The challenge of mixed fisheries-management

Wednesday 07 Sep 16
by Line Reeh


Clara Ulrich
DTU Aqua
+45 35 88 33 95

What is MSY?

Maximum sustainable yield is, theoretically, the largest yield (catch) that can be taken from a specific fish stock over an indefinite period under constant environmental conditions. It is measured in tonnes. The 2013 reform of the European Common Fisheries Policy (CFP) set as a strategic objective to achieve an exploitation rate consistent with maximum sustainable yield (FMSY) at the latest by 2020 for all stocks. The MSY concept has been used in fisheries management for more than 50 years. So far only single species related reference points are used in management although it is well known that species interact with each other.

New tools to quantify and monitor mixed-fisheries interactions are being developed to help address the challenge of mixed-fisheries management. In particular, the Fcube approach (fleets and fisheries forecast), developed by professor Clara Ulrich, DTU Aqua and colleagues, has delivered mixed-fisheries considerations as part of the annual ICES advice since 2009, measuring the inconsistencies across the different single-stock TAC (Total Allowable Catch) advice for the following year when stocks are caught together by the same fleets. Until now, these considerations did not aim to provide a single-best, mixed-fisheries TAC advice, but rather to raise managers’ awareness of the potential TAC mismatches at the regional level. So while the mechanisms creating over-quota discards became increasingly understood, no regional integrated management solutions were yet introduced. The present study extends an approach that has been followed by ICES using Fcube since 2009.

Evaluation of FMSY ranges as a tool to combine long-term single-stock targets with flexible, short-term, mixed-fisheries management requirements

The 2013 reform of the Common European Fisheries Policy set as a goal to achieve an exploitation rate consistent with maximum sustainable yield (FMSY) by 2020 at the latest for all fish stocks. 
However, achieving single species maximum sustainable yield (MSY) in complex fisheries targeting multiple species (mixed fisheries) is challenging because achieving the objective for one species may mean missing the objective for another. An example is the mixed demersal roundfish fisheries in the North Sea where a fisheries targeting North Sea haddock have contributed to a decline in the North Sea cod stock, and discards have increased as the cod quota were reduced. 

Mixed-fisheries are challenging

Recognizing this fundamental mixed-fisheries issue, new approaches have emerged out of intense political, institutional, and scientific activity. A task force comprising the three main EU institutions (EU Commission, EU Parliament, and EU Council of Fisheries Ministers) suggested using ranges of or around FMSY as flexible targets of “pretty good yield” for the regional management plans, thus considering MSY as a desirable multidimensional area rather than a point estimate, which would allow for more flexibility in management targets.

A new study, led by Clara Ulrich as part a EU funded Myfish-project, recently published in the ICES Journal of Marine Science, investigates potential of FMSY ranges to combine long-term single-stock targets with flexible, short-term, mixed-fisheries management requirements applied to the main North Sea demersal stocks

The objectives are to evaluate the ability of using FMSY ranges to diminish the conflict between MSY management of single stocks and the possibility to deliver operational regional management based on mixed-fisheries considerations, Professor Clara Ulrich, DTU Aqua and co-authors write:

“Our approach is independent of the actual definition of MSY ranges, and could be applied to any defined interval. Ultimately, the concept of ranges could be extended and potentially asymmetrized to include other ecological and economic considerations.”

The authors show that sustained fishing at the upper bound of the range may lead to unacceptable risks when technical interactions occur. Consequently, an objective method is suggested that provides an optimal set of fishing mortality within the range, minimizing the risk of total allowable catch mismatches among stocks captured within mixed fisheries, and addressing explicitly the trade-offs between the most and least productive stocks. 

The ICES Journal paper: 

Clara Ulrich, Youen Vermard , Paul J. Dolder, Thomas Brunel, Ernesto Jardim, Steven J. Holmes, Alexander Kempf, Lars O. Mortensen, Jan-Jaap Poos, and Anna Rindorf: Achieving maximum sustainable yield in mixed fisheries: a management approach for the North Sea demersal fisheries

ICES Journal of Marine Science (2016), doi:10.1093/icesjms/fsw126

Part of the Myfish-project

The study was carried out as part of the four-year EU funded Myfish-project (Maximising yield of fisheries while balancing ecosystem, economic and social concerns) aimed at developing new Maximum Sustainable Yield indicators that can ensure high levels of fishery yield while respecting ecological, economic and social aims.  The objective of the Myfish project was to face these difficulties and provide examples of scientific advice on MSY consistent with all aspects of sustainability.

Results from the project are highlighted in a Myfish Policy brief and a booklet
Myfish policy brief:
Myfish Legacy Booklet: