In 2018, the Alabama catfish industry was facing an oversupply issue, as evidenced by a falling fish price paid to producers. Adding to this problem was an over-abundance of "Big Fish" on farm inventories. These farms typically utilize watershed ponds that are deeper than levee ponds and can be difficult to partially harvest effectively, particularly when ponds are irregular in shape and pond bottoms have not been re-worked for long periods of time. Multiple batch production systems are the norm and require frequent partial harvests to increase yields and reduce detrimental issues, such as catfish escaping the seine and growing into the "Big Fish" size category. Catfish processors have defined "Big Fish" as catfish greater than 4 pounds. Once this threshold weight is reached, catfish are too large for the mechanized cutting lines at the processing plants and must be hand filleted at the expense of more time, labor and removing line workers from their regular work. In 2018, catfish processors paid varying amounts for 4-6 pound "Big Fish" and the price range varied from zero to $0.50-$0.60 per pound as processors have limited markets for this larger size. Farmers often do not receive compensation for fish larger than 6 pounds, which are deemed unacceptable and logged as "weigh backs". Much of the "Big Fish" problem can be linked to inefficiencies related to seining and seining frequency but there are other important factors such as market demand conditions, pond type, and pond renovation schedules. Despite widespread adoption of hybrid catfish, there is scant scientific documentation of age as it relates to growth within the catfish production system, with large hybrids being reported by farmers to exceed 50 lbs in some instances.
Therefore, we undertook this study to determine ways to reduce "Big Fish" in pond inventories and have begun by determining the age of "Big Fish", how long fish have been in the pond and the economic cost to the industry. To age catfish, we collected 50 fish from each harvest event to determine the age of different size classes (range: 1.5 - 34.0 lb) in commercial ponds to provide information on catfish age at harvest. We documented catfish length, weight, sex, and collected otoliths from each individual fish sampled to determine their weight and respective age (years). Otoliths were extracted following the methods of Buckmeier et al (2002) and read by two independent readers to determine age (Maceina and Sammons 2006). Mean length-weight at age was compared between ponds and species using an analysis of variance (ANOVA) and growth analysis using an Analysis of Covariance (ANOCOVA) method to compare the slopes of total length to log10 age regressions (Sammons et al. In Press). Collectively, the information garnered in this study has provided needed information on quantities and percentages of "Big Fish" that remain in pond inventories, size variation among the long-term catfish that continually escape harvest, fish ages, and harvest efficiency. This information will be used to develop helpful, economical scenarios to mitigate this issue.