Predator-prey overlap in three dimensions: cod benefit from capelin coming near the seafloor ...

• Main Authors: Fall, Johanna, Johannesen, Edda, Englund, Göran, Johansen, Geir Odd, Fiksen, Øyvind
• Format: Dataset
• Language: English
• Published: Dryad 2021
• Subjects: spatial ecology; Vertical distribution; Stomach contents; consumption rate; FOS: Biological sciences; Barents Sea; atlantic cod; Gadus morhua
• Online Access: https://dx.doi.org/10.5061/dryad.4j0zpc89q; https://datadryad.org/stash/dataset/doi:10.5061/dryad.4j0zpc89q

Spatial overlap between predator and prey is a prerequisite for predation, but the degree of overlap is not necessarily proportional to prey consumption. This is because many of the behavioural processes that precede ingestion are non-linear and depend on local prey densities. In aquatic environments, predators and prey distribute not only across a surface, but also vertically in the water column, adding another dimension to the interaction. Integrating and simplifying behavioural processes across space and time can lead to systematic biases in our inference about interaction strength. To recognise situations when this may occur, we must first understand processes underlying variation in prey consumption by individuals. Here we analysed the diet of a major predator in the Barents Sea, the Atlantic cod (Gadus morhua), aiming to understand drivers of variation in cod’s feeding on its main prey capelin (Mallotus villosus). Cod and capelin only partly share habitats, as cod mainly reside near the seafloor and ... : The data was collected by Norwegian vessels participating in the Norwegian-Russian Barents Sea Ecosystem Survey in 2004-2015. The survey covers the entire ice-free Barents Sea in August-October each year and follows a regular grid design with sampling stations spaced approximately 65 km apart, collecting data on environmental conditions, species composition and abundance for several trophic levels. We selected stations from areas where cod and capelin overlap spatially (Fall, et al. 2018), i.e., stations were both species were observed. At each station, a CTD (Conductivity-Temperature-Depth) probe is lowered to measure depth-specific temperature, a Campelen 1800 demersal shrimp trawl is used for near-bottom sampling over a distance of 1.4 km (0.75 nautical miles, nmi), and a pelagic trawl (‘Harstad trawl’, Godø, et al. 1993) samples the upper approximately 60 m of the water column. Continuously during the survey, Simrad EK60 echo sounders with 18, 38, 120 and 200 kHz split beam transducers (on some vessels ...