In iantaylor-NOAA/Lingcod_2021: Estimate the Status of Lingcod off the US West Coast in 2021

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Lingcod status and structure

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Lingcod STAT

July 12, 2021
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Background

.pull-left-60[ - Lingcod are a value target species for commercial and recreational fisheries

• Declared overfished coastwide in 1999 and rebuilt in 2005

• Stocks were last assessed in 2017

• Lots of data, more so for the north

• Data not necessarily very informative about key quantities

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By Magnus Kjaergaard, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=882582

By John Crofts, Public Domain,
https://commons.wikimedia.org/w/index.php?curid=17985885

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Changes for 2021

• Changed stock boundary (more on this later)

• Re-analyzed all data inputs from the raw data (except trawl logbook index)

• Added new data from 2017 - 2020

• Added new ages from some earlier years

• Updated biology parameters (length-weight and maturity)

• Revisited selectivity and retention assumptions

• Estimated mortality and steepness with priors

• Used Bayesian diagnostics helped determine problematic parameters

• Developed a new workflow for the assessment as an R package: https://github.com/pfmc-assessments/lingcod/

• Posted model results to the web for easy exploration: https://iantaylor-noaa.github.io/Lingcod_2021/

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Overview of results: time series

.pull-left-40[ - 2021 results not directly comparable to 2017 due to boundary change

• Both stocks estimated above the $B_{40\%}$ reference point in 2021

• North stock estimated as having never been overfished (below $B_{25\%}$)

• South stock estimated as having been overfished during the period 1990 - 2011

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Lingcod biology

.pull-left[ - Lingcod have faster dynamics than many of the groundfish on this coast: - faster growth, - earlier maturing, - fewer old individuals observed

• Exhibit sex-specific differences in behavior and distribution

• Additional ageing for 2021 made possible new age-based maturity curves

• Frequently encountered in bottom trawl survey but declines in occurrence from 200-400 m ]

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Age- and length-based functional maturity

Presence/absence of lingcod in the NWFSC West Coast Groundfish Bottom Trawl Survey (WCGBTS) by 25 m depth increments. ] --- ### Stock structure 1 .pull-left[ - Longo et al. 2020 found genetic differentiation along the coast: > evidence suggests that the distinct genetic cline in lingcod is most likely a product of selection driven by change (continuous and/or discontinuous) in environmental conditions - No clean break between areas - Presence of "admixed individuals" in northern California also noted - Additional genetic research ongoing ] .pull-right[ 

Figure 2 from Longo et al. 2020. https://doi.org/10.1111/eva.13037

] --- ### Stock structure 2 .pull-left[ - Cape Mendocino (40°10' N) chosen to split north and south stocks - Transition zone exists rather than a clear break between north and south populations - Sample sizes were low for each sampling location inhibiting clear boundaries - Cape Mendocino is a biogeographic break for many stocks - Splitting data from California at 40°10' N was more straightforward than other options - Areas modeled as independent populations - Model output aligns with Individual Fishing Quota boundaries ] .pull-right[ 

Chosen stock boundaries for 2021 assessments.

] --- ### Stock structure 3 .pull-left[ - Point Conception (34°27' N) was discussed as additional break due to differences in biogeography in the Southern California Bight - Genetic analysis does not suggest a break at that point - Splitting the data available for the south into areas may lead to less reliable parameter estimates and a worse tool for management - Other options are available for spatial management of fisheries in California ] .pull-right[ 

Chosen stock boundaries for 2021 assessments.

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Bathymetry of the U.S. west coast.

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Chosen stock boundaries for 2021 assessments.

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iantaylor-NOAA/Lingcod_2021 documentation built on Oct. 30, 2024, 6:42 p.m.