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A brief primer on salmon fisheries and harvest data

 

Fishery management context

  • Generally the nature and approach to annual salmon harvest management falls along a spectrum determined by the relative stock abundance and productivity and the degree to which stocks of different productivities occur within fishing areas.  Fisheries in the southern portion of the North American range focus largely on managing impacts on depleted populations while northern fisheries typically managing harvest for relatively healthy and productive mixtures of wild stocks and species. 

  • In northern BC and Alaska, typical salmon ecosystems are relatively intact, with productive habitats and robust populations.  The management 'paradigm' often reflects regulating large commercial harvests and relatively high harvest rates.  Significant harvests and fishing activity provide managers with more opportunities for in-season run size updates and in-season adjustments of fishing effort and catch to better account for errors in pre-season run size forecasts.   Intensive fisheries sampling and data collection activities occur but their extent can be limited by the size of geography, duration/size of harvests and availability of fishery monitoring resources.  With notable exceptions, populations within species in northern regions tend to have higher and similar inherent levels of productivity than salmon populations in the southern part of their range.  The fraction of the annual stock size taken at harvest often exceeds that returning to spawn.

  • In southern BC, Washington, Oregon, California and Idaho, fisheries management is more often driven by the need to strictly limit harvest impacts on weak stocks.  In the coterminous US threatened and endangered species listings under ESA magnify this need and the intent of harvest is to target hatchery fish while minimizing impacts on weak, wild stocks.  This management of scarce resources requires intensive pre-season planning and in-season monitoring to control and verify impacts on stocks needing protection, including extensive stock identification.  Robust in-season run size updating tools based on fisheries, such as those used for abundant Bristol Bay sockeye, typically are not possible because the impact of necessary test fishing to update run sizes, in most cases, would exceed allowable exploitation rates.   Stocks in this southern end of the range typically  have highly variable maximum allowable harvest rates and in many cases, the fraction of fish harvested of an annual population can only be a small portion of the total catch plus escapement.

  • The structure of fishery management tends to focus on aggregates of populations within a species, region of origin, and run timing for the purpose of specifying escapement goals and making in-season fishery management decisions, because the impacts of a fishery on many individual populations can be difficult/expensive to predict/monitor and impractical to manage within short-time frames and mixed-stock fishing areas.  Depending on the conservation status of component populations and their respective productivity, the implications of a given fishery objective can have widely varying impacts on managing for the diversity and abundance of component populations vs. aggregate population groups.

  • The overall harvest rates for individual species, stocks and region of origin differ considerably, depending on their productivity, status and management objective.  

  • In addition, hatchery fish have high allowable harvest rates because of high early survival caused by protected incubation and rearing environments, while wild stocks are able to sustain lower average harvest rates to maintain optimal production.  Thus mixtures of hatchery and wild fish in co-located fishing areas historically have created mixed-stock fishery management problems when harvest is driven by the desire to fully harvest available hatchery fish rather than staying at or below allowable harvest rates of wild stocks.  In a number of instances, current management has attempted to utilize differential harvest strategies for hatchery and wild fish, such as with mark-selective fisheries and segregated fishing zones for hatchery fish.  Nevertheless these mixed-stock management challenges still exist in many fishing areas.

Types of fisheries

The types of fisheries below generally reflect a gradient from higher to lower degrees of mixed-stock origins and maturities in their order of description. 

  • Ocean salmon recreational and commercial troll are hook and line fisheries on stocks that are highly mixed in terms of region of origin as well as maturing and immature fish.  Translating fishery sampling data into population-specific metrics typically requires use of stock identification techniques and cohort models to derive estimates that can be combined with estimates of comparable population metrics for area specific spawning escapements.

  • Pre-terminal salmon commercial, recreational, subsistence and ceremonial  fisheries also occur in inside marine entry areas for major river basins.  Commercial fisheries in these areas use various gears (e.g., hook and line, gillnet, purse seine and reef nets).  These fisheries typically target fish that are maturing on return migrations to their rivers of origin but can include some mixture of immature fish not destined to spawn that year.

  • Terminal salmon fisheries also occur in the commercial, recreational, subsistence and ceremonial forms noted above, but these typically occur within river basins on maturing fish that are actively migrating upstream toward their spawning grounds.   Additional gears such as beach seines, fish wheels and weirs are sometimes used by First Nations or treaty tribal fishers in BC or the US, respectively.

  • This range of fisheries is managed by a number of federal, state and treaty Indian or First Nation authorities, and each jurisdiction has its own respective fishery monitoring programs.  In many cases the monitoring obligations are defined through interjursidictional agreements such as the Pacific Salmon Treaty.  However, quality assurance and quality control is the ultimate responsibility of each monitoring organization and may vary based on a range of circumstances.

Managing for sustainable harvest rates and populations

  • Managers estimate several key parameters, some of which are needed in-season for more terminal area fisheries.  Typically these involve some kind of escapement target, but in some areas or for some stocks the management targets are set in terms of harvest rates or exploitation rates.  For example, B.C. Chinook and coho stocks of conservation concern are managed to exploitation rate limits instead of harvest rate limits because of their biology (fishery distribution in Canada and the U.S. and age-specific vulnerability to fishing gear and size restrictions).    
  • Given an escapement target, then, managers use various means to estimate run size and expected escapement as the run and fishery develop.
  • Managers also employ methods to at least crudely assess harvest performance as the run and fishery develop (e.g., effort, catch numbers, age, sex, length data).
  • Managers require an understanding of run timing to plan fishery openings and escapement monitoring and to use this information to draw conclusions about in-season status (e.g., to discern between a small run vs. a late large run). For instance, low catch rates early in the season could indicate low returns or they could indicate a late return.
  • After the fishing season, managers need an accurate accounting of harvest and escapement to evaluate their performance, monitor changes in stock productivity and ensure that harvest and population sizes are remaining sustainable. 
  • Many of the techniques that are used to establish escapement goals require a number of derived statistics such as brood year-specific returns derived from catch, escapement, and age-class distribution for both catch and escapement.
  • Fishery data may not be representative of the total population return, for instance where fisheries may be selective for certain size or sex components of the run (e.g., due to size-selective net fisheries, timing of the fishery vs. timing of the run, or minimum size limits in sport fisheries).  As a result, age-class distribution can differ significantly between catch and escapement.

Additional resources on fishery management

Fishery managers routinely prepare fishery monitoring and plans and post-season reports document the basis and performance of annual harvest management.  The following information sources are provided as typical examples of such documents that could be referenced to gain more in depth information about the status of current salmon management in  North American jurisdictions:

  • Alaska Department of Fish and Game annual management reports can be found here. 
  • Recent examples of Fisheries and Oceans Canada's Pacific Region Integrated Fisheries Management Plans for salmon can be located here.  
  • The Pacific Fisheries Management Council's salmon management plan for fisheries off the coasts of California, Oregon and Washington can be found here while additional annual status documents for these council fisheries can be located here.  

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