JFS: Organochlorines, Organophosphates, and Pyrethroids in Channel Catfish, Rainbow Trout, and Red Swamp Crayfish from Aquaculture Facilities C.R. SANTERRE, R. INGRAM, G.W. LEWIS, J.T. DAVIS, L.G. LANE, R.M. GRODNER, C.-I. WEI, P.B. BUSH, D.H. XU, J. SHELTON, E.G. ALLEY, AND J.M. HINSHAW ABSTRACT: Channel catfish (Ictalurus punctatus), rainbow trout (Oncorhynchus mykiss), and red swamp crayfish (Procambarus clarkii) were collected from 8 southern states in the United States and analyzed for 34 organochlorine, organophosphate, and pyrethroid compounds. Approximately 45% of catfish, 72% of trout, and 92% of crayfish contained no detectable residues. Most residues detected were well below action limits for fish. Chlorpyrifos, for which there is no established tolerance, was detected in catfish; however, residues of this pesticide were not detected in samples collected after the 1st year of the study. The data collected during this study further support the safety of aquaculture products. Key Words: pesticide, fish, aquaculture, action limit, residue Introduction THE INCREASING NUMBER OF STATE HEALTH ADVISORIES INVOLving contaminants in wild fish has led to increased consumer awareness and sensitivity to contaminated fish and has motivated the aquaculture industry to collect data to support the safety of farm-raised products. Very often the mass media does not distinguish between wild fish and fish produced in controlled aquacultural facilities. In 1993, the Food and Drug Administration (FDA 1994b) incorporated an aquaculture survey into their annual pesticide monitoring program. Samples collected included both aquatic and marine species, such as catfish, trout, crayfish, shrimp, oysters, salmon, tilapia, among others. Catfish were found to contain chlorpyrifos (< 0.02 ppm), diazinon (trace), and dimethyl 2,3,5,6-tetrachloroterephthalate (Dacthal, < 0.09 ppm). Since there were no established tolerances for these compounds in fish, the catfish containing these residues were considered adulterated and not acceptable for distribution. Residues of the banned pesticides dichlorodiphenyltrichloroethane (DDT) and chlordane were also detected in the fish samples; however, these residues were below the established action limits (FDA 1998) enforced by the agency. The FDA (1994b) also noted that 44% of aquaculture products tested contained no detectable residues. The contaminants measured were selected due to their persistence in the environment. In an attempt to survey a greater number of production and processing sites, multi-residue methods (MRM) were used rather than the more expensive single residue methods (SRM). The objective of this study was to collect and analyze the edible portion of farm-raised channel catfish (Ictalurus punctatus), rainbow trout (Oncorhynchus mykiss), and red swamp crayfish (Procambarus clarkii) to determine if residues previously reported in wild fish could be found. 2000 Institute of Food Technologists Results and Discussion AVERAGE MOISTURE AND LIPID CONTENT FOR CATFISH FILLETS were 75.9% and 6.9%, respectively. Average lipid for wild catfish was reported to be 2.4% (Nettleton and others 1990). The higher fat content indicates that pond-raised catfish have a larger reservoir for absorption of lipophilic environmental contaminants. The average moisture and fat in trout fillets were 75.8% and 4.0%, while the averages in crayfish tail flesh were 80.1% and 1.5%, respectively. Residues of DDT (incl. o,p -DDD, o,p -DDE, p,p -DDD, p,p - DDE, p,p -DDT and p,p -DDD olefin) were detected in 55.3% of catfish samples (Table 1). The lower limit of quantitation for each form of DDT was 0.01 ppm (wet basis; wb). Residues were also detected in 27.3% of trout and 7.9% of crayfish samples. The predominant form of DDT in fish was p,p -DDE, which was