Status of Stocks & Multispecies Assessment Program
Annual Catch Limits Workshop
The AFSC hosted a national workshop to discuss scientific considerations associated with implementing the annual catch limit (ACL) provisions of the Magnuson-Stevens Reauthorization Act of 2006 (MSRA). The workshop, sponsored by the NMFS Office of Science and Technology and Office of Sustainable Fisheries, was held 15-17 May in Seattle. The need for such a workshop arose as a result of the following new language in the MSRA (italics added).
Section 302(g): “Each scientific and statistical committee shall provide its Council ongoing scientific advice for fishery management decisions, including recommendations for acceptable biological catch, preventing overfishing, maximum sustainable yield, and achieving rebuilding targets, and reports on stock status and health, bycatch, habitat status, social and economic impacts of management measures, and sustainability of fishing practices.”
Section 302(h): “Each Council shall, in accordance with the provisions of this Act ... develop annual catch limits for each of its managed fisheries that may not exceed the fishing level recommendations of its scientific and statistical committee or the peer review process established under subsection (g).”
Section 303(a): “Any fishery management plan which is prepared by any Council, or by the Secretary, with respect to any fishery, shall ... establish a mechanism for specifying annual catch limits in the plan (including a multiyear plan), implementing regulations, or annual specifications, at a level such that overfishing does not occur in the fishery, including measures to ensure accountability.”
Because the terms “annual catch limits” and “measures to ensure accountability” are not defined in the MSRA, NMFS is expected to develop regulations to assist Councils in the implementation of the above requirements. Although the development of such regulations provided the context within which the workshop was held, the workshop was not designed to develop specific regulatory recommendations. Rather, the goal was to engage in an interregional, management-science discussion which would explore the breadth of current and potential approaches and the merits of potential follow-up workshops to develop technical guidance.
The workshop was attended by NMFS scientists from all of the regional science centers as well as members of many of the Fishery Management Councils. All regions of the country were represented, from the U.S. Virgin Islands to Hawaii. The presentations and discussions revealed the wide variety of approaches used to assess fish stocks and manage fisheries in the U.S. and the difficulty of imposing a common ACL requirement on such a diverse group of management styles.
Four topics were addressed in the workshop: assessment support for ACL determination, quantifying and communicating uncertainty in assessment forecasts, the roles of the scientific and statistical committee and peer review, and data-limited situations. These topics were addressed through presentations by NMFS scientists and follow-up discussion by the workshop participants. Three SSMA Program scientists (Grant Thompson, Rebecca Reuter, and Olav Ormseth) made presentations at the workshop.
Thompson’s presentation focused on how to address uncertainty in the context of fishery management. Using an illustration from archery, he showed that a strategy of aiming for a goal (the “bull’s-eye”) offers better performance than the alternative strategy of achieving a given probability of missing the target entirely. In the context of fishery management, this means that a strategy of maximizing the expected net benefits obtained from fishing offers better performance than the alternative strategy of achieving a given probability of hitting some limit reference point such as a minimum biomass level. Decision theory offers the tools necessary to implement such a strategy. In the decision-theoretic approach, the optimal level of fishing is determined by the statistical uncertainty implied by the data and the level of risk aversion implied by the managers’ utility function. Previously, most applications of decision theory to fishery management have been made within a single-species context. In those applications, it is clear that a risk-averse utility function results in an inverse relationship between the level of uncertainty and the optimal level of fishing. Recently, the decision-theoretic approach has been extended to a multispecies context. To date, various types of uncertainty have been considered, including process error (random natural variability), assessment error (imprecise estimates of current biomass), and harvest control (implementation) error.
Reuter worked with stock assessment staff who conduct assessments on non-target and data-poor species to describe recent challenges relating to our current assessment strategies for nontarget species and assemblages in the North Pacific groundfish fisheries. Using examples from past stock assessments for BSAI Other Rockfish and BSAI Other species such as sculpins, octopus, and squid, Reuter outlined the following assessment challenges:
Nontarget species are lumped into various species complexes.
These complexes are assessed using a single biomass that may reflect only the most abundant species.
Lack of data, such as limited catch history, limited biomass data, and limited life history characteristics, makes estimation of reference points difficult.
The main point in the presentation was to discuss whether an annual catch limit is the best way to assess and manage these species and, if not, what other assessment and management strategies can be used under the MSRA.
Ormseth and Jane DiCosimo of the North Pacific Fishery Management Council staff presented a two-part presentation on potential alternatives for assessing nontarget/data-poor species. The first part of their presentation considered whether management approaches designed to maximize/optimize yield are appropriate for species that are not commercial fishery targets. Alternative approaches were discussed, including minimum retention allowances and time/area closures. It was suggested that some form of quota may still be required for species with sensitive life histories, such as sharks. Instead of the traditional ABC/OFL (acceptable biological catch/overfishing level) framework, quotas for these species might be based on measures related to population stability such as those used to describe the status of threatened or endangered species. Of course, establishing such alternatives begs the question of how to determine which species/assemblages qualify for these approaches. One suggestion was to base the decision on the ratio of fishing mortality to total mortality, where a sufficiently high ratio might trigger additional protections (such as quotas) or shift the species into the target species category.
By Grant Thompson, Rebecca Reuter, and Olav Ormseth
