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From verge of collapse
ecosystem-based fisheries management
Rainer Froese
RD3 Seminar
GEOMAR, Kiel, 15.05.2014
Overview of fisheries-related research
The reformed Common Fisheries Policy
The MSY concept
New approaches to estimate MSY
Safe biological limits
Size matters
Overview of fisheries-related research
Fisheries-relevant Research in Recent Years
See www.fishbase.de/rfroese for PDFs
Martell, S. and R. Froese, 2013. A simple method for estimating MSY from catch and
resilience. Fish and Fisheries 14: 504-514, doi:10.1111/j.1467-2979.2012.00485.x
Froese, R. and M. Quaas. 2013. Rio+20 and the reform of the Common Fisheries
Policy in Europe. Marine Policy 39:53-55, doi.org/10.1016/j.marpol.2012.10.007
Villasante, S., D. Gascuel and R. Froese. 2012. Rebuilding fish stocks and changing
fisheries management, a major challenge for the Common Fisheries Policy reform in
Europe. Ocean and Coastal Management 70:1-3,
Froese, R. and M. Quaas. 2012. Mismanagement of the North Sea cod by the
European Council. Ocean and Coastal Management 70:54-58,
Quaas, M., R. Froese, H. Herwartz, T. Requate, J.O. Schmidt and R. Voss. 2012. Fishing
industry borrows from natural capital at high shadow interest rates. Ecological
Economics, doi:10.1016/j.ecolecon.2012.08.002
Froese, R. and A. Proelss. 2012. Is a stock overfished if it is depleted by overfishing? A
response to the rebuttal of Agnew et al. to Froese and Proelss “Evaluation and legal
assessment of certified seafood”. Marine Policy 38:548-550,
Froese, R. and A. Proelss. 2012. Evaluation and legal assessment of certified seafood.
Marine Policy 36:1284-1289, doi:10.1016/j.marpol.2012.03.017
Froese, R., D. Zeller, K. Kleisner and D. Pauly. 2012. What catch data can tell us about
the status of global fisheries. Marine Biology 159: 1283-1292, doi:10.1007/s00227012-1909-6
Kleisner, K., D. Zeller, R. Froese and D. Pauly. 2012. Using global catch data for inferences on
the world's marine fisheries. Fish and Fisheries doi: 10.1111/j.1467-2979.2012.00469.x
Norse, E.A., S. Brooke, W.W.L. Cheung, M.R. Clark, I. Ekeland, R. Froese, K.M. Gjerde, R.L.
Haedrich, S.S. Heppell, T.Morato, L.E. Morgan, D. Pauly, R. Sumaila and R. Watson. 2012.
Sustainability of deep-sea fisheries. Marine Policy 36:307-320,
Pauly, D. and R. Froese. 2012. Comments on FAO's State of Fisheries and Aquaculture, or
'SOFIA 2010'. Marine Policy 36:746-752.
Froese, R. and M. Quaas. 2011. Three options for rebuilding the cod stock in the eastern
Baltic Sea. Marine Ecology Progress Series 434:197-2011
Froese, R. 2011. Fishery reform slips through the net. Nature 475:7
Froese, R., T.A. Branch, A. Proelß, M. Quaas, K. Sainsbury and C. Zimmermann. 2011. Generic
harvest control rules for European fisheries. Fish and Fisheries 12:340-351
Khalilian, S., R. Froese, A. Proelss, T. Requate. 2010. Designed for Failure: A Critique of the
Common Fisheries Policy of the European Union. Marine Policy 34:1178-1182
Froese, R. and A. Proelß. 2010. Rebuilding fish stocks no later than 2015: will Europe meet
the deadline? Fish and Fisheries 11:194-202,
Froese, R. 2008. The continuous smooth hockey stick: a newly proposed spawnerrecruitment model. Journal of Applied Ichthyology 24: 703-704,
Froese, R., A. Stern-Pirlot, H. Winker and D. Gascuel. 2008. Size Matters: How Single-Species
Management Can Contribute To Ecosystem-based Fisheries Management. Fisheries
Research 92:231-241
Froese, R. 2004. Keep it simple: three indicators to deal with overfishing. Fish and Fisheries
The Reformed Common Fisheries Policy
The new CFP
Article 2.2
• The CFP shall apply the precautionary approach to
fisheries management, and shall aim to ensure that
exploitation of living marine biological resources
restores and maintains populations of harvested
species above levels which can produce the
maximum sustainable yield.
