Comparison of the Precision of Ages and Growth from Three Traditional Techniques Used for Introduced Blue Catfish

Age and growth information is used to understand populations’ life history and ecology and monitor their trends. Such information is useful for evaluating the success of establishment of introduced populations. Prior studies have validated age determination methods for various catfishes, but none have been validated for blue catfish. We compared precision of age estimates and back-calculated growth after using one lethal and two non-lethal, traditional age determination techniques for introduced blue catfish in Georgia. Blue catfish (n=153) were collected by experimental gillnets set overnight at 12 standardized stations at Lake Oconee, Georgia. Two non-lethal techniques requiring the pectoral spines (articulating process and basal recess) and one lethal technique requiring lapilli were used to determine the ages of the fish. Two readers independently assigned ages, and conflicts were resolved by a concert read. The Frasier-Lee method was used to back-calculate growth for each fish. Hierarchical models we used to compare precision in back-calculated length estimates and growth among the three techniques. Two readers found the highest precision for otolith-based age assignments (83.5%) and lowest for basal recess cross-sections (71.4%). The hierarchical model indicated that back-calculated length was variable among fish from ages 1-3 for all three techniques compared. Back-calculated length was variable between the otolith and basal recess at age-4 and age-8. Our study suggests the articulating process and otolith techniques yielded the highest precision and are adequate for age determination of blue catfish. The techniques compared should be validated for blue catfish in a future study.