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ARS Home » Southeast Area » Stoneville, Mississippi » Warmwater Aquaculture Research Unit » Research » Publications at this Location » Publication #230551
Title: Tolerance of Channel Catfish Fry to Abrupt pH Changes

Author
item MISCHKE, C - MISS. STATE UNIVERSITY
item WISE, D - MISS. STATE UNIVERSITY

Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2008
Publication Date: 7/15/2008
Citation: Mischke, C.C., Wise, D.J. 2008. Tolerance of Channel Catfish Fry to Abrupt pH Changes. North American Journal of Aquaculture. 70:305-307.

Interpretive Summary: Survival of fry in ponds during the first phase of channel catfish culture is highly variable among ponds and farms. In an effort to explain survival variability, studies were conducted to determine the tolerance of catfish fry to abrupt pH changes. Small, sudden increases in pond water pH (less than one pH unit) will cause 10% mortality in 8-day-old fry, and an increase of about 1.5 pH units will cause 50% mortality. Based on the results of this study, attention to pH is important when fry are moved from the hatchery to ponds with a higher pH than the hatchery water. Moving fry from the hatchery to ponds in the morning may be helpful because pondwater pH is lowest near dawn. By monitoring pond pH at stocking, some of the variability in fry survival may be eliminated.

Technical Abstract: Fry survival in the catfish industry is variable and failure to survive cannot be completely attributable to diseases, fertilization practices, or lack of zooplankton abundance. The variability in fry survival may be related to current handling and stocking methods. When stocked, fry are transferred relatively quickly from hatchery water to pond water. Generally, temperature differences are monitored between hatchery water and pond water, but little attention is paid to pH differences. We conducted studies to determine the tolerance of channel catfish Ictalurus punctatus fry to pH changes. Catfish fry showed a high tolerance for decreasing pH values, but a relatively low tolerance for increasing pH values. We estimate that an increase in pH of 0.7 units will cause 10% mortality in 8-d-posthatch catfish fry, and an increase of 1.4 pH units will cause 50% mortality. We recommend that farmers monitor pH before stocking fry and stock ponds that tend to increase in pH throughout the day early in the morning.