Chronic effects of a monogenean Ligictaluridus floridanus (Ancyrocephalidae) infection on channel catfish (Ictalurus punctatus) growth performance

In aquaculture, acute infections may result in fish mortality, but in many cases the chronic effects of infections are not readily detected, and may result in a decrease in fish growth. Ligictaluridus floridanus is a gill monogenean parasite prevalent on channel catfish (Ictalurus punctatus) farms in Northeastern Mexico. In order to assess and evaluate the impact of the chronic infection with this monogenean, 400 six-month-old catfish fingerlings from a hatchery, with a fork length of 10-15 cm were used in this study. Catfish naturally infected with L. floridanus (parasite abundance was 18) were divided in two groups of 200 fish. One group was treated with formalin, and infection was eliminated during a week, while the other group was not treated, and was used as a control. In total, Ill fish of each group were selected, placed into aquaria, and observed for 12 weeks. Indicators of growth such as fork length, mean weight, condition index, specific growth rate, feed conversion index and feed consumed were assessed. Significant differences (P < 0.05) between the treated group and control were found in the mean weight (127.85 g and 107.63 g) and specific growth rate (1.79 and 1.58), respectively. No significant differences were found in the other growth indicators assessed. We proved that growth performance of channel catfish is affected by infection with L. floridanus, which influence the farm economy. This is the first report on the effect of L. floridanus on the growth performance of channel catfish.