Transgenerational marking of brown troutSalmo trutta f.f.,using an84Sr spike

Abstract

The maternal transmission of a naturally occurring and non-toxic minor isotope of strontium (84Sr) to the central otolith region of the progeny of a typical European freshwater fish species, brown trout, Salmo trutta f.f. L. was accomplished. The focus was to apply minimum doses of a non-toxic solution at physiological salt concentration to minimise potential adverse effects on the fish. Female spawners were intraperitoneally injected with doses of 12.5 and 30.2 μg 84Sr kg−1 fish. Eggs were stripped and the resulting progeny were reared in a hatchery for about 1 year before sampling the otoliths. Strontium isotope ratios in the otoliths of the offspring were measured by cross-sectional line scans using laser ablation-multiple collector-inductively coupled plasma mass spectrometry (LA-MC-ICPMS). Otolith cores of marked juveniles showed a significantly elevated 84Sr/86Sr ratio compared with control fish and to otolith regions created after hatching. Mass marking of cohorts of progeny from individually spiked brown trout with Sr isotopes is therefore possible for dispersal and migration studies without the necessity of handling eggs and applying other larval marking methods like immersion.