Marine Research Findings of the VECTORS Project

This website provides access to the research results of the VECTORS project, which can be used to support marine management decisions, policies and governance as well as future research and investment. VECTORS was a large scale project that brought together more than 200 expert researchers from 16 different countries. It examined the significant changes taking place in European seas, their causes, and the impacts they will have on society.

Spatio-temporal variability of the North Sea cod recruitment in relation to temperature and zooplankton

This study investigates changes in the productivity of lower trophic levels as drivers of ecosystem change, in particular, how spatio-temporal changes in temperature and plankton have impacted the recruitment of North Sea cod.


A major change in the distribution of North Sea cod recruits was identified in the late 1990s. In particular a significant decrease in cod recruits could be related with environmental change (i.e. change in temperature and zooplankton quantity and quality) rather than with the size of the cod adult stock.

The analysis of records of age-1 North Sea cod recruits collected from 1974 to 2011 in the first quarter of the year (Q1-IBTS data) and used as an index of cod recruitment in the previous year, highlighted: (i) a period from 1974 to the late 1990s, in which recruits were relatively abundant and mainly concentrated in the shallow sheltered nursery areas along the British and European continental coastlines and around Dogger Bank; (ii) a recent period starting in 1998, in which a significant depletion of cod juveniles was recorded in most North Sea regions.

The decrease in cod recruits was mainly explained by SST increase, particularly during spring, rather than by the size of the adult stock.

Zooplankton biomass, and in particular the relative decrease of energy-rich copepods such as Calanus finmarchicus (as indicated by the ratio between C. finmarchicus biomass/total Calanus spp. biomass) were also negatively correlated with the number of recruits.


Long-term spatially-resolved observations were used to produce regional distribution models that could be further used to predict the abundance of North Sea cod recruits based on temperature and zooplankton food availability.

Generalized Additive Models (GAMs) and polynomial Linear Models (GLMs) were produced to calculate the number of cod recruits based on spring temperature and Calanus ratio for 8 different regions that cover the main recruitments areas of North Sea cod1.


Lead Author:

Delphine Nicolas & Priscilla Licandro
Agrocampus Ouest (AGRO)
Date of research: July 2013

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Variability in gelatinous zooplankton 

Alien Species database 

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 266445
© Vectors 2015. Coordinated by Plymouth Marine Laboratory.