Spatial distribution and feeding rate of gelatinous predators in inshore areas off Crimean coast in winter 2016

Abstract

Gelatinous predators are the most important components of the Black Sea ecosystem. In spite of the numerous studies of different aspects of their biology (horizontal and vertical distribution, bioenergetical indices of the growth and energy transformation on organism and population levels) data on population conditions and their functioning in winter period is very scarce. In present study data on numerical abundance, biomass, size structure of jellyfish predators (Aurelia aurita, Mnemiopsis leidyi, Beroe ovata и Pleurobrachia pileus) and feeding intensity of two dominated species (A. aurita, M. leidyi) were investigated on 17 stations in inshore waters near Crimea in winter 2016. Sampling was carried out with the modified Bogorov – Rass net with 80 cm diameter, mesh 300 mkm by vertical tows from the bottom to the surface (0–100 m). Biomass of A. aurita varied from 30 to 1990 g·m-2 with higher values in the southern region. Other species biomass was much lower (maximum values are 170 g·m-2 of M. leidyi and 60 g·m -2 of P. pileus). High biomass of B. ovata (85 g·m-2), comparable with the summer values, was observed at a station in the northern shelf. A significant difference in biomass of the species between the regions was not revealed except a difference in B. ovata biomass in the northern and southern regions (p < 0.05). The bulk of all species populations were formed by adult individuals. The Bivalvia veligers were the main food items in A. aurita and different Copepoda stages – in M. leidyi. Daily rations in A. aurita were 0.009–0.107, in M. leidyi – 0.02–0.28 % C body and were much lower of jellyfish food requirements at that temperature conditions.

Keywords

• Black Sea
• jellyfish
• distribution
• feeding
• respiration rate
• food requirements