Foraging energetics of North Sea birds confronted with fluctuating prey availability

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.

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Explaining diet composition of North Sea cod (Gadus morhua): prey size preference vs. prey availability

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f03-007 ◽

2003 ◽

Vol 60 (2) ◽

pp. 140-150 ◽

Cited By ~ 55

Author(s):

Jens Floeter ◽

Axel Temming

Keyword(s):

North Sea ◽

Diet Composition ◽

Gadus Morhua ◽

Prey Size ◽

Prey Availability ◽

Weight Ratio ◽

Fish Prey ◽

Gear Efficiency ◽

Species Specific ◽

Size Preference

The nature and significance of size preference for fish prey in the diet selection of North Sea cod (Gadus morhua L.) was analysed. The analysis combined information on size-specific abundance derived from bottom trawl surveys with prey size frequencies in cod stomachs from the International North Sea Stomach Database. To estimate the abundance of all potential fish prey in the sea, a length-based number spectrum was calculated, corrected for gear efficiency by the application of a species-specific correction factor, and weighted by local predator abundance to take the spatialtemporal overlap between cod and its prey into consideration. A prey size preference model for cod feeding on fish is presented. Results showed that the preferred predator-to-prey weight ratio is an exponentially increasing function of predator size and an exponentially decreasing function of the slope of the number spectrum. More than 75% of fish found in the stomachs of North Sea cod originated from the least preferred quartile of the prey size range, indicating that prey abundance is the main determinant of the diet composition.

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The feeding strategy of dabLimanda limandain the southern North Sea: linking stomach contents to prey availability in the environment

Journal of Fish Biology ◽

10.1111/j.0022-1112.2005.00918.x ◽

2005 ◽

Vol 67 ◽

pp. 125-145 ◽

Cited By ~ 40

Author(s):

H. Hinz ◽

I. Kröncke ◽

S. Ehrich

Keyword(s):

North Sea ◽

Prey Availability ◽

Feeding Strategy ◽

Stomach Contents ◽

Southern North Sea

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Nine decades of North Sea sole and plaice distribution

ICES Journal of Marine Science ◽

10.1093/icesjms/fsr031 ◽

2011 ◽

Vol 68 (6) ◽

pp. 1090-1104 ◽

Cited By ~ 79

Author(s):

Georg H. Engelhard ◽

John K. Pinnegar ◽

Laurence T. Kell ◽

Adriaan D. Rijnsdorp

Keyword(s):

Climate Change ◽

North Sea ◽

Prey Availability ◽

Habitat Modification ◽

Climate Change Effects ◽

The North ◽

Research Survey ◽

Short Time Span ◽

Distribution Shifts ◽

Short Time

Abstract Engelhard, G. H., Pinnegar, J. K., Kell, L. T., and Rijnsdorp, A. D. 2011. Nine decades of North Sea sole and plaice distribution. – ICES Journal of Marine Science, 68: 1090–1104. Recent studies based mainly on research survey data suggest that within the North Sea, sole Solea solea and plaice Pleuronectes platessa have exhibited distribution shifts in recent decades—on average southward for sole and northward to deeper waters for plaice. Various hypotheses may account for such shifts, including climate change effects and more intensive fishing in southern and shallower waters; but the relatively short time-span of datasets analysed so far (∼3 decades) has complicated the separation of these two effects. We have made use of a unique dataset of catch and effort data for British North Sea trawlers; these cover nine decades (spanning the period 1913–2007) and are spatially detailed by ICES rectangle (0.5° latitude by 1° longitude). We quantify, for the first time, long-term distribution changes of North Sea sole and plaice over a period approaching a century, and demonstrate that the distribution shift in plaice was attributable to climate change rather than to fishing, but that both climate and fishing played a role in the distribution shift of sole. The discussion also highlights the potential impact of additional factors, including eutrophication, prey availability, and habitat modification.

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