Diet of Engraulis encrasicolus in the northern Adriatic Sea (Mediterranean): ontogenetic changes and feeding selectivity

Abstract

Ontogenetic variation in the diet of Engraulis encrasicolus (L.) was examined in the northern Adriatic Sea, off the River Po delta, by stomach contents analysis. Anchovy (10 to 130 mm total length) were collected during a 1 wk cruise in October 2002. Feeding activity was mainly diurnal in all the length classes: stomach fullness, calculated for each 10 mm size class, was always higher during the day than at night, with maximal values measured for the 40 to 49 and 50 to 59 mm size classes. All analysed life stages of E. encrasicolus had a strictly zooplanktivorous diet based on a few species of copepods. The principal prey of E. encrasicolus were small-sized copepods, measuring about 0.2 to 0.3 or 0.5 to 0.6 mm in prosoma length. The copepods Euterpina acutifrons and Oncaea spp. dominated anchovy diet during the day, both in terms of frequency, number and biomass, in all anchovy size classes. During the night, bivalve larvae were also important dietary items, with Oncaea spp. and E. acutifrons making up > 69% of total prey number for all anchovy size classes. Within the considered size range, the dimensions of particles does not seem to be a limiting factor in food selection, and no relationship was found between anchovy length and the maximal dimension of ingested prey. Ivlev's electivity index confirmed that European anchovy was able to select specific food items and preferred small copepods such as E. acutifrons and Oncaea spp., and bivalve and decapod larvae. KEY WORDS: Anchovy · Late larvae · Stomach contents · Prey selection · ZooplanktonResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 392: 193-209, 2009 Several studies on Engraulis species have demonstrated that anchovy can feed by filtering or particulate feeding (O'Connell 1972, James 1987, James & Findlay 1989, van der Lingen 1994, Bulgakova 1996, van der Lingen et al. 2006, 2009. The ability to switch between these feeding modes makes anchovy highly opportunistic and flexible foragers, which are able to maximize their energy intake through employing the feeding mode most appropriate to a particular food environment. Given this ability, the diet of anchovy, which is generally comprised of mesozooplanktonic prey, may also include smaller particles such as phytoplanktonic cells (King & Macleod 1976, Mikhman & Tomanovich 1977, Bulgakova 1996. The feeding behaviour of anchovies and the resulting variability or breadth in their food intake make field and laboratory studies regarding selectivity the only means of predicting their diet in any particular ecosystem. Robert et al. (2008) recently pointed out the importance of carrying out field studies coupling fish gut contents analysis and prey availability assessment. In fact, the knowledge of prey availability is essential in order to understand the relative importance of food categories and to assess prey selectivity. Moreover, Robert et al. (2008) stressed the importance of obtaining high taxonomical resolution in the identification of prey in sel...

Importance of the Rio de la Plata estuarine front (southwestern Atlantic Ocean) in the feeding ecology of Argentine anchovy, Engraulis anchoita (Clupeiformes, Clupeidae

“…These results agree with those frequently reported for European anchovy (Tudela & Palomera, 1997;Plounevez & Champalbert, 1999, 2000Borme et al, 2009).…”

Plankton in the open Mediterranean Sea: a review

“…In the Adriatic Sea, sardine adults and larvae seem to feed on phytoplankton too (Rasoanarivo et al, 1991), while sprats feed on copepods, decapod larvae, cladocerans and chaetognaths (Ticina et al, 2000). Borme et al (2009) report that the principal prey of all size classes of E. encrasicolus in the NW Adriatic Sea are small-sized copepods (0.2-0.6 mm in prosome length), such as Euterpina acutifrons and Oncaea spp. These authors comment that the observed preference of anchovy for these few copepod species might be related to their abundance, but also to species-specific behavioural (e.g., swimming patterns, patchy distribution) and/or physical characteristics (e.g., colour, bioluminescence) of the prey.…”

Trophodynamics of anchovy in a non-upwelling system: direct comparison with sardine

“…Anchovies in temperate, non-upwelling areas forage primarily during daytime, exhibiting maximum stomach contents at dusk, with a rapid decrease thereafter (Mediterranean: Tudela & Palomera 1995, Plounevez & Champalbert 2000, Borme et al 2009; Bay of Biscay: Plounevez & Champalbert 1999; Ku ro shio Current region: van der Lingen 2009 and references therein). In contrast, in upwelling systems, anchovy feeding peaks at dusk or night (e.g.…”

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