Research Document - 2016/053
Mesoscale modelling of fisheries productivity metrics in reservoirs: lessons learned from NSERC’s HydroNet 2010-2015
By D. Boisclair, G. A. Rose and G. Bourque
Abstract
The general objective of the NSERC HydroNet project “mesoscale modelling of fisheries productivity metrics in reservoirs” is to contribute to the development of knowledge and tools that improve our capacity to estimate and predict metrics of fisheries productivity in reservoirs. This project was conducted on Lac du Bonnet, Manitoba, a hydropower reservoir on the Winnipeg River. This project was divided in two components that correspond to different types of methodologies and logistical challenges: a pelagic zone component (> 3 m deep) and a littoral zone component (< 3 m).
The pelagic zone component used hydroacoustic surveys to develop fish size spectra. Hydroacoustic survey data accuracy can be improved easily by correcting for boat avoidance. Hydroacoustic is a consistent and repeatable method to describe size spectra in freshwater bodies. Size spectra derived in this reservoir are consistent with theoretical expectations of aquatic ecosystem size structure and provide description of intra- and inter-annual changes in the state of aquatic communities.
The littoral zone component used a range of sampling techniques (seine, gill nets, boat electrofishing) to compare models of diverse fisheries productivity metrics (abundance, biomass, richness), taken at different times (2012-2013, day and night), as a function of a variety of habitat variables (local, e.g. macrophyte cover; lateral, e.g. shore use; contextual, e.g. distance to major tributary). A number of conclusions were derived from these analyses on how best to sample fish communities in a reservoir with the purpose of developing fish-environment relationships. Sampling more sites within a year may be preferable than repeatedly sampling fewer sites within this year. Modelling (or validating) fish-environment relationships in reservoirs may require more than a single year of sampling. Seining may be superior at estimating species richness than other sampling gears. Electrofishing may be the best sampling gear to develop fish-environment relationships in the littoral zone of reservoirs. A combination of local and contextual habitat variables should be used to explain variation in fisheries productivity metrics in the littoral zone of reservoirs and to identify important productivity areas of reservoirs. The explanatory capacity of relationships between total fish abundance and environmental conditions is higher when sampling fish at night than at day. A series of predictive relationships between fisheries productivity metrics and environmental conditions was also provided.
Knowledge and tools developed by the present project may be useful to inform the decision-making process regarding the development or operation of hydropower facilities, and, if authorities recognize the knowledge and tools developed by the present study, augment the clarity, the consistency, and the certainty of the decision-making process.
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