Dr. James Thorson^1
1SAFS
November 29, 2016 9:00 (PST): FSH 203

A hands-on discussion and tutorial for using FishStats to estimate spatio-temporal abundance indices, distribution shifts, and range expansion in 2017 stock assessments

Collaborators and I have been developing, testing, and documenting spatio-temporal models and software for single- and multi-species analysis of fishery and/or survey data.  R packages for implementing these models are now publicly available and documented through www.FishStats.org, a spatio-temporal toolbox for fisheries science.

In this Think Tank, I will present a small number of slides (<15 total) to recap recent model developments and applications.  I will then lead a discussion of different applications for which FishStats could be useful in 2017 stock assessments, e.g., estimating survey indices, standardizing fishery catch rates, estimating distribution shifts or range expansion/contraction, or identifying multispecies associations.  With input from attendees, I will then provide a semi-structured, hands-on demonstration of how different modelling goals can be achieved.

I encourage attendees to bring a laptop and to install a recent version of R (e.g., 3.3.1) and appropriate Rtools (if using a windows OS).  Attendees will install other necessary software (including INLA and TMB) as we go through tutorials together.

Samuel Johnson^1  
1  Simon Fraser University

November 22, 2016 9:00 (PST): FSH 203

I am interested in finding the conditions that favour joint stock assessments for multiple flatfish species using hierarchical models. Hierarchical multi-level modeling approaches are being increasingly applied in stock asssessment to share information across stocks and species. These so-called “Robin Hood” approaches borrow information from data-rich to potentially improve assessments for data poor species; however, little research exists to demonstrate the boundary conditions where hierarchical approaches outperform single species models. In this talk, I present a hierarchical surplus production modeling approach for a multi-species flatfish complex in British Columbia, Canada. If applicable, the hierarchical modeling approach could help provide more up-to-date assessments for species last assessed in the 1990s!

Christine Stawitz^1
1SAFS
November 08, 2016 9:00 (PST): FSH 203

How do changing somatic growth rates affect estimation of management quantities in fisheries stock assessments, and can such growth changes be detected?

A substantial body of work suggests that somatic growth in marine fish is plastic, and thus growth rates may change substantially in response to both extrinsic (i.e. climate) and intrinsic (i.e. competition) factors. Additionally, such changes in somatic growth rate may substantially affect population dynamics of marine fish. However, these changes in growth rate are not incorporated into many fisheries stock assessment models and, consequently, management advice. Growth rate changes are difficult to incorporate in management models, since such models are already highly parameterized and often contain temporal variation in observational parameters which are confounded with somatic growth parameters, such as fisheries selectivity. In this analysis, we evaluate the detectability of temporal changes in somatic growth and how such changes may impact fisheries management quantities. We examine these questions using a simulation framework, employing an operating and estimation model closely modeled on stock assessment models for North Pacific groundfish and the Stock Synthesis 3 (SS3) program. Simulated variation in population processes, including growth, recruitment, and fishing, is derived directly from empirical estimates. We test, first, if regime-like growth shifts can be detected using realistic quantities of time series data. We find regime-like patterns in growth rates are not detectable in population models without many decades of high-quality composition data, even when process error is low. Secondly, we find such changes, while difficult to detect, can introduce substantial bias into management reference points, particularly current depletion levels. This suggests more work is needed to increase estimability of temporal growth changes and incorporate them into fisheries stock assessment models.

Peter Kuriyama^1 
1SAFS
October 11, 2016 9:00 (PST): FSH 203

Resolving issues of hook saturation, hook competition, and fixed-site design in the Southern California hook-and-line survey

The Southern California hook-and-line survey has been conducted by the Northwest Fisheries Science Center since 2004 to monitor the untrawlable habitat of the Southern California Bight. Data from the survey have been used in stock assessments and supporting research for a number of shelf rockfish species, such as bocaccio (Sebastes pauicispinis) and vermilion rockfish (S. miniatus). However, an index of abundance estimated from hook-and-line data may be biased due to the fixed-site design of the survey and issues with hook saturation and hook competition. Here, I will present empirical results from the hook-and-line data and results of a simulation study exploring the biases associated with aspects of the survey. Bocaccio are the most sampled species in the survey, and sites with low catch rates of bocaccio have high catch rates of vermilion rockfish. Preliminary results from the simulations indicate that hook saturation causes estimates of abundance to be negatively biased at large population sizes. Additionally, hook competition leads to positively biased indices of abundance, and weighting catch rates by site leads to the least biased index of abundance. These results identify methods of incorporating hook-and-line data from untrawlable habitat into stock assessments and identify biases that are applicable to general hook-and-line survey methods.

Paul Dolder^{1
1 MARES Doctoral Programme on Marine Ecosystem Health and Conservation}
October 04, 2016 9:00 (PST): FSH 203

Progressing scientific advice and management of mixed demersal fisheries in
Europe

In Europe, scientific advice for managing multi-gear, multi-country mixed
fisheries is rapidly developing. Reforms to the EU’s Common Fisheries Policy
have given priority to the development and implementation of fishery-based
management plans and emphasize the importance of understanding how technical
interactions impede effective management of all stocks caught in mixed
fisheries. Modelling approaches which i) characterize these interactions and,
ii) can simulate a range of management options to contrast their bio-economic
impact, are gaining prominence. In this talk I’ll give an overview of the
developments happening within the EU and the ICES frameworks and highlight how
my PhD research aims to improve our ability to understand fleet behavioural
dynamics in mixed fisheries so that managers can better evaluate different
management options.