The use of age and growth techniques to quantify the age structure of carryover hybrid catfish (female Channel Catfish x male Blue Catfish) in commercial ponds in West Alabama

Authors: PALMER, JULIA - Auburn University; JAMES, JESSE - Auburn University; SAKARIS, PETER - Auburn University; KELLY, ANITA - Auburn University; ABDELRAHMAN, HISHAM - Auburn University; Beck, Benjamin; ROY, LUKE - Auburn University

Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2024
Publication Date: 10/29/2024
Citation: Palmer, J., James, J.P., Sakaris, P.C., Kelly, A.M., Abdelrahman, H., Beck, B.H., Roy, L.A. 2024. The use of age and growth techniques to quantify the age structure of carryover hybrid catfish (female Channel Catfish x male Blue Catfish) in commercial ponds in West Alabama. North American Journal of Aquaculture. 2024(00):1-18. https://doi.org/10.1002/naaq.10353.
DOI: https://doi.org/10.1002/naaq.10353

Interpretive Summary: In West Alabama, catfish Ictalurus spp. producers routinely face the challenge of fish that exceed market size (aka “Big Fish”) in their commercial ponds. These fish are skilled at evading seine nets during harvest and can increase in size significantly before subsequent harvests occur. This is problematic for catfish producers because processing plants prefer catfish within the 0.45–1.81-kg range and farmers are paid a premium price for catfish of this size. Due to their larger size and growth potential, hybrid catfish (female Channel Catfish Ictalurus punctatus × male Blue Catfish I. furcatus) can become a more significant issue than Channel Catfish if they evade harvest. The objective of this study was to describe and quantify the age structure and growth rate of hybrid catfish that evade capture and remain in commercial ponds following harvest and grow beyond acceptable market size as defined by catfish processing plants (i.e., Big Fish). Hybrid catfish were collected from 12 recently harvested commercial ponds in West Alabama from December 2021 to August 2022 using an electroshocking boat. Total length (mm), body weight (kg), and sex of collected fish were recorded, and otoliths were removed to estimate fish age and determine total length and total body weight at estimated ages. Result: In this study, 1005 hybrid catfish were collected with the successful age estimation for 1001 catfish, ranging from 1 to 11 years. Results of this study indicate that hybrid catfish exceeded the premium size threshold in 2.72 years ± 8 months. Additionally, from age 2 to age 3, the average hybrid catfish gained 2.90 kg, growing from 0.40 to 3.30 kg. Growth rate was significantly affected by sex; males overall were predicted to weigh more than females. Hybrid catfish should be completely harvested from commercial pondsfollowing 1 year of harvest to receive the premium price per kilogram of live fish. If a complete harvest is unsuccessful, farmers can receive a discounted price per kilogram of leftover hybrid catfish based on current market trends.

Technical Abstract: Objective: In West Alabama, catfish Ictalurus spp. producers routinely face the challenge of fish that exceed market size (aka “Big Fish”) in their commercial ponds. These fish are skilled at evading seine nets during harvest and can increase in size significantly before subsequent harvests occur. This is problematic for catfish producers because processing plants prefer catfish within the 0.45–1.81-kg range and farmers are paid a premium price for catfish of this size. Due to their larger size and growth potential, hybrid catfish (female Channel Catfish Ictalurus punctatus × male Blue Catfish I. furcatus) can become a more significant issue than Channel Catfish if they evade harvest. The objective of this study was to describe and quantify the age structure and growth rate of hybrid catfish that evade capture and remain in commercial ponds following harvest and grow beyond acceptable market size as defined by catfish processing plants (i.e., Big Fish). Methods: Hybrid catfish were collected from 12 recently harvested commercial ponds in West Alabama from December 2021 to August 2022 using an electroshocking boat. Total length (mm), body weight (kg), and sex of collected fish were recorded, and lapilli otoliths were removed to estimate fish age and determine total length and total body weight at estimated ages. Result: In this study, 1005 hybrid catfish were collected with the successful age estimation for 1001 catfish, ranging from 1 to 11 years. Results of this study indicate that hybrid catfish exceeded the premium size threshold in 2.72 years ± 8 months. Additionally, from age 2 to age 3, the average hybrid catfish gained 2.90 kg, growing from 0.40 to 3.30 kg. Growth rate was significantly affected by sex; males overall were predicted to weigh more than females based on the weight-at-age model. Conclusion: Hybrid catfish should be completely harvested from commercial ponds following 1 year of harvest to receive the premium price per kilogram of live fish. If a complete harvest is unsuccessful, farmers can receive a discounted price per kilogram of leftover hybrid catfish based on current market trends.