present in all of the fish samples that contained detectable residues (Table 2). The next most prevalent residue was p,p -DDD, which was detected in 66.2% of the positive catfish samples and Table 1 Non-violative and violative residues in channel catfish, rainbow trout and red swamp crayfish samples FDA Channel Red Total Action catfish Rainbow swamp samples limit Producer Processor Total trout crayfish analyzed (ppm) (197) (60) (257) (33) (38) Number of samples containing detectable, non-violative residues & (percent of total) a DDT b 5.0 90 52 142 9 3 (35.0%) (20.2%) (55.3%) (27.3%) (7.9%) Chlordane b 0.3 2 3 5 0 0 (0.8%) (1.2%) (1.9%) PCB b 2.0 11 7 18 3 0 (4.3%) (2.7%) (7.0%) (9.1%) Dieldrin 0.3 3 4 7 1 0 (1.2%) (1.6%) (2.7%) (3.0%) Hexachloro- none 0 2 2 0 0 benzene (0.8%) (0.8%) Heptachlor 0.3 2 3 5 0 0 epoxide (0.8%) (1.2%) (1.9%) Number of samples containing violative residues & (percent of total) a Chlorpyrifos 0 17 10 27 0 0 (6.6%) (3.9%) (10.5%) asamples may have contained residues of more than one measured contaminant. Violative residues exceed FDA enforcement guidelines. b Includes congeners, isomers, degradation products, and metabolites. Vol. 65, No. 2, 2000 JOURNAL OF FOOD SCIENCE 231
Residues in Fish... Food Microbiology and Safety Sensory and Nutritive Qualities of Food 11% of the trout samples. Approximately 5% of the positive catfish samples contained the parent compound, p,p -DDT. For the samples containing detectable residues only, the average total DDT in catfish, trout and crayfish were 0.043 ppm, 0.013 ppm and 0.047 ppm, respectively. The percentages of the FDA s action limit for each average total residue are 0.86%, 0.26%, and 0.94%, respectively. These percentages would be significantly reduced if all of the samples, including those samples that did not have detectable residues, were included in the averages. The ranges for DDT residues were 0.01 to 0.29 ppm, 0.01 to 0.04 ppm, and 0.01 to 0.11 ppm, respectively. Even though DDT has been banned in the United States since the 1970s, it is still a pesticide that is commonly detected in foods more than 30 years later. This may be due to the environmental persistence of DDT, as well as, its continued use throughout the world. Reinert (1970) and Niethammer and others (1984) reported levels of total DDT in wild channel catfish as high as 6.9 and 17.0 ppm (wb), respectively. However, more recent reports have found a maximum total DDT to be 0.083 ppm (Christiansen and others 1991) and 0.04 ppm (Winger and others 1990) in wild channel catfish. Schmitt and others (1990) reported a reduction in average DDT residues in freshwater fish collected from 112 sites nationwide between 1976 and 1984. They reported that average DDT in 1976 through 1977 was 0.37 ppm (whole fish), which decreased by 1984 to 0.26 ppm. They also found that maximum total DDT residues peaked at 10.62 ppm in 1978 through 1979. The gradual reduction of DDT residues appears likely due to the removal of this pesticide s registration. Nettleton and others (1990) analyzed 8 composite samples (2 subsamples of a 10 fish composite collected 4 times) collected at quarterly intervals and found average total DDT residues in pond-raised channel catfish of 0.22 ppm. This is higher than the average 0.043 ppm of total DDT residue reported in this study, especially since the average levels for each contaminant included only those samples with detectable residues. It is apparent from our findings that pond-raised channel catfish generally contain considerably less DDT than their wild counterparts. Residues of chlordane (including oxychlordane, trans-nonachlor, - and -chlordane) were only detected in catfish (Table 1). The lower limit of quantitation for each chlordane residue was 0.01 ppm (Table 2). A total of 1.9% of samples contained detectable residues for an average total of 0.045 ppm, which is 15.0% of the FDA s action limit. The range for chlordane residue was 0.03 to 0.092 ppm. Residues of trans-nonachlor, - and -chlordane were most commonly detected in samples that were positive for chlordane. Chlordane, currently banned, was widely used to treat for termites and is also persistent in the environment. Chlordane residues in wild channel catfish from the Missouri River were reported by Christiansen and others (1991) at less than 0.153 ppm. This is close to the average levels for freshwater fish reported by Schmitt and others (1990) of 0.11 ppm. They also found maximum total chlordane residues to peak in 1978 through 1979 at 6.69 ppm and decrease in 1984 to 2.75 ppm. This contrasts with the maximum total chlordane of 0.092 ppm reported here. Residues of PCB (including Aroclor 1242, 1248, 1254, and 1260) were detected in 7.0% of catfish and 9.1% of trout samples (Table 1). The lower limit of quantitation for each Aroclor was 0.05 ppm. Nine catfish samples were found to contain residues of Aroclor 1242. However, it was detected at concentrations below the lower quantitation limit and was reported in trace amounts (Table 2). The predominant pattern of PCB in catfish was Aroclor 1260, which was quantifiable in 7 samples. Three samples (9.1%) of trout had trace levels of Aroclor 1260. A total of 3.5% of samples contained quantifiable residues for an average total of 0.133 ppm, which is 6.6% of the FDA s action limit. The range for PCB 232 JOURNAL OF FOOD SCIENCE Vol. 65, No. 2, 2000 Table 2 Number of channel catfish, rainbow trout, and red swamp crayfish samples containing residues, average total residues, range and percent of FDA s action limits LOQ a Catfish Trout Crayfish (ppm) (257) (33) (38) DDT o,p-ddd 0.01 6 0 0 o,p -DDE 0.01 0 0 0 p,p -DDD 0.01 94 1 0 p,p -DDE 0.01 142 9 3 p,p -DDT 0.01 7 0 0 p,p -DDD olefin 0.01 0 0 0 No. of positive 142 9 3 samples Avg. total 0.043 0.013 0.047 DDT (ppm) b Percent of action 0.86% 0.26% 0.94% limit (5 ppm) Range (ppm) 0.01 to 0.29 0.01 to 0.04 0.01 to 0.11 Chlordane -chlordane 0.01 5 0 0 -chlordane 0.01 4 0 0 Oxychlordane 0.01 0 0 0 trans-nonachlor 0.01 5 0 0 No. of positive 5 0 0 samples Avg. total 0.045 0 0 chlordane (ppm) b Percent of action 15.00% 0 0 limit (0.3 ppm) Range (ppm) 0.03 to 0.092 0 0 PCB Aroclor 1242 0.05 9T c 0 0 Aroclor 1248 0.05 0 0 0 Aroclor 1254 0.05 2 0 0 Aroclor 1260 0.05 7 3T c 0 No. of positive samples 18 3 0 Avg. total PCB (ppm) b 0.133 0 0 Percent of 6.65 % 0 0 action limit (2.0 ppm) Range (ppm) 0.07 to 0.32 0 0 Dieldrin 0.01 No. of positive samples 7 1 0 Avg. dieldrin (ppm) b 0.019 0.01 0 Percent of 6.33 % 3.33 % 0 action limit (0.3 ppm) Range (ppm) 0.01 to 0.03 0.01 0 Hexachlorobenzene (HCB) 0.01 No. of positive samples 2 0 0 Avg. HCB (ppm) b 0.01 0 0 Percent of action NA d NA d NA d limit (none) Range (ppm) 0.01 0 0 Heptachlor epoxide 0.01 No. of positive samples 5 0 0 Avg. heptachlor 0.012 0 0 epoxide (ppm) b Percent of action 4.00% 0 0 limit (0.3 ppm) Range (ppm) 0.01 to 0.02 0 0 Chlorpyrifos 0.01 No. of positive samples 27 0 0 Avg. chlorpyrifos (ppm) b 0.072 0 0 Percent of action >100% 0 0 limit (0 ppm) Range (ppm) 0.01 to 0.37 0 0 alower limit of quantitation baverage for each pesticide was calculated from positive samples only. ctrace d Not applicable
residues was 0.07 to 0.32 ppm. Niethammer and others (1984), Winger and others (1990), and Christiansen and others (1991) reported maximum total PCB in wild channel catfish of 1.47, 0.09, and 0.43 ppm, respectively. Schmitt and others (1990) reported maximum total PCB in 1976 through 1977 at 70.6 ppm, which increased to 92.8 ppm in 1978 through 1979 and decreased in 1984 to 6.7 ppm. This contrasts with the maximum total PCB detected in this study of 0.32 ppm. They also found that the average total PCB of 0.89 ppm in 1976 through 1977 decreased by 1984 to 0.39 ppm. This average is 3 times higher than the 0.13 ppm reported here. The study by Nettleton and others (1990) did not detect PCB residues in pond-raised channel catfish. Residues of dieldrin were detected in 2.7% of catfish and 3.0% of trout samples (Table 1). The average dieldrin in catfish and trout was 0.019 and 0.01 ppm, respectively. These levels are 6.3% and 3.3% of the FDA s action limit for the combined concentration of dieldrin and endrin in fish. The ranges for dieldrin residues in catfish and trout were 0.01 to 0.03 and 0.1 ppm, respectively. Niethammer and others (1984), Winger and others (1990), and Christiansen and others (1991) reported maximum dieldrin in wild channel catfish of 0.09, 0.01, and 0.11 ppm, respectively. These levels are comparable to the 0.03 ppm maximum reported here but less than the 5.01 ppm levels (1976 through 1977), reported by Schmitt and others (1990). They found that maximum levels of dieldrin decreased to 1.39 ppm in 1984. This is higher than the 0.019 ppm reported here but comparable to the 0.08 ppm reported by Nettleton and others (1990) for pond-raised channel catfish. Residues of hexachlorobenzene (HCB) were detected in 0.8% of catfish, but there were no detectable residues in trout or crayfish (Table 3). The average HCB in catfish was 0.01 ppm, which is the lower limit of quantitation for this compound (Table 2). There is no established action limit for HCB in fish. Residues of heptachlor epoxide were detected in 1.9% of catfish, but there were no detectable residues in trout or crayfish (Table 3). The average heptachlor epoxide in catfish was 0.012 ppm which is close to the lower limit of quantitation for this compound (Table 2). This level is 4.0% of the FDA s action limit for Materials and Methods SAMPLES WERE COLLECTED BETWEEN 1993 AND 1995 FROM 8 southern states (Table 3). As part of this investigation, numerous chlorinated compounds along with several organophosphates and pyrethroids were measured (Table 4) in farmraised channel catfish, rainbow trout, and red swamp crayfish. Researchers collected a total of 257 catfish, 33 trout, and 38 crayfish samples at quarterly intervals during a 3-y period. Catfish samples were collected both from production sites (197 samples) and processors facilities (60 samples). Catfish and trout fillets, including belly-flaps from 10 fish (0.5 to 1 kg in size; approximate length of 35 to 41 cm) and 5 kg raw, unpurged crayfish tail meat, including vein, were harvested from production sites. In addition, 5 kg frozen fillets were collected from processors sites. Samples were frozen, encoded, and sent to a central processing facility where the fish samples were re-encoded and prepared for analysis. Individual composite samples were prepared by passing the thawed, raw tissue twice through a meat grinder. Between samples, all utensils were cleaned thoroughly with detergent, rinsed with water, dried, and then rinsed with 2-propanol (ACS grade, Fisher Scientific, Pittsburgh, Pa., U.S.A.). The samples were placed in glass bottles and stored at -23 C and in cryogenic Table 3 Sample distribution for channel catfish, rainbow trout and red swamp crayfish Channel catfish Rainbow Red swamp Producer processor Total trout crayfish (197) (60) (257) (33) (38) Alabama 23 17 40 0 0 Florida 39 4 43 0 0 Georgia 31 0 31 15 0 Louisiana 28 13 41 0 23 Mississippi 33 23 56 0 0 North Carolina 0 0 0 13 0 Tennessee 3 0 3 5 0 Texas 40 3 43 0 15 heptachlor epoxide in fish. The range for heptachlor epoxide residues was 0.01 to 0.02 ppm. Chlorpyrifos was the only pesticide detected in catfish that exceeded its tolerance (0 ppm) limit in fish. During the 1st year of the study, chlorpyrifos was found in 27 catfish samples (10.5% for the overall study). Due to the withdrawal of chlorpyrifos from selected production areas, no subsequent residues of this pesticide were detected in samples collected after the first year of the study. As seen in Table 1, residues were detected in catfish samples from production (6.6%) and processing (3.9%) locations. The average and range for chlorpyrifos in catfish were 0.072 ppm and 0.01 to 0.37 ppm, respectively (Table 2). Residues that were not measured in any of the samples during the study included mirex, heptachlor, methoxychlor, endrin, endosulfan, BHC, diazinon, malathion, methyl- or ethyl-parathion, cypermethrin, and fenvalerate. The results from this study definitely draw a contrast in contaminant levels between aquaculture products and wild fish. The risk to the consumer of obtaining contaminated fish from aquaculture sources is lower than for wild fish; however, due to the sporadic nature of environmental contaminants and the lack of sufficient differentiation among fish products, the aquaculture industry should incorporate pesticide residue testing into their routine quality assurance programs. tubes at 85 C. Samples were shipped to a testing facility for subsequent analysis for pesticides. The analytical facility was selected following a proficiency test that involved 6 laboratories. Interested participants from the competing laboratories were required to analyze fish samples with known quantities of pesticides and Aroclors. Acceptance criteria required that all positive residues be reported with no false positives. In addition, 90% of all reported values were required to be within 40% of spiked values, and all reported values were required to be within 75% of spiked values. As a part of the quality control program for this study, some samples with detectable residue were re-encoded and returned to the analytical facility for analysis. A total of 18.6% of catfish, 12.1% of trout, and 13.2% of crayfish samples were retested. Personnel at the testing facility had no knowledge of the identity of the samples or the location from which they were collected. To determine moisture, a 5-g sample was weighed, placed in an air oven at 105 C for 24 h, and then reweighed. Loss in weight during drying was used to determine moisture content. Extraction of fat and pesticide residues from fish tissue was performed using a modified FDA (1994a) method. After thawing overnight and mixing, a 5-g sample was placed into a glass Vol. 65, No. 2, 2000 JOURNAL OF FOOD SCIENCE 233
Residues in Fish... Food Microbiology and Safety Sensory and Nutritive Qualities of Food beaker and mixed with 75 g of anhydrous sodium sulfate (Fisher Scientific). Samples were then placed in a desiccator at room temperature for at least 12 h. The mixture was transferred into a pre-rinsed 35 mm 90 mm glass (extra coarse, size 22) thimble containing a plug of glass wool. Samples were extracted with a Soxhlet apparatus for at least 7 h with 300 ml hexane (Burdick and Jackson, Muskegon, Mich., U.S.A.) at a turnover rate of 4 to 5 times per h. Included in each run of 10 samples was a matrix blank and spike. Recoveries for the matrix spikes of 80% and 120% were acceptable. The extract was evaporated to less than 5 ml by rotary hypobaric evaporation at 40 C and transferred to a pre-weighed, 16 mm 125 mm screw-top tube. The remaining solvent was evaporated to dryness and weighed to determine fat content. The extracted lipid was dissolved in 5 ml petroleum ether (distilled to a cut-off of 50 C, Phillips 66 Petroleum Ether 30-60, Bartlesville, Okla., U.S.A.) and this solution was partitioned 4 times with 30 ml acetonitrile (Burdick and Jackson, Muskegon, Mich., U.S.A.), saturated with petroleum ether by shaking vigorously for 2 min each time. Each time, the separated