Science Advisory Report  2016/051

NSERC's HydroNet: consolidating five years of research designed to develop knowledge and tools about the effects of hydroelectric facilities on aquatic ecosystems

Summary

• This Science Advisory Report (SAR) provides advice to policy and management arising from five years of research exploring how to best estimate and predict various metrics of fisheries productivity on aquatic systems impacted by hydropower production, to aid in implementing the Fisheries Protection Provisions (FPP) of the Fisheries Act (2012). Research documents reviewed at the meeting consolidated research under four themes, and the scientific advice provided is organized accordingly:
  1. Key physical and chemical drivers of fisheries productivity in various Canadian regions (Lapointe et al. 2015). This theme included presentation of a useful remote sensing tool for quantifying fish habitat that will be available in the proceedings of the workshop, with more detail available in Hugue et al., 2015.
  2. Modelling the effects of chemical and physical drivers on fisheries productivity metrics across rivers of varying hydrological regimes (Boisclair et al. 2016a);
  3. Mesoscale modeling of fisheries productivity metrics in reservoirs (Boisclair et al. 2016b); and
  4. Upstream passage and entrainment of fish at hydropower dams (Gutowsky et al. 2015).
• HydroNet developed a series of empirical models linking fish productivity metrics to environmental conditions. As with any empirical model, these models are most applicable to systems with similar environmental and/or biological conditions as found in the HydroNet systems, however, the general relationships observed may be applicable on a broader basis.

Physical and Chemical Drivers

• The alteration of flow regimes was assessed with a useful office-based approach that uses readily available hydrometric data sets. It can serve as a complementary analysis to indicators of hydrological alteration (or as a substitute where insufficient historical data are available). The flow regime of regulated rivers can be placed in a regional context by quantifying the degree of anomaly of various aspects of their flow regime relative to regimes of unregulated systems (meaning systems unregulated by a dam, see Glossary in the Appendix) and other regulated systems of broadly similar watershed characteristics located in the same region.
• The degree of flow anomaly in relation to unregulated systems and other regulated systems could help guide the degree of study required, or help prioritize systems for study that are to be regulated.
• An analysis of thermal data from paired regulated vs. unregulated rivers demonstrated important differences in the thermal regimes of storage and peaking systems (systems with reservoirs) vs. unregulated systems.
• Various statistical tools to describe the thermal regime of rivers were developed and compared, and advice is provided regarding the selection of thermal models and their use in management decisions. Given that collecting temperature data is relatively inexpensive and straightforward, and given the biological importance of temperature, the collection of temperature data should be considered for incorporation into monitoring programs.
• An analysis of the literature (mostly North American systems) revealed strong relationships between total phosphorus and fish biomass that were regionally dependent. However, if species richness is factored in, regional differences no longer existed. Including mean depth improved models further, and there was no difference between lakes and reservoirs.
• The literature-derived nutrient-fish biomass model for rivers and streams had a different slope than for lacustrine systems, but there was no difference between regulated and unregulated rivers. However, a paired regulated-unregulated analysis was not conducted and this question should be explored further.
• A method that couples current sub-meter resolution satellite imagery with in situ depth transects to create low cost maps of water depth (and velocity if discharge is known) for very long river segments (many tens of km long) was developed. Application and cautions for this remote sensing method are briefly described below in the Analysis section.

Biological Drivers

• Fisheries productivity metrics (density, biomass, species richness) in rivers located downstream of run-of-the-river facilities tend to be similar to unregulated rivers.  Rivers located downstream of storage dams had 33% higher biomass but 1.7% lower species richness than predicted for an unregulated river. Rivers located downstream of peaking facilities have 39%, 48%, and 13% lower fish densities, biomass, and species richness, respectively, than that predicted for unregulated rivers.
• A number of metrics of flow regimes at the analysed peaking facilities were highly anomalous relative to the suite of unregulated rivers studied in HydroNet. Thus a peaking facility that is less strongly anomalous relative to unregulated rivers may not have the same negative effect on fisheries productivity metrics. An among-river comparison of a multidimensional index of flow anomaly (derived from 105 flow metrics) hinted that there may be a threshold beyond which a significant negative effect on biota occurs. Further research should be conducted to confirm whether such a threshold exists.
• Results from projects aimed at developing fish-environment relationships for a variety of fisheries productivity metrics, at a range of organismal scales (total fish community, guild of species, species, combinations of species and size classes), spatial scales (site, habitat type, river segment), and using multiple modelling techniques (multiple regression, artificial neural networks, phylogenetic habitat modelling) were presented.
• The models developed identified key environmental drivers in rivers. Under the correct circumstances, these models could be used to predict the future state of fisheries productivity metrics (different organismal scales) in rivers (different spatial scales). These tools may be used to predict the effects, to identify mitigation measures, and to assess residual effects of hydropower on fisheries productivity metrics in rivers.

Mesoscale Modelling in Reservoirs

• The reservoir work was largely a methodological study with the objective of testing a variety of methods to determine the most appropriate for sampling reservoirs in monitoring programs.
• Hydroacoustic methods were evaluated as a viable sampling method for the pelagic zone (> 3m depth) in reservoirs. The results on fish size classes fit theoretical expectations and were found to be consistent and repeatable.
• Several different methods (boat electrofishing, seining, and gill netting) were explored as viable sampling methods for the littoral zone (< 3m depth). Each of these methods has benefits and limitations and the research document contains many recommendations on what, when, and how sampling should be conducted in the littoral zone in a reservoir.
• Fish-environment relationships were derived when possible, however, there were large differences in relationships between years suggesting that modelling and validating such relationships requires multiple years of sampling.
• A combination of local (e.g., macrophyte coverage) and contextual (e.g., distance to large tributaries) habitat variables appeared useful in explaining variation in fisheries productivity metrics in the littoral zone of reservoirs.

Fish Passage

• Any new fishways should be evaluated for fish attraction and passage efficiency (see Glossary for definitions). From an ecological perspective, providing fish passage minimizes impacts where the dam is altering fish passage. However, the need for fish passage should be evaluated on a case-by-case basis using a community-based approach including considerations of the habitat availability after project development.
• Fishway evaluation should include biological (e.g. attraction, full passage, etc.) and hydraulic (e.g., velocity, turbulence) data collection and associated modeling using a multidisciplinary team.
• The evaluation of fish passage success through a fishway should be based on site-specific, a-priori, biologically based targets linked to fisheries management or conservation objectives. Simply monitoring a complete passage of fish through the fishway (i.e., capture in a trap at the top) is not sufficient to evaluate passage success, since there is a need to know the number of fish seeking and attempting passage to establish a success rate. Ideally such information is then considered in the context of the population biology of target species/populations.
• Entrainment risk assessments using desktop methods represent a first step in evaluating the need for, and prioritization of, more detailed studies.
• Modelling the physical environment of the forebay (including flow field dynamics and water temperature) is critical to understand factors leading to entrainment. Thus, entrainment is best evaluated by a multidisciplinary team including engineers and biologists.
• Entrainment must be considered on a species-specific and life-stage basis, covering all relevant spatial (fine and coarse) and temporal (e.g., diel, seasonal) scales.

This Science Advisory Report is from the national peer review meeting of September 15-17, 2015 on the NSERC's HydroNet: consolidating five years of research designed to develop knowledge and tools about the effects of hydroelectric facilities on aquatic ecosystems. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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