An Investigation into the Effects of Elevated Water Hardness on Channel Catfish Egg Viability

Abstract

Channel catfish (Ictalurus punctatus) are a popular sportfish across the United States and are often stocked to enhance fishing opportunities. There has been increased research into their life history, management, and population characteristics over recent decades. In a study conducted on channel catfish recruitment in Thunderbird Reservoir, Oklahoma, researchers found that recruitment was negatively associated with total annual water hardness, hypothesizing that larval fish survival decreased when water hardness was > 170 mg/L. To test this hypothesis, we investigated the effects of water hardness on channel catfish egg hatch rates to determine if total water hardness impacts the survivability of larva. Fertilized eggs were obtained from the Holdenville State Fish Hatchery, Oklahoma and transferred to the Oklahoma Fishery Research Laboratory. Eggs were divided and placed in tanks of seven water hardness levels (78 [control], 100, 200, 300, 500, 1000, 3000 mg/L CaCo3). Overall survival, hatch rate, and larval abnormalities were recorded and analyzed for differences between hardness levels and fish. Water hardness did not influence survival or growth early in life in our study. However, we did observe that the spawning matrix deteriorated in higher hardness concentrations (≥ 500 mg/L). Future studies should investigate the effects of water hardness on channel catfish survival post yolk-sac abortion to determine if mortality increases later in life and determine if water quality optima vary between catfish populations at smaller spatial extents. Future work examining the effects of varying water chemistry levels on egg/larval fish survival can replicate our methods, providing additional insight into the early life history of Channel Catfish or other catfish species.