Interest in cultivating freshwater drum (Fig. 1) is growing because they serve as host species for the propagation of various freshwater mussels, including the endangered scaleshell (Leptodea leptodon), Texas heelsplitter (Potamilus amphichaenus), and Salina mucket (Potamilus metnecktayi). While collecting wild-caught fish is an alternative for propagation, it may harm freshwater drum populations and raise disease concerns at propagation facilities. Additionally, wild-caught fish often do not adapt well to laboratory environments, resulting in low survival rates. Despite extensive information on the natural spawning behaviors and life cycle of freshwater drum, there is limited knowledge regarding their propagation in a hatchery setting.
We carried out a range of experiments from 2020 to 2024 using wild-caught fish to propagate drum in both indoor laboratory and earthen pond settings. Research focused on culture methods, feed preferences, gamete assessment, spawning techniques, egg incubation, and larval grow-out trials.
The long-term survival of adult wild-caught fish was suboptimal, with high handling mortality and susceptibility to diseases, particularly Ichthyophthirius multifiliis. Furthermore, these fish typically rejected commercial diets and often refused natural foods for long durations. Juvenile wild-caught fish also faced disease susceptibility and had difficulty accepting various food types. However, once acclimated and trained to consume commercial diets, juvenile fish became domesticated and were more tolerant to handling. During the spring, we collected gametes approximately every two weeks to evaluate and stage the eggs for optimal hormone induction timing. Spawning protocols were established using human chorionic gonadotropin (HCG), with dosages and latency periods identified. Eggs were successfully incubated in glass aquariums with added aeration. Hatching began two days post-fertilization at 22°C. Feeding trials tested rotifers, live artemia, and a krill-based commercial diet; however, hatchling survival was 0% across all treatments after two weeks, despite a few fish consuming small amounts of artemia.
In summary, significant progress has been made in developing freshwater drum propagation methods; however, further research is required for consistent propagation in controlled environments to ensure a reliable supply of healthy host fish for successful mussel propagation. Future experiments could integrate spawning in ponds following hormone induction, along with further investigation of effective larval feeding protocols.