acetonitrile layer was transferred into a 1-L separatory funnel, containing 650 ml deionized water, 40 ml saturated NaCl solution (Fisher Scientific), and 100 ml petroleum ether. The separatory funnel, containing the combined extracts, was shaken vigorously for 2 min. Following phase separation, the aqueous layer was removed and extracted twice by shaking with 100 ml petroleum ether. The aqueous layer was then discarded and the petroleum ether extracts combined and washed with 2 100-mL portions of water containing, 5 ml saturated NaCl. The petroleum ether extract was then evaporated under a stream of nitrogen to less than 5 ml for Florisil cleanup. The extract was transferred to a glass chromatographic column (22 mm i.d.) containing 20 g activated Florisil (PR Grade, 60-100 mesh, U.S. Silica Co., Berkeley Springs, W.V., U.S.A.). Florisil was activated at 130 C for 24 h and cooled to room temperature. The Florisil was topped with 1-cm layer of anhydrous sodium sulfate. The prepared column was rinsed with 50 ml petroleum ether and the extract was transferred onto the column. The column was eluted with 200 ml 6% anhydrous diethyl ether (Fisher Scientific; containing 2% ethanol, Quantum Chemicals Corp., Cincinnati, Ohio, U.S.A.)/94% petroleum ether (Fraction I) followed by 200 ml 15% diethyl ether (containing 2% ethanol)/85% petroleum ether (Fraction II) and finally with 200 ml 50% diethyl ether (containing 2% ethanol)/ 50% petroleum ether. Fractions I (containing hexachlorobenzene, -BHC, -BHC, -BHC, -BHC, oxychlordane, heptachlor, methoxychlor, heptachlor epoxide, - and -chlordane, transnonachlor, PCBs, o,p -DDD, o,p -DDE, p,p -DDD, p,p -DDE, p,p -DDT and p,p -DDD olefin, -chlordane, mirex, endosulfan I and ethyl chlorpyrifos), II (containing dieldrin, endrin, endosulfan II, diazinon, ethyl and methyl parathion, cypermethrin, and fenvalerate), and III (containing endosulfan sulfate and malathion) were concentrated and exchanged into hexane to a final volume of 10 ml. An aliquot of each extract References Christiansen CC, Hesse LW, Littell B. 1991. Contamination of the channel catfish (Ictalurus punctatus) by organochlorine pesticides and polychlorinated biphenyls in the Missouri River. Trans. Nebraska Acad. Sci. 18:93-98. [FDA] Food and Drug Administration. 1994a. Pesticide Analytical Manual. Volume 1, 3rd ed. Washington, D.C.: Food and Drug Administration. Transmittal No. 94-1. Form FDA 2905a; PB94-911899. [FDA] Food and Drug Administration. 1994b. Pesticide Program: Residue Monitoring 1993. Washington, D.C.: Food and Drug Administration. 21 CFR Parts 109 and 509. p 1-23. [FDA] Food and Drug Administration. 1998. Action Levels for Poisonous or Deleterious 234 JOURNAL OF FOOD SCIENCE Vol. 65, No. 2, 2000 Table 4 Residues of environmental contaminants measured in channel catfish, rainbow trout and red swamp crayfish Organochlorines Polychlorinated biphenyls (PCB) - Aroclor 1242, 1248, 1254, 1260) a Hexachlorobenzene Mirex Heptachlor and heptachlor epoxide Methoxychlor Dieldrin and endrin Endosulfan I, II and sulfate Dichlorodiphenyltrichloroethane (DDT) - o,p -DDD, o,p -DDE, p,p - DDD, p,p -DDE, p,p -DDT and p,p -DDD olefin) Benzene hexachloride ( -, -, - BHC {lindane}) Chlordane (oxychlordane, trans-nonachlor, - and -chlordane) Organophosphates b Chlorpyrifos-ethyl Diazinon Malathion Methyl-parathion Ethyl-parathion Pyrethroids a Cypermethrin Fenvalerate Lower Limit of Quantitation = 0.01 g/g for all analytes except a 0.05 g/g and b 0.02 g/g was transferred to 2-mL injection vials for analysis by electron capture gas chromatography. Fraction I was transferred to a silicic acid column for additional cleanup where necessary to separate PCBs from other organochlorines. Three fractions were eluted from a column (8 mm i.d.) containing 5 g silicic acid (CC4 