Physiological Changes in the Red Drum after Long‐Term Freshwater Acclimation
Abstract The effect of long‐term freshwater acclimation on the blood and plasma ion composition of Red Drum Sciaenops ocellatus was investigated with the goal of elucidating the necessity of ion remediation. Four replicates ( n = 50) of freshwater‐acclimated (FW) fish (1.6 ± 0.2 g) were raised in 25...
| Published in: | Journal of Aquatic Animal Health |
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| Main Author: | |
| Format: | Article in Journal/Newspaper |
| Language: | English |
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Wiley
2013
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| Online Access: | http://dx.doi.org/10.1080/08997659.2013.788582 https://afspubs.onlinelibrary.wiley.com/doi/pdf/10.1080/08997659.2013.788582 |
| Summary: | Abstract The effect of long‐term freshwater acclimation on the blood and plasma ion composition of Red Drum Sciaenops ocellatus was investigated with the goal of elucidating the necessity of ion remediation. Four replicates ( n = 50) of freshwater‐acclimated (FW) fish (1.6 ± 0.2 g) were raised in 25‐m 3 tanks supported by 140,000 L of recirculating water. Four replicates ( n = 50) of seawater (SW) fish groups were placed in 40‐m 3 offshore cages at 32–35 psu. Blood was collected from 100 fish (FW = 578 ± 50 g; SW = 686 ± 45 g) of each group (FW, SW) after 8 months of rearing. During the grow‐out phase, the survival of FW and SW fish was 57.5% and 92.2%, respectively. The water ion composition (mainly the Ca 2+ /K + [43%] and Ca 2+ /Mg 2+ ratios [1%]) explained 56.6% of the plasmatic ion variability in the fish groups. Freshwater exposure produced significant reductions in osmolality and in several plasma indicators (Na + , Cl − , and Mg 2+ ); the K + levels from FW fish were the most compromised parameter. The water Ca 2+ /Na + ratio had a greater influence (44%) on the plasma chemistry parameters, mainly glucose and creatinine. Freshwater‐acclimated fish had a higher percentage of hematocrit, hemoglobin, and red blood cells than SW fish, but the water quality explained only 12.5% of the blood parameter variability between the FW and SW groups. The results support the conclusion that Red Drum tolerates salinity variations and can adopt a relatively stable condition for short periods; however, the data suggest that Red Drum have only a limited ability to withstand a hyposmotic environment for long periods due to their limited ability in maintaining K + concentrations without external supplementation. Freshwater environments with high Ca 2+ /Na + , Ca 2+ /K + , and Ca 2+ /Mg 2+ ratios appear to be a chronic stress factor that should be considered in future experiments. Received June 11, 2012; accepted March 17, 2013 |
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