Science Policy and Planning for Understanding the Effects of Oceanographic Conditions and Recruitment on Council-Managed Finfish Species

This cross-FMP initiative responds to issues raised during the Council’s work on both the second (ecosystem indicators) and third (scenario planning for climate change) ecosystem initiatives, particularly addressing the need to better understand and integrate climate and ocean conditions information affecting the abundance of fish stocks into the fisheries management process.  Under the scenario planning portion of the CCI, the Council considered future management challenges under greater climate variability and more or less species’ abundance.  This initiative would build from those scenarios to ask about the potential effects of climate variability on Council-managed species’ recruitment.  This initiative would also address FEP Objectives 1a, 1b, 2a, 3a, 6a, 6b, and 6c by identifying research and monitoring needs explored in the FEP, helping to better understand trophic energy flows, availability of harvestable stocks to fishing communities, and sharing information across species and fisheries management challenges. 

Many factors, including harvest rates, affect abundance of adult fish populations.  A major influence on adult population dynamics for finfish species is recruitment year class strength.  Mortality of fish larvae is extremely high, but once a fish survives its first year, rates of natural mortality are greatly reduced, and it is relatively likely that the individual will survive to become an adult and reproduce.  If recruit abundance is high in a given year, then it is also likely that adult population sizes will be high in the years following until the year class reaches senescence. 

Understanding the mechanistic causes of fluctuations in fish population abundances, including any potential links to climate and oceanographic conditions, is of utmost importance for multiple FMPs and for ecosystem-based management.  Despite more than a century of research, the factors driving recruitment strength have been elusive for most fishes worldwide and in the CCE in particular.  The Council has extensive experience with the challenges of managing fisheries in the face of ecological surprises associated with unpredicted shifts in recruitment class strength, including the extraordinarily strong recruitment classes of overfished rockfish species in the early 21st century, and the dramatic recent fluctuations in anchovy year class strength.  Although understanding processes driving recruitment is difficult, the time is right to make significant progress in this field. 

Over the past two decades, technologies have emerged that give us a novel perspective on factors impacting stock abundances.  For example, environmental DNA technology can provide unprecedented clarity on the prey field of larval fishes and the effects of those prey fields on larval mortality (testing the Hjort 1926 classic critical period hypothesis).  In addition, high powered Individual Based Models that use Regional Ocean Modeling output are being developed to track fish from “cradle to grave,” with the objective of identifying ocean conditions that facilitate high recruitment.  At present, multiple researchers on the West Coast are pursuing these and many other lines of research seeking to elucidate recruitment drivers for myriad fishes.

This initiative would bring together various researchers that traditionally have not worked together and would leverage new developments in ocean modeling and observation to examine recruitment dynamics from multiple perspectives with the goal of identifying the most important factors dictating year class strength.  To implement this initiative, the Council would assemble an ad hoc science advisory committee to convene a workshop or series of workshops to coordinate science planning and foster collaboration on understanding the effects of near- and medium-term oceanographic conditions on juvenile survivability and recruitment of commercially- and recreationally-important finfish species to West Coast fisheries. The advisory committee could consist of Federal, state, tribal and academic scientists, and others the Council deems appropriate to the task.  Depending on the interest and availability of the Council’s SSC, this project could be led, facilitated, monitored, or reviewed by the SSC or SSC members. 

An intermediate objective for these workshops would be:

  1. An inventory and planning process for developing new indicators of larval recruitment. The inventory of available tools to model recruitment dynamics could include, for example, such emerging tools as:
    1. High resolution video monitoring
    2. eDNA to resolve larval and juvenile predator and prey fields
    3. Chemical biomarkers such as compound-specific stable isotope analysis
    4. Regional Ocean Modeling System models to fuel Individual Based Modeling
  2. An assessment of the feasibility of combining the inventoried tools to produce robust forecasts of year class strengths.

If developing such a multi-method framework proves feasible, further development would also integrate the effects of oceanographic variability on larval survivability and recruitment.  The goal would then be to help the Council, scientists, and the public better understand the status of managed stocks and the effects of environmental drivers on the statuses of different stocks.  More significantly, scientific work growing out of this initiative could identify how and whether to incorporate information on environmental drivers into stock assessments, and could refine our ideas about the relevance of ESR indicators to the abundance of managed stocks.