Citation:

Gordon, D., M. Smith, M. Wratschko, D. Agard, L. Holden, S. Wilcox, AND Jim Lazorchak. A New Approach for the Laboratory Culture of the Fathead Minnow, Pimephales promelas. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 33(1):126-133, (2014).

Impact/Purpose:

This paper describes a new mass culture system initiated at USEPA, Cincinnati, Ohio, for fathead minnows, which are used extensively in aquatic ecosystem research. The paper compares the new system versus the previous system in daily egg production, water usage, and labor hours; the new system was found to have increased egg production and cost savings in water usage and labor hours compared to the old system. With increased numbers of fathead minnows and other aquatic organisms cultured with this system, animals of all life stages are readily available for both in-house and export to collaborative organizations without loss of deliverables. This system is housed in the only EPA aquatic research facility that has been certified by the international Association for Assessment and Accreditation of Laboratory Animal Care (AAALAC).

Description:

Fathead minnows (Pimphales promelas) are routinely cultured for use in aquatic toxicology studies. Most culture systems consist of a series of 4 to 30 individual tanks with a varied number of breeding pairs in each tank. A new mass culture system described here consists of six 50-gallon stainless steel tanks, each tank containing 76 fish (16 males and 60 females) and 18 spawning substrates/tank. Spawning results are compared to the previous individual tank system using 22 twenty-gallon glass aquaria, each containing 2 male and 14 female fish and 4 spawning substrates per tank. From March 1998 to September 1999 (19 months), this mass system produced an average of 4105 eggs per day compared to a similar 19-month average of 2465 eggs per day with the previous system. Labor and maintenance were reduced with the new system since only six large tanks, as opposed to 22 glass aquaria, needed to be cleaned on a routine basis. In addition, the stainless steel tanks eliminated aquaria glass breakage and daily water usage was reduced by 45%. This culture system required the same amount of floor space as the 22 aquaria without the need of elevated racks and, thus, reduced safety risks. Analysis of reference toxicant data from fish cultured using both systems indicated no change in the sensitivity of the test animals. The potassium chloride acute LC50 mean for fish from the glass aquaria culture system was 800 mg/l with a C.V. of 21.1%. The potassium chloride acute LC50 mean for the fish from the mass culture system was 785 mg/l with a C.V. of 14.9%. There was no change in the mean LC50 values for fish cultured using both systems, but the C.V. was reduced by 28% for the fish in the new mass culture system. Analysis of different variables from 2009 egg production data concluded that a 6 or 7:1 female:male ratio had a significantly positive impact on egg production levels and recommended that 6-month-old breeding stock should be introduced to the spawning tanks in mid-spring for optimal egg production during the rest of the year. Implementation of a stainless steel mass culture system significantly increases efficiency of egg production, reduces “turnaround delay” of mature animal availability for toxicity and molecular testing, and reduces labor time and costs and inherent safety hazards when compared to glass aquaria systems.

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