Science Advisory Report 2020/013

Science Advice on the Effectiveness of Spawning Habitat Creation for Substrate Spawning Temperate Fish

Summary

• Literature reviews and meta-analyses were conducted on the effectiveness of creation, restoration, and enhancement of fish spawning habitat (hereinafter referred to as manipulation of spawning habitat) in temperate zones. In the context of manipulating freshwater spawning habitat, the evidence suggests that these actions can: 1) attract substrate spawning fishes, 2) result in spawning, 3) result in egg survival, and 4) produce age-0 fish. Whether these manipulations and their results translate to population-level productivity improvements was not directly explored.
• The reviews considered marine spawning habitat manipulation, but because few targeted spawning habitat manipulations occurred in the marine environment, limited evidence was available for review. Future reviews could focus on evaluating the effectiveness of manipulations more common in marine habitats (e.g. nursery function).
• There were only a few groups of fish (e.g. salmonids) and some intervention types where the evidence base was sufficient to reach quantitative conclusions on effectiveness. There is greater uncertainty for other groups of fish. Nonetheless, if careful consideration is given to the habitat attributes and the biology and life history of the focal species, substrate spawning manipulation techniques that were reviewed may attract substrate spawning fishes, result in spawning, result in egg survival, and produce age-0 fish (Table 1).
• The success of manipulating spawning habitat for substrate spawning fish is dependent on physical attributes of the site, such as: hydrology, fluvial geomorphology, fetch, water level dynamics, shoreline energy characteristics, water quality, and accessibility, as well as biological attributes of the site, for example, if spawners are available.
• Changes to flow and water level are recognized as an important component of spawning habitat manipulation but were not included in this advice as they are the subject of a separate ongoing systematic literature review.
• There was recognition that there are thousands of spawning habitat manipulation projects conducted by governments of various levels, environmental non-governmental organizations (ENGOs), and industry that were not captured in this review because the effectiveness of these interventions was either not assessed, not assessed appropriately, or the data were not available in accessible formats.
• The magnitude of benefits differed between reviews and was dependent on the quality of studies included in the reviews, with higher quality studies (e.g., appropriate controls, replication, more rigorous planning, etc.) demonstrating a greater effectiveness of the habitat manipulation. The cause of this result is uncertain, however, the higher level of planning at all stages (i.e. from concept, to build, to monitoring) that likely accompanied more robustly designed monitoring programs may be a contributing factor to effectiveness.
• Monitoring is essential to understand the effectiveness of spawning habitat manipulations. The appropriate level or type of monitoring can be project dependent and more information is found in DFO (2012) (effectiveness monitoring Science Advisory Report), Smokorowski et al. (2015), and DFO (2019) (functional monitoring Science Advisory Report).
• Many monitoring programs provide low-value information despite the collection of large amounts of data, as was evidenced by the many number of studies excluded from the systematic review. Minimum evaluation criteria for monitoring programs are presented herein that would allow the data’s inclusion in systematic reviews and meta analyses, allowing a broader understanding of effectiveness of spawning habitat manipulations.
• To evaluate the contribution (beyond the effectiveness discussed above) of the spawning habitat manipulation projects to population-level productivity of fish, other information is required. For example, whether manipulating fish spawning habitat results in population-level effects depends in part on whether spawning habitat is a limiting factor to a population, amongst other factors, presented below.
• Spawning habitat manipulations often have impacts on ecosystem components (e.g., other fish species and life stages, habitat functions and physical attributes) beyond the targeted spawning habitats and species, and should thus be considered when determining the overall effectiveness of habitat manipulation. 
• Given the understanding that there are significant amounts of information that were not included in the syntheses due to lack of accessibility, it is strongly recommended that a comprehensive system, based on the advice herein is established to provide standardized data collection, reporting, management and accessibility for further analysis of effectiveness.

This Science Advisory Report is from the January 22-24, 2019, Science advice to the Fisheries Protection Program on the effectiveness of spawning habitat creation for substrate spawning temperate fish. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

Science Advisory Report 2020/013 (PDF, 980 KB)

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