Feeding guilds of western Mediterranean demersal fish and crustaceans: an analysis based in a spring survey

Abstract

SUMMARY: The MEDITS-99 sampling was performed along all the Iberian Peninsula coasts of the western Mediterranean (from the Alborán Sea to Cape Creus) in a space-scale of 1000 Km N-S, at depths ranging between 27-790 m. Fish and decapod crustaceans were dominant in the megafaunal compartment sampled by trawling. Based on both the fish and the decapod crustacean compositions, a comparison of trophic guilds has been attempted, with fish and decapods classified as: 1) migrator macroplankton feeders (mM), 2) non-migrator macroplankton feeders (nmM), 3) nektobenthos-suprabenthos feeders (NS), 4) epibenthos feeders (Epib), 5) large detritus-scavengers (Sca), 6) infaunal feeders (Inf), 7) deposit feeders (Dep) and 8) small detritivorous feeders (Det). Multivariate techniques showed the following differences in the trophodynamics of the megafaunal assemblages along the coasts of the Iberian Peninsula: 1) crustaceans (mainly decapods) have different trophic structures on the shelf and on the slope; 2) on the slope, fish exhibited more clear changes as a function of the geographical gradient than crustaceans; and 3) trophodynamics of bathyal fish showed some geographic variations between the Alborán Sea, the Catalano-Balearic Basin, and the Algerian Basin (Vera Gulf and Alicante sectors), with a progressive north-south increase in planktophagous species.Key words: feeding guilds, demersal fish, decapod crustaceans, western Mediterranean, trawl survey, Mediterranean. turnovers than shallow-water or littoral systems and their carrying capacity is expected to be lower. Since most of the target species are slow growing, overexploitation can be detected in deep-sea fisheries only after some years or decades after the beginning of a fishery (Atkinson, 1994;Bowering and Brodie, 1994;Koslow, 1997).In addition to indices such as abundance, or harvest-induced mortality (Hutchings and Myers, 1994), to quantify changes and the impact in the carrying capacity of a system, trophodynamic aspects can be studied (Petersen and Curtis, 1980;Robinson and Ware, 1994; Christensen, 1995, among others). Trophodynamic studies constitute the base of massbalance models (i.e ECOPATH models), which have increasingly been considered for the study and management of marine ecosystems (Robinson and Ware, 1994;Wolff, 1994;Christensen, 1995;Pauly and Christensen, 1995). In practice, however, great difficulties exist in developing such models in deepwater systems, because only scarce data have been published on important quantitative aspects such as secondary production (Cartes and Sorbe, 1999;Cartes et al., 2000), and daily rations (Maynou and Cartes, 1997;1998;, with only some preliminary trophic balances constructed for the mid-slope depths . Trophodynamic studies in deep-sea systems have often focused on species of commercial interest (Macpherson, 1985;Bulman and Koslow 1992, Maynou andCartes 1997), whereas by-catches and studies on the lowest trophic levels, i.e. those compartments that sustain the trophic webs and fisheries, have received, in general...

Balearic Islands vs Algeria: two nearby western Mediterranean elasmobranch assemblages with different oceanographic scenarios and fishing histories

“…Similarly, the higher values detected for these descriptors on the middle slope of Algeria could be explained by favourable environmental conditions and/or the low fishing pressure historically exerted on these bottoms. The unusually high primary production of the nearby Alboran sea (Cartes et al, 2002), along with the influence of Atlantic currents entering the Mediterranean through the Strait of Gibraltar, the stable presence of the Almeria-Oran front, and the existence of numerous submarine canyons, provide an environmental scenario that is favourable to the enrichment of the deep waters on the Algerian slope. Furthermore, according to Nouar (2001), the deep sea red shrimp fishery (below 400 m depth) remained unexploited at the end of the last century owing to the lack of deep-water trawling equipment, though it started to increase steadily at the beginning of the current century (Mouffok et al, 2008).…”

Demersal and epibenthic assemblages of trawlable grounds in the northern Alboran Sea (western Mediterranean)

“…The outer shelf group was characterised by typical shelf species, such as Octopus vulgaris, Arnoglossus spp., Callyonimus maculatus, Pagellus acarne and Cepola macrophthalma (Ungaro et al, 1999;Gaertner et al, 2002;González and Sánchez, 2002;Kallianiotis et al 2004), most of them of benthophagous feeding habits. Cartes et al (2002) described shelf fishes and crustaceans as more dependent on benthic resources, while plankton resources are utilised more by slope species. This pattern is a consequence of the decrease in benthic biomass with depth and the higher density of zooplankton offshore at the shelf break (Cartes et al, 2002).…”

“…Cartes et al (2002) described shelf fishes and crustaceans as more dependent on benthic resources, while plankton resources are utilised more by slope species. This pattern is a consequence of the decrease in benthic biomass with depth and the higher density of zooplankton offshore at the shelf break (Cartes et al, 2002). Slope groups, including the Seco de los Olivos seamount, were dominated by M. poutassou, which is a key trophic species that represents a link between nekton and demersal communities.…”

“…The Texel-Faial criteria for the identification of species and habitats that need protection, defined by OSPAR (2003), requires a detailed knowledge of the quality, structure and functioning of the ecosystems and/or habitats proposed as MPAs. Despite the ecological and economical interest of the area, there is a lack of studies on Alboran demersal and epibenthic communities, with the exception of a few studies in the western Mediterranean focusing on demersal fish (Cartes et al, 2002;Gaertner et al, 2005), elasmobranch distribution (Bertrand et al, 2000), crustaceans (Abelló et al, 2002;Cartes et al, 2002) and cephalopod assemblages (González and Sánchez, 2002) that include the Alboran Sea as one of the regions studied.…”

Deep sea megafaunal assemblages off the northern Iberian slope related to environmental factors

“…This is a very interesting result since it is not very common to find "barriers" in deeper, more stable, communities (e.g. Cartes et al, 2002;Carney, 2005), and these boundaries have been mainly related to depth rather than geographical gradients .…”