EVALUATION LOW LEVELS OF SALINITY ON HEMATOLOGICAL PARAMETERS AND HEALTH STATUS OF CHANNEL CATFISH REARED IN MULTIPLE-CROP PONDS

Authors: O'NEAL, CLIFFORD - SOUTHERN IL UNIV.; HAWKE, JOHN - LSU; Weirich, Charles

Submitted to: Journal of Aquatic Animal Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2005
Publication Date: 3/1/2006
Citation: O'Neal, C.C., Hawke, J.D., Weirich, C.R. 2006. Evaluation low levels of salinity on hematological parameters and health status of channel catfish reared in multiple-crop ponds. Journal of Aquatic Animal Health. 18:1-10.

Interpretive Summary: Although the majority of channel catfish Ictalurus punctatus in the southern US including Louisiana are produced in freshwater ponds, several producers in the state's northern parishes have access to groundwater sources containing low levels of salinity ranging from 1 to 4 g/L. In addition, Louisiana possesses extensive coastal areas that may be suitable for pond-based aquaculture. Both surface and groundwater sources supplying these coastal areas are typically brackish, with salinities ranging from 1 to over 10 g/L. While research findings suggest that low levels of salinity may prove to be beneficial with respect to catfish production and disease resistance, studies to date have been conducted under culture conditions dissimilar to those employed currently by the catfish industry. The present study was conducted to determine the effect of low levels of salinity on hematology and health status of catfish reared under commercial-like conditions in ponds. Results indicated that, although evaluated hematological parameters (total protein, hematocrit, leukocrit, and osmolality) were greater with increasing salinity (up to 3 g/L), all values were within ranges reported normal for channel catfish. Regarding health status, fish reared at a salinity of 3 g/L seemed to exhibit less parasitic infections, but no apparent differences in disease incidence due to bacterial pathogens were observed for fish cultured in ponds maintained at different salinity levels. These findings suggest that catfish aquaculture could be successful in areas with access to low levels of salinity; however, no added health benefits from low levels of salinity should be expected.

Technical Abstract: A one-year study was conducted to determine the effect of low levels of salinity on selected hematological parameters (total protein, hematocrit, leukocrit, and osmolality) and health status of channel catfish Ictalurus punctatus reared in multiple-crop ponds. Two thousand catfish were stocked into each of 15, 0.08-ha ponds (five replicates per treatment = environmental salinity). Ponds were maintained at freshwater conditions (nominal salinity = 0 g/L) or adjusted to salinities of 1.5 or 3 g/L by NaCl addition. Total protein, hematocrit, and osmolality of fish reared at salinities of 1.5 and 3 g/L were significantly higher than values of these parameters measured for fish reared in freshwater. Although leukocrit of fish reared at a salinity of 3 g/L was significantly higher than that of fish reared at a salinity of 1.5 g/L or in freshwater, levels of this parameter were within normal ranges reported for channel catfish at each environmental salinity. While two bacterial diseases known to routinely affect channel catfish: enteric septicemia of catfish (ESC) and motile aeromonad septicemia (MAS), were observed at each salinity level tested, columnaris disease was not observed during the study. Parasitic infections appeared to be less severe for fish reared at low levels of salinity compared to freshwater. Although hematological parameters measured in this study were higher at increased salinities, values were within ranges reported normal for channel catfish. Results of this study suggest that catfish aquaculture could be successful in areas with access to low levels of salinity; however, no added health benefits from low levels of salinity should be expected.