The contribution of external inputs of food (food falls, litter and other antropogenic remains) in the diet of large fish (6 teleosteans, 3 sharks), dominant top predators in deep Balearic basin (western Mediterranean) were analyzed at depths between 500 to 2300 m. The analyses were based on stomach/intestine contents. The identification was based on a multianalysis approach, comprising traditional morphological features, morphometric analysis (e.g. on a bird skull) and by molecular analyses (DNA barcoding method), being the last an useful tool for the identification of large (undigested) food falls. Remains of a number of inorganic anthropogenic materials (plastic bags, carton, plastic fibres: microplastics) appeared regularly in guts of deep-sea fish analyzed (e.g. in Trachyrhynchus scabrus and Mora moro) though always with low frequency (9.1% as much) and negligible weight (< 2% of diet). In our sampling, covering an area of ca. 12 swept km2, large food falls contribute poorly to whole fish diets, e.g. in shark's diet were 4.5% in weight in Centroscymnus coelolepis and 11% in Galeus melastomus. However, the importance of food falls increased locally (i.e. per haul). Hence, sharks (e.g. Carcharinidae, likely Prionace glauca, own C. coelolepis) flesh, identified after molecular analysis, represented to 66.6% of C. coelolepis diet at 1750 m and cetacean blubbler 70.8% of diet at 2250 m. The arrival of remains of livestock/farm animals (beef flesh, goat bones) were also evidenced by molecular analyses having similar whole contribution to deep-sea sharks diet (ca. 5.5%) than natural food falls. These remains, which origin is by human activity, may significantly alter the food web of oligotrophic environments like the deep Mediterranean. Food falls, both of natural and anthropogenic origin, were mainly found in fish collected close to canyon axis, also the case of the only cetacean fall documented in the deep Balearic Basin, an small (ca. 1.2 m) striped dolphin Stenella coeruleoalba collected in a haul at 1750 m depth off Barcelona coast.

14th Deep-Sea Biology Symposium (DSBS), 31 August 2015 - 04 September 2015, Aveiro

Peer Reviewed