Review of the IEAB Fish Tagging Cost Effectiveness Model

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In response to the Northwest Power and Conservation Council’s June 2013 request, the ISAB reviewed the Independent Economic Analysis Board’s report: Cost-Effectiveness of Fish Tagging Technologies and Programs in the Columbia River Basin (IEAB document 2013-1). The IEAB Fish Tagging (FT) model determines how many (juvenile) fish should be tagged with what type of tags (CWT, PIT, genetic) to satisfy a set of required outcomes (for example, a minimum number of tags detected at a location so that estimates of survival have a certain precision).

Overall, the IEAB report is thoughtful and well written. The objectives of the modeling effort are explained well, and, for the most part, the assumptions (and their rationale) of the model are given.

The model is deterministic – it always arrives at the same outputs given the same inputs – and uses average values of various parameters such as in-river survival or ocean survival. However, there is often a large variation in parameter values among years and among stocks. Consequently, several sensitivity analyses are required. For example, the model should be run under poor survival conditions to see if the conclusions are robust. Further, cost estimates are imprecise and are constantly changing, so multiple modeling runs should be made to identify the price points at which conclusions would change.

The model provides a cost-effectiveness analysis to determine the minimum number of fish that must be tagged so that a certain number are detected or recovered for an indicator (e.g., smolt-adult return rate) addressing a specific management question (e.g., is the stock self-sustaining). The current model does not evaluate program effectiveness.

Examining program effectiveness requires that managers determine and rank the information needed for the indicators. For example, is an estimate of reach survival to Bonneville for smolts from stock X more or less valuable than an estimate of smolt-to-adult-return (SAR) survival for stock Y. Tag numbers and tag types would then be determined at the project level to meet these goals and tradeoffs between tag numbers, tag costs, and precision of the metric of interest could then be investigated. The IEAB report discusses the need for regional coordination and rationalization of tagging efforts to gain greater cost-effectiveness and program effectiveness but makes no explicit recommendations.

The ISAB offers several recommendations toward further development of the IEAB model to improve its usefulness for fish management in the Columbia River Basin. Specifically:

  • Incorporate elements to evaluate program effectiveness. This requires all parties involved in the Columbia River Basin fish programs collaborate in developing a priority list of the many indicators (more than 100) identified by the IEAB.
  • Focus on rationalization of the PIT-tagging program given the very large infrastructure already in place and the overlapping objectives of different studies (e.g., estimating in-river and transport survival, evaluating effectiveness of habitat improvements, measuring straying rates, and so forth). This evaluation should also consider tradeoffs between improving detection rates (e.g., more arrays on dams) vs. ongoing costs and handling effects of tagging more fish.
  • Incorporate otolith marking and acoustic tagging methods in the model. Otolith marking programs can mark 100% of hatchery fish at relatively small costs, while acoustic tags can have a very high detection efficiency, which imply much fewer fish need to be tagged.
  • Incorporate synergies between different tag types, especially genetic methods. Genetic methods are expected to undergo great technological improvements in the near future and often provide complementary information to other tag-types.

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