CFP and the Ecosystem Approach
Preamble of CFP
Whereas: ...
• (11) The CFP should contribute to the protection of the
marine environment, to the sustainable management of
all commercially exploited species, and in particular to
the achievement of good environmental status by
2020, as set out in Article 1(1) of Directive 2008/56/EC
of the European Parliament and of the Council1.
• (13) An ecosystem-based approach to fisheries
management needs to be implemented, environmental
impacts of fishing activities should be limited and
unwanted catches should be avoided and reduced as far
as possible.
CFP and the Ecosystem Approach
• Article 4.1 (9) 'ecosystem-based approach to fisheries
management' means an integrated approach to managing
fisheries within ecologically meaningful boundaries which
seeks to manage the use of natural resources, taking account
of fishing and other human activities, while preserving both
the biological wealth and the biological processes necessary
to safeguard the composition, structure and functioning of
the habitats of the ecosystem affected, by taking into
account the knowledge and uncertainties regarding biotic,
abiotic and human components of ecosystems;
Article 4.1 (11) 'low impact fishing' means utilising selective
fishing techniques which have a low detrimental impact on
marine ecosystems or which may result in low fuel emissions,
or both;
CFP and Protected Areas
Preamble of CFP
• (22) In order to contribute to the conservation of living
aquatic resources and marine ecosystems, the Union
should endeavour to protect areas that are biologically
sensitive, by designating them as protected areas. In such
areas, it should be possible to restrict or to prohibit fishing
activities. When deciding which areas to designate,
particular attention should be paid to those in which there
is clear evidence of heavy concentrations of fish below
minimum conservation reference size and of spawning
grounds, and to areas which are deemed to be biogeographically sensitive. Account should also be taken of
existing conservation areas. [....]
Article 8, Establishment of fish stock recovery areas
1. The Union shall, while taking due account of existing
conservation areas, endeavour to establish protected
areas due to their biological sensitivity, including areas
where there is clear evidence of heavy concentrations of
fish below minimum conservation reference size and of
spawning grounds. In such areas fishing activities may be
restricted or prohibited in order to contribute to the
conservation of living aquatic resources and marine
CFP and Minimizing Impact of Fishing
• Article 2.3 The CFP shall implement the
ecosystem-based approach to fisheries
management so as to ensure that negative
impacts of fishing activities on the marine
ecosystem are minimised, and shall endeavour
to ensure that aquaculture and fisheries
activities avoid the degradation of the marine
• Article 4.1 (17) 'minimum conservation reference size' means
the size of a living marine aquatic species taking into account
maturity, as established by Union law, below which
restrictions or incentives apply that aim to avoid capture
through fishing activity; such size replaces, where relevant,
the minimum landing size;
The MSY concept
MSY, Bmsy and Fmsy
MSY is the maximum sustainable yield
Biomass (B) is the weight of the fish in the sea
Bmsy is the biomass that can produce MSY
Fmsy is the fishing pressure that eventually
results in Bmsy and MSY
• A stock is and remains in good status if
B > Bmsy and F < Fmsy
Background of the MSY Concept
Schaefer 1954; BioDivPopGrowthMSY.xls
Surplus Production Implications
• Surplus production (Y) is the production of
biomass beyond what is needed to maintain
current population size
• If a fishery only catches the surplus
production, then the population size remains
• If a fishery catches more, then the population
• If it catches less, then the population grows
Surplus Production Implications
• Surplus production has a maximum at about
half of unexploited population size B∞
• Keeping a population at 0.5 B∞ allows catching
MSY forever
• A population is kept stable if the fishing rate F
equals the intrinsic growth rate rt
• MSY is reached at ½ B∞ and ½ rmax
• Thus, MSY is reached at Fmsy = ½ rmax
New Approaches to Estimate MSY
MSY from Catch and Resilience
• For a population to sustain a history of output
such as catch, it needs to have had a certain
size and productivity
• If you know the time series of annual
production (biomass taken out for human
use), and you know the productivity of the
species, then you can calculate biomass and
reference points
Catch-MSY Method
Martell & Froese 2013
Output of the Catch-MSY method showing “viable” pairs surplus production rate r and
unexploited biomass k for North Sea cod. The red line indicates all r-k pairs that would result in
the same estimate of MSY; the red circle indicates the geometric. While the estimate of MSY is
robust, the geometric mean r = 0.24 depends on the lower bound for r.
