Physiology & Reproduction: Quagga Mussel
Characterising the full annual reproductive cycle of Quagga mussels across a depth gradient (1–250 m) in Lake Constance, asking what deep populations are actually doing down there.
Overview
Quagga mussels (Dreissena rostriformis bugensis) have colonised Lake Constance from the surface down to several hundred metres depth. Shallow populations are well-studied and clearly reproducing. But what about the deep ones?
This is largely unknown. Deep-water environments in Lake Constance are cold (~4–6 °C year-round), dark, and food-poor. Whether populations living at 60, 100, or 250 m depth reproduce at all, and if so, how much and when, has never been measured in a European lake. Yet these deep populations can reach high densities and may contribute substantially to the larval pool that drives continued spread.
The Core Question
Do deep-water Quagga mussel populations meaningfully contribute to reproduction?
This matters for two reasons. First, quantitative fecundity data for Quagga mussels essentially do not exist: the available data are almost entirely for the Zebra mussel. Second, if deep populations reproduce less, later, or not at all, that changes how we understand the invasion dynamics of this species in deep Alpine lakes.
Approach
Monthly sampling across five depth strata (1, 15, 60, 100, and 250 m) over a full annual cycle in Lake Constance, covering both reproductive output (gonad staging, egg production) and physiological condition. The dataset will yield the first complete reproductive cycle characterised across a full depth gradient for this species in Europe.
Fieldwork planned: September 2026.