OECD 203: Fish, Acute Toxicity Test

Protection of the fish community in freshwater is an important issue because fish play a major role in trophic cascades and as food resource for human beings. Therefore the impact of plant protection products, industrial chemicals, biocides and medicinal products that may get into aquatic environment has to be assessed on fish.

Study Design

Test organisms

ibacon performs fish tests with a variety of species:

  • Oncorhynchus mykiss (rainbow trout)
  • Danio rerio (zebrafish)
  • Pimephales promelas (fathead minnow)
  • Cyprinus carpio (common carp)
  • Oryzias latipes (Japanese medaka)
  • Lepomis macrochirus (bluegill sunfish)

Course of the test

Depending on the results of a range-finding pre-test, either a dose response study or a limit study is performed. The stability of the test item is important for the selection of the study design. If the test item is not stable under test conditions, the test media is renewed in defined intervals (semi-static test design) or a flow through test design is perform.

Juvenile fish are exposed for 96 hours to determine mortality and symptoms of intoxication. The fish are observed after approx. 2 hours and after 24, 48, 72, 96 hours. Seven individuals are exposed per control and test item concentration.


A dose response study allows calculating EC50(EC20, EC10), NOEC (No Observed Effect Concentration) and LOEC (Lowest Observed Effect Concentration) for mortallity.

Guidelines and literature

  • OECD Guideline for Testing of Chemicals, Section 2, No. 203: "Fish, Acute Toxicity Test"
  • Commission Directive 92/69/EEC, Annex Part C, C.1: "Acute Toxicity for Fish", Official Journal of the European Communities No. L383A
  • EPA Ecological Effects Test Guidelines OPPTS 850.1075 Fish Acute Toxicity Test, Freshwater and Marine