Small pelagic fish feeding patterns in relation to food resource variability: an isotopic investigation for Sardina pilchardus and Engraulis encrasicolus from the Bay of Biscay (north-east Atlantic)

Abstract

Small pelagic fish represent an essential link between lower and upper trophic levels in marine pelagic ecosystems and often support important fisheries. In the Bay of Biscay in the north-east Atlantic, no obvious controlling factors have yet been described that explain observed fluctuations in European sardine Sardina pilchardus and European anchovy Engraulis encrasicolus stocks, in contrast to other systems. The aim of this study was therefore to investigate to which extent these fluctuations could be trophodynamically mediated. The trophic ecology of both fish species was characterised over three contrasting periods (spring 2010 and 2011 and autumn 2011) in the area, in relation to potential variation in the abundance and composition of the mesozooplankton resource. Stable isotope analyses of carbon (δ 13 C) and nitrogen (δ 15 N) were performed on potential mesozoplanktonic prey items and in the muscle of adult fish, as well as in the liver whenever available, and mixing models were applied. In both springs, the mesozooplankton resource was abundant but qualitatively different. During this period of the year, results based on muscle isotope values in particular showed that S. pilchardus and E. encrasicolus likely do not compete strongly for food. On the medium term, E.encrasicolus always presented a greater trophic plasticity than S. pilchardus, both in terms of feeding areas and in the size of the mesozooplanktonic prey consumed. In autumn, mesozooplankton abundances were lower, and it was likely that S. pilchardus and E.encrasicolus share food resources during this period. No clear links between the variation in the mesozooplanktonic resource and the trophic segregation maintained between adults of both fish species in spring could be made. Although a certain potential exists for trophodynamically mediated fluctuations of both species under specific abiotic conditions (i.e. due to the existing trophic segregation in spring in particular), the overall results suggest that fluctuations in abundance of both fish species are probably not directly linked to their trophic ecology in the Bay of Biscay, at least at the level of adult individuals.

Low diversity of helminth parasites in Sardina pilchardus and Engraulis encrasicolus (Clupeidae) from the Bay of Biscay

“…Similarities in the helminth parasites of S. pilchardus and E. encrasicolus recorded both in our field study (three species of Ascaridoidea in the Bay of Biscay) and in their entire geographical distribution (12 trophically-transmitted taxa in common among Digenea, Cestoda, Nematoda and Acanthocephala) highlighted feeding similarities. Such similarities have been previously demonstrated between these two small planktivorous pelagics using analyses of stomach contents and stable isotopes despite a greater trophic plasticity for E. encrasicolus (Morello and Arneri 2009;Chouvelon et al 2014Chouvelon et al , 2015. In the Bay of Biscay, S. pilchardus and E. encrasicolus mainly feed with small-to medium-sized copepods (e.g., Acartia sp.…”

“…and Temora sp.) (Chouvelon et al 2014(Chouvelon et al , 2015. These copepods probably act as intermediate hosts for the Ascaridoidea recorded here; S. pilchardus and E. encrasicolus serving as trophic links in both Anisakis and Hysterothylacium life cycles (Køie 1993;Mattiucci and Nascetti 2008;Kijewska et al 2009).…”

“…First, they are both suspension and raptorial feeders, and their flexible, dual planktivorous diet includes diverse taxa, e.g. crustaceans of various sizes (copepods, cladocerans, euphausiids, amphipods and decapods), appendicularians and fish eggs and larvae, depending on the season and fish size (Bacha and Amara 2009;Morello and Arneri 2009;Petitgas 2010;Atkinson et al 2014;Chouvelon et al 2014Chouvelon et al , 2015. Second, they are preyed on by many predator species such as planktonic chaetognaths (as larval fish), demersal and medium to large pelagic fish, marine mammals, and seabirds (Morello and Arneri 2009;Petitgas 2010;Certain et al 2011).…”

Trophic niche overlap of sprat and commercial small pelagic teleosts in the Gulf of Lions (NW Mediterranean Sea)

“…In the Gulf of Lions, Pethybridge et al (2014) reported that no competition of sprats with anchovies and sardines during winter 2011 was apparent on the basis of lipid biomarkers. In the Bay of Biscay, Chouvelon et al (2015) hypothesised that anchovies and sardines are potential competitors for food in autumn, but not in spring.…”

PENERAPAN TEKNOLOGI HIDROAKUSTIK UNTUK PENGUKURAN SEBARAN SPASIAL DAN TEMPORAL IKAN PELAGIS KECIL DI LAUT BANDA Application of Hydroacoustic Technology to Measure Spatial and Temporal Distribution of Small Pelagic Density in Banda Sea

“…Jenis ikan pelagis kecil di Laut Banda antara lain ikan layang, selar, belanak, julungjulung, ikan terbang, teri, tembang, lemuru, golok-golok, dan kembung. Ikan pelagis kecil merupakan elemen penting dari ekosistem laut karena berada di tingkat menengah dalam jaringjaring makanan, sehingga memainkan peran yang cukup penting dalam menghubungkan (-37,90) -(-37,70) tingkat bawah dan atas tropik makanan (Checkley et al 2009;Chouvelon et al 2015). Populasi ikan pelagis kecil berfluktuasi disebabkan oleh variabilitas lingkungan dan karena siklus hidup yang relatif singkat (2-3 tahun) (Palomera et al 2007).…”