Transcript Developing tools for EBFM in Australia

Reviewing the harvest strategy for the
Commonwealth small pelagic fishery
Tony Smith
Hobart, October 17, 2014
CSIRO WEALTH FROM OCEANS FLAGSHIP
Outline
• What is a harvest strategy?
• The current SPF harvest strategy
• The review
• Results
• Next steps
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What is a harvest strategy?
A harvest strategy is the set of rules used to make decisions about
catch or effort levels in a fishery
• typically decisions are made every year, e.g. deciding on the
annual total allowable catch (TAC)
• the input to a harvest strategy is information on the current or
recent status of the stock
• a decision rule is used to translate stock status into a management
decision (catch level)
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The current SPF harvest strategy
• Input into the strategy is the latest egg survey estimate of stock
size for each stock
• There are three “tier” levels for the harvest strategy depending on
how recent the information is on stock size
• Tier 1: survey in last 5 years
• Tier 2: survey older than five years
• Tier 3: no recent survey
• The TAC is set using a harvest rate (HR) applied to the most recent
survey estimate – a proportion of that estimate
• e.g. Tier 2: the HR is 7.5%, so if the most recent stock size is
10,000t, the TAC would be750t
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The current SPF harvest strategy
For the current harvest strategy
• The Tier 1 HR averages 15% (steps 20, 17.5, 15, 12.5, 10 each year
as the survey ages)
• The Tier 2 HR is 7.5% (half Tier 1), with a maximum possible value
of 5,000 t
• The Tier 3 TAC is set at 500 tonnes
• In 2014-15, the harvest rate for all eastern stocks and for the
western blue mackerel stock is at or below 7.5% (Tier 2)
• In 2014-15, the harvest rate for western redbait and western jack
mackerel is capped at the 5,000 t limit for Tier 2
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The review
• The current SPF harvest strategy was adopted in 2009
• It is normal practice to review these every five years or so
• This review was funded by FRDC and CSIRO
• Two objectives:
1. Provide advice on best practice reference points for the four
main target species
2. Provide advice on suitable harvest rates to achieve management
objectives for the four main target species in the SPF*
* Note: east and west stocks considered separately
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Methods – objective 1
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Methods – objective 2
• Test different harvest strategies to see which ones best meet
management objectives (achieve targets and avoid limits)
• The targets (e.g. biomass relative to unfished biomass) will be
informed by results from objective 1
• The limits are specified in the Commonwealth Harvest Strategy
Policy – less than 10% chance of falling below 20% of unfished
biomass
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Results – objective 1
• Simulated different depletion levels for each stock and for all
stocks together
• Looked at how other species and trophic groups in the model
changed in abundance due to effects of fishing the SPF species
• Basic finding – minimal impact on predators and other species in
the ecosystem
• Why?
• No species rely entirely on SPF species
• Most predators are opportunistic feeders (eat what is available)
• From previous work – get bigger impacts of fishing krill or
mesopelagics (lantern fish, myctophids)
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Results – objective 2
• Looked at harvest rates that would result in a 50% chance of being
above or below B50 (half the unfished biomass)
• HR varies across the species:
•
•
•
•
Blue mackerel – 23%
Jack mackerel – 12%
Redbait – 10%
Sardine – 33%
• Taking account of uncertainties (probability of exceeding the
limits) could lower the values for blue mackerel and sardines slightly
• Tier 2 HR – still likely to be half that for Tier 1
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Next steps
• Draft report considered by the SPF resource assessment group
• Technical review of report by FRDC
• Advice to the management advisory committee and to AFMA
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Thank you
Oceans and Atmosphere
Research Flagship
Tony Smith
WEALTH FROM OCEANS