The Common Fisheries Policy State of Resources and Ecosystems Rainer Froese, GEOMAR, Germany 10 December 2014 Sustainable Fisheries Internal Seminar S&D PECH Working Group
Dec 14, 2015
The Common Fisheries PolicyState of Resources and Ecosystems
Rainer Froese, GEOMAR, Germany10 December 2014
Sustainable Fisheries Internal SeminarS&D PECH Working Group
Overview
• Revisiting MSY, Fmsy, Bpa and Bmsy
• State of Resources• State of the Ecosystems• Rebuilding stocks above MSY-Level• Minimizing the Impact of Profitable Fishing• Summary
Revisiting MSY, F, Fmsy, Bpa and Bmsy
• MSY is the maximum catch that a stock can deliver long-term
• Bmsy is the biomass that can produce MSY
• Bpa is the biomass below which recruitment may be compromised
• F is the fraction of the fish (present during the year) that are caught
• Fmsy is the F that leads to MSY and Bmsy, albeit in infinite time
Management Framework
0 100 200 300 400 500 6000
200
400
600
800
1000
1200
Spawning stock size
Rec
ruit
s
cons
tant
recr
uit-p
er-s
paw
ner r
atio
SSBlimconstant recruitmentBpa
Outside safebiological limits
proxyBmsy
Froese et al. 2014
State of the Resource: Stock Size
• The offical reference points for safe biological limits (Bpa) are often based on the lowest stock size ever observed (Bloss)
• With Bpa properly estimated, 52% of the stocks were outside of safe biological limits, and 12% were severely depleted. (Froese et al. 2014)
State of the Resource: Stock Size
• CFP requires rebuilding of stocks above Bmsy
• There are no official reference points for Bmsy
• But 2*Bpa can be used as a proxy for Bmsy • In 2013, 88% of the stocks were below the
proxy for Bmsy Froese et al. 2014)
State of the Resources: Fishing Mortality F
• Fisheries science holds that sustainable fishing mortality Fmsy has to be less than natural mortality M
• However, official estimates of Fmsy exceeded natural mortality M in 76% of the stocks
• Fishing mortality in 2013 exceeded natural mortality in 73% of the stocks, including those that were severely depleted (Froese et al. 2014)
State of the Resource: Maturity
• Fisheries science and common sense hold that fish shall reproduce before being caught
• In 74% of the stocks, the age at first capture was below the age at first maturity (Froese et al.
2014)
State of the Ecosystems
• What is the minimum stock size that still allows species to fulfil their ecosystem role as prey or predators?
• Fisheries science holds that 2/3 of unexploited population size may be a lower limit for regular fish (with F ~ 0.8 Fmsy) and ¾ may be a lower limit for forage fish (with F ~ 0.5 Fmsy)
(Froese et al. in prep)
FisherySeals
Harbour Porpoise
Adult Cod Juvenile Cod
Other Demersal Fish Sprat
Adult HerringJuvenile Herring
Other Pelagic Fish
Flatfish
(Sea-) Birds
Benthic Meiofauna
Zooplankton
Bacteria/Microorganisms
Benthic Producers
Benthic Macrofauna
Detritus / DOM
Phytoplankton
4
5
Tro
ph
ic L
evel
3
2
Pelagic Macrofauna
Food Web of the Western Baltic Sea Sprat is a central food organisms and „natural“ predators must compete for it with the fishery.
Opitz & Garilao unpublished
State of the Ecosystems
• What is the age and size structure that allows a population to reproduce and fulfil its ecosystem role as prey or predator?
• The natural length at first maturity is about 1/3 to ½ of maximum length
• The natural average length of parents is about 2/3 of maximum length
• Starting fishing at about ½ of maximum length allows all fish to reproduce and leads to natural average length; it also maximizes catch and biomass for a given F (Froese et al. in
prep.)
Maximizing Profits of Fishers
• Profit of fishers is the difference between the value of the catch and the cost of fishing
• Cost of fishing is a function of the abundance of fish
• Highest profits are obtained at about 1.2 Bmsy
• 1.2 Bmsy is therefore the target biomass level in Australia
Summary
• In 2013, about ¾ of the stocks were too small, were fished too hard, and were caught before reaching maturity
• For stocks to rebuild above levels that can produce MSY, F has to be smaller than Fmsy
• For minimizing impact of fishing and maximizing profits, F should not exceed 0.8 Fmsy and length at first capture should be about half of maximum length
• For forage fish (herring, sprat, anchovy, …) to fulfil their crucial ecosystem duties, F <= 0.5 Fmsy