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  • 1
    ISSN: 1749-7345
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Maximum handling sizes, prey size and species preferences, and ad libitum consumption rates were determined for three size classes of redear sunfish Lepomis microlophus feeding on Physa gyrina and Helisoma trivolvis, two common aquaculture-pond snails which serve as intermediate hosts for fish parasites. Maximum handling-size experiments indicated that redear sunfish as small as 14-cm total length were capable of consuming all sizes of Physa typically observed in ponds, whereas only redear sunfish of at least 32-cm total length are capable of consuming all commonly observed sizes of pond-dwelling Helisoma. When presented with a range of sizes of both snail species, redear sunfish consumed higher proportions of smaller- and medium-sized snails; the largest snails offered were uneaten or consumed in relatively small quantities. Multiple linear regression was applied to consumption data to develop a simple model for predicting mean daily ad libitum consumption rate (g/g per d) for redear sunfish feeding on snails with temperature (20–27 C) and fish total length (9–24 cm) as independent variables. Our findings will facilitate prediction of numbers of redear sunfish of a given size required to control populations of Physa and Helisoma in ponds. Such predictions will enable pond owners to quickly evaluate whether stocking redear sunfish as a control agent for undesirable snail populations will be economically and logistically feasible. Findings also indicate potential limitations in the use of redear sunfish to control populations of Helisoma due to the inability of redear sunfish as large as 24-cm total length to consume the largest 30–40% of Helisoma commonly observed in ponds and to the expense of stocking larger fish (32-cm total length) capable of consuming all sizes of Helisoma.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract In situ contaminant and water quality studies were conducted with striped bass prolarvae,Morone saxatilis, in two major spawning areas of the Chesapeake Bay in 1990 to explore the possible effects of water quality and contaminants conditions on survival. Three 96-hin situ survival studies with striped bass prolarvae were conducted at three stations in the Potomac River and three stations in the upper Chesapeake Bay during a major portion of the spawning season (13–20°C). Water quality parameters, inorganic contaminants and organic contaminants were monitored in the water column at these three stations during the experiments. Concentrations of 10 metals associated with precipitation events occurring at field sites on the Potomac River and upper Chesapeake Bay were also determined. Survival of prolarvae ranged from 2 to 17.5% in all three 96-h tests conducted in the Potomac River. Control survival was greater than 79%. Survival of prolarvae during experiment 3 (all stations combined for each experiment) was significantly lower than survival of prolarvae during experiment 1. The low survival of prolarvae during experiment 3 occurred concurrently with a reported “fish kill” on the Potomac River. Chromium (14 μg/L) and zinc (119 μg/L) concentrations exceeding U.S. EPA water quality criteria were reported from a 48-h composite sample taken during experiment 3. Lower than normal pH conditions (6.8 and 6.9) were also documented during this experiment. Arsenic, chromium, and zinc may have been stressful. Survival of prolarvae at the three stations during upper Chesapeake Bay tests ranged from 36 to 52.5% for 96-h exposures but was slightly lower (23–34.5%) during a 120-h exposure. Control survival was 〉81% in all experiments. Survival of prolarvae during all experiments in the upper Bay was similar to natural survival that occurs with this life stage. Adverse water quality and contaminant conditions were not reported in the upper Chesapeake Bay striped bass spawning area. Detectable concentrations of cadmium (0.80 and 0.89 μg/L), aluminum (5.4 μg/L), chromium (1.1 μg/L), and zinc (2.5 μg/L) were reported in acidic precipitation samples (pH 3.4) collected from the Potomac River site. Surface water concentrations of these metals did not increase in the Potomac River study area after the precipitation events. The following metals were detected in acidic precipitation (pH 4.06–5.12) in the upper Chesapeake Bay: 22.1 μg/L Al; 1.1, 1.8, 2.3 μg/L Cd; 1.2 μg/L Cu; 2.7 and 3.1 μg/L Pb and 4.6 μg/L Zn. Concentrations of Al (22.1 μg/L) and Pb (3.1 μg/L) in precipitation corresponded with increased concentrations in the surface waters at a nearby station in the upper Chesapeake Bay study area.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-2959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The objective of this two-year study was to determine the efficacy of an automated limestone slurry doser to neutralize acidic pulses and improve water quality conditions for enhancing survival of early life stages of migratory fish species in a Maryland coastal plain stream. Implications for survival of early life stages of migratory fish species such as yellow perch (Perca flavescens), white perch (Morone americana), blueback herring (Alosa aestivalis) and alewife (Alosa pseudoharengus) are discussed based on the improved chemical conditions in the dosed area of the stream. Despite problems with overdosing in 1991 and failure of the stage transducer to work properly in 1992, the doser was generally effective in neutralizing acidic pulses (pH depressions) in the stream during three major rain events in both years. Chemical conditions (pH and inorganic monomeric aluminum) reported in the non-dosed area during major rainfall events were potentially stressful to both alewife and blueback herring although neither species was reported spawning in the stream during either year. Mitigating the potential impact of acidic conditions on early life stages of important migratory fish species was not sufficient to ensure spawning. It is therefore recommended that habitat improvement measures and well designed fish stocking programs be implemented concurrently with doser operations if the goal is to create optimum spawning conditions for migratory species.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-5141
    Keywords: acidification ; Index of Biotic Integrity ; physical habitat ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study was designed to: (1) evaluate the ecological status of acid-sensitive and non acid-sensitive Maryland coastal plain streams using biological (Index of biotic Integrity [IBI] for fish), chemical and physical habitat conditions; (2) determine if a low IBI for coastal plain stream fish can be related to stream sensitivity from acidic inputs and (3) correlate land use activities and watershed size in the coastal plain streams with biological, chemical and physical conditions. IBI values obtained using 12 community metrics for Maryland coastal plain stream fish demonstrated that there were no significant differences in these values when acid-sensitive and non-acid-sensitive streams were compared. However, other complementary data in acid-sensitive streams such as absence of the acid-sensitive species, blacknose dace and higher numbers and biomass of tolerant species suggested that these streams may be impacted. IBI values were also found to be negatively correlated with various trace metals in acid-sensitive streams but not in non-acid-sensitive areas. Chemical conditions such as trace metals and nutrients were associated with land use activities. Highest concentrations of trace metals (chromium, nickel, and cadmium) were found in streams with the highest percentage of low residential housing. Nitrate concentrations were significantly higher in streams found in agricultural areas than in forested areas. Agriculturally dominated streams with highest nitrate concentrations (〉 10 mg l-1) also contained the highest percentage of livestock feeding operations. The mean IBI score for streams draining agricultural land was higher than the mean value for forested streams when all streams were compared. However, when several streams that were only marginally forested (〈 50%) were removed from the analysis, the IBI scores did not differ significantly by land use. Two physical habitat indices exhibited a strong associated with each other. Each habitat index also correlated with IBI values.
    Type of Medium: Electronic Resource
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