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.

Assessing effects of changes on stocks, fleets and management in the North Sea saithe fishery

It is increasingly acknowledged that the performance of future fisheries management relies to a large extent on how well one is able to evaluate and forecast the combined biological and economic impacts of management measures. An integrative bio-economic model was developed, including the economics of multiple fleets, the impact of fishing on stock development and the spatio-temporal interplay of fleets and fish stocks. This approach is based on the bio-economic optimisation and simulation model “FishRent”. To show the potential of the extended model it was applied to a case study, namely the North Sea saithe fishery, where the stock has been declining despite the existence of a long-term management plan. Furthermore, there has never been an impact assessment that takes into account the fleet dynamics and their impact on the fish stock under different management plan options.


Simulations demonstrate that A2 and B1 have differing impacts on individual fleet segments from different nations and home ports. Even when A2 or B1 did result in little change in overall net profits, there were winners and losers, and the distribution of gains and losses may not be intuitively obvious.

This result is part of the analysis that has been done in WP2.3. The model allowed to assess short- and long-term economic consequences of the A2 and B1 scenario for multiple fleet segments. As costs (i.e. fuel costs due to long distance from port) associated with each area differed between fleet segments, profit rates varied also considerably between fleet segments and areas, resulting in the spatial heterogeneity in the fishery.


Fleet segments tended to follow the seasonal migration pattern of saithe resulting in higher fishing mortality rates when the stock was concentrated on spawning or feeding grounds. Effort tended to concentrate where fish abundance was high, but economic costs played also an important role in effort allocation.

This finding is part of WP 3.3. The predicted spatio-temporal variability in fishing effort distributions is consistent with real observations of seasonal effort distributions, supporting the assumption that fishermen are able to “predict” the seasonal pattern of species distributions. Moreover, results suggest that commercial CPUEs that are currently used in the saithe stock assessment as a proxy for stock abundance do not just reflect the fish abundance they also depend on economic variables such as steaming costs. The predictions are also consistent with the response of a German saithe fisherman when asked how their fishing effort is distributed throughout the year.


Benefits of area closures were distributed heterogeneously among fleet segments. Increases of saithe stock size were offset by increases in cod by-catches. A discard ban may not achieve the Common Fisheries Policy reform objective of reduced unwanted catches. Instead it involves high costs in terms of maximal 29% lower profits.

These findings are part of the work that has been done in WP6.4. They are relevant for North Sea saithe fishery managers. First, given the results a temporal area closure at the spawning ground of saithe is likely to better protect SSB of saithe. As the spawning ground of saithe is generally known, this type of closure could be a realistic option to prevent a further decline of SSB of saithe. Moreover, results suggest that the economic consequences of the discard ban will depend on the quota availability of the limiting species and that a discard man will affect multiple fish stocks with some benefiting and others being negatively impacted.

Lead Author:

Sarah Simons
vTI-Institute of Sea Fisheries (vTI-SF)
Date of research: September 2014

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Ecosystem service changes in an offshore MPA

Fishing vessels interactions with other activities 

Habitat suitability of native and invasive species 

Impact of environmental changes on North Sea herring

Invasive species and ballast waters mitigation 

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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.