New CMSY-Method in prep.
• Same approach as in Catch-MSY
• New, objective approach to determine rmax
• This results in surprisingly good estimates of
biomass time series, Bmsy and Fmsy
• Formal Bayesian approach under
Herring in the Gulf of Riga I
1) assumed r-k space
2) rmax in upper half
3) < 1% outliers in k
4) minimize SE of MSY
4-step zoom-in on area used to estimate geometric mean r, k and MSY
Herring in the Gulf of Riga II
Fisheries reference points MSY (bold red line in upper left graph), Fmsy = 0.5 r and Bmsy = 0.5 k
Herring in the Gulf of Riga III
Blue lines are prior biomass windows, medium resilience is prior for r. Red line is observed
Biomass, black line predicted biomass, with 5th and 95th percentile. Required data are catch.
Herring in the Gulf of Riga IV
Catch/biomass ratio u as proxy for F. Dotted line is umsy. Black line is predicted, red line
is observed.
Herring in the Central Baltic
Better fit possible by replacing defaults with “informative priors”.
North Sea Herring
Safe biological limits
The Past Common Fisheries Policy
(until 2013)
• Apply a precautionary approach to fishing
• Keep fish stocks within safe biological limits
Safe Biological Limits
Conceptual drawing of the hockey stick relationship between spawning stock size and recruitment. SSBlim
marks the border below which recruitment declines, SSBpa marks a precautionary distance to SSBlim, and
2 * SSBpa can be used as a proxy for SSBmsy, the stock size that can produce the maximum sustainable catch.
(Froese et al. submitted)
Status of European Stocks
Extending the trends
in the last 3 years for the
95% confidence limits…
Based on the ICES Stock Summary database 10/2013 with data for 45 stocks. Update of Froese & Proelss 2010
Quality of Scientific Advice
• Fisheries science holds that mortality caused by
sustainable fishing (Fmsy) should be less than
natural mortality (M) caused by e.g. predation,
diseases, natural hazards or old age
• Doubling mortality reduces life time and
reproductive phase by half and also reduces
average size and fecundity
• However, in 29 of 38 stocks (76%) with available
data, the ICES estimate of Fmsy exceeded M, on
average by 62%
(Froese et al. submitted)
Fishing Mortality may be Higher
True F/Fmsy may be higher because
of unrealistically high Fmsy
in 76% of the stocks
Based on the ICES Stock Summary database 10/2013 with data for 45 stocks
(Froese et al. submitted)
Quality of Scientific Advice
• ICES provides estimates of the border of safe
biological limits (SSBpa). Below SSBpa
recruitment may be reduced and the stock is
at increased risk of collapse
• In 14 of 43 stocks (33%) with available data,
the ICES estimate of SSBpa fell below the
median estimate of three independent
scientific methods.
Hake Southern Stock
Froese et al. submitted
Underestimation of Safe Biological Limits
ICES three independent methods
Analysis of stock-recruitment data for North Sea Doggerbank Sandeel (san-ns1), with three different methods. [S-R_HS_5_san-ns1.r]
(Froese et al. submitted)
Stock Biomass may be Lower
True SSB/SSBpa may be lower
because of unrealistically low SSBpa
in 33% of the stocks
Based on the ICES Stock Summary database 10/2013 with data for 45 stocks
(Froese et al. submitted)
Common Sense Rules for
Ecosystem-based Management
Only catch fish for direct human consumption
Only catch species with high resilience
Do not damage the ecosystem
Take less than nature
Let fish grow and spawn before capture
Size Matters (Froese et al. 2008, Froese et al. in prep)
Three important points in the life of species with
indeterminate growth:
• Length at maturity (Lm90)
• Length Lmax dW/dt where growth is maximum
• Length Lopt where cohort biomass is maximum
Natural Selection “Economizes”
Organisation of Reproduction
• reproduction happens when production of
tissue is maximum
• Lm90
<= Lmax dW/dt (= in semelparous, < in iteroparous)
• Lm90
<= Lopt (then topt = generation time)
• Lmax dW/dt = Lopt (then most offspring are produced when
production of tissue is maximum)
Basic Equations
𝑁𝑡 = 𝑁0 𝑒 −𝑀 𝑡
𝑊𝑡 = 𝑊∞ (1 − 𝑒 −𝐾
1 − 𝑒 −𝐾 𝑡−𝑡 0
𝑑𝑡 = 3 𝐾 𝑊∞
𝐿𝑜𝑝𝑡 = 𝐿∞
𝐿𝑐 _𝑜𝑝𝑡
𝑅 = 𝑊∞
𝑅 = 𝐹 𝑊∞
𝑒 −𝑀 𝑡 𝑐 −𝑡 𝑟
𝑡−𝑡 0
− 1
− 𝑒 −𝐾 𝑡−𝑡 0
𝐾(3𝐹 + 2𝑀)
= 𝐿∞
(𝐹 + 𝑀)(3𝐾 + 𝑀)
3 𝑒 −𝐾 𝑟1
3 𝑒 −2𝐾 𝑟1
𝑒 −3𝐾 𝑟1
𝑀 + 𝐹 𝑀 + 𝐹 + 𝐾 𝑀 + 𝐹 + 2𝐾 𝑀 + 𝐹 + 3𝐾
− 𝑀+𝐾
1 − 𝑒 −𝑀 𝑟2 𝑒 −𝑀 𝑟2
− 3𝑒 −𝐾 𝑟3
−2𝐾 𝑟3
1 − 𝑒 − 𝑀+2𝐾
𝑀 + 2𝐾
𝑒 − 𝑀+𝐾 𝑟2
𝑒 − 𝑀+2𝐾 𝑟2
1 − 𝑒 − 𝑀+3𝐾
−3𝐾 𝑟3
𝐹 + 𝑀 + 2𝐾
𝑀 + 3𝐾
𝑒 − 𝑀+3𝐾 𝑟2
𝐹 + 𝑀 + 3𝐾
Economizing Reproduction
Life history strategies for the timing of reproduction: A) semelparous, B) iteroparous with
parental care, C) broadcast spawners. Note: Blue line is not to scale.
Froese and Pauly 2013
Tradeoff between generation time and
peak fecundity
Froese et al. in prep.
Timing of spawning
Based on 232 studies.
Froese and Pauly 2013
Size Matters!
Biomasse of a cohort (e.g. cod) vs length. Maturity is reached at Lm90 = 59 cm. Maximum
growth and high fecundity is reached at Lopt = 86 cm. However, legal fishing starts at Ll = 35 cm.
Froese et al. 2008
Fishing with Fmsy starting at Ll will not
rebuild the stocks
Cohort biomasse (e.g. cod) without fishing (bold curve) and with F = Fmsy fishing
Starting at legal length (dotted curve).
Froese et al. 2008
Fishing with F=M starting at Lcopt
rebuilds the stock
- Large biomass (~ 1.2 Bmsy)
- Higher catch
- Lower cost
Unexploited cohort biomass (bold curve), with Fmsy –fishing (dotted curve), and with
F=M fishing starting at Lcopt (dashed curve), so that the mean length in the catch and
In the exploited part of the stock equals Lopt.
Froese et al. in prep.
Impact of Fishing on Size Structure
Length-frequency without fishing (bold curve), with F = Fmsy fishing after Ll , and with F = M
Fishing after Lcopt. With Lcopt fishing all fish reach maturity and about 2/3 reach Lopt. With
Fmsy fishing after Ll , only 2/3 reach maturity and only 1/3 reach Lopt.
Froese et al. in prep.
Thank You