Inhibiting fungus on largemouth bass eggs with copper sulfate and its toxicity to fry and juveniles

Authors: Straus, David - Dave

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/5/2019
Publication Date: 7/29/2019
Citation: Straus, D.L. 2019. Inhibiting fungus on largemouth bass eggs with copper sulfate and its toxicity to fry and juveniles[abstract]. Aquaculture Drug Approval Workshop, Bozeman, MT, July 29 - August 1, 2019. 25:41.

Interpretive Summary:

Technical Abstract: This study determined the effectiveness of copper sulfate (CuSO4) to inhibit fungal growth (caused by Saprolegnia spp.) on largemouth bass (LMB; Micropterus salmoides) eggs spawned on/in fiber mats in high alkalinity/hardness waters (384 ppm and 452 ppm, respectively). Experiments also determined toxicity of CuSO4 to LMB fry and juveniles. An untreated control and three CuSO4 concentrations (10, 20, and 40 mg/L) were tested under a flow-through scenario in the effectiveness experiment. Eggs were treated daily until hatching began. Fungal load at time of hatch was heavy in the untreated controls, moderate in the 10 and 20 mg/L treatments and light in the 40 mg/L CuSO4 treatments. Fungus samples were identified as Saprolegnia salmonis through genetic sequencing. The 24 h median lethal concentration (LC50) values on LMB sac and swim-up fry were 32.0 and 4.6 mg/L CuSO4, respectively; the No Observed Effect Concentrations (NOEC) was 16.0 and 0.125 mg/L CuSO4. LMB swim-up fry were very sensitive to CuSO4, as would be expected. Juvenile LMB are extremely tolerant to CuSO4 and their 24 h LC50 values were 185.5 mg/L and the NOEC was 64 mg/L. This is our latest study to confirm that CuSO4 is an inexpensive, important resource for hatcheries to control of egg fungus in high alkalinity/hardness waters.