The Functional Response of a Generalist Predator

Smout, Sophie; Asseburg, Christian; Matthiopoulos, Jason; Fernández, Carmen; Redpath, Stephen M.; Thirgood, Simon; Harwood, John

doi:10.1371/journal.pone.0010761

Cited by 93 publications

(111 citation statements)

References 49 publications

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Section: Importance Of Salmon In Harbour Seal Dietmentioning

confidence: 81%

“…If the remains of some prey species are less likely to be found because scats containing them are less likely to be collected, this could lead 274 Sharples et al: Harbour seal diet in southeast Scotland to bias. We are unable to investigate this for harbour seals, but Smout (2006) found no bias in estimates of grey seal diet as a result of foraging offshore and species-specific differences in passage times of prey remains through the gut.There are no robust estimates of salmon stock size but estimates can be made from the rod and line catches and assumptions of the catchability of salmon by fishermen in different seasons. Rod and line catches of salmon are available for the Rivers Tay, Earn and Eden combined (the Tay being the main salmon fishing river).…”

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confidence: 81%

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Seals, sandeels and salmon: diet of harbour seals in St. Andrews Bay and the Tay Estuary, southeast Scotland

Sharples

Arrizabalaga²,

Hammond³

2009

Mar. Ecol. Prog. Ser.

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Harbour seal populations have declined by up to 40% around northern and eastern Britain since 2000 due to unknown causes; prey availability is one important factor that could be contributing to the decline. We estimate the diet and prey consumption of a population of harbour seals in southeast Scotland, using analysis of hard prey remains recovered from scats, to investigate change in the importance of sandeels over 6 yr spanning the local sandeel fishery closure. The study site includes Special Areas of Conservation for harbour seals as well as vulnerable salmon stocks. We estimate the extent of harbour seal predation on salmon in the area. In St. Andrews Bay, harbour seal diet was heavily dominated by sandeels, especially in winter and spring. Gadoids (whiting, cod) and flatfish (dab, plaice, flounder) were the other main prey. The proportion of sandeels in the diet was remarkably consistent over time (71 to 77%), but the average size of sandeels consumed increased following the closure of the fishery. In the Firth of Tay, sandeels were prevalent in winter, but the diet in the rest of the year was dominated by salmonids: salmon comprised 64% of the diet in summer and sea trout comprised 40% of the diet in autumn. Thus marked differences in diet were evident at a fine spatial scale. The effects of the sandeel fishery closure on harbour seals were equivocal, but harbour seals that haul out in SE Scotland are clearly dependent on sandeels; re-opening the fishery could thus have a negative impact and be inadvisable. We found evidence that local harbour seal predation could be impacting salmon stocks but the high uncertainty in estimates of seal diet and salmon stock size preclude the provision of management advice at this time. KEY WORDS: Faecal sampling · Fisheries · North Sea · Prey availability · Phoca vitulina · Special Area of Conservation Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 390: [265][266][267][268][269][270][271][272][273][274][275][276] 2009 level by a fundamental lack of information on predator diet. In the North Sea, there is good recent information on the diet of grey seals and some relatively recent information on cetacean diet , Windsland et al. 2008. However, most information on harbour seal diet in the North Sea is at least 10 yr old (Tollit & Thompson 1996, Tollit et al. 1997, Brown & Pierce 1998, Hall et al. 1998, Brown et al. 2001, Middlemas et al. 2006.One heavily exploited fish that is important to many predator species in the North Sea is the lesser sandeel Ammodytes marinus (Furness & Tasker 2000). North Sea landings of sandeels fluctuated between 700 000 and 1 110 000 tonnes (t) from 1994 to 2002 but declined to around 200 000 t in 2007 (ICES 2007). Some seabirds are heavily reliant on sandeels in summer for feeding their chicks while in the nest (Wanless et al. 1998), and concern has been expressed about the effects on predators of local concentrated fishing effort in areas where they congregate (Furness & Tasker 200...

