Modeling temporal variation in recruitment in fisheries stock assessment: A review of theory and practice

Maunder, Mark N.; Thorson, James T.

doi:10.1016/j.fishres.2018.12.014

Cited by 47 publications

(33 citation statements)

References 122 publications

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“…Stige et al (2019) explored patterns of recruitment in six economically important marine fish populations and found that variation was size-and stage-specific, perhaps related to competition for limiting habitat. However, despite these and many similar studies, our understanding of factors affecting recruitment in wild fish populations is still considered poor (Maunder & Thorson, 2019), in part due to the simplifying assumptions we make when statistically analysing recruitment data (Dickey-Collas, Hintzen, Nash, Schön, & Payne, 2015). Our limited understanding of the factors causing variation in recruitment has hindered the development of fish stock assessment models and threatens to render them obsolete in the future (Subbey, Devine, Schaarschmidt, & Nash, 2014).…”

Section: Introductionmentioning

confidence: 99%

Environmental conditions modify density‐dependent salmonid recruitment: Insights into the 2016 recruitment crash in Wales

et al. 2020

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1. Understanding the effects of density-dependent and density-independent factors on recruitment is often inhibited by difficulties quantifying their relative contributions in highly variable recruitment data. Use of data-driven statistical methods with data that include one or more extreme recruitment events could help overcome these difficulties. 2. Juvenile Atlantic salmon and trout abundances in Wales have declined over the last 2 decades, and 2016 was a notably poor recruitment year in rivers around southern Europe, including England and Wales. The 2016 recruitment crash coincided with extreme winter weather conditions, leading to speculation that unusually warm temperatures and high flows adversely affect salmonid recruitment and caused the 2016 crash, although this remains untested. 3. We developed data-driven statistical models to: (1) describe juvenile salmonid recruitment from density-dependent and density-independent factors; and (2) assess whether the density-independent factors probably contributed to the 2016 salmon recruitment crash. We compiled salmon and trout young-of-year juvenile abundances from electrofishing surveys, egg deposition estimates and river flow and air temperature data from 2001-2017 for seven Welsh rivers, broadly representative of rivers around Wales. We used river flow and air temperature data to derive ecologically and behaviourally meaningful density-independent explanatory variables. 4. Salmonid recruitment in Wales was best described using density-dependent and density-independent factors, especially for salmon: after accounting for a concave relationship with egg deposition, salmon juvenile abundance was reduced under (1) warmer spawning temperatures that might inhibit spawning, and (2) higher flood frequencies during pre-emergence and emergence that might washout eggs or alevins. Results were less clear for trout, perhaps because they are behaviourally more plastic. 5. Our findings provide empirical support for general and predictable effects of temperature and flow during spawning and emergence on salmonid-especially salmon-recruitment in Wales. Furthermore, we suggest that the 2016 salmon recruitment crash was caused-in part-by particularly inclement spawning and

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Section: Introductionmentioning

confidence: 99%

Environmental conditions modify density‐dependent salmonid recruitment: Insights into the 2016 recruitment crash in Wales

et al. 2020

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“…This assumption was made because a previous study suggested that a shift in climatic conditions had changed spawning areas and stock abundances for both autumn‐spawning and winter‐spawning stocks (Sakurai et al, 2000). The changes in a i,y and b i,y both led to changes in productivity and were therefore likely to be confounded (Maunder & Thorson, 2019). The variation in a i,y changes both maximum recruits per spawner and maximum recruitment, and thus affects the expected recruitment at both high and low spawning abundances.…”

Section: Methodsmentioning

confidence: 99%

State‐space modeling clarifies productivity regime shifts of Japanese flying squid

et al. 2020

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Regime shifts of climatic and environmental conditions potentially affect the productivity of fishery resources, posing challenges in stock management. The stocks of the Japanese flying squid (Todarodes pacificus) are suspected to suffer from regime shifts, but detecting the occurrence of regime shifts in this species is generally difficult and unreliable because the short‐lived nature of this species inherently confounds the effect of regime shifts with observation and process errors. Here we developed a new state‐space assessment model to evaluate the influence of regime shifts on the spawner‐recruit relationship of the Japanese flying squid. The model simultaneously estimates the population dynamics of multiple stocks that could share some life history parameters, thereby stabilizing parameter inference. We demonstrate that two regime shifts in productivity around 1991 and 2015 caused two‐ to threefold changes of maximum sustainable yields. The model with regime shifts clarifies the relationship between fishing pressure and spawner abundance that is difficult to detect in a model with no regime shift. The state‐space approach is a promising tool for accurately assessing stock status by separating the recruitment process from observation errors and is expected to contribute to the effective management of marine biological resources sensitive to regime shifts.

