A field experiment on trophic relations within the benthic boundary layer (BBL) over an oligotrophic continental shelf

- An innovative sampler for the assessment of BBL macrofaunal diversity and abundance.
- epi- and hyper-benthic animals are more accessible as food for demersal fish.
- Peracarids and decapods constitute the prey base in the diet of demersal fish.
- Demersal fish feeding preferences with respect to prey availability.

The benthic boundary layer (BBL) macrofauna consists of epibenthic, hyperbenthic and zooplanktonic organisms with different degrees of mobility and bottom dependence. The top-level predators within this habitat include demersal fish species. The BBL species are considered to be the most readily available prey for these fish making them an attractive source of food and therefore key taxa in marine food webs. The present study is a field experiment in the oligotrophic continental shelf of Heraklion Bay (Cretan Sea, eastern Mediterranean) investigating the ways in which demersal fish utilize BBL sources as food. Species diversity patterns derived from samples collected by using a modified hyperbenthic sledge as well as different benthic, hyperbenthic and pelagic samplers are described. These patterns are compared with those derived from stomach content analysis of demersal fish species inhabiting the same area. Results reveal that BBL macrofaunal communities which comprise most of the available prey communities are largely exploited by demersal fish species. Furthermore, the application of different samplers provides complementary information on prey selectivity of macrofaunal organisms by demersal fish species, highlighting further the trophic interactions within the BBL habitat.

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