depth strata one and depth strata two (>4.5–7.5 m) at Bowline, though each was significantly greater than depth strata three (>7.5 m). Mean fish density from depth strata one was significantly greater than from depth strata two and depth strata three at Indian Point, during September. During tests for interaction among environmental groupings, Bowline's mean fish density was significantly greater under near field, shallow depth (depth strata one), and dark conditions during July and August. This trend shifted to depth strata two during September at Bowline. Mean fish densities at Indian Point were significantly greater for shallow depths and darkness. Overall fish abundance at Indian Point declined to 1.77–1.86% of July and August values during September and showed no significant trend regarding environmental interactions. Generally, the two power plants exhibited similar trends in mean fish abundance with respect to environmental groupings. Bowline's isolated and bathymetrically complex near field lagoon concentrated pelagic fish compared to the river proper. Hydroacoustics were useful in providing a detailed map of fish distribution relative to each power plant over the course of a few days each month. Information gained suggests the use of hydroacoustics to define fish distributions could mitigate negative effects to fish at existing and proposed power plants, through sighting of power plant water intake structures or by providing a biological basis for modified production cycles.

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