Ontogenetic behavior and migration of kaluga, Huso dauricus

Abstract

We conducted laboratory experiments with early life stages of kaluga sturgeon, Huso dauricus, from the middle reach of the Amur River to quantify ontogenetic behavior and compare their behavior with similar laboratory data collected previously on young kaluga from the Amur River. Our hatchling free embryos initiated an intense downstream migration that peaked on day 1, and continued strongly to day 3, decreased strikingly during days 4–6, and ceased on day 7 (8-day migration). Migrants preferred a bright habitat (illuminated and white bottom), open habitat, and swam-up far above the bottom (daily median distance, 3.5 m). On days 21–22, larvae initiated a second downstream migration of similar intensity (four fish passes per 5 min), with a peak at 34–35 days. Juveniles continued a slow intensity migration (one fish pass per 5 min) until day 66, indicating a long-duration migration style by early life stages that would carry them far downstream from a spawning site. Free embryos, larvae and early-juveniles also strongly preferred open habitat, suggesting a similar use of this habitat type by wild individuals of these three life stages. The behavior and migration of our kaluga early life stages were similar to the young kaluga studied previously, but the migration of the two groups was different in major ways. This result suggests there are at least two breeding stocks in the river, each with a slightly different early behavior. If correct, culture programs for stock enhancement must ensure breeding populations are not mixed, which would produce non-adapted early life stages. Genetics studies are needed to identify the kaluga populations in the Amur River.