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“…Distinguishing recruitment process and observation error is important for 89 accurately detecting regime shifts (King et al 2015;Maunder and Thorson 2019). such as abundance and fishing mortality as random effects have been developed and is 92 effective at separately estimating process and measurement errors (Nielsen and Berg 93 2014;Miller and Hyun 2017;Okamura et al 2018).…”

Section: Introduction 43mentioning

confidence: 99%

State-space Modeling Clarifies Productivity Regime Shifts of Japanese Flying Squid

Nishijima

Kaga

Okamoto

et al. 2020

Preprint

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19 20 ABSTRACT (150-200 words) 21 Regime shifts of climatic and environmental conditions potentially affect productivity 22 of fisheries resources, posing challenging issues to stock management. The stocks of the 23 Japanese flying squid (Todarodes pacificus) are suspected to suffer from regime shifts, 24 but their detection is difficult and possibly doubtful because the nature of short-lived 25 species readily makes the effect of regime shifts confounded with observation errors. 26 Here we developed a new state-space assessment model to evaluate the influence of 27 regime shifts on spawner-recruitment relationship of the Japanese flying squid. The 28 model simultaneously estimates the population dynamics of multiple stocks that could 29share some life history parameters, making parameter inference stable. We demonstrate 30 that two-time regime shifts of productivity around 1991 and 2015 caused two-to 31 three-fold changes of maximum sustinabile yields. The model with regime shifts 32 clarifies the relationship between fishing pressure and spawner abudance that is difficult 33to detect in a model with no regime shift. The state-space approach will be a promising 34 tool to accurately assess stock status by separating recruitment process from observation 35 errors and contribute tothe management of marine biological resources sensitive to 36 regime shifts. 37 38 Keywords (up to 5) 39 Japanese common squid; MSY reference points; multistock modeling; state-space stock 40 assessment model (SAM) ; template model builder (TMB) 41Although these international circumstances require the estimation of MSY worldwide 62 (Costello et al. 2012;Martell and Froese 2013; Punt et al. 2014;Ichinokawa et al. 2017), 63 the existence of regime shifts makes the calculation of MSY challenging, because 64 regime shifts are likely to generate multiple stock-recruitment relationships and thus 65 multiple MSY-based reference points. It is suggested that although management advice A possible solution to estimation difficulty and unstability is joint modeling of 108 multispecies or multistocks rather than per-stock analysis (Thorson et al. 2013). 109Dynamics of multiple species and stocks could be partially correlated if they share 110 environmental conditions (Thorson and Minto 2015;). The 111 assumption on a species having the same life history paramter between different stocks 112 could be valid and enable parsimonious and stably predictive modeling. Fortunately, 113 there are two different stocks of the Japanese flying squid (autumn-spawning stock and 114 winter-spawning stock) that have been independently assessed (Kaga et al. 2019; 115 Kubota et al. 2019), but may have correlated dynamics (Hoshino et al. 2014). 116 In this article, we developed a new model for multistocks of annual life-span 117 species, called 'SAMUIKA' (State-space Assessment Model Used for IKA (squid in 118 Japanese)), to investigate whether and how regime shifts occur in productivity of the 119 Japanse flying squid. We firstly performed intensive model selecti...

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Modeling temporal variation in recruitment in fisheries stock assessment: A review of theory and practice

Cited by 47 publications

References 122 publications

Environmental conditions modify density‐dependent salmonid recruitment: Insights into the 2016 recruitment crash in Wales

Environmental conditions modify density‐dependent salmonid recruitment: Insights into the 2016 recruitment crash in Wales

State‐space modeling clarifies productivity regime shifts of Japanese flying squid

State-space Modeling Clarifies Productivity Regime Shifts of Japanese Flying Squid

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