Effects of three frozen storage methods on wet weight of fish

[Display omitted] •Wet weight is frequently measured for fisheries studies.•We investigated the effects of three frozen storage methods on wet weight and percent dry weight of fish.•Post-thaw wet weight differed from prestorage wet weight for all storage methods.•Failure to account for changes in wet weight of frozen fish can lead to substantial bias of percent dry weight estimates. Wet weight is one of the most common biological descriptors collected for fisheries research. Freezing is frequently used to preserve fish prior to processing in a lab, and wet weights are often collected for thawed fish. Freezing may affect the wet weight of fish and result in biased values for weight based metrics. Our objectives were to determine the effects of three frozen storage methods, size class of fish, and duration of storage on the changes in wet weight of emerald shiner (Notropis atherinoides) and rudd (Scardinius erythrophthalmus), and how failure to account for changes in wet weight affects percent dry weight estimates. Two size classes of emerald shiner and three size classes of rudd were collected from the upper Niagara River, New York. Fish were weighed immediately after being euthanized and then glazed with water, frozen in water, or vacuum-sealed and stored at −25°C for 3 or 6 months. After measuring post-thaw wet weight, fish were dried to a constant weight and percent dry weight was calculated based on prestorage wet weight and post-thaw wet weight. Then, we compared species specific prestorage wet weights to post-thaw wet weights for each storage method. Analysis of variance was used to investigate the effects of storage method, size class, and duration stored on wet weights of each species. Prestorage and post-thaw percent dry weights were compared to illustrate the effects of frozen storage on a commonly used weight-based metric. Emerald shiner and rudd wet weights differed from initial weights for all storage methods. Percent change in wet weight of emerald shiner was affected by interactions among storage method, size class, and duration stored, while percent change in wet weight of rudd was affected by the interaction between fish size class and storage method. Overall, storage method and size class had the greatest effects on changes in wet weight following frozen storage. Post-thaw wet weight increased from initial wet weight for fish frozen in water and decreased for vacuum-sealed and glazed fish, and smaller fish generally experienced greater cha