Novel Techniques for Marking Largemouth Bass Otoliths: Transgenerational and Barium-Diffusion Marking

Fisheries biologists often require information about specific fish or groups of fish, which makes marking fish for future identification an essential tool. We tested two novel marking techniques for naturally-reproduced Largemouth Bass during early life-history stages: transgenerational and barium osmosis marking. For transgenerational marking, adult Largemouth Bass were given treatments of a barium injection, strontium injection, or no injection (control) and released into three experimental ponds. Adults were allowed to spawn naturally in the ponds, and subsamples of their offspring were collected at ~10 d and ~100 d for evaluation of marking success. Otoliths were dissected from collected fish, sectioned, and analyzed using laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) for elevated barium or strontium at the core; indicating a successful mark. For barium osmosis marking, we immersed fry in a 0, 0.1, 0.25, 1, or 2.5-mg/L barium chloride solution for 24, 48, or 72-hr trials. These fish were then transferred to experimental tanks and fed a mixture of artemia and Lumbriculus spp. Fish were harvested at 91 d or when mortality occurred to evaluate the success of barium mark on the otoliths using LA-ICPMS.  Chemical markers are anticipated to be useful in evaluating habitat needs for Largemouth Bass.