Initial baseline blood chemistry of the oyster toadfish, Opsanus tau.

Blood chemistry is commonly used to explore the dynamics of health in captive animals in biomedical facilities. Yet, studies of blood serum chemistry in teleost fish are almost nonexistent (1). Such information would be beneficial in determining the baseline health and physiology of captive animals. Physiological assays would allow pre-screening of experimental subjects and decrease the loss of time, effort, and animals by indicating which fish are most suited to survive the rigors of surgery, experimentation, and long-term maintenance. In mariculture, early indication of disease or infection would allow therapeutic measures to be. taken to alleviate adverse conditions and resultant death or disease. The oyster toadfish, Opsanus tuu, is a valuable vertebrate model for biomedical research (2, 3), but little is known about its blood chemistry. This study’s objective is to establish some initial baseline values for blood parameters that may be important in understanding the health of the captive toadfish. Male and female toadfish of various sizes (200-1200 g; 1833 cm-standard length) were selected from the holding tanks in the Marine Resources Center (MRC) of the Marine Biological Laboratory. Selection was based on the alertness (erect fin position), integument appearance, and regular respiration of the fish-the same characteristics investigators currently use to choose’ toadfish for experiments. Blood was collected in July 1997 (n = 20) and June 1998 (n = 40), between 0800 and 1000 h, from recently captured fish that had been acclimated for l-2 weeks in MRC holding tanks. These fish were taken from the general population in the holding tanks, and therefore their health status was unknown. Consequently, any fish that died within 45 days of the initial blood sampling (less than 10%) were excluded from the study. Within 1.5 min after the fish were anesthetized in a 0.001% solution of MS-222 (tricaine methanesulfonate), blood was drawn by caudal puncture. A 3ml heparinized syringe and a 25gauge needle were used to extract l-3 ml of mixed arterio-venous blood. Each fish was then weighed, measured, sexed, and tagged with an Avid radio tag. Only one blood sample was taken from each fish. The percentage of the blood volume composed of red blood cells (hematocrit) was determined by transferring a portion of each blood sample directly from the syringe into capillary tubes, which were centrifuged and then read using a Monoject Scientific Critocaps micro-hematocrit capillary tube reader. The remaining blood