Science Advisory Report  2015/011

Science Guidance for Fisheries Protection Policy: Advice on Equivalent Adult Calculation

Summary

• Consistency in decision making by FPP would be aided by the development of a methodology that can place a diverse range of impacts on a single scale with respect to their effects on fish and fish habitat. Such methodologies would benefit from having a ‘common currency’ for measurement or estimation of fishery productivity.
• The preferred options for projects are first to avoid impacts on fish or fish habitat and second to minimize unavoidable impacts. The advice in this SAR is for cases where feasible options for avoidance and minimization of potential impacts have all been applied, and there is still a risk of some degree of serious harm.
• The goal of these analyses was to develop a ‘common currency’ related to fisheries productivity that could be used to inform and standardize the development of regulatory thresholds or decision points for the FPP. It was concluded that the approach has promise, but the quantitative results of the current analyses are still preliminary in nature. However, the conceptual approach and analytical methods were considered to be a sound foundation for estimating metrics for these uses.
• Use of area per recruit (APR) estimates in setting thresholds or triggering decisions on appropriate regulatory pathways will support decisions for generic cases, but their robustness for specialized cases needs to be explored.
• Risk-based thresholds based on area associated with a chosen number of recruits (i.e., 1 APR, 5 APR, etc.) can be identified using continuous cumulative frequency distributions, or through the use of quantile (or other interval) analysis.
• Both the preliminary compilation of data and the generic analysis suggest most APR estimates range from 100-1000 m² for freshwater fish species typical of Canadian freshwaters (Figure 2). Smaller values were associated with riverine species, and for species of small body size that occur at high density. Expansion of the existing dataset and the inclusion of regional or ecological covariates are likely to result in more accurate and precise estimates of APR.
• Production foregone, the production of biomass (g∙m^-2∙y^-1) provided a complementary metric of productivity to equivalent adults but it was not an alternative to APR.
• If sufficient data are available, and if the scale of the project warrants a detailed assessment, production foregone may be a preferred alternative to AE, as production accounts for all biomass contributions to ongoing productivity, including the biomass of fish that die during the time interval but become available to other trophic levels.
• At present the coarse estimates at national scale are the best information available for general use, and indicate that the EA approach is feasible for coarse level binning of projects. The currently available estimates of APR range from 100-1000 m². The order of magnitude range in estimates conveys a sense of their uncertainty in any particular project review situation. Factors other than APR (such as, regional fisheries objectives, habitat quantity) will also apply. Research is underway that may clarify appropriate habitat type or regional stratification criteria and scales and the resultant reduction in uncertainty.
• If EA relationships do differ among habitats or regionally, then the estimates from pooling data from the various habitats or regions would have greater uncertainty. Hence a risk-based framework managing risks at coarse levels of stratification will require that APR thresholds triggering higher levels of regulatory review be set lower (less area potentially impacted) than if the estimates were more precise.
• Although the scientific basis for the use of adult equivalents and, when appropriate, forgone productivity is sound, the data available to this meeting for estimating values for these metrics come from a limited subset of species, habitat types, and regions. Hence there is uncertainty about how robust the quantitative estimates would be if used in management. Additional data sources were identified during the peer review process, and these are being added to the data base used in the analyses. In the meantime, the order of magnitude range of these estimates is supported by the currently available data and analyses and could be used with the appropriate level of caution given the level of uncertainty.

This Science Advisory Report is from the June 9-10, 2014 National Peer Review on “Science Guidance for Fisheries Protection Policy: Advice on Equivalent Adult Calculation”. 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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