CoDINA - Cod: DIet and food web dyNAmics

Informations

Funding country

Norway

Acronym

-

URL

-

Start date

1/1/2016

End date

12/31/2021

Budget

922,746 EUR

Fundings

Abstract

What determines the menu of the Barents Sea cod - a model study on the cod's diet and the Barents Sea food web The project CoDINA-Cod: DIet and food web dyNAmics is a Norwegian-British-Russian joint project led by the Institute of Marine Research. CoDINA addresses the connection between the Barents Sea cod and its main prey. Capelin, smaller cod (cannibalism), other species of fish and various crustaceans are the most important elements in the menu. A central question is how this interaction is affected by the size of the cod stock, the presence of many large cod and the general state of the ecosystem. The aim of CoDINA is to increase the understanding of the dynamics of the food chain in the free water masses of sub-Arctic ecosystems. More specifically, we study predator-prey interactions in the Barents Sea. Our starting point is especially the variability in cod diet compositing in space and time. We examine how this is related to variation in the environment, including climate, and characteristics of the stocks of cod itself and their main prey. We model multi-species interactions with various types of statistical (data-driven) and more analytical models. The quality of results from statistical analyses and models depends on the data being available. This is especially the case when studying phenomena that vary at different scales in both space and time. Therefore, preparation and quality control of data within the Norwegian-Russian stomach database was a central task in the first phase of CoDINA. Information from more than 269,000 stomachs from 1984-2016 is now available. In parallel, the final portion of a British cod stomach data set for the western Barents Sea from 1930-1970s was digitized, processed and quality controlled. The two data sets were then merged. The data set has been made openly available and an article on it has been accepted for publication. Based upon the Norwegian-Russian stomach database the trends in cod diet with increasing age/size have been examined and predator-prey interactions and prey-size selectivity assessed. Shifts in diet with increasing cod size were observed, with fish becoming gradually more important prey. Diet varied significantly inter-annually during 1984-2016, consistent with changes in prey species abundance. Differences were also observed between seasons, with capelin generally dominating the diet in winter, whereas cod, polar cod, and other small fish species were prevalent in the summer/autumn months. This work has been published in ICES Journal of Marine Science and presented at several occasions. In CoDINA we have also studied variability patterns in cannibalism among cod in the Barents Sea. The database is here used to investigate how cannibalism fluctuates with the size distribution of cod. This work is accepted and soon ready for publication. In a fourth manuscript we explore how the expansion of the cod's living area to the north and east affects the ecosystem in the NE Barents Sea and especially to what extent cod has contributed to the observed decline of the arctic fishes there. The first results on this were presented at the 18th Norwegian-Russian fisheries science symposium in Murmansk in 2018 and the manuscript for a scientific article is now being finalized. The amount of snow crabs in the Barents Sea has increased a lot during the 2000s. Analysis of the cod stomach data also show a clear increase in the amount of snow crab consumed by larger cod. This is an example of how information sampled by cod may be applied to make indicators of ecosystem state. This work is accepted for publication in ICES Journal of Marine Science. At CEFAS, UK, work has been done on developing, customizing, and testing so-called Ecopath models to our purposes. A manuscript on this has been written. The University of Sheffield has a research fellow, funded by NERC, who is working closely with CoDINA. He is developing and applying a climate-based distribution model for cod and their prey in the Barents Sea (a so-called maximum entropy model). The stomach database is used to verify the model results.