Science Advisory Report 2018/025

Developing regional benchmarks for fisheries productivity for nearshore marine habitats

Summary

• The development of regional community-based benchmarks of fisheries productivity for nearshore marine habitats was considered feasible.
• Fisheries productivity is best expressed in terms of the total fish production of each species. Production potential is defined as the production from all age classes of a fish species that use a type of nearshore habitat at some point in their life cycle; this was considered a useful metric as a benchmark for fisheries productivity.
• Standing stock abundance or biomass of fish was recognized as a useful metric in freshwater habitats and will likely be useful in some circumstances for marine habitats.
• A model that estimates production per age class of individual species from estimates of density of at least one age class and knowledge of life history parameters was developed and its use was supported.
• Model outputs can be used to estimate total fish community production or the production of select species, and can evaluate the relative contributions of different habitats to fisheries productivity. Thus the model can estimate loss of productivity that might result from development projects that impact habitats or the potential gains from offsetting measures.
• Preliminary results from the Atlantic coast of Nova Scotia demonstrated differences in fish density and metrics of production among eelgrass, rockweed, and bare habitats. This supports the utility of stratification by habitat type.
• An evaluation of stratification at larger spatial scales was not possible due to shortcomings of datasets that were available. Thus, it was not possible to demonstrate the utility of regional stratification when estimating fisheries productivity.
• Area-per-recruit (APR) is a metric of the contribution of nursery habitat to adult fish production. It was determined that it is feasible to calculate APR for nearshore marine habitats, but more analyses are needed to evaluate the reliability of estimates.
• The utility of the regional benchmark approach is limited by the availability of information on the abundance, biomass and productivity of fish and invertebrates in marine nearshore and coastal habitats across the range of habitat types and regions. There is a need for spatially and temporally extensive monitoring programs that sample a diversity of habitats (with standardized protocols that include species-specific age or size determination) for the development of regional benchmarks.
• While deemed feasible there remains a number of uncertainties with respect to the usage of the benchmark approach in nearshore marine habitats. The potential for sampling protocols to underestimate densities emphasizes the need to estimate capture probability for each sampling method and habitat type. The presence of depressed populations may also bias the results towards underestimating the habitat production potential.

This Science Advisory Report is from the March 28-30, 2017 Science Advice on Marine Productivity Benchmarks meeting. 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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