scholarly journals Integrating disparate datasets to model the functional response of a marine predator: a case study of harbour porpoises in the southern North Sea

2021 ◽  
Author(s):  
Janneke Ransijn ◽  
Phillip Hammond ◽  
Mardik Leopold ◽  
Signe Sveegaard ◽  
Sophie Smout
Keyword(s):  
Functional Response ◽  
North Sea ◽  
Prey Species ◽  
Prey Availability ◽  
Stomach Contents ◽  
Prey Consumption ◽  
Predator Species ◽  
Marine Predator ◽  
Southern North Sea ◽  
Foraging Range

1. Quantifying consumption and prey choice for marine predator species is key to understanding their interaction with prey species, fisheries, and the ecosystem as a whole. However, parameterising a functional response for large predators can be challenging because of the difficulty in obtaining the required datasets on predator diet and the availability of multiple prey species. 2. This study modelled a Multi-Species Functional Response (MSFR) to describe the relationship between consumption by harbour porpoises (Phocoena phocoena) and the availability of multiple prey species in the southern North Sea. Bayesian methodology was employed to estimate MSFR parameters and to incorporate uncertainties in diet and prey availability estimates. Prey consumption was estimated from stomach contents data of stranded harbour porpoises. Prey availability to harbour porpoises was estimated based on the spatial overlap between prey distributions, estimated from fish survey data, and porpoise foraging range in the days prior to stranding predicted from telemetry data. 3. Results indicated a strong preference for sandeel in the study area. Prey switching behaviour (change in preference dependent on prey abundance) was confirmed by the favoured Type III functional response model. Variation in the size of the foraging range (estimated area where harbour porpoises could have foraged prior to stranding) did not alter the overall pattern of the results or conclusions. 4. Integrating datasets on prey consumption from strandings, predator foraging distribution using telemetry and prey availability from fish surveys into the modelling approach provides a methodological framework that may be appropriate for fitting MSFRs for other predators.

scholarly journals Integrating disparate datasets to model the functional response of a marine predator: A case study of harbour porpoises in the southern North Sea

2021 ◽  
Author(s):  
Janneke M. Ransijn ◽  
Philip S. Hammond ◽  
Mardik F. Leopold ◽  
Signe Sveegaard ◽  
Sophie C. Smout
Keyword(s):  
Functional Response ◽  
North Sea ◽  
Marine Predator ◽  
Southern North Sea

scholarly journals Modelling prey consumption and switching by UK grey seals

2013 ◽  
Vol 71 (1) ◽  
pp. 81-89 ◽  
Author(s):  
Sophie Smout ◽  
Anna Rindorf ◽  
Philip S. Hammond ◽  
John Harwood ◽  
Jason Matthiopoulos
Keyword(s):  
Functional Response ◽  
Prey Species ◽  
Prey Availability ◽  
Prey Consumption ◽  
Prey Abundance ◽  
Generalist Predators ◽  
Commercial Fish ◽  
Predator Pit ◽  
Estimation Of Missing Data ◽  
Type 3

Abstract Smout, S., Rindorf, A., Hammond, P. S., Harwood, J., and Matthiopoulos, J. Modelling prey consumption and switching by UK grey seals. – ICES Journal of Marine Science, 71: . Grey seals (Halichoerus grypus) are adaptable generalist predators whose diet includes commercial fish species such as cod. Consumption by the seals may reduce the size of some fish stocks or have an adverse effect on stock recovery programmes, especially because predation may trap sparse prey populations in a “predator pit”. To assess the likely impact of such effects, it is important to know how consumption and consequent predation mortality respond to the changing availability of prey. We present a model of grey seal consumption as a function of the availability of multiple prey types [a Multi-Species Functional Response (MSFR)]. We fit this MSFR to data on seal diet and prey availability (based on the overlap between the distributions of predators and prey). Bayesian methodology was employed to account for uncertainties in both dependent and independent variables, improve estimation convergence by the use of informative priors, and allow the estimation of missing data on prey availability. Both hyperbolic (Type 2) and sigmoidal (Type 3) functional response models were fitted to the data and the Type 3 model was clearly favoured during model selection, supporting the conclusion that seal–prey encounter rates change with prey abundance (sometimes referred to as “switching”). This suggests that some prey species may be vulnerable to predator pit effects. The fitted model reproduced contrasts in diet observed between different regions/years and, importantly, added information to the prior distributions of prey abundance in areas where the availability of some prey species (such as sandeels) was not known. This suggests that the diet of predators such as seals could provide information about the abundance and distribution of prey in areas that are not covered by fisheries and research surveys.

