Environmental Progress - Spring 1999

Fish Monitoring Programs Work To Ensure a Safe Catch

Catching them is fun; contaminant testing ensures that eating them is safe.

Freshly caught fish are filleted in the field to collect sample material.

Samplers look for specific sizes and species.

When people go fishing, they expect a relaxing day outdoors; with a little luck they can even bring home supper. Anglers want a pleasant day by the stream or lake, followed by a tasty and healthy meal; they don't want to worry about long-term health effects from chemical residues in the fish. For more than 90 percent of the anglers in Illinois, chemical residues in fish are not a problem. For the few waters where a problem exists, the Illinois Fish Contaminant Monitoring Program (IFCMP) works to ensure that anglers fishing in Illinois can select fish for home consumption which are safe for everyone in the family.

The IFCMP is made up of representatives of the Illinois Departments of Agriculture, Public Health (IDPH), Natural Resources (IDNR), Nuclear Safety, and the Illinois Environmental Protection Agency (EPA). Despite strong public support for the program, for several years until recently there was no money to fund the laboratory analyses needed to determine the chemical residues in fish. Because of the concerns about health risks presented by these residues, all of the state agencies involved joined efforts to reinvigorate the fish monitoring program. As a result, the Illinois legislature provided new funding for analytical work to be done by the IEPA's Division of Laboratories.

Funds cover testing fish but not the cost of collecting them.

The legislature's appropriation provided funds only for the analysis of fish, and to date there has been no additional money for the IDNR's work of catching the appropriate samples. Since the fisheries people have added the work of collecting samples for residue analysis to their normal workload without additional staff, sometimes sampling proceeds at a slow pace. The IDNR biologists routinely monitor the dynamics and health of the fish population at many lakes and streams each year, but in order to get a proper sample of a particular fish species for chemical analysis, three to five fish of the same species, closely matched for length and weight, must be collected. Composite fish samples are collected so that one individual fish does not skew the findings for a species. This may seem like a relatively easy task, but it can be hard enough to get one fish of a particular species, let alone three to five fish of a particular species, and of approximately the same size -- any angler knows how cooperative fish can be on any given day!

In order to collect a lot of fish in a short period of time, the IDNR uses an electroshock technique, which stuns the fish and causes them to float to the surface. The stunned fish are then netted and sorted. Those fish chosen for sampling are filleted (i.e., the edible portion is removed) in order to present an accurate picture of what ends up on the dinner table. The several individual fillets that make up the composite sample are packaged together in aluminum foil, labeled, and frozen. The rest of the stunned fish are returned to the water (where perhaps they tell tales of kidnapping and medical testing by large alien beings?)

Once in the laboratory, the fish are thawed just enough to let the fillets go through a large meat grinder (a.k.a. the Bass-o-matic). Large fillets must be sawed into chunks before grinding. To safely saw up large fish chunks, Chris Dinardo of the Springfield laboratory built a special aluminum miter box. To hold the miter box and the large chunks of frozen fish, special aluminum mesh gloves which would not look out of place on a knight in armor are worn by the tester. These gloves are to protect the hands of the person who is sawing the fish, because the saw sometimes veers off the fish. The chunks of sawed up fish are fed through the grinder three times, to thoroughly mix the fillets. The resulting fish flesh blend, looking like white ground beef, is split into several 20 gram packages. The grinder, saw, and miter box are thoroughly washed and rinsed after each sample; disposable gloves worn are worn over the mesh gloves and are discarded after each fish to avoid cross contamination between samples. If the sample composite was from a predator species such as bass, a separate container will be prepared and sent to the Champaign laboratory for mercury analysis. Only the predator species are analyzed for mercury because little fish are eaten by big fish and those larger fish give clues to how much mercury is present in that body of water.

Analysis calls for extract of fish flesh

To analyze the fish, an extract of the fish flesh must be prepared, using a method for removing organic contaminants from fish tissue that has evolved over time. The laboratory is currently using a method called accelerated solvent extraction (ASE from the Dionex company) which involves mixing a solvent with a measured weight of fish flesh, and agitating the mixed materials under pressure. After a specified amount of time, the solvent will contain the fish fats and the chemical residues stored in those fats. Alternately, the fish flesh may be mixed with the solvent, and then bombarded with sonic waves to disrupt the flesh and remove the fats and residues. In either procedure, the residues that were contained in the edible fish fillets are now concentrated in the solvent.

The final step prior to instrumental analysis is to remove the fats, which would interfere with the analysis. This is done by cleaning the solvent extract twice, which results in two fractions, one containing polychlorinated biphenyls (PCBs) and one containing banned or restricted pesticides. These two fractions are analyzed separately on gas chromatographs equipped with electron capture detectors, which are the most sensitive methods of detecting low levels of pesticides and PCBs. Any residues detected are confirmed in a second analysis, and the results are calculated, reviewed, and reported to the IFCMP members.

Once the validated residue data for a given year are received, the IFCMP members determine whether the fish can be given "thumbs up" or whether the residues require further action. This may be a request for additional samples to better characterize the level of contamination (for newly sampled waters), the issuance of a new fish advisory (for resampled waters), or the revision or elimination of an existing advisory, where appropriate. All new advisories and changes to existing advisories are then announced by the IDPH in a state-wide press release at the beginning of the fishing season; the advisories are also listed in the annual Illinois Fishing Information booklet distributed with each fishing license.

Although only about 10 percent of Illinois sport fishing occurs for fish in problem areas currently, the IFCMP strives to provide this important information to those who want to enjoy the many health benefits of eating fish while avoiding the risks of chemical residues in the catch. After all, if you are lucky enough or skillful enough to catch your supper, you should also be confident that you and your family can eat it safely.