Cinetica Peces

ticaAquaculture 221 (2003) 657 – 665
www.elsevier.com/locate/aqua-online

Residue depletion of oxytetracycline from fillet
tissues of northern pike and walleye
Jeffry A. Bernardy a,*, Chue Vue a, Mark P. Gaikowski a,
Guy R. Stehly a, William H. Gingerich a, Allen Moore b
a
U.S. Department of the Interior, U.S. Geological Survey, Biological Resources Division,
Upper Midwest EnvironmentalSciences Center, 2630 Fanta Reed Road, La Crosse, WI 54603, USA
b
Iowa Department of Natural Resources Fisheries Bureau, Rathbun Research,
15053 Hatchery Place, Moravia, IA 52571-8933, USA

Received 18 September 2002; received in revised form 30 January 2003; accepted 3 February 2003

Abstract
The broad-spectrum antibacterial drug oxytetracycline (OTC) is used in the U.S. to treat
certaindiseases in salmonids and catfish. This study was conducted to support an extension of
the OTC label to include all cool-water fish species cultured at U.S. public aquaculture facilities
by satisfying human food safety requirements. Juvenile northern pike (Esox lucius; mean weight:
117 g) and walleye (Stizostedion vitreum; mean weight: 59 g) were fed OTC-medicated diets
near the maximum legaltreatment rate (82.7 mg OTC-HCl/kg fish/day for 10 days) and near the
lower limit of the water temperature range for most disease outbreaks in these species (14 and
16 jC, respectively). Two trials were conducted simultaneously with northern pike, one using
commercially medicated feed and the other using on-site OTC top-coated feed. A third trial was
performed with walleye using on-site OTCtop-coated feed. Fillet tissues were collected and
OTC free base (OTC-base) concentrations were determined by high performance liquid
chromatography. The maximum mean OTC-base concentrations in the fillet tissue were 319 ng/g
in northern pike (skinless) and 721 ng/g in walleye (skin-on), both well below the current
tolerance limit of 2000 ng/g OTC-base. The log-linear loss of OTC-base from thefillet tissues
was monophasic, with terminal phase half-lives of 5.9 days in northern pike fed commercial
medicated feed, 6.7 days in northern pike fed top-coated feed, and 10.5 days in walleye fed topcoated feed. The data supported a zero withdrawal time in juvenile northern pike and walleye

* Corresponding author. Tel.: +1-608-783-6451; fax: +1-608-783-6066.
E-mail address:jeffry_bernardy@usgs.gov (J.A. Bernardy).
0044-8486/03/$ - see front matter. Published by Elsevier Science B.V.
doi:10.1016/S0044-8486(03)00136-4

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J.A. Bernardy et al. / Aquaculture 221 (2003) 657–665

fed OTC at the approved dose level for 10 days at water temperatures down to 14 and 16 jC
respectively.
Published by Elsevier Science B.V.
Keywords: Oxytetracycline; Northern pike; Walleye; Fillettissue; Depletion

1. Introduction
Oxytetracycline (OTC) is a drug approved by the U.S. Food and Drug Administration
(FDA) to control ulcer disease, furunculosis, and bacterial hemorrhagic septicemia in
salmonids and to control bacterial hemorrhagic septicemia in catfish (Code of Federal
Regulations, 1996). The U.S. FDA approved treatment dose ranges from 2.5 to 3.75 g/100
lb fish/day(55.1 to 82.7 mg OTC HCl equivalent/kg body weight/day) for a duration of 10
days. Oxytetracycline is also approved in the U.S. to mark salmonid skeletal tissue in
population assessment studies and to control gafkemia in lobsters (Code of Federal
Regulations, 1996). The current U.S. FDA tolerance limit for OTC in edible portions of
salmonid, catfish, and lobster is 2000 ng/g OTC free base(OTC-base; Federal Register,
1996).
Supplementary efficacy data submitted by Investigational New Animal Drug (INAD)
coordinators (Schmidt et al., 1999) revealed that OTC appears to control mortalities
associated with Aeromonas hydrophila in northern pike (Esox lucius). Supplemental
efficacy trials were also conducted on smallmouth bass (Micropterus dolomieui) and
paddlefish (Polyodon spathula)...