At its meeting of 25 January 2012, the Science and Statistical Committee (SSC) of the New England fishery Management Council (NEFMC) was requested by Paul Howard, the Executive Director of the NEFMC to (a) identify information that may influence interpretation of the Gulf of Maine cod stock assessment results; (b) specify whether the possible influence of these elements warrants a closer examination at a future SSC or other meeting; and (c) provide advice on the structure and timing of any future meeting the SSC believes is warranted. Examples of such information might include:
- Fishery dependent CPUE;
- Natural mortality assumptions in light of evidence of predation mortality;
- Recreational catch estimates that may be revised;
- Assuming 100% mortality of hook caught and released fish (commercial and recreational);
- The assumed stock structure for cod off the Northeastern US and Atlantic Canada and recent information of stock structure;
- Uncertainty in survey calibration coefficients;
- The assumption of flat-topped survey selectivity;
- Report by Butterworth and Rademeyer, Jan. 2012; and
- Any other limitation deemed important.
Due to time limitations, the SSC was not able to reach consensus on the majority of topics identified in the list above. While many opinions were expressed by individual SSC members on a wide range of topics that could influence assessment results, consensus could only be achieved regarding four topics as warranting further investigation:
- stock structure (including spatial aspects),
- the change from MRFSS to MRIP recreational catch estimates,
- discard mortality rate, and
- use of catch per unit effort (CPUE) information.
|In a memo from the SSC to Paul J. Howard, Executive Director, NEFMC, dated 27 February 2012, the SSC proposed a three-phase process for re-evaluating, and possibly revising, the spatial basis for assessment and management of Atlantic cod, including the following objectives at each step:|
- Summarize the potential implications of defining inappropriate stock boundaries and ignoring sub-stock structure within stock units, as well as the potential advantages and disadvantages for both science and management of revising the status quo units, in order to provide a commonly understood rationale for this investigation.
- Overlay tagging, genetic, life history, and other data on the current management units to estimate rates of mixing and, conversely, independence and evaluate key assumptions of assessment models, essentially testing the null hypothesis of the status quo configuration.
- Develop a synthesis of those same tagging, genetic, life history, and other data to determine whether one or more alternative spatial configurations are more likely than the status quo. This synthesis should include the Gulf of Maine, Georges Bank, the Mid-Atlantic Bight, and the Scotian Shelf.
- Characterize the mechanisms that drive spatial finer scale dynamics of cod populations and the fishing fleet, including habitat status and distribution, behavioral diversity, oceanography, predator-prey dynamics, and other factors.
- Provide advice on spatially-explicit management goals and strategies based on the synthesis of processes driving finer scale patterns, whether a new spatial configuration is adopted or not.
- Summarize the practical limitations of changing stock units for both science and management.
- Analyze the advantages and disadvantages of either maintaining the status quo or adopting different spatial configurations through simulation modeling.
- Conduct new assessments on new stock units, if warranted.
The SSC memo was forwarded by the NEFMC to the Northeast Fisheries Science Center (NEFSC). The Gulf of Maine Research Institute was subsequently asked by the Acting Director of NEFSC, Dr. William Karp, to convene a workshop to address the recommendations concerning cod stock structure in the SSC report. Based on follow-up conversations and correspondence with staff from NEFSC and the workshop steering committee members, it was decided to focus the workshop primarily on addressing the objectives outlined by the SSC for Phase I of the proposed 3 phase process. This proposal is a response to the request from Dr. Karp.