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Section: Importance Of Salmon In Harbour Seal Dietmentioning

confidence: 81%

mentioning

confidence: 81%

Seals, sandeels and salmon: diet of harbour seals in St. Andrews Bay and the Tay Estuary, southeast Scotland

Sharples

Arrizabalaga²,

Hammond³

2009

Mar. Ecol. Prog. Ser.

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“…Nevertheless, development of methods accounting for multiple prey functional responses and predator and prey behavior are of growing interest (e.g. Scharf et al, 2008;Smout et al, 2010). Accordingly, within the context of biological control, further research is needed to test under which situations the parameters of the functional response models and their derivates such as the maximum attack rate could be suitable stand-alone surrogates of the suppression potential of a biological control agent.…”

Section: Methods Limitationsmentioning

confidence: 99%

A simulation-based method to compare the pest suppression potential of predators: A case study with spiders

et al. 2018

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A B S T R A C TAssessing and comparing the pest killing capacity of predators is a crucial but laborious task during the implementation of sustainable farming systems. Critical attributes of assessment include quantifying predator's attack rate (a) and handling time (T h ). The maximum attack rate (T/T h ) (i.e. the maximum number of prey that can be attacked by a predator during the time interval (T) considered) could be a more precise and interpretable indicator of the potential suppression of pests exerted by a predator; however, its calculation only provides a point estimator usually derived from incomplete datasets (e.g. unbalanced or low replicated experimental designs) that could lead to draw wrong conclusions. We introduce simaR (simulation of maximum attack rates using R), an R library that generates 95% confidence intervals around estimates of the maximum attack rate that can be easily and intuitively used to compare across species. We validated the simulation method and used the empirical results of a controlled laboratory experiment to compare the maximum attack rates of spiders across a range of Medfly prey densities and illustrate how to use simaR with non-replicated partial data. Applying our method we found a significant effect of temperature on the maximum attack rate of two different guilds of spiders, the orb-weaver A. cucurbitina and the ambusher S. globosum that was not relevant regarding their attack rate and handling time. Our method compares different predator species and/or experimental conditions in a simple and reproducible procedure through an accurate, easy-to-use, fast and statistically robust analysis, based on simulation and bootstrapping, that can be used to assess the pest suppression potential of predators by simulating their functional responses from low-effort laboratory trials.

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“…Prediction of consumer impact has been assessed through the use of comparative functional response analyses (Smout et al 2010;Alexander et al 2012;Alexander et al 2013;Dick et al 2013;Dick et al 2014;Laverty et al 2014;Wasserman et al 2016a, b;Dick et al 2017). This method has been pioneered for the prediction of invasive species impacts in comparison to trophically analogous native species Paterson et al 2015;Dick et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Effects of acute and chronic temperature changes on the functional responses of the dogfish Scyliorhinus canicula (Linnaeus, 1758) towards amphipod prey Echinogammarus marinus (Leach, 1815)

South

Dick

2017

Environ Biol Fish

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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 BPredator Acclimated^, BPrey Acclimated^, BBoth Acclimated^, and BBoth 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 nonacclimated and acclimated prey, whereas acclimated predators had significantly higher maximum feeding rates towards acclimated prey as compared to nonacclimated 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.

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The Functional Response of a Generalist Predator

Cited by 93 publications

References 49 publications

Seals, sandeels and salmon: diet of harbour seals in St. Andrews Bay and the Tay Estuary, southeast Scotland

Seals, sandeels and salmon: diet of harbour seals in St. Andrews Bay and the Tay Estuary, southeast Scotland

A simulation-based method to compare the pest suppression potential of predators: A case study with spiders

Effects of acute and chronic temperature changes on the functional responses of the dogfish Scyliorhinus canicula (Linnaeus, 1758) towards amphipod prey Echinogammarus marinus (Leach, 1815)

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