Jesse T. Trushenski

Safety of AQUI-S 20E (10% Eugenol) as a Sedative for Freshwater Fish

AbstractAQUI-S 20E (10% eugenol) has been shown to be an effective fish sedative for freshwater finfish, but to be approved for use in the United States, the U.S. Food and Drug Administration must be provided with data demonstrating the product is safe to treated animals. Accordingly, we evaluated the safety of AQUI-S 20E when used to sedate Rainbow Trout Oncorhynchus mykiss, Yellow Perch Perca flavescens, and Channel Catfish Ictalurus punctatus. After identifying the highest effective concentrations likely to be used by fisheries biologists to sedate each species to handleable, replicate groups of fish were exposed to this intended concentration (1×) or a 50% higher eugenol concentration (1.5×) for periods of time adequate to effectively sedate 80% of fish to handleable (ET80) or for predetermined treatment periods exceeding the ET80. These predetermined treatment doses (40 and 60 mg eugenol/L for Rainbow Trout, 80 and 120 mg eugenol/L for Yellow Perch, and 100 and 150 mg eugenol/L for Channel Catfish), ...

Comparison of Sampling and Detection Methods for Chinook Salmon and Steelhead Naturally Infected with Myxobolus cerebralis

Myxobolus cerebralis (Mc) is a myxozoan parasite causing whirling disease in hatchery- and natural-origin salmonids. To minimize spread of this parasite and the incidence of its associated disease, fish health professionals routinely screen fish for Mc before stocking or moving the fish to Mc-free waters. Sample collection for Mc traditionally entails lethal sampling of cranial tissue followed by pepsin-trypsin digest (PTD) and screening of the sample for mature myxobolid myxospores (PTD method); however, nonlethal sampling methods would be advantageous in some circumstances, such as when dealing with rare or otherwise valuable fish. Accordingly, we compared Mc detections in cranial cartilage by using the PTD method with PCR assays of fin biopsies collected from juvenile Chinook Salmon Oncorhynchus tshawytscha and adult steelhead O. mykiss. Cranial samples were also analyzed using PCR methods for comparative purposes. Results indicated that Mc could be detected by PCR in fin clips, but the results generated by this approach differed significantly from those associated with PTD- and/or PCR-based analysis of cranial cartilage samples. Polymerase chain reaction-based analysis-of individual head samples and head digest pools in both species as well as fins in steelhead-yielded more positive detections than PTD analysis alone. The PCR-based analysis of head and fin tissues yielded different Mc detection rates in both species, but the nature of the detection disparity varied depending on the species and/or life stage of the fish. We conclude that for lethal cranial samples, neither PTD nor PCR should be used alone, but using these techniques in concert may provide the most complete and accurate estimation of Mc presence in a group of salmonids. If imperiled or highly valuable fish are in question, nonlethal fin samples may be used to generate some information regarding Mc status, with the understanding that parasite DNA detections do not necessarily signify mature infections or disease.

Different Dietary Lipid Sources Affect Plasma Lipid Composition but Not Stress Tolerance or Growth of Hybrid Striped Bass

AbstractTo determine whether dietary lipid sources used in regimens to replace fish oil differentially impact the production performance and physiological status of hybrid Striped Bass (White Bass Morone chrysops × Striped Bass M. saxatilis), the growth performance and stress response of fish raised on diets containing oil from fish, canola, corn, or flaxseed were evaluated. Production performance was unaffected by diet. Net-chasing and handling stress challenges elicited changes in hematology consistent with the generalized stress response, and there was a significant main effect of stressor exposure (P < 0.01) on both plasma cortisol and osmolality, as well as a main effect of lipid source (P < 0.05) on plasma osmolality. Across diets, cortisol and osmolality levels were highest 1 h after stressor exposure (411 ng/mL and 385 mOsm/kg, respectively) but decreased significantly by 4 h poststressor (169 ng/mL and 332 mOsm/kg, respectively). The plasma lipid fatty acid (FA) profile was influenced by diet and...

Extrusion Temperature and Pellet Size Interact to Influence Growth Performance of Hybrid Striped Bass Fed Industrially Compounded Aquafeeds

AbstractThe objective of this experiment was to jointly assess the possible influences of aquafeed extrusion temperature and pellet size and uniformity on growth performance of juvenile hybrid Striped Bass (White Bass Morone chrysops × Striped Bass M. saxatilis). A diet formulated to meet or exceed the nutritional requirements of hybrid Striped Bass was coupled with different feed manufacturing strategies to yield a range of compositionally identical but physically distinct feeds. Batches of feed were extruded at 107 ± 6°C or 127 ± 3°C through dies estimated to yield pellets that were “small” (3 mm), “recommended” (4 mm), or “large” (5 mm) relative to the size ranges suggested for the target fish size. Portions of the uniformly small and large feeds were combined (25:75, 50:50, and 75:25 ratios of small : large pellets) to create additional mixed-sized feeds. Fish were stocked in a recirculating aquaculture system (fish size: 19.6 ± 0.7 g [mean ± SE]; 10 fish/tank) comprising thirty-six 119-L circular tan...