Biologger attachment and retention in channel catfish (Ictalurus punctatus)

Accelerometers capture detailed, real-time information over extended periods, offering perspective on the movements, physiology, and behavior of free-roaming animals in varying environments. Within economically significant aquaculture systems, acceleration can be used as a quantitative surrogate for metabolism and contribute data for energy models and fish welfare indices. For channel catfish ( Ictalurus punctatus ), the most commonly cultured fish in the United States, little is known about how various attachment types (either external or internal) might impact the acceleration-metabolism relationship or, for internally attached tags, how well fish can retain tags given the species' propensity to expel foreign objects. We placed accelerometers either internally or externally in channel catfish and took simultaneous measurements of acceleration and metabolic rate over increasing water velocities in a flume. For internal attachments, we also examined retention time of accelerometer units of varying shapes that had similar volumes (the manufacturer's original shape that was rectangular and designed for hydrodynamics while attached to an outer fin, a flattened cylindrical shape, and an oval shape). We found a distinct relationship between metabolism and acceleration in relation to water velocity given the location of accelerometer placement, with a 23 % lower metabolic rate and 43 % lower acceleration for fish with internal accelerometers compared to external accelerometers. This translated to a lower metabolic-ODBA relationship for internal accelerometers which is likely indicative of an effect of drag and tail undulations for units that were externally attached. When looking at retention, we found that the manufacturer's accelerometer shape drastically increased the chances of mortality over the course of 15 weeks (71 % mortality compared to 20 % for the oval shape and 8 % for the flattened cylinder). The odds of retention dropped by 66 %, 72 %, and 67 % for the oval, flattened cylindrical, and manufacturer's shapes over 10 weeks, respectively. Notably, channel catfish had a remarkable propensity to expel tags implanted into the peritoneal cavity, with no accelerometer tags retained after 15 weeks, a propensity which has been documented in other studies on catfish and in other species such as rainbow trout ( Oncorhynchus mykiss ). We recommend that users determine acceleration-physiology relationships in relation to tag placement before broad scale use and that flattened cylindrical shapes are used for internal tags. This work further emphasizes the need for groundwork for biologging technology before it is used as a tool for improving management of aquaculture operations. • Accelerometer attachment and shape can vary in channel catfish. • Acceleration-metabolism-velocity relationships were examined for various attachments. • Retention of various internal shapes was also examined. • Relationships were higher for external attachments from drag or tail undulations. • Cylindrical shapes lowered the chance of mortality and had higher retention.