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

Abstract

Anchovies and sardines hold a very important position in pelagic ecosystems and are usually found in species pairs, exhibiting fluctuations in abundance. In upwelling systems, alternations in small pelagic fish have been hypothesized to be, at least partly, trophically mediated. In non-upwelling areas, direct comparisons of sardine and anchovy trophodynamics are lacking, which represents an impediment to our understanding of forage fish interactions. In the present study, we analyzed the diel feeding periodicity, daily ration and diet composition of anchovy Engraulis encrasicolus in a coastal area of the eastern Mediterranean. Τhe anchovy feeding parameters and diet compositions were then compared with published data on sardine Sardina pilchardus, captured in the same set of pelagic trawl hauls and analyzed using identical methods. Both anchovy and sardine foraged in daytime in summer, and mainly at night in winter. Their feeding intensities per daily sampling time were highly correlated. In both species, daily consumption was significantly and similarly related to fish size and per capita food availability. In terms of dietary carbon, intraspecific dietary differences between juveniles and adults were insignificant. Copepods (especially large ones) were the main energy source for both species. In contrast to adult sardines, anchovies did not consume phytoplankton, and ingested large prey (including decapod larvae) more frequently. Both species broadened their trophic niche in summer; dietary differences between the stratification and mixing periods mostly reflected corresponding changes in prey availability in the field. The strong size-based partitioning of plankton resources described for anchovy and sardine in upwelling systems was not corroborated in the Mediterranean Sea. KEY WORDS: Diet · Daily ration · Trophic ecology · Small pelagic fish · Mediterranean SeaResale or republication not permitted without written consent of the publisher

Seasonal changes in otolith increment width trajectories and the effect of temperature on the daily growth rate of young sardines

“…The duration of metamorphosis is known to be related to temperature: in laboratory experiments for the summer flounder (Paralichthys dentatus) and the Pacific tarpon (Megalops cyprinoides), Keefe and Able (1993) and Chen et al (2008), respectively, showed that the course of metamorphosis was clearly temperature dependent. Also, in a recent study, Nikolioudakis et al (2014) demonstrated that morphological changes associated with metamorphosis are more abrupt in species developing in summer (high temperature) but more gradual in those developing in winter (low temperature).…”

“…Also, in a recent study, Nikolioudakis et al . () demonstrated that morphological changes associated with metamorphosis are more abrupt in species developing in summer (high temperature) but more gradual in those developing in winter (low temperature).…”

Disentangling the effects of inherent otolith growth and model-simulated ecosystem parameters on the daily growth rate of young anchovies

“…Anchovy juveniles feed exclusively on mesozooplankton (Nikolioudakis et al 2014b), and postflexion anchovy larvae derive the bulk of their energy from mesozooplankton (Borme et al 2009). Coupled hydro-biogeochemical models, many of which are currently being developed and validated in several ecosystems around the world, comprise a unique means of simulating prey fields available for planktivorous fish on a daily basis.…”

Mesozooplankton biomass and abundance in Cyprus coastal waters and comparison with the Aegean Sea (eastern Mediterranean)

“…These taxa exert a significant grazing impact on phytoplankton and microzooplankton (Siokou-Frangou et al, 2002;Gaudy et al, 2003;Zervoudaki et al, 2007), modulate the response of the microbial food web to nutrient availability (Pasternak et al, 2005), and are the major prey of small pelagic fish (Tudela & Palomera, 1997;Nikolioudakis et al, 2014). Coastal Mediterranean mesozooplankton communities are typically more abundant than in the open Sea, but less diverse in terms of species composition and can differ in terms of species dominance (Gaudy, 1985;Fernández de Puelles et al, 2003).…”