New Test Detects Pesticides in Fish

MUNICHResearchers at Fraunhofer Institute for Molecular Biology and Applied Ecology IME for the first time have developed a system to test whether chemical substances accumulate in cultivated fish that are fed contaminated feed. The discovery is significant since half of all fish consumed worldwide come from fish farms.

Fish feed producers are facing a dwindling supply of ingredients in feed, including fishmeal and fish oil, which are slated to be replaced by crops, such as soya, maize and rape that may contain pesticides from the fields.

First, we test whether ingestion of the feed leads to a build-up of pesticide residues in fish tissue, and we look to see which degradation products or metabolites result from the fishs metabolic processes. Essentially, the more fat-soluble a substance is, the higher the probability of it accumulating in fish," said Dr. Christian Schlechtriem, a scientist at the IME. Our tests form the basis for later studies on feeding. The results determine whether these subsequent studies, which ascertain maximum pesticide residue levels, are required."

To detect and identify pesticide residues and their metabolites, a radio-labeled test substance is added to the pellet feed, and a powerful filtering system prevents the dissolved test substance from accumulating in the water. The flesh of the fish is then tested for pesticide residues using highly sensitive analytical methods which permit even the smallest quantities of a substance to be detected with certainty.

Our new test leaves no stone unturned in the search for pesticides and their degradation products in fishfrom breeding through to tissue analysis in the laboratory," said Dr. Dieter Hennecke, head of the IMEs ecological chemistry department.

The European Commission will soon publish new data requirements for fish as part of the approval process for pesticides. Every producer and importer who intends to bring a new pesticide onto the European market not only will need to register it but also provide information proving it cannot accumulate in the edible parts of fish. The fish test developed at the IME will supply the information required.