Date of Graduation

2001

Document Type

Thesis

Degree Type

MS

Committee Chair

Patricia Mazik

Abstract

West Virginia aquaculture is an expanding industry currently characterized by smallscale, widely dispersed farms. In 2000, state sales of rainbow trout Oncorhynchus mykiss reached US$611,000. To facilitate future expansion with a focus on product quality as well as production efficiency, identification of limiting factors and new or alternative management techniques are needed. Objectives of this three-month study were to identify how carbon dioxide, a common water quality problem in the region, affects the growth and physiological stress responses of intensively cultured rainbow trout. Growth (weight, specific growth rate, thermal growth coefficient, and condition factor) and physiological stress responses (hematocrit, plasma chloride, glucose, cortisol, and calcium) were quantified. Rainbow trout (261.6 + 24.7 g, mean + SEM) were exposed for 94 d at 13.1 + 0.2oC to one of three free carbon dioxide treatments: a control (22.1 + 2.8 mg/L), medium (34.5 + 3.8 mg/L), or high (48.7 + 4.4 mg/L). During the study, 10 fish/tank were removed at 0, 28, 56, and 84 d for growth and physiological assessments. Fish were also challenged to an acute stress (lowered water levels and confinement) at 93 d during which 5 fish/tank were removed for assessment at –0.5, 0.5, 3.0, 5.5, 9.5, 12, and 24 h. Fish exposed to chronically elevated free CO2 showed significantly decreased specific growth rates and lowered condition factors, although survival remained at or close to 100% for all treatment groups. Rainbow trout from the control treatment had significantly higher final weights (643.9 + 17.4 g) than the medium or high treatment fish (558.9 + 17.4 g and 508.7 + 17.4 g, respectively). Plasma chloride was significantly lower in the high (108.1 + 0.8 mEq/L) and medium (115.0 + 0.8 mEq/L) treatment fish compared with the control fish (120.5 + 0.8 mEq/L) from 28 d through the end of the chronic study (84 d). Significant differences among treatments were not detected for hematocrit, cortisol, glucose, or calcium during the chronic exposure. Fish in all treatments displayed an integrated stress response while simultaneously subjected to the acute stress challenge and chronically elevated carbon dioxide. Hematocrit and plasma chloride showed distinct treatment-dependent responses. At the 0.5 h peak following the acute (confinement) stress, high CO2 fish displayed an impaired (lower) hematocrit (39.0 + 0.8%) compared to control and medium CO2 fish (41.9 + 0.8 and 41.0 +0.8%, respectively). Plasma chlorides from the medium and high CO2 fish were significantly lower (123.7 + 1.4 and 118.6 + 1.4 mEq/L, respectively) than the control (133.4 + 1.4 mEq/L) from 3.0 h through the end of the study (24 h)

Download

Share

COinS