Indexing starvation mortality to assess its role in the population regulation of Northern cod

Regular, Paul M.; Buren, Alejandro D.; Dwyer, Karen S.; Cadigan, Noel G.; Gregory, Robert S.; Koen‐Alonso, Mariano; Rideout, Rick M.; Robertson, Gregory J.; Robertson, Masumi; Stenson, Garry B.; Wheeland, Laura J.; Zhang, Fan

doi:10.1016/j.fishres.2021.106180

Cited by 26 publications

(12 citation statements)

References 55 publications

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“…Lack of prey can induce starvation mortality, as observed for Northern cod (Regular et al, 2022) and hypothesized for other local stocks (Cadigan et al, 2022), and could have affected the collapse and recovery trajectories of plaice and yellowtail. These flounder species consume similar benthic (e.g., amphipods and crustaceans) and forage fish prey (e.g., sand lance [Ammodytes dubius, Ammodytidae] and capelin [Mallotus villosus, Osmeridae]) on the Grand Banks, although forage fish provide a larger contribution to the diet of plaice (Bruno et al, 2000;Gonzalez et al, 2006).…”

Section: Overviewmentioning

confidence: 85%

“…Despite continued calls for the application of ecosystem-based fisheries management (Denit, 2017;DFO, 2007;Koen-Alonso et al, 2019), tactical fisheries management continues to be primarily based on single-species stock assessments that rarely quantitatively integrate the effects of ecosystem drivers on fish stock productivity (Skern-Mauritzen et al, 2016 but see Marshall et al, 2019;Pepin et al, 2022). Contrary to the historical population dynamics assumption of stationary productivity (i.e., lack of temporal variability in the population's rate of growth), fish stock productivity varies over time in response to bottom-up (Regular et al, 2022;Szuwalski et al, 2015) and top-down processes (Baum & Worm, 2009;Neuenhoff et al, 2018). Given the increasing ability of state-space stock assessment models to estimate timevarying parameters (Punt et al, 2020;Stock & Miller, 2021), further exploration of the population and ecosystem processes (e.g., mean ocean climate, primary and secondary production) driving variability in stock productivity over time may yield improved management outcomes.…”

Section: Introductionmentioning

confidence: 99%

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Testing models of increasing complexity to develop ecosystem‐informed fisheries advice

Robertson,

Cadigan,

Regular

et al. 2024

Fish and Fisheries

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Despite continued calls for the application of ecosystem‐based fisheries management, tactical fisheries management continues to be heavily reliant on single‐species stock assessments. These stock assessments rarely quantitatively integrate the effects of ecosystem processes on fish stock productivity. This lack of integration is ultimately driven by the complexity of interactions between populations, ecosystems and fisheries, which produces uncertainty when defining which processes to include and how to include them. Models developed using a structured hypothesis testing framework would allow formalizing uncertainties while underscoring the importance of incorporating different population and ecosystem processes to explain non‐stationary stock productivity. Here, we develop a conceptual framework for extending and comparing population dynamics models of increasing complexity. We illustrate the utility of the framework by investigating the population and ecosystem processes that most likely affected the differential recovery of two flatfish populations (American plaice and yellowtail flounder) on the Newfoundland Grand Banks over the past three decades. We found that yellowtail flounder population dynamics were primarily driven by recruitment variability, which was negatively affected by warmer climatological conditions, as indicated by an integrated regional climate index. Meanwhile, American plaice population dynamics were affected by a combination of temporal variability in recruitment and natural mortality, where natural mortality increased during colder than average conditions. By exploring hypotheses about the effects of population and ecosystem processes on population dynamics, this modelling framework will improve understanding about the drivers of shifts in population productivity while serving as a transparent and robust approach to support ecosystem‐based fisheries management.

