In-season near real-time management of catch quotas are enabled through the use of a substantial at-sea observer program. On larger vessels, catch weights are obtained through the use of motion compensated state of the art scales that can continuously weigh fish as they move along a conveyor belt. To ensure that they are accurate, these state of the art “flow scales” are tested daily and must be tuned to be within 3% of known test weights. However, the accuracy of flow scales during daily tests may not reflect their accuracy during normal use throughout a 24 hour period. The observer program collects weights of at-sea samples on separate scales. There is opportunity to compare the multiple thousands of weights of sampled fish from both scales. The goal of this project is to determine the in situ accuracy of flow scales and identify the factors (if any) that contribute to scale weight variance. This work is important to test the assumption that flow scale weights are accurate within acceptable tolerance throughout a 24 hour period.