Experimental evaluation of the spawning periods of whitefish (Coregonus lavaretus complex) in Lake Mondsee, Austria
Wanzenböck, Josef; Pamminger-Lahnsteiner, Barbara; Winkler, Kathrin; Weiss, Steven J.
The integrity of a native Alpine whitefish population (Coregonus lavaretus species complex) in Lake Mondsee may have been impaired through potential hybridisation and introgression by stocking of Baltic origin whitefish for many decades. However, ecological niche differentiation with regard to different spawning times (November to early December for the introduced population, mid-December to mid-January for the native population) might facilitate reproductive isolation preserving the independence of the native population. We experimentally studied spawning activity of the two populations in an aquaculture setting to complement genetic and morphometric analysis. Despite identical culturing conditions with regard to water chemistry and temperature, day length, tank size etc., complete temporal segregation in spawning activity of the two whitefish populations was maintained in each of two spawning seasons, whereas some overlap was apparent when the two seasons were combined. Spawning time of first-time spawners was not significantly different from repeat spawners in the introduced population, however, it was retarded in native fish by almost one month when the firsttime spawners (all native fish in the first season) were compared to repeat spawners in the second season (the same individuals). Our results generally confirm the reported differences in spawning time of the two groups and suggest a potential mechanism contributing to reproductive isolation. Differences in the onset of spawning of at least one month indicate distinct reactions to triggering factors and genetic rather than environmental control of spawning activity.