scholarly journals Making inference from wildlife collision data: inferring predator absence from prey strikes

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3014 ◽  
Author(s):  
Peter Caley ◽  
Geoffrey R. Hosack ◽  
Simon C. Barry
Keyword(s):  
Prey Species ◽  
Red Fox ◽  
Prey Availability ◽  
Numerical Response ◽  
Practical Application ◽  
Ecological Inference ◽  
Predator Species ◽  
New Approach ◽  
Predictive Probability ◽  
Irreducible Uncertainty

Wildlife collision data are ubiquitous, though challenging for making ecological inference due to typically irreducible uncertainty relating to the sampling process. We illustrate a new approach that is useful for generating inference from predator data arising from wildlife collisions. By simply conditioning on a second prey species sampled via the same collision process, and by using a biologically realistic numerical response functions, we can produce a coherent numerical response relationship between predator and prey. This relationship can then be used to make inference on the population size of the predator species, including the probability of extinction. The statistical conditioning enables us to account for unmeasured variation in factors influencing the runway strike incidence for individual airports and to enable valid comparisons. A practical application of the approach for testing hypotheses about the distribution and abundance of a predator species is illustrated using the hypothesized red fox incursion into Tasmania, Australia. We estimate that conditional on the numerical response between fox and lagomorph runway strikes on mainland Australia, the predictive probability of observing no runway strikes of foxes in Tasmania after observing 15 lagomorph strikes is 0.001. We conclude there is enough evidence to safely reject the null hypothesis that there is a widespread red fox population in Tasmania at a population density consistent with prey availability. The method is novel and has potential wider application.

Intrapopulation variation in the diet of franciscana dolphin (Pontoporia blainvillei) off southern Brazil

2021 ◽  
pp. 1-17
Author(s):  
Manuela Bassoi ◽  
Eduardo R. Secchi ◽  
Daniel Danilewicz ◽  
Ignacio B. Moreno ◽  
Roberta A. Santos ◽  
...  
Keyword(s):  
Sexual Maturity ◽  
Linear Models ◽  
Prey Species ◽  
Prey Availability ◽  
Prey Selection ◽  
Feeding Habits ◽  
Stomach Contents ◽  
Brazilian Coast ◽  
Pontoporia Blainvillei ◽  
Franciscana Dolphin

Abstract The franciscana dolphin (Pontoporia blainvillei) is a coastal dolphin endemic to the western South Atlantic Ocean. The dolphin is listed as vulnerable in the IUCN Red List, with incidental catches in gillnet fisheries the greatest conservation concern for this species. Insights into the feeding habits of this dolphin are essential to understand its distribution, movements and use of habitat, which are fundamental for effective management of the species. The feeding habits of franciscana dolphins were investigated from analyses of stomach contents of animals incidentally caught by two fishing operations from southern and northern regions of the southern Brazilian coast. In this study we investigate the existence of intrapopulation (sexual maturity and sex-related) variation in the diet of the franciscana dolphin, evaluating the spatial (northern and southern geographic areas) and seasonal influences. The analyses were based on Linear and Generalized Linear Models (LM and GLM). The majority of identified prey species were bottom-dwelling teleosts and the squid Doryteuthis sanpaulensis. The most important prey differed spatially and seasonally between northern and southern regions of the study area, and our results revealed significant differences between sexes and sexual maturity stages, mainly related to prey species sizes. This variation might indicate differences in prey selection, availability or habitat use patterns among these groups. In any case, these dietary differences are likely to minimize intraspecific competition for food resources, and/or indicate spatio-temporal variation in prey availability.

