February 15-18, 2009 Washington State Convention Center Seattle ...

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PHYSIOLOGICAL EVALUATION OF A CANDIDATE MARINE BAITFISH Fundulus seminolis
FOLLOWING SEAWATER ACCLIMATION
Matthew A. DiMaggio*, Cortney L. Ohs and B. Denise Petty
University of Florida
School of Forest Resources and Conservation
Fisheries and Aquatic Sciences Program
Indian River Research and Education Center
2199 South Rock Rd.
Fort Pierce, FL 34945 USA
mdimaggi@ufl.edu
US baitfish production had a 2005 farm gate value of $38 million. Aquaculture of marine baitfish species is still in its relative
infancy and increasing coastal property values are forcing marine aquaculture inland. Osmoregulatory limitations of candidate
marine aquaculture species need to be evaluated to determine feasibility of production and marketing. The seminole killifish,
Fundulus seminolis, is a naturally stenohaline freshwater killifish which has recently emerged as a candidate for marine baitfish
aquaculture.
Research specimens were collected from a local water body and screened for pathogens, preceding introduction into the research
system. Treatment groups were subjected to a gradual salinity change from 0 to 32 g/L over predetermined time periods
with freshwater controls for each corresponding time period. Acclimation times of 24, 48, 72, and 96 h were chosen with approximate
salinity increases of 5.3, 2.7, 1.7, and 1.3 g/L, respectively, every 4 h. The final salinity of 32 g/L was attained 4 h
prior to the termination of each treatment. Once the specified acclimation time had been reached the treatment group and its
corresponding control were sacrificed and blood and tissues were collected. Plasma osmolality, sodium, potassium, chloride,
hematocrit, change in body weight, and muscle water content were subsequently determined. Temperature, dissolved oxygen,
pH, TAN, nitrite, total alkalinity, and total hardness were monitored throughout the experiment.
Plasma sodium, chloride, and osmolality values were all significantly (p < 0.0001) elevated for all seawater acclimated fish
when compared with their corresponding freshwater controls. Body weight change revealed variable weight loss across all
control and saline acclimated groups; however, seawater acclimated body weight change values were significantly higher (p
< 0.0001) when compared with values obtained from control fish. Muscle water content percentages corroborated the body
weight change data, showing significantly less water (p < 0.0001) in the muscle samples of seawater acclimated fish compared
with their freshwater counterparts. The hypertonic seawater exposure significantly (p = 0.0007) elevated plasma potassium
concentrations in all but the 48 h acclimation treatment (p = 0.1000). Conversely, hematocrit percentages were variable and
only the 96 h acclimation treatment differed significantly (p = 0.0337) from the 96 h control.