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Section: Overviewmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Testing models of increasing complexity to develop ecosystem‐informed fisheries advice

Robertson,

Cadigan,

Regular

et al. 2024

Fish and Fisheries

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“…At the same time, however, they report that population of an important cod prey, capelin, was also declining to very low levels. Because both fish are highly exploited, the source of the cod population decline and its low condition might therefore be the overfishing of its prey – causing decreased carrying capacity and starvation‐induced mortality (Mullowney & Rose, 2014; Regular et al, 2022) – rather than fisheries of cod itself. Here, advice to reduce cod fishing due to its low condition index would not have much benefit for the recovery of its population, and the starvation‐induced mortality would persist.…”

Section: Discussionmentioning

confidence: 99%

Fish condition as an indicator of stock status: Insights from condition index in a food‐limiting environment

2023

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Individual performance defines population dynamics. Condition index -a ratio of weight and some function of length -has been louded as an indicator of individual performance and recommended as a tool in fisheries management and conservation.However, insufficient understanding of the correlation between individual-level processes and population-level responses hinders its adoption. To this end, we use composite modelling to link individual's condition, expressed through the condition index, to population-level status. We start by modelling ontogeny of European pilchard (Sardina pilchardus, Clupeidae) as a function of food and constant temperature using Dynamic Energy Budget theory. We then provide a framework to simultaneously track the individual-and population-level statistics by incorporating the dynamic energy budget model into an individual-based model. Lastly, we explore the effects of fishing pressure on the statistics in two constant and food-limited environmental carrying capacity scenarios. Results show that, regardless of the species' environmental carrying capacity, individual condition index will increase with fishing mortality, that is, with reduction of stock size. Same patterns are observed for gilthead seabream (Sparus aurata, Sparidae), a significantly different species. Condition index can, therefore, in food-limited populations, be used to (i) estimate population size relative to carrying capacity and (ii) distinguish overfished from underfished populations. Our findings promote a practical way to operationally incorporate the condition index into fisheries management and marine conservation, thus providing additional use for the commonly collected biometric data. Some real-world applications, however, may require additional research to account for other variables such as fluctuating environmental conditions and individual variability.

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“…[Colour online. ] reproductive investment (Rideout and Rose 2006) and mortality (Regular et al 2022), and not on spawning location, as the main feeding season on capelin in summer follows the spawning season during and after inshore migration. Capelin distribution is, however, highly likely to influence post-spawning distribution (e.g., Templeman 1966;Rose 1993;O'Driscoll et al 2000), and it is possible that northward expansion of capelin could spur cod to undertake northward summer movements, which lead to spawning shifts.…”

Section: Distribution Shiftsmentioning

confidence: 99%

Congruence of stock production and assessment areas? An historical perspective on Canada’s iconic Northern cod

Rose

Rowe

2022

Can. J. Fish. Aquat. Sci.

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Fisheries management requires spatially congruent production and assessment areas. Canada’s Northern cod, initially considered a stock complex distributed from northern Labrador to northern Grand Bank, had its northern boundary reduced to southern Labrador in the early 1970s. Spatial incongruence has resulted in spawning stock biomass (SSB) and recruitment (R) between historical and recent eras. To investigate temporal changes, four stanzas of SSB and R were derived from statistical Perron breaks. In stanza 1, the 1960s, spawning off northern Labrador coincided with higher SSB and R than in following stanzas from the 1970s onward. SSB-R relationships that include 1960s data do not represent potential production from a more southerly distributed stock. Loglinear models of R (density-dependent models did not improve fit) indicated SSB had greatest effect, and with indices of climate and south-north distribution explained 86% of variance. Lack of density-dependence suggests long-standing recruitment overfishing, making reference points problematic. SSB growth is suggested as an alternative management target. Rebuilding the Northern cod to historic abundance requires a full “portfolio” of spawning from northern Labrador to the Grand Bank (a re-managed 2+3KL stock). With a contracted range, lower production should be anticipated.

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Indexing starvation mortality to assess its role in the population regulation of Northern cod

Cited by 26 publications

References 55 publications

Testing models of increasing complexity to develop ecosystem‐informed fisheries advice

Testing models of increasing complexity to develop ecosystem‐informed fisheries advice

Fish condition as an indicator of stock status: Insights from condition index in a food‐limiting environment

Congruence of stock production and assessment areas? An historical perspective on Canada’s iconic Northern cod

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