Cyprinid prey remains in otter Lutra lutra faeces: some words of caution

Abstract

This study investigates errors associated with the recovery of cyprinid remains in otter Lutra lutra spraints. Cyprinid fishes (Cyprinidae – the carps) comprise the largest family of freshwater fishes in the world with around 2000 known species. They form the major group of freshwater fishes in Europe with a total of 80 species, 16 of which occur in Britain (Winfield & Nelson, 1991). These fishes are commonly taken by otters Lutra lutra throughout the predator's geographical range, their prevalence in the diet apparently varying in relation to their abundance. No more than three species are commonly recorded as otter prey in Britain, Ireland, and Scandinavia (e.g. Wise, Linn & Kennedy, 1981; Kyne, Smal & Fairley, 1989; Erlinge, 1967, respectively), while at least five are in eastern Poland and southern Spain (e.g. Brzezinski, Jedrzejewski & Jedrzejewska, 1993; Lopez-Nieves & Hernando, 1984, respectively). These fishes offer an opportunity to investigate otter prey selection on relatively complex prey communities (cf. Carss et al., 1998) as they form mixed-species assemblages (Winfield & Nelson, 1991). However, Carss (1995) concluded that if studies of otter feeding ecology were to become more than mere lists of prey items, there was an urgent need to quantify current spraint analysis techniques and their associated errors more rigorously than before. This is undoubtedly true for studies which attempt to determine the species- and size-composition of cyprinids in the diet of otters.