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ARS Home » Southeast Area » Stuttgart, Arkansas » Harry K. Dupree Stuttgart National Aquaculture Research Cntr » Research » Publications at this Location » Publication #161253
Title: EFFECTS OF SALINITY ON GROWTH, SURVIVAL, AND SELECTED HEMATOLOGICAL PARAMETERS OF JUVENILE COBIA RACHYCENTRON CANADUM

Author
item DENSON, MICHAEL - SC NATURAL RESOURCES
item STUART, KEVIN - SC NATURAL RESOURCES
item SMITH, THEODORE - SC NATURAL RESOURCES
item Weirich, Charles
item SEGARS, ALBERT - SC NATURAL RESOURCES

Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2003
Publication Date: 12/1/2003
Citation: Denson, M.R., Stuart, K.R., Smith, T.I., Weirich, C.R., Segars, A.L. 2003. Effects of salinity on growth, survival, and selected hematological parameters of juvenile cobia rachycentron canadum. Journal of the World Aquaculture Society. 34(4):496-504.

Interpretive Summary: Interest in cobia Rachycentron canadum as a potential aquaculture candidate for the U. S. has increased greatly in recent years, primarily due to the success of initial culture efforts in Taiwan. This large marine finfish possesses a high market value and research has shown that this species exhibits extremely fast growth rates. However, little is known about the effect of salinity on growth and survival of larval and juvenile cobia. In addition, limited information exists with respect to the affects of salinity on physiology of this species. The present study was conducted to determine the effect of salinity on growth, survival, and selected hematological parameters of juvenile cobia. Fish were reared for 10 weeks at three salinity levels; 5 ppt, 15 ppt and 30 ppt. Growth and survival were determined through biweekly sampling. Blood samples obtained at termination of the study were analyzed to determine hematocrit, blood osmolality and total protein. Results indicated that the overall growth of fish was significantly reduced at lower salinities. In addition, although no difference in survival existed between salinity levels tested, fish reared at a salinity of 5 ppt appeared to be in poor health. Fish reared at this salinity level also had lowered hematocrit and osmolality levels. These findings reveal that, while cobia can tolerate exposure to low salinity environments for short periods of time without mortality, moderate to high salinities are required for sustained growth and health of this species.

Technical Abstract: Cobia Rachycentron canadum juveniles (119.7 mm TL, weight 8.5 g) were reared for 10 weeks at three salinity levels; 5 ppt, 15 ppt and 30 ppt. Growth and survival were determined through biweekly sampling. Blood samples obtained at termination of the study were analyzed to determine hematocrit, blood osmolality and total protein. Results indicated that the overall growth of fish was significantly affected by salinity. Mean (± SE) total length (TL) and weight of fish reared at a salinity of 30 ppt were 201.7 ± 2.6 mm and 47.6 ± 1.9 g, respectively, followed by fish reared at 15 ppt (182.2 ± 1.7 mm, 34.1 ± 1.6 g), and 5 ppt (168.3 ± 5.8 mm TL, 28.3 ± 2.3 g). Differences in specific growth rates among treatments for the 10-week period were also significant. No differences were detected in mean survival among fish reared at salinities of 5, 15, and 30 ppt (84, 94, and 94 %, respectively). However, fish reared at salinity 5 ppt appeared to be in poor health as skin lesions, fin erosion and discoloration were evident. Analysis of blood revealed that, while no differences existed among treatments with respect to plasma total protein, fish reared at a salinity of 5 ppt exhibited significantly reduced hematocrit (25% vs. >30%) and plasma osmolality values (318 vs. >353 mmol/kg) relative to fish reared at higher salinities. Cobia can tolerate exposure to low salinity environments for short periods of time without mortality, however, moderate to high salinities are required for sustained growth and health of this species.