USE OF OTOLITH MICROCHEMISTRY TO INVESTIGATE THE ENVIRONMENTAL HISTORY OF EUROPEAN EEL ANGUILLA-ANGUILLA

Environmental history of the European eel Anguilla anguilla (L.) colle cted from Swedish brackish waters and lakes was studied by examining s trontium (Sr) and calcium (Ca) in their otoliths with wavelength dispe rsive X-ray spectrometry on an electron microprobe. The Sr/Ca ratios i n the otoliths changed with both ontogenetic development and salinity of the habitat. A peak Sr/Ca ratio of approximately 2 x 10(-2) was obs erved in the marine phase of the otoliths, corresponding to the period when a leptocephalus metamorphosed into a glass eel. The ratios decre ased to 5.72 (+/-0.32) x 10(-3) at yellow eel stage when the fish live d in brackish water and to 3.7 (+/-0.20) x 10(-4) in fresh water. The ratios were significantly different between brackish and fresh water ( p < 0.00001). Several relatively higher Sr bands were found in otolith s of eel from brackish waters but not in the eels from fresh water. Sa linity probably influences Sr deposition more than does temperature or somatic growth rates.