THE EFFECT OF OTOLITH STORAGE METHODS ON THE CONCENTRATIONS OF ELEMENTS DETECTED BY LASER-ABLATION ICPMS

Otoliths of male (1+ year old) Terubok, tropical shad Tenualosa loll f rom the Lupar River, Sarawak, were treated in different ways to assess the effect of post-capture storage on element concentrations in the o tolith core and edge detected by laser-ablation inductively coupled pl asma mass spectrometry (ICPMS). Five treatments were compared: rapid r emoval and dry storage; fish kept 5 h after capture then otoliths remo ved; rapid removal and stored in alcohol; fish frozen for 24 h then ot oliths removed; and storage of intact head in alcohol for several week s. Seven elements were detected at the core and edge of otoliths (Li, Na, Mg, Mn, Co, Sr, Ba). Of these, Na, Mg, Co and Ba differed among tr eatments, being highest in treatments where the otolith remained in th e head. Variation in element measurements due to treatment effects was similar to within-otolith variation for the other elements and was le ast variable in the fresh treatment. The variation in concentration be tween the core and edge was more significant than other sources of var iation (up to 100 times) for some elements. These differences were pro bably due to physiological factors (ontogenetic) or to yearly changes in water chemistry. The results indicate that the method of otolith st orage, especially freezing whole fish, can have a small, but measurabl e, effect on the concentrations of Na, Mg, Co and Ba. (C) 1998 The Fis heries Society of the British Isles.