Progress with Assessment of Data-Limited Stocks

Rainer FroeseVilm, 21.01.2014

Overview

• Important Highlights from the CFP-Reform• Proxy-Stock Assessment based on DATRAS• Peak-Preview on New Assessment Method for

MSFD-GES

Useful Quotes from the CFP (0)

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.

• In order to reach the objective of progressively restoring and maintaining populations of fish stocks above biomass levels capable of producing maximum sustainable yield, the maximum sustainable yield exploitation rate shall be achieved by 2015 where possible and, on a progressive, incremental basis at the latest by 2020 for all stocks.

Useful Quotes from the CFP (I)Preamble of CFPWhereas: ...• (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.

• (16) The CFP should pay full regard, where relevant, to animal health, animal welfare, food and feed safety.

Useful Quotes from the CFP (II)

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 bio-geographically sensitive. Account should also be taken of existing conservation areas. [....]

Useful Quotes from the CFP (III)• 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 environment.

• Article 4.1 (8) 'precautionary approach to fisheries management', as referred to in Article 6 of the UN Fish Stocks Agreement, means an approach according to which the absence of adequate scientific information should not justify postponing or failing to take management measures to conserve target species, associated or dependent species and non-target species and their environment;

Useful Quotes from the CFP (IV)• 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;

Useful Quotes from the CFP (V)

• 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;

Useful Quotes from the CFP (VI)Article 7.1 Measures for the conservation and sustainable exploitation of marine biological resources may include... • (b) targets for the conservation and sustainable exploitation of

stocks and related measures to minimise the impact of fishing on the marine environment;

• (d) incentives, including those of an economic nature, such as fishing opportunities, to promote fishing methods that contribute to more selective fishing, to the avoidance and reduction, as far as possible, of unwanted catches, and to fishing with low impact on the marine ecosystem and fishery resources;

• (h) pilot projects on alternative types of fishing management techniques and on gears that increase selectivity or that minimise the negative impact of fishing activities on the marine environment;

Useful Quotes from the CFP (VII)

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 ecosystems.

Proxy-Stock Assessment based on DATRAS

DATRAS: Millions of Survey Recordshttp://datras.ices.dk

SMALK: Length-WeightNeeded to turn length into weight and biomass

North Sea flounder: 25,609 observations of length and weight; 42 outliers were removed. Weight = 0.007 * Length3.16 [SMALK_Analysis_25.r]

SMALK: GrowthNeeded to turn length into age

North Sea flounder: 25,501 observations of length and age. Length-at-age = 48 * (1 – e-0.11 * (age – 2.8)) [SMALK_Analysis_25.r]

SMALK: Length & Age at MaturityNeeded for proxy recruits and spawners

North Sea flounder: 10,814 observations of length, age, and state of maturity. Female length where 90% are mature is 23 cm, age is 2-3 years. [SMALK_Analysis_25.r]

Average catch in numbers of North Sea cod resulting from one hour of trawling with standardized survey gears. The bold line represents a three-year moving average to reduce scatter and facilitate interpretation of trends. The dotted line indicates the mean catch of the time series. [MSFD_8.pdf]

CPUE in Area 6

CPUE by Length

North Sea dab. a)shows the raw data. The red line indicates individuals above 50% maturity;b) shows immature individuals as proxy for recruits; d) shows length converted to biomass of mature (red) and all fish (black); c) shows total mortality Z over the respective previous two years and scaled exploitation rate u+M, both as a proxies for F, with indication of M [MSFD_8.pdf].

a) b)

c)d)

CPUE by Length

North Sea dab: preliminary stock-recruitment relationship based on CPUE in weight as proxy biomass of mature fish and number of young fish (= proxy-recruits) two years later, derived from length composition in standardized survey catches. A hockey stick was fitted by a rule-based procedure. The dotted vertical line indicates proxy SSBpa as the precautionary borderline to potentially compromised recruitment. [MSFD_8.pdf]

CPUE by Length

North Sea dab. a)shows the raw data. The red line indicates individuals above 50% maturity;b) shows immature individuals as proxy for recruits; d) shows length converted to biomass of mature (red) and all fish (black); c) shows total mortality Z over the respective previous two years and scaled exploitation rate u+M, both as a proxies for F, with indication of M [MSFD_8.pdf].

a) b)

c)d)

Peak-Preview on New Assessment Method for MSFD-GES

Catch-MSY RevisitedMartell & 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.

Catch-MSY Improved

Minimizing uncertainty in r and k leads to an objective lower bound of r (blue line) and to an objective estimate of the maximum rate of population increase r = 0.42 and the corresponding unexploited biomass k.

Stock Status for Data-limited Stocks

North Sea cod: The black line shows the biomass predicted by the CMSY-method. The red line shows observed total biomass. The vertical blue lines show the prior biomass windows used asfilters by the CMSY-method. The upper dotted line represents the unexploited biomass k and the lower dotted line represents Bmsy, as estimated by CMSY.

k

Bmsy

Western Baltic Cod

Icelandic cod: The black line shows the biomass predicted by the CMSY-method. The red line shows observed total biomass. The vertical blue lines show the prior biomass windows used asfilters by the CMSY-method. The upper dashed line represents the unexploited biomass k, the middle dotted line represents Bmsy, and the lower dashed line represents Bpa.

k

Bmsy

Bpa

Exploitation Rate for Data-limited Stocks

Icelandic cod: exploitation rate catch/biomass as predicted by the CMSY method(black line) and as observed (red line). The dotted line represents a proxy for MSY-compatible exploitation.

umsy

Conclusions

• The new CFP contains many regulations in support of marine conservation

• For most data-limited stocks in the ICES area, DATRAS contains sufficient information to estimate LWR, growth, maturity and relative abundance, needed for proxy assessment

• Combining survey results with catch data leads to reasonable proxies for stock status and exploitation pressure

• The new Catch-MSY method will estimate MSFD reference points for most data-limited stocks