REVIEW, CONCEPT, AND SYNTHESIS The role of intraguild predation in the population dynamics of small pelagic fish Xabier Irigoien • Andre ´ de Roos Received: 18 January 2011 / Accepted: 6 April 2011 / Published online: 6 May 2011 Ó Springer-Verlag 2011 Abstract In this paper, we argue that understanding marine ecosystem functioning requires a thorough appre- ciation of the role of intraguild predation to system dynamics. The theoretical predictions of intraguild preda- tion models might explain some of the community features observed in marine ecosystems such as low diversity in upwelling and productive systems and species alternation in response to moderate external forcing. Finally, we argue that an ecosystem approach to fisheries requires that the size–structure of fish populations should be taken into account and that it is extremely important to account for the predators of early stages (eggs and larvae) to gain a thorough understanding of the key interactions between species. Introduction Intraguild predation (abbreviated as IGP), referring to the process of competitors eating each other (Polis et al. 1989; Holt and Polis 1997), is a widespread phenomenon in ecosystems (Arim and Marquet 2004). It is basically a special case of omnivory and particularly important in pelagic habitats because the lack of refuges (Finke and Denno 2002) and also because the maximum absolute swimming speed is limited by size (Bainbridge 1958). Intraguild predation can be found at all trophic levels in marine ecosystems, for example, copepods feeding on ciliates and phytoplankton (Gismervik and Andersen 1997; Irigoien et al. 1998), copepods feeding on other copepods eggs and zooplankton (e.g., Kang et al. 2000; Bonnet et al. 2004; Lopez Urrutia et al. 2004; Durbin et al. 2008), jel- lyfish on jellyfish (Titelman et al. 2007; Hosia and Titel- man 2011) and pelagic fish feeding on the eggs of pelagic and demersal fish (Ko ¨ster and Mo ¨llmann 2000). In this paper, we focus on small pelagic fish because of the interplay with human activities, but the consequences of IGP merits research at all trophic levels. Most eggs and early larvae of pelagic fish are planktonic and hence potential prey for planktivorous fish species that compete for food with their parents (e.g., Valdes-Szeinfeld 1991; Paradis et al. 1996; Pepin 2006; Garrido et al. 2008). The flip side of this coin is that adult fish feed on competitors of their juveniles (Walters and Kitchell 2001). Both effects are included in the diverse range of mechanisms that go under the heading of intraguild predation (Fig. 1). Although widespread, marine ecology research and fisheries science have paid rather little attention to recent developments of ecological theory on intraguild predation. Intraguild predation provides a clear example of a large body of knowledge developed through experiments, observations, and modeling (e.g., Mylius et al. 2001; Diehl and Feissel 2001; Woodward and Hildrew 2002; Hart 2002; Borer et al. 2003; Finke and Denno 2004; van de Wolfshaar et al. 2006; Borer et al. 2007) that is available but not applied. However, an understanding of its effects is particularly important in the context of an ecosystem approach to fisheries management. Although there are exceptions both in research and modeling (e.g., Bailey and Houde 1989; Ko ¨ster and Mo ¨llmann 2000; Shin and Cury Communicated by M. A. Peck. X. Irigoien (&) AZTI—Tecnalia, Herrera kaia, 20110 Pasaia, Spain e-mail: xirigoien@azti.es A. de Roos Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94248, 1090 GE Amsterdam, The Netherlands 123 Mar Biol (2011) 158:1683–1690 DOI 10.1007/s00227-011-1699-2