Abstract
Predation is a strong driver of population dynamics and community structure and it is essential to reliably quantify and predict predation impacts on prey populations in a changing thermal landscape. Here, we used comparative functional response analyses to assess how predator-prey interactions between dogfish and invertebrate prey change under different warming scenarios. The Functional Response Type, attack rate, handling time and maximum feeding rate estimates were calculated for Scyliorhinus canicula preying upon Echinogammarus marinus under temperatures of 11.3 °C and 16.3 °C, which represent both the potential daily variation and predicted higher summer temperatures within Strangford Lough, N. Ireland. A two x two design of “Predator Acclimated”, “Prey Acclimated”, “Both Acclimated”, and “Both Unacclimated” was implemented to test functional responses to temperature rise. Attack rate was higher at 11.3 °C than at 16.3 °C, but handling time was lower and maximum feeding rates were higher at 16.3 °C. Non-acclimated predators had similar maximum feeding rate towards non-acclimated and acclimated prey, whereas acclimated predators had significantly higher maximum feeding rates towards acclimated prey as compared to non-acclimated prey. Results suggests that the predator attack rate is decreased by increasing temperature but when both predator and prey are acclimated the shorter handling times considerably increase predator impact. The functional response of the fish changed from Type II to Type III with an increase in temperature, except when only the prey were acclimated. This change from population destabilizing Type II to more stabilizing Type III could confer protection to prey at low densities but increase the maximum feeding rate by Scyliorhinus canicula in the future. However, predator movement between different thermal regimes may maintain a Type II response, albeit with a lower maximum feeding rate. This has implications for the way the increasing population Scyliorhinus canicula in the Irish Sea may exploit valuable fisheries stocks in the future.
Highlights
Temperature is a driver of interspecific interactions through mediating metabolism (Arrhenius 1889; Brown et al 2004) and locomotion (Dell et al 2011; Dell et al 2014), attack speed (Nowicki et al 2012), feeding rates (Iacarella et al 2015), and growth (Savage et al 2004; Pörtner and Knust 2007)
It is difficult to derive accurate conclusions from thermal responses modeled across numerous systems (Grigaltchik et al 2012), but it is widely agreed that temperature change alters ecological stability (Dell et al 2014; Gilbert et al 2014)
The present study presents the functional responses of juvenile Scyliorhinus canicula preying on live Echinogammarus marinus under the ambient temperature of 11 ± 0.09 °C and attempts to elucidate whether there is a change in the functional response when temperature is increased to 16.3 ± 0.20 °C, a value chosen as it is in line with future Sea Surface Temperature (SST) increase predictions (Sokolov et al 2009)
Summary
Temperature is a driver of interspecific interactions through mediating metabolism (Arrhenius 1889; Brown et al 2004) and locomotion (Dell et al 2011; Dell et al 2014), attack speed (Nowicki et al 2012), feeding rates (Iacarella et al 2015), and growth (Savage et al 2004; Pörtner and Knust 2007). Thermal responses are understood to be an underlying mechanism behind predator – prey dynamics (Berlow et al 2009; Rall et al 2010; Englund et al 2011), but predicting the outcome of such interactions under future abiotic scenarios is highly problematic (Le Quesne and Pinnegar 2011) This is partly due to multiple layers of real world complexities such as habitat heterogeneity (MacNeil et al 2004; Ferner et al 2009; Alexander et al 2015; Barrios-O’Neill et al 2015), light (Koski and Johnson 2002), multiple predator effects (Lang et al 2012; Alexander et al 2013; Wasserman et al 2016a). It is difficult to derive accurate conclusions from thermal responses modeled across numerous systems (Grigaltchik et al 2012), but it is widely agreed that temperature change alters ecological stability (Dell et al 2014; Gilbert et al 2014)
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