International Journal of Limnology

The long-term decline of the whitefish (Coregonus lavaretus) population in the boreal lake Pyhäjärvi, southwest Finland is described. Whitefish decline was associated with decreases in fecundity, winter survival of embryos, and larval density. The spawning stock was kept small by intensive fishery.

Our study introduces the first Bayesian Delay-Difference model adapted to whitefish fisheries in peri-alpine lakes. By analyzing various data, the model accurately estimates annual biomass, recruitment, stage structure of landings, and fishing mortality. These insights are invaluable for comprehending the historical trends and impacts of fishing activities on these stocks.

From the beginning of the 1980s, professional fishermen and recreational anglers, together with state services and researchers from INRA, developed an applied research program focusing on the improvement and optimisation of salmonid stocking in the Lakes Geneva and Bourget. The aim of thispaperis to retrospectively retrace the key stages of this program and its main impacts on society.

We exploredpotential drivers of larval coregoninedistributions in Lake Geneva, France and Lake Superior, USA. Depth and wind were important drivers in both lakes, date was important in Lake Geneva, and available preydensity was not important. Understanding the importance of these factors can help elucidate mechanisms regulating larval survival.

Time series of 22 vendace (Coregonus albula) populations were applied to estimate the population-specific average length-at-age and survival in early life and mature life stages. These vital rates differed widely between populations and temporally within a population. Theearly life survivalis set by the factors external to the vendace population. It is expected to decrease due to climate change, increasing the risk of local extinctions.

The Detroit River once supported a substantial lake whitefish (Coregonus clupeaformis) fishery until the early 1900s. As a result of almost 50 years of efforts to improve water and habitat quality, lake whitefish have begun to spawn in the river and viable eggs were collected. Genetic analysis of larval fish hatched from eggs collected in the field between 2005 and 2018 found thatover 80% of the hatched larvae had parents originating from Lake Erie. The estimated number of lake whitefish parents at Fighting Island decreased in the most recent collections possibly due to loss of habitat on spawning reefs due to sedimentation or a change in sample design. Our results provide additional evidence that restored spawning habitat in the Detroit River is again being used by lake whitefish and continued reproduction at these sites may improve the Great Lakes portfolio of ecological and genetic diversity.

In our study of the spawning behaviour of lake whitefish, we observed fish using a variety of habitat types during the spawning season, including a rocky spawning shoal, sandy substrates, and steeper slopes. Both sexes moved shallower at night and deeper during the day, with males moving more at night and females more during the day. This study could help inform stewardship efforts aimed at lake whitefish spawning habitat restoration and protection.

Our paper reviews the restoration and conservation strategies applied towards coregonines (e.g., whitefishes, ciscoes) across Europe, Asia, and North America. The highlighted strategies included 1) stocking of hatchery-reared fish, 2) controlling invasive species, 3) translocating fish, 4) restoring habitat, and 5) eliminating harvest or creating protected areas.

This study focuses on the effects of urban wastewater on macroinvertebrate communities in the upper Ouémé basin in Benin. We found similar responses in African invertebrates to those observed in other parts of the world. However, we unexpectedly observed a stronger impact during the wet season than during the dry season. Furthermore, community resilience did not depend primarily on the distance downstream of the wastewater input, but rather on a combination of several factors.