Addressing the “black hole”. Is it possible to reduce transportation stress and catfish fingerling losses right after stocking?

Authors: TUTTLE, JAMES - Auburn University; ROY, LUKE - Auburn University; KELLY, ANITA - Auburn University; BRUCE, TIMOTHY - Auburn University; ABDELRAHMAN, HISHAM - Texas A&M University; Garcia, Julio; Beck, Benjamin

Submitted to: Fish Farming News
Publication Type: Popular Publication
Publication Acceptance Date: 12/13/2025
Publication Date: 12/17/2025
Citation: Tuttle, J., Roy, L., Kelly, A., Bruce, T., Abdelrahman, H., Garcia, J.C., Beck, B.H. 2025. Addressing the “black hole”. Is it possible to reduce transportation stress and catfish fingerling losses right after stocking?. Fish Farming News. 2025(2):1-16. https://doi.org/agriculture.auburn.edu/wp-content/uploads/2025/12/AFFC-Fall-2025.pdf.

Interpretive Summary: Channel and hybrid catfish are raised across the southern United States, and Alabama produces about one third of all domestic food-sized catfish. Since there are no commercial catfish hatcheries in Alabama, catfish are transported to farms as fingerlings or stockers. Most of these come from Mississippi or Arkansas, meaning these fish must be transported in large fiberglass or stainless-steel hauling tanks for up to six hours or more. Transportation can be very stressful and there are a lot of things that that can lead to dead fish in the hauling tanks, or fish so stressed that they die shortly after stocking ponds. The term used to describe this phenomenon of unexpected losses or seemingly missing juvenile fish is called the “Black Hole”. Currently the main cause of the Black Hole phenomenon is thought to be bacterial infections, mostly Columnaris disease. If the Black Hole problem is the result of Columnaris outbreaks shortly after stocking, then we need to reduce fingerling transport stress. The main objective of this project was to determine if a less labor-intensive/cost-effective way to reduce transport stressors was available. One option is to use a commercially available water conditioner that would increase the slime layer on catfish. Water conditioners are used often in salmon, trout, and other cold-water fish species, but it is very rarely used in warm water fish. For this study We chose a product that is less expensive than salt as one gallon of this water conditioner could treat just over 15,000 gallons of water. This experiment used 720 Marion strain channel catfish (I. punctatus) fingerlings (average = 0.44 ounces) and splitting them into two even groups. The fish were transported 158 miles in 64oF oxygenated water from Greensboro, AL to Auburn, AL at a density of 0.45 kg/L. One group was exposed to the water conditioner (V) and the second group was not (NV). After the 2 hour and 48-minute drive, the two containers of 360 fish were each split into 4 separate groups. The findings of this experiment were unexpected. Under the conditions that existed in this experiment the use of a commercial water conditioner did not reduce transport stress. There are other types of commercial water conditioners and other options available to the industry, but there are many more factors that can contribute to this complex Black Hole problem. This issue will require more research and more experiments to ultimately find effective management solutions.

Technical Abstract: Channel and hybrid catfish are raised across the southern United States, and Alabama produces about one third of all domestic food-sized catfish. Since there are no commercial catfish hatcheries in Alabama, catfish are transported to farms as fingerlings or stockers. Most of these come from Mississippi or Arkansas, meaning these fish must be transported in large fiberglass or stainless-steel hauling tanks for up to six hours or more. Transportation can be very stressful and there are a lot of things that that can lead to dead fish in the hauling tanks, or fish so stressed that they die shortly after stocking ponds. The term used to describe this phenomenon of unexpected losses or seemingly missing juvenile fish is called the “Black Hole”. Currently the main cause of the Black Hole phenomenon is thought to be bacterial infections, mostly Columnaris disease. If the Black Hole problem is the result of Columnaris outbreaks shortly after stocking, then we need to reduce fingerling transport stress. The main objective of this project was to determine if a less labor-intensive/cost-effective way to reduce transport stressors was available. One option is to use a commercially available water conditioner that would increase the slime layer on catfish. Water conditioners are used often in salmon, trout, and other cold-water fish species, but it is very rarely used in warm water fish. For this study We chose a product that is less expensive than salt as one gallon of this water conditioner could treat just over 15,000 gallons of water. This experiment used 720 Marion strain channel catfish (I. punctatus) fingerlings (average = 0.44 ounces) and splitting them into two even groups. The fish were transported 158 miles in 64oF oxygenated water from Greensboro, AL to Auburn, AL at a density of 0.45 kg/L. One group was exposed to the water conditioner (V) and the second group was not (NV). After the 2 hour and 48-minute drive, the two containers of 360 fish were each split into 4 separate groups. The findings of this experiment were unexpected. Under the conditions that existed in this experiment the use of a commercial water conditioner did not reduce transport stress. There are other types of commercial water conditioners and other options available to the industry, but there are many more factors that can contribute to this complex Black Hole problem. This issue will require more research and more experiments to ultimately find effective management solutions.