Development of New Intensive Hatchery Methods for Rosy Red Fathead Minnow

Abstract

Fathead minnow Pimephales promelas farming practices have remained relatively unchanged for decades. To develop new intensive hatchery methods for the rosy red fathead minnow (a color variant of the fathead minnow), we evaluated spawning substrate preferences, egg mimics, anti-fungal treatments for eggs, and fry stocking densities. Rosy red fathead minnow laid significantly more eggs on a single-layer substrate than on a multilayered substrate but showed little preference between a firm substrate and a flexible substrate. The fish strongly preferred nesting substrates with glass-bead egg mimics over plain (control) substrates or substrates with painted-dot mimics. Eggs treated with chemicals (formalin or hydrogen peroxide at 500, 1,000, or 1,500 mg/L) had higher hatch rates (62.3–81.7%) than did controls (34.3%). The once-daily hydrogen peroxide treatment was equally effective as multiple applications (2–3 applications/d) and resulted in fewer deformities. When newly hatched rosy red fathead minnow fry were stocked at densities of 49, 198, 346, 495, and 643 fry/m² in pools for 85 d, mean fish weight decreased logarithmically with final density (R ² = 0.953), while yield increased with initial density (R ² = 0.846). A cost analysis for fry production levels of 10, 30, 50, and 70 million fry found that the most costly stage was egg collection followed by fry holding, egg incubation, and egg removal. Estimated costs to produce 1 million fry decreased from US$514 to $356 with increasing fry production, indicating economies of scale. Use of spawning substrates with glass-bead egg mimics has the potential to decrease these costs by increasing egg collection efficiency.