Date of Graduation

2000

Document Type

Thesis

Degree Type

MS

Committee Chair

Kyle J. Hartman

Abstract

Bay anchovy (Anchoa mitchilli) form a fundamental link in US Atlantic Coast estuaries converting zooplankton biomass to edible fish protein for recreationally and commercially important fish species such as striped bass (Morone saxatilis), bluefish (Pomatomus saltarix), and weakfish (Cynoscion regalis) and are often consumed by many species of seabirds. Bay anchovy numerically dominate the Hudson River ichthyofauna composition from May through November and are considered an important link in the Hudson River Estuary food chain. Power plant entrainment and impingement may negatively affect the bay anchovy population in the Hudson River, based on the pelagic nature and distribution of all life stages found relative to intake areas. To fully investigate power plant impacts and model bay anchovy populations, the reproductive biology of bay anchovy needs to be described in the Hudson River Estuary. Bay anchovy are widely distributed along the US Atlantic Coast (Gulf of Maine south to Florida) and latitudinal similarities and/or differences in reproductive biology and life history parameters may exist in the Hudson River Estuary compared to other Atlantic Coast estuarine systems. This research was initiated because no reproductive data on bay anchovy exists from the Hudson River Estuary. Bay anchovy eggs, larvae and adults were collected in 1996 and 1997 from the following locations: Hudson River Estuary (Varranzano Narrows north to Poughkeepsie, NY); Arthur Kill and Kill Van Kull; East River and western Long Island Sound; lower NY Harbor and Raritan Bay; and Jamaica Bay (1997 only). A combination of ichthyoplankton vertical tows and mid-water trawls were conducted from July through September in 1996 and from May through September in 1997. Samples were collected and processed to determine the spawning season and daily spawning times, estimate reproductive parameters and egg mortality rates, and to determine the distribution and abundance of eggs, larvae, and adults. The bay anchovy spawning season was estimated to last from the end of May to mid September based on back calculated ages of larvae. Daily spawning began between 2000 and 2200 hours and lasted until 0600 hours during the peak of the spawning season. The average size spawning female weighed 3.0 grams and measured 75 mm total length (66 mm fork length) and spawned a mean of 506.1 eggs/g. Greater than 70% of females spawned nightly between June and July and the ratio of males to females was found to be 1:1. Instantaneous hourly egg mortality rates ranged from 0.06 to 0.24 and more than 85% of daily spawned eggs died before hatching. Eggs, larvae and adults were found throughout the entire study area and were most abundant in June and July. No apparent geographic breaks in egg, larvae, or adult distribution were observed and all life stages were found to be homogeneously distributed throughout the study area. Daily spawning duration of bay anchovy in the Hudson River Estuary was found to be much longer than previously documented data from Chesapeake Bay. The percent of eggs dying before hatch was greater in the Hudson River Estuary compared to Great

South Bay, NY and from Chesapeake Bay. Hudson River Estuary spawners were both larger in weight and length compared to both Delaware and Chesapeake Bays and were found to produce fewer eggs per gram of female than Chesapeake Bay spawning females. All life stages of bay anchovy were distributed throughout my study area and compares to distribution results found in Delaware and Chesapeake Bays. Noteworthy differences in reproductive parameters exist, suggesting latitudinal differences from more southerly estuaries.

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