In 2023, Arkansas produced 56.9% of the baitfish and 27.7 % of the sportfish total sales in the United States. Producers consistently report that common grackles (Quiscalus quiscula; hereafter grackle) and other blackbirds predate baitfish and sportfish from holding vats under sheds and on spawning mats in brood ponds. Despite depredation loss being a producer concern for decades, no studies have quantified the extent of these losses for this bird species. Therefore, the objectives of our study were to characterize foraging patterns of blackbirds within holding sheds and at spawning mats in brood ponds, measure the amount of prey items consumed by blackbirds, and quantify the economic impact of depredation by blackbirds.
During the 2024 and 2025 summer production seasons, we conducted focal observations and camera surveys on ponds with spawning mats and vats under sheds from five baitfish and three sportfish farms between mid-March and July. After surveys, actively foraging blackbirds were collected using air rifles and gavaged with 20 cc of phosphate-buffered saline to stop digestion for subsequent diet analysis. Stomach contents were sorted, identified to lowest classification level, dried at 60°C for 22-24 hours, and weighed to calculate diet type proportions. Sixteen grackles were randomly selected for diet analysis through DNA methods.
Of the 148 processed grackles, 109 (73.6%) consumed fish from ≥4 different species. In 2024 depredation events peaked in mid-April and again at the end of May with golden shiners (Notemigonus crysoleucas) being the most targeted fish species. From in person surveys, grackles were more efficient predators under the sheds, removing 5.6 product/hour compared to 1.5 product/hour on spawning mats. Data from the 2025 season is currently being collected and analyzed. Results of this study will be used to guide best management practices for mitigating losses to blackbird depredation at commercial baitfish and sportfish farms.