Hypoxia?induced growth rate reduction in two juvenile estuary?dependent fishes.
As eutrophication of coastal waters increases, water quality issues such as hypoxia have come to the forefront of environmental concerns in North Carolina. Many fisheries in North Carolina are dependent on estuaries for essential nursery habitat. Chronic hypoxia during the summer has become a common occurrence in North Carolina estuaries, increasing the exposure of juvenile fish to hypoxic conditions. I conducted a laboratory study to investigate how various degrees of hypoxia affect growth rates of juvenile spot (Leiostomus xanthurus) and Atlantic menhaden (Brevoortia tyrannus) at two different temperatures. For a two?week period I exposed fish to one of four constant dissolved oxygen (DO) levels (6.0, 4.0, 2.0, or 1.5 mg O2 l-1), at one of two temperatures (25ºC or 30ºC). A fifth DO treatment, included for spot at 30ºC, allowed DO to fluctuate from 10.0 mg O2 l-1 during the day to 2.0 mg O2 l-1 at night. This diel fluctuation follows the natural DO cycle in tidal estuarine creeks. Growth measurements were recorded at the beginning, middle, and end of experiments. In all trials, growth rates at 1.5 mg O2 l-1 were significantly lower than growth rates in the 6.0, 4.0, 2.0 mg O2 l-1, and fluctuating treatments. The reduction in growth rate ranged from 31% to 89% among trials. Hypoxia is often associated with fish kills, which attract attention in the media and research. However, sublethal levels of hypoxia typically are more prevalent and may affect fish on a more frequent basis. Hypoxia does not need to be lethal to have detrimental effects on juvenile estuary?dependent fishes.
Advisor:James A. Rice; Joseph Hightower; William Swallow
School:North Carolina State University
School Location:USA - North Carolina
Source Type:Master's Thesis
Keywords:fisheries and wildlife sciences
Date of Publication:04/24/2002