scholarly journals Making inference from wildlife collision data: inferring predator absence from prey strikes

2016 ◽  
Author(s):  
Peter Caley ◽  
Geoffrey R Hosack ◽  
Simon C Barry
Keyword(s):  
Prey Species ◽  
Red Fox ◽  
Prey Availability ◽  
Numerical Response ◽  
Practical Application ◽  
Ecological Inference ◽  
Predator Species ◽  
New Approach ◽  
Predictive Probability ◽  
Irreducible Uncertainty

Wildlife collision data are ubiquitous, though challenging for making ecological inference due to typically irreducible uncertainty relating to the sampling process. We illustrate a new approach that is useful for generating inference from predator data arising from wildlife collisions. By simply conditioning on a second prey species sampled via the same collision process, and by using a biologically realistic numerical response functions, we can produce a coherent numerical response relationship between predator and prey. This relationship can then be used to make inference on the population size of the predator species, including the probability of extinction. The statistical conditioning enables us to account for unmeasured variation in factors influencing the runway strike incidence for individual airports and to enable valid comparisons. A practical application of the approach for testing hypotheses about the distribution and abundance of a predator species is illustrated using the hypothesized red fox incursion into Tasmania, Australia. We estimate that conditional on the numerical response between fox and lagomorph runway strikes on mainland Australia, the predictive probability of observing no runway strikes of foxes in Tasmania after observing 15 lagomorph strikes is 0.001. We conclude there is enough evidence to safely reject the null hypothesis that there is a widespread red fox population in Tasmania at a population density consistent with prey availability. The method is novel and has potential wider application.

scholarly journals Vulnerability of a Top Marine Predator in One of the World’s Most Impacted Marine Environments (Arabian Gulf)

2021 ◽  
Author(s):  
Bruno Diaz Lopez ◽  
Séverine Methion ◽  
Himansu Das ◽  
Ibrahim Bugla ◽  
Maitha Al Hameli ◽  
...  
Keyword(s):  
Habitat Use ◽  
Bottlenose Dolphin ◽  
Prey Availability ◽  
Arabian Gulf ◽  
Marine Environments ◽  
Marine Habitat ◽  
Predator Species ◽  
Marine Predator ◽  
Conservation Measures ◽  
Abundance Estimates

Abstract Knowledge of the habitat use of wildlife in highly impacted areas is essential to identify areas of biological importance and to implement appropriate conservation measures. The Arabian Gulf represents one of the most extreme marine environments and is considered one of the regions in the world with the greatest anthropogenic impact. Information on the habitat use and abundance of marine top predator species is however lacking, despite being a prerequisite for effective planning of conservation measures. Here, we provide novel information for the Indo-Pacific bottlenose dolphin (Tursiops aduncus) in the Arabian Gulf (Abu Dhabi, United Arab Emirates). Data from 80 daily surveys conducted between June 2014 and November 2019 were used both to assess correlates of bottlenose dolphin habitat use and relative density and to calculate mark-recapture abundance estimates. This study confirms the strong adaptability and tolerance of this top marine predator to extreme environmental conditions within a highly heterogeneous and impacted marine habitat. The observed preferences for areas with less human pressure were likely a result of the interactions of environmental factors with prey availability and human disturbance. This study also provides the first abundance estimates for a bottlenose dolphin population in the Arabian Gulf. Our findings support the call for increased marine protected areas and the creation of transboundary conservation areas in the region. Regional connectivity should be of value to marine predators whose wide distribution and vulnerability to human activities means that alteration of their habitats can result in population declines and eventual local or regional extinctions.

