Catfish production represented 56% of the total freshwater aquaculture production in the United States in 2020. Hybrid catfish (female channel catfish Ictalurus punctatus × male blue catfish I. furcatus) is rapidly replacing the channel catfish as the fish of choice in the catfish industry of the southern United States. Hybrid catfish appear to tolerate handling and transport well, but no studies have specifically addressed these stressors. This study aimed to comprehensively evaluate the survival rates and physiological stress responses of hybrid catfish across multiple stages of their handling, harvesting from ponds, transport, unloading, and subsequent electrical stunning at the processing plant. Hybrid catfish from ten earthen ponds were observed and sampled before and after they were seined, held in a holding net (sock) in the pond, loaded into truck-mounted transport tanks, and unloaded into holding tanks at the processor. Fish were also sampled after being electrically stunned before processing. Blood samples from 12 individual fish from each sampling point were collected and immediately centrifuged to yield 1.2 mL of pooled plasma. Samples were stored at -80°C until analyzed. The ten independent harvest and transport events were monitored over a year-long period to explore the influence of water temperature on survival and various physiological responses in hybrid catfish. Plasma cortisol, glucose, lactate, and osmolality were monitored as indicators of the primary stress response, the secondary stress response, the degree of anaerobic metabolism, and water balance, respectively. Cortisol was determined by enzyme-linked immunoassay; glucose was determined by the glucose oxidase method; lactate was determined by the lactate oxidase method; and osmolality was determined with a vapor pressure osmometer.
The preliminary analysis of results indicated that harvesting and transporting processes significantly increased cortisol concentrations in both warm (25–32°C) and cool (9–16°C) water temperatures. Moreover, the harvesting, transporting, and unloading process significantly affected plasma glucose and lactate concentrations but not plasma osmolality. Despite the observed stress responses, the overall survival rates remained high, suggesting the fish’s remarkable ability to withstand and adapt to the challenges posed by harvest and transport processes. Based on our findings, it appears that hybrid catfish tolerate harvest and transport well under current management practices. The fish survived, demonstrated an expected stress response, appeared to remain largely aerobic during the events, and maintained water balance.