Laboratory Estimation of Net Trophic Transfer Efficiencies of PCB Congeners to Lake Trout (Salvelinus namaycush) from Its Prey

Summary

A technique for laboratory estimation of net trophic transfer efficiency of polychlorinated biphenyl (PCB) congeners to piscivorous fish from their prey is presented. To maximize applicability of the laboratory results to the field, the piscivorous fish should be fed prey fish that are typically eaten in the field.

Abstract

A technique for laboratory estimation of net trophic transfer efficiency (γ) of polychlorinated biphenyl (PCB) congeners to piscivorous fish from their prey is described herein. During a 135-day laboratory experiment, we fed bloater (Coregonus hoyi) that had been caught in Lake Michigan to lake trout (Salvelinus namaycush) kept in eight laboratory tanks. Bloater is a natural prey for lake trout. In four of the tanks, a relatively high flow rate was used to ensure relatively high activity by the lake trout, whereas a low flow rate was used in the other four tanks, allowing for low lake trout activity. On a tank-by-tank basis, the amount of food eaten by the lake trout on each day of the experiment was recorded. Each lake trout was weighed at the start and end of the experiment. Four to nine lake trout from each of the eight tanks were sacrificed at the start of the experiment, and all 10 lake trout remaining in each of the tanks were euthanized at the end of the experiment. We determined concentrations of 75 PCB congeners in the lake trout at the start of the experiment, in the lake trout at the end of the experiment, and in bloaters fed to the lake trout during the experiment. Based on these measurements, γ was calculated for each of 75 PCB congeners in each of the eight tanks. Mean γ was calculated for each of the 75 PCB congeners for both active and inactive lake trout. Because the experiment was replicated in eight tanks, the standard error about mean γ could be estimated. Results from this type of experiment are useful in risk assessment models to predict future risk to humans and wildlife eating contaminated fish under various scenarios of environmental contamination.

Introduction

Of all of the factors affecting the rate at which fish accumulate contaminants, the efficiency with which fish retain contaminants from the food that they eat is one of the most important^1-3. Risk assessment models have been developed to predict future risks to both people and wildlife eating contaminated fish under various scenarios of environmental contamination, and the reliability of these predictions critically depends on the accuracy of the estimates of the efficiency at which fish retain contaminants from their food⁴.

The efficiency with which the contaminant in the food ingested by the predator is transported ....

Protocol

1. Laboratory Experiment

1. Obtain the prey fish to be fed to the predator fish during the experiment. Preferably these prey fish should be captured in the field, frozen, and stored at about -30 °C. Consider commercial fishing operations as a potential source for the prey fish.
2. Introduce the predator fish into the laboratory tanks to be used for the experiment. Up to 15 predator fish have been introduced into each of 870-L tanks, and up to 30 predator fish have been introduced into each of 2,380-L tanks in previous studies^16,18.
3. Acclimate the predator fish to a diet of the selected prey fish. Once acclimated, the predator fish s....

Results

Lake trout showed a substantial amount of growth during the experiment, as the initial lake trout mean weights ranged from 694 to 907 g while the final lake trout mean weights ranged from 853 to 1,566 g (Table 1). The average amount of food consumed by a lake trout during the course of the 135-day experiment ranged from 641 to 2,649 g. Mean PCB congener concentrations in the lake trout increased during the experiment, as mean PCB congener concentrations ranged from 0.01 to 7.14 ng/g (wet-weight basis) at.......

Discussion

For the most accurate estimates of γ, the experimenter must be able to accurately track both the amount of food placed in each of the tanks and the amount of uneaten food in each of the tanks during the course of the experiment. To accomplish this, the experimenter must be able to remove all of the uneaten food from the tanks and accurately determine its weight. In addition to accurate tracking of the food actually eaten by the predator fish, accurate estimation of γ may also depend on sufficient duration of th.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
870-L fiberglass tanks	Frigid Units	RT-430-1
2,380-L fiberglass tanks	Frigid Units	RT-630-1
Tricaine methanesulfonate (Finquel)	Argent Chemical Laboratories, Inc.	C-FINQ-UE-100G	Eugenol could also be used as an anesthetic.
Ashland chef knife	Chicago Cutlery	SKU 1106336
Cutting board	Williams-Sonoma	3863586
Hobart verical mixer (40 quart)	Hobart Corporation
1.9-L food processor	Robot Coupe, Inc.	RSI 2Y1
Polyethylene bags (various sizes)	Arcan Inc.
I-Chem jars	I-Chem	220-0125
Top-load electronic balance	Mettler Toledo	Mettler PM 6000
Sodium sulfate, anhydrous - granular	EMD	SX0760E-3
Glass extraction thimbles (45 mm x 130 mm)	Wilmad-Lab Glass	LG-7070-114
Teflon boiling chips	Chemware	919120
Rapid Vap nitrogen sample concentrator	Labconco	7910000
N-Vap nitrogen concentrator	Organomation	112
Soxhlet extraction glassware (500 ml)	Wilmad-Lab Glass	LG-6900-104
Hexane	Burdick & Jackson	Cat. 211-4
Dichloromethane	Burdick & Jackson	Cat. 300-4
Silica gel	BDH	Cat. BDH9004-1KG
Labl Line 5000 mult-unit extraction heater	Lab Line Instruments
Agilent 5973 GC/MS with chemical ionization	Agilent	5973N
Internal standard solution	Cambridge Isotope Laboratories	EC-1410-1.2
PCB congener calibration standards	Accustandard	C-CSQ-SET
DB-XLB column (60 m x 0.25 mm, 0.25 micron)	Agilent/ J&W	122-1262