Special, Mallinckrodt Chemicals, Phillipsburg, N.J., U.S.A.). Silicic acid was activated at 130 C and added to the column while still hot, then topped with 1 cm anhydrous sodium sulfate. The fractions were obtained by the elution of 20 ml petroleum ether followed by 100 ml petroleum ether and then 20 ml of 1% acetonitrile, 19% hexane, and 80% methylene chloride (Burdick & Jackson). PCBs are found in Fraction II. Each fraction was concentrated and exchanged into hexane at the appropriate volume. An aliquot of each extract was transferred to 2 ml injection vials for gas chromatographic analysis. Samples were analyzed using a Varian 3600 electron capture gas chromatograph fitted with dual 0.53 mm i.d. 30 m capillary columns (DB-5 and DB-608; J&W Scientific, Folsum, Calif., U.S.A.), a Varian 8100 autosampler, and a DS-654 Data Station (quantifying using peak area). Extracts were injected into a single inlet that was split into the dual columns. Instrument settings were as follows: injector and detector temperatures, 230 C and 300 C, respectively; hydrogen carrier gas; nitrogen make-up gas; temperature program-start at 150 C held 5 min, ramped at 5 C/min to 170 C, held 10 min, ramped at 10 C/min to 220 C and held 20 min; total run time, 44 min. Results were reported on a wet basis (wb), dry basis (db), and on a percent fat basis (fb). All standards were obtained from EPA Repository (Research Triangle Park, N.C., U.S.A.). Substances in Human Food and Animal Feed. Food and Drug Administration (21 CFR Parts 109 and 509). p 1-18. Nettleton JA, Allen Jr WH, Klatt LV, Ratnayake WMN, Ackman RG. 1990. Nutrients and chemical residues in one- to two-pound Mississippi farm-raised Channel Catfish (Ictalurus punctatus). J. Food Sci. 55:954-958. Niethammer KR, White DH, Baskett TS, Sayre M.W. 1984. Presence and biomagnification of organochlorine chemical residues in Oxbow Lakes of northeastern Louisiana. Arch. Environ. Contamin. Toxicol. 13:63-74. Reinert RE. 1970. Pesticide concentrations in Great Lakes fish. Pest. Monitoring J. 3:233-240. Schmitt CJ, Zajicek JL, Peterman PH. 1990. National contaminant biomonitoring program:
Residues of organochlorine chemicals in U.S. freshwater fish, 1976-1984. Arch. Environ. Contam. Toxicol. 19:748-781. Winger PV, Schultz DP, Johnson WW. 1990. Environmental contaminant concentrations in biota from the lower Savannah River, Georgia and South Carolina. Arch. Environ. Contam. Toxicol. 19:101-117. MS 19990521 received 5/14/99; revised 11/16/99; accepted 12/28/99. The authors appreciate assistance from Jeanine Kee, Nitin Khanna, Taekyun Park, and Dr. Michael Masser. We are grateful to the USDA Southern Regional Aquaculture Center (Contract Nos. 90-38500-5099; 91-38500-5909; 93-38500-8393) and the National Fisheries Institute for providing funding. Author Santerre is with the Dept. of Foods and Nutrition, 1264 Stone Hall, Purdue Univ., West Lafayette, IN 47907-1264. Authors Ingram, Lane, and Alley are with the Mississippi State Chemical Laboratory, Mississippi State, MS 39762. Authors Lewis and Shelton are at the School of Forest Resources, Univ. of Georgia, Athens, GA 30602. Davis is at Texas A&M Agricultural Extension Service, College Station, TX 77843. Grodner is at the Dept. of Food Science, Louisiana State Univ., Baton Rouge, LA 70803. Author Wei is at the Dept. of Food Science and Human Nutrition, Univ. of Florida, Gainesville, FL 32611-0370. Bush is with the Georgia Cooperative Extension Service, Univ. of Georgia, Athens, GA 30602. Xu is with the Dept. of Fisheries and Allied Aquacultures, Auburn Univ., Auburn, AL 36849. Author Hinshaw is with the Dept. of Zoology, North Carolina State Univ., Raleigh, NC 27695. Address inquiries to Charles R. Santerre (E-mail: santerre@purdue.edu). Vol. 65, No. 2, 2000 JOURNAL OF FOOD SCIENCE 235