Simple and portable methods for assessing the physiological state of channel catfish Ictalurus punctatus would be valuable tools in field situations where problems with blood storage and transportation occur. This study compared the use of handheld lactate and glucose meters with established laboratory methods in stressed (fatigued) and unstressed (control) channel catfish fingerlings. The results obtained from the Accutrend (Roche Diagnostics Corp.) lactate meter and the Accu-Chek Advantage (Roche Diagnostics) glucose meter were consistently lower (P , 0.05) than those obtained with the laboratory reference method. However, significant differences (P , 0.0001) were found between the control and fatigued fish for both lactate and glucose, regardless of the method of analysis. Both handheld meters were found to be reliable and suitable for use in field or laboratory situations where relative measurements are acceptable. The costs associated with using the handheld meters were higher than those associated with accepted laboratory methods; however, the initial capital investment was lower for the handheld meters. Ease of use, portability, and rapidity of sample analysis make the handheld meters attractive alternatives to traditional laboratory methods.

Commercially produced, food‐size channel catfish Ictalurus punctatus that were harvested using routine procedures had significant elevations in plasma cortisol, glucose, and lactate compared with preharvest fish captured from open ponds. Blood samples were taken from 10 fish in each of two treatments (liquid oxygen diffuser‐ and paddlewheel‐aerated holding socks) and four sampling periods (before harvest, after socking, before loading, and before unloading) during each of 10 harvest events. Water column temperatures averaged approximately 27°C during the study. Ten fillet samples were taken from fish held overnight in paddlewheel‐ and liquid oxygen‐aerated holding socks during some harvest events. Mean plasma cortisol levels averaged 3.02 ng/mL before harvest, 84.38 ng/mL immediately after socking, 135.22 ng/mL after 18 h in the sock (i.e., before loading onto the truck), and 128.54 ng/mL after 2–3 h on the truck (i.e., before unloading). Mean plasma glucose levels averaged 34.7 mg/dL before harvest, 95.41 mg/dL after socking, 134.53 mg/dL before loading, and 134.86 mg/dL before unloading. Mean plasma lactate levels averaged 2.43 mmol/L before harvest, 13.24 mmol/L after socking, 11.53 mmol/L before loading, and 7.88 mmol/L before unloading. These results should not be considered maximal until additional studies are conducted with average water temperatures at their highest. There were significant changes within treatment over 7 d of refrigerated storage for fillet pH, color, and drip loss; however, there were no consistent trends between treatments. Results indicate that routine capture and hauling procedures are stressful to commercially produced, food‐size channel catfish under the examined conditions and that using liquid oxygen for aerating fish in holding socks does not significantly improve fillet quality or reduce stress levels.

Four hauling trips of approximately 6 h each were conducted to investigate effects of loading density on survival of golden shiners Notemigonus crysoleucas. Commercially graded golden shiners (mean weight 6 SE, 3.3 6 0.04 g) were transported at densities of 120, 180, and 240 g of fish/L of water in insulated hauling tanks that were filled with fresh well water, chilled with unchlorinated block ice, and aerated with pure oxygen. The criterion for determining success or failure was golden shiner survival. Transportation at a given density was deemed successful if survival both at trip's end and at 18 h postdelivery was at least 99%. At all three hauling densities evaluated, survival exceeded 99% both at trip's end and at 18 h postdelivery. Furthermore, increasing loading density had no effect on whole-body cortisol concentrations, demonstrating that no significant stress response occurred. Un-ionized ammonia concentration increased with loading density (range, 0.05-0.46 mg/L) but had no effect on fish survival. Results of this study indicate that golden shiners can be successfully (!99% survival) transported for up to 6 h at a density of 240 g/L in well water chilled with unchlorinated block ice and aerated with pure oxygen. Higher loading densities could mitigate the effect of escalating transport cost for commercial farmers.

We compared the swimming performance of juvenile pond-cultured and wild-caught channel catfish Ictalurus punctatus using a fixed-velocity, time-to-fatigue protocol as a measure of overall fitness. Swimming performance of juvenile catfish from each source was determined at 10-cm/s intervals between speeds of 30 and 120 cm/s. The identified swimming performance categories included sustained speeds (swimming speeds without fatigue in times !200 min: aerobic metabolism); prolonged speeds (swimming speeds with fatigue in times !20 s but ,200 min: mixed aerobic and anaerobic metabolism); and burst (swimming speeds with fatigue in times ,20 s: anaerobic metabolism). The maximum sustained swimming speed (maximum speed without fatigue in times !200 min) was 40 cm/s for both pond-cultured and wildcaught juveniles. The maximum prolonged swimming speed (maximum speed with fatigue in times !200 min) was 90 and 100 cm/s for wild-caught and pond-cultured juvenile catfish, respectively. The swimming performance of pond-cultured and wild-caught juvenile catfish differed significantly only at 120 cm/s, which was a burst swimming speed for wild-caught juveniles and a prolonged swimming speed for pond-cultured juveniles. The burst swimming speed for pond-cultured juveniles was not determined but was estimated to be more than 120 cm/s. The total length, standard length, fork length, and condition factor of juvenile pondcultured and wild-caught catfish were not significantly different. The reported swimming performance data provide important information on the overall fitness (e.g., ability to obtain prey and avoid predation) of juvenile pond-cultured and wild-caught catfish that will benefit fisheries managers considering the stocking of juvenile pond-cultured channel catfish in managed lakes and rivers as well as research scientists developing and evaluating improved strains of channel catfish for commercial production.

This study was conducted to gain a better understanding of the effect of exposure to the myxozoan Henneguya ictaluri (the agent of proliferative gill disease [PGD]) on host physiology by measuring the variation in selected blood characteristics in three differently affected host taxa (channel catfish Ictalurus punctatus, blue catfish I. furcatus, and blue catfish 3 channel catfish hybrid fingerlings). Forty-five fish of each host taxon were exposed to PGD, and 10 fish of each host taxon were sampled at 24, 96, and 168 h. Fish were weighed, blood was collected and analyzed for a suite of physiological variables, and wet mount preparations of gill clips were examined grossly for the presence of cartilage breaks. The results of this study are consistent with the current knowledge regarding H. ictaluri infections in blue catfish, channel catfish, and blue catfish 3 channel catfish hybrids. Chondrocytic lysis was observed in channel catfish and hybrid catfish at 96 and 168 h but was not observed in blue catfish. There was an observed reduction in oxygen partial pressure (pO 2 ) and an increase in carbon dioxide partial pressure (pCO 2 ) at 96 h in the blood of channel catfish and hybrid catfish, but these changes were not exhibited by blue catfish. For all species, pH decreased as lactate concentrations increased. The lack of physiological changes and the absence of H. ictaluri sporozoites and DNA in gill tissue lead us to speculate that H. ictaluri is unable to establish infection in blue catfish. Current research investigating the mechanisms of infection and portals of parasite entry into blue catfish, channel catfish, and blue catfish 3 channel catfish hybrids is underway to better elucidate the defenses employed by blue catfish against H. ictaluri.