Nonlinearity in interspecific interactions in response to climate change: Cod and haddock as an example

Abstract

Climate change has profound ecological effects, yet our understanding of how trophic interactions among species are affected by climate change is still patchy. The sympatric Atlantic haddock and cod are co‐occurring across the North Atlantic. They compete for food at younger stages and thereafter the former is preyed by the latter. Climate change might affect the interaction and coexistence of these two species. Particularly, the increase in sea temperature (ST) has been shown to affect distribution, population growth and trophic interactions in marine systems. We used 33‐year long time series of haddock and cod abundances estimates from two data sources (acoustic and trawl survey) to analyse the dynamic effect of climate on the coexistence of these two sympatric species in the Arcto‐Boreal Barents Sea. Using a Bayesian state‐space threshold model, we demonstrated that long‐term climate variation, as expressed by changes of ST, affected species demography through different influences on density‐independent processes. The interaction between cod and haddock has shifted in the last two decades due to an increase in ST, altering the equilibrium abundances and the dynamics of the system. During warm years (ST over ca. 4°C), the increase in the cod abundance negatively affected haddock abundance while it did not during cold years. This change in interactions therefore changed the equilibrium population size with a higher population size during warm years. Our analyses show that long‐term climate change in the Arcto‐Boreal system can generate differences in the equilibrium conditions of species assemblages.

Stock collapse and its effect on species interactions: Cod and herring in the Norwegian‐Barents Seas system as an example

“…Indeed, changes of population structure linked to overexploitation have been shown to affect how a population responds to climate and exploitation forcing (Brosset et al, 2019;Durant & Hjermann, 2017;Hidalgo, Rouyer, et al, 2012;Rouyer et al, 2011). In this study, we show that in addition, the occurrence of a collapse is creating a nonlinearity in the species interactions that may eventually impact the functioning of the food chain similar to what was observed for the effect of climate warming (Ciannelli et al, 2013;Dingsør et al, 2007;Durant et al, 2020).…”

“…Many marine ecosystems are increasingly susceptible to sudden nonlinear transformations due to climate warming (Hoegh‐Guldberg & Bruno, 2010). Nonadditive effect of the environment (i.e., climate) on population dynamics has been observed in both terrestrial (Stenseth et al, 2004, 2015) and marine systems (Ciannelli et al, 2013; Dingsør et al, 2007) and may lead to different population equilibrium (Durant et al, 2020). This is particularly true for the Atlantic cod (Fauchald et al, 2011; Frank et al, 2011; Scheffer et al, 2001; Sguotti et al, 2019; Vasilakopoulos & Marshall, 2015).…”

Empirical evidence of nonlinearity in bottom up effect in a marine predator–prey system

“…In this study, we show that a nonlinearity in the species interactions has an impact on population dynamics and affects our understanding of the functioning of the food chain similar to what was observed for the effect of climate warming [6,12]. Stock assessment is conducted on a single species basis but increasingly incorporates some known interaction between the species of interest and climate or other species [44].…”

“…The analyses were based on a Gompertz state-space model [12] reparameterized as in Stenseth et al [4] incorporating competition (intra-and interspecific, respectively a i,i (with the intra-specific interaction set to 1 [4,28]) and a i,j ) and environmental variables (a i,st and a i,nao ) effects. The model (table 1: equation ( 1)) incorporated also a Gaussian distributed stochastic term (ε) to acknowledge our inadequate understanding of the complexity of the dynamics of population i (i.e.…”

Mixed interactions among life history stages of two harvested related species

“…Temperature variation can also affect the strength of the interaction between cod and haddock. An increase in cod abundance is associated with increased temperature, negatively affecting the haddock population abundance (Durant et al, 2020 ). However, the effect of temperature is less critical at age‐0 than for the other juvenile stages.…”