Individual specialization and trophic adaptability of northern pike ( Esox lucius ): an isotope and dietary analysis

Abstract

Northern pike (Esox lucius) are often considered to be specialist piscivores, but under some circumstances will continue to eat invertebrates as adults. To examine effects of fish assemblage composition on the trophic ecology of pike, we combined stable isotope analysis (SIA) of carbon and nitrogen and stomach content analysis (SCA) on pike from five lakes in northern Alberta, three of which contain only pike ("pike-only") and two that also contain yellow perch (Perca flavescens) or white sucker (Catostomus commersoni) ("pike-other"). Fish were more important as prey and empty stomachs, which often characterize piscivores, were significantly more frequent in pike-other than in pike-only lakes. However, even though invertebrates were more important for pike in pike-only lakes, SIA and SCA indicated that invertebrates were also an important component of pike diets in pike-other lakes. SIA and SCA also revealed considerable intrapopulation variation in trophic ecology, with individuals in some populations differing by as much as two trophic levels. Comparisons of stomach contents and isotope signatures of the same fish suggested that within these variable populations, specialization on invertebrates or fish was a long-term trait of some individuals. SIA indicated that trophic position increased and diets shifted to a greater importance of littoral prey as pike grew in pike-only lakes, but not in lakes with other fish present. Trophic adaptability in northern pike is expressed at both the population level, where the trophic ecology is sensitive to differences in prey regimes, and at the organismal level, in the form of intrapopulation variation and individual specialization.

Post-glacial dispersal patterns of Northern pike inferred from an 8800 year old pike (Esox cf. lucius) skull from interior Alaska

“…Increased autochthonous production from~10,300 cal yr BP peaked at~9500 cal yr BP (Wooller et al, 2012a) and the development of this productive lacustrine environment probably provided a habitat and food web to support an aquatic predator such as a Northern pike. Certainly the trophic level of the fish specimen (1.8e2) from the core is consistent with the opportunistic, predatory feeding ecology of Northern pike (e.g., Beaudoin et al, 1999;Paradis et al, 2008;Cott et al, 2011;Sepulveda et al, 2013;Lepak et al, 2014). Our finding also shows Bold signifies the date for the pike specimen referred to in the paper.…”

“…Modern Northern pike have been shown to adapt their feeding ecology and subsequently lower their trophic level during periods when the availability of higher trophic level diet items, such as prey fish, is reduced (Beaudoin et al, 1999;Venturelli and Tonn, 2006). The magnitude of variation in the d 15 N values of the sediment (range ¼ À1.7e7.0‰) (Wooller et al, 2012a) and Cladoceran ephippia (range ¼ À2.2e9.7‰) (Wooller, unpublished data) throughout the entire sediment core indicates that any trophic level estimation of this type is only realistic when comparing the stable isotope data from analyses of taxa from the same or similar time period/depth.…”

First report on the importance of alien gobiids in the diet of native piscivorous fishes in the lower Vistula River (Poland)

“…The aforementioned predatory fishes are considered as typical opportunists, very flexible in their feeding habits, capable of changing their diet spectra rapidly in response to changes in the abundance and vulnerability of available prey (Mann 1982;Chapman, Mackay 1984;Adams 1991;Beaudoin et al 1999;Brylińska 2000). They usually focus their feeding effort on the most abundant and easy to catch prey available in the environment, according to the optimal foraging theory (Werner, Hall 1974).…”

Effects of Forest Fire on Young-of-the-year Northern Pike, <em>Esox lucius</em>, in the Northwest Territories

“…Northern Pike fry eat invertebrates such as insect larvae and large zooplankton that is primarily found in shallow vegetated areas (Scott and Crossman 1973;Bry 1996;Beaudoin et al 1999). These same types of vegetated areas existed where fire affected Tibbitt Lake.…”

“…These same types of vegetated areas existed where fire affected Tibbitt Lake. Where invertebrates are limited in terms of abundance or due to interspecific competition, cannibalism may increase (Beaudoin et al 1999). It is possible that the quality and quantity of invertebrates were greater in undisturbed habitat at the unburned sites, and offered better feeding opportunities to Y-O-Y Northern Pike compared to those from the burned sites.…”