EXPOSURE OF FEMALE JUVENILE RAINBOW-TROUT TO ALKYLPHENOLIC COMPOUNDS RESULTS IN MODIFICATIONS TO GROWTH AND OVOSOMATIC INDEX

The alkylphenol ethoxylates (APEOs) are a major group of nonionic surf actants. Biodegradation of these compounds is incomplete during sewage treatment; thus, they are ubiquitous aquatic pollutants. All the main degradation products of APEOs were recently demonstrated to have estr ogenic properties in vitro, but their effects in vivo remain to be est ablished. In this study, female juvenile rainbow trout (Oncorhynchus m ykiss Walbaum) were exposed to octylphenol, nonylphenol (NP), nonylphe nol diethoxylate, and nonylphenol mono-carboxylic acid (NP1EC) at envi ronmentally relevant concentrations (Experiment 1: 1, 10, and 50 mu g/ L; Experiment 2: 1, 10, and 30 mu g/L). Exposure to APEOs commenced at hatch (day 0) and was terminated on day 22 (Experiment 1) or day 35 ( Experiment 2). Body weight and fork length of representative samples o f fish from each treatment group were recorded at intervals up to 108 d (Experiment 1) or 466 d (Experiment 2). In Experiment 1, significant differences in size of the exposed fish, related to treatment, were s till apparent on day 108, 86 d after withdrawal of the treatments. The se observations were confirmed during Experiment 2, in which significa nt changes in body weight and fork length as a consequence of exposure to the compounds were observed approx. 15 d after exposure was termin ated. These differences were sustained for at least 466 d in the case of NP and NP1EC. In addition, the ovosomatic index (OSI) of fish expos ed to NP and NP1EC was significantly affected zby the treatment. Survi val of fish in the natural environment is strongly influenced by body size, and an appropriate OSI is a crucial factor in successful reprodu ction. Therefore, exposure of natural populations of fish to these che micals at concentrations currently measurable in the aquatic environme nt may have an impact on the performance of those populations.