Mammal Research

, Volume 60, Issue 3, pp 217–231 | Cite as

Fish selection by riverine Eurasian otters in lowland England

  • Kathryn R. Grant
  • Lauren A. HarringtonEmail author
Original Paper


Eurasian otters (Lutra lutra) may conflict with humans using fish stocks for food, income or recreation. Understanding fish selection by otters is important for predicting and managing potential conflicts. We used spraint analysis to describe the diet of Eurasian otters on rivers in the Upper Thames Valley, lowland England, in summer and winter, focusing specifically on the species and size of fish consumed. We assessed the proportion of fish consumed that were of potential commercial or sporting value (the ‘Potential Value’ category). Within this group, we assessed relative selection for family and length by comparing fish found in otter diet with their local availability. Local availability was estimated from UK Environment Agency electrofishing survey data. Fish represented 46 % (relative frequency of occurrence, RFO) of total otter diet, with fish of Potential Value representing 19 % (RFO). In the Potential Value category, cyprinids were relatively avoided; percids and esocids were relatively preferred. Most (∼80 %) fish prey items originated from fish 4–13 cm in length, 3 % from fish > 20 cm. Smaller (0–10 cm) percids and cyprinids, and larger (16–20 cm) esocids, were preferred. In summer, diet was broad, comprising 31 % (RFO) fish, 24 % birds and 14 % crayfish. In winter, diet was predominantly fish (68 % RFO) with crayfish and birds accounting for ∼5 % each. In summer, most fish consumed (70 % RFO) were the relatively slow-swimming common bullhead (Cottus gobio). Significantly more of the faster-swimming cyprinids were consumed in winter, presumably because they are easier to catch when the water is colder.


Otters Fisheries Predation Fish prey selection Human-wildlife conflict Spraint analysis 



We gratefully acknowledge the assistance of Andrew Harrington, and several volunteers, collecting spraints, Ralph Windham for carrying out the initial analysis of prey groups, Paul Johnson for statistical advice, Dr. Robert Britton for assistance with fish scales, Dr Alison Poole for assistance with fish species and Graham Scholey for comments on an earlier version of the manuscript. We would also like to thank the Environment Agency for providing data on fish availability and David Macdonald for supporting the wider project on riparian mustelids, of which this work was a part. We thank David Cote and one anonymous reviewer for helpful comments on an earlier version of this manuscript.

Compliance with ethical standards

KG carried out this study for her Final Honours Student project as part of her undergraduate degree at Oxford University; LAH was funded by the Esmée Fairbairn Foundation when samples were collected between 2003 and 2006. This article does not contain any studies with human participants or animals performed by any of the authors. Spraint samples were collected from riverbanks without any direct contact with otters.


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Copyright information

© Mammal Research Institute, Polish Academy of Sciences, Białowieża, Poland 2015

Authors and Affiliations

  1. 1.Lady Margaret HallUniversity of OxfordOxfordUK
  2. 2.Wildlife Conservation Research Unit, Department of ZoologyUniversity of OxfordAbingdonUK
  3. 3.Biological Form and Function Group, Institute of Molecular Plant SciencesUniversity of EdinburghEdinburghUK

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