scholarly journals Making inference from wildlife collision data: inferring predator absence from prey strikes

2016 ◽  
Author(s):  
Peter Caley ◽  
Geoffrey R Hosack ◽  
Simon C Barry
Keyword(s):  
Prey Species ◽  
Red Fox ◽  
Prey Availability ◽  
Numerical Response ◽  
Practical Application ◽  
Ecological Inference ◽  
Predator Species ◽  
New Approach ◽  
Predictive Probability ◽  
Irreducible Uncertainty

Wildlife collision data are ubiquitous, though challenging for making ecological inference due to typically irreducible uncertainty relating to the sampling process. We illustrate a new approach that is useful for generating inference from predator data arising from wildlife collisions. By simply conditioning on a second prey species sampled via the same collision process, and by using a biologically realistic numerical response functions, we can produce a coherent numerical response relationship between predator and prey. This relationship can then be used to make inference on the population size of the predator species, including the probability of extinction. The statistical conditioning enables us to account for unmeasured variation in factors influencing the runway strike incidence for individual airports and to enable valid comparisons. A practical application of the approach for testing hypotheses about the distribution and abundance of a predator species is illustrated using the hypothesized red fox incursion into Tasmania, Australia. We estimate that conditional on the numerical response between fox and lagomorph runway strikes on mainland Australia, the predictive probability of observing no runway strikes of foxes in Tasmania after observing 15 lagomorph strikes is 0.001. We conclude there is enough evidence to safely reject the null hypothesis that there is a widespread red fox population in Tasmania at a population density consistent with prey availability. The method is novel and has potential wider application.

Feeding of small whiting (Merlangius merlangus) in the central and southern North Sea

1999 ◽  
Vol 79 (5) ◽  
pp. 957-960 ◽  
Author(s):  
S. Singh-Renton ◽  
P.J. Bromley
Keyword(s):  
North Sea ◽  
Stomach Contents ◽  
Crangon Crangon ◽  
Daily Consumption ◽  
Invertebrate Prey ◽  
Southern North Sea ◽  
The Mean ◽  
Merlangius Merlangus

The stomach contents of 899 whiting, Merlangius merlangus (Pisces: Gadidae), from the central and southern North Sea, were analysed. Crustacea and fish comprised 90% on average by weight of the food observed. Crustacean prey sizes usually ranged from 0.2 to 0.6 g. The mean daily consumption of a common invertebrate prey, Crangon crangon, was estimated to be 0.1 g for a whiting weighing 150 g.

Biological reference points for fish stocks in a multispecies context

2001 ◽  
Vol 58 (11) ◽  
pp. 2167-2176 ◽  
Author(s):  
Jeremy S Collie ◽  
Henrik Gislason
Keyword(s):  
Life History ◽  
Growth Rates ◽  
Prey Species ◽  
Prey Availability ◽  
Mortality Rates ◽  
Reference Points ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Predator Species ◽  
Life History Parameters

Biological reference points (BRPs) are widely used to define safe levels of harvesting for marine fish populations. Most BRPs are either minimum acceptable biomass levels or maximum fishing mortality rates. The values of BRPs are determined from historical abundance data and the life-history parameters of the fish species. However, when the life-history parameters change over time, the BRPs become moving targets. In particular, the natural mortality rate of prey species depends on predator levels; conversely, predator growth rates depend on prey availability. We tested a suite of BRPs for their robustness to observed changes in natural mortality and growth rates. We used the relatively simple Baltic Sea fish community for this sensitivity test, with cod as predator and sprat and herring as prey. In general, the BRPs were much more sensitive to the changes in natural mortality rates than to growth variation. For a prey species like sprat, fishing mortality reference levels should be conditioned on the level of predation mortality. For a predator species, a conservative level of fishing mortality can be identified that will prevent growth overfishing and ensure stock replacement. These first-order multispecies interactions should be considered when defining BRPs for medium-term (5–10 year) management decisions.

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