An ecosystem approach to coastal fisheries in Pacific island countries

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An ecosystem approach to coastal fisheriesin
Pacific island countries
Coastal Fisheries Policy and Planning Course,
28/01/08 8/02/08, Apia, Samoa

• byMichael KingBased on a presentation given at
  the HOF meeting in Noumea, 2007

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Starting from a basic system, a fishery is
A fish stock with an input of fishing effort and
an output of catch
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Conventional fisheries management
Controls on amount of fishing (eg licences) and
quantity of fish caught (eg quotas)
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However, a fishery is part of an ecosystem
The ecosystem will be affected by both fisheries
and non-fisheries impacts.
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an Ecosystem Approach to Fisheries (EAF)
Controls to protect ecosystems added to usual
controls on amount of fishing and quantity of
fish caught
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Both fishing activities and non-fishing
activities affect ecosystems
EAF is usually concerned with impacts of fishing
activities.However, many HOFs believe that
non-fisheries activities (eg sewage disposal,
coastal development) result in more harmful
impacts on coastal ecosystems
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Hard to distinguish between effects of
overfishing and environmental impacts on stock
sizes.No theories and models to help.
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What are the effects of negative impacts on
ecosystems?
Useful here to look at the factors that regulate
populations including fish stocks
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The regulation of populations
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Stock growth and biomass
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Effects of impacts on ecosystem
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The objective of EAF is thesustainable use of
marine ecosystems and management that
provides for present needs while allowing for
the needs of future generations. In Pacific
Islands, high rates of population increase means
this should be of great concern. Rates of about
4 pa in some islands will result in populations
doubling in less than 19 years!
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What are the key issues in EAF? These relate to
target species overfishingnon-target
speciesecosystem issues(including non-retained
species) environmental issuesfishing
communities societyLook at these issues in
detail
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Target species overfishing in which
recruitment cannot replace numbers lost.
.. but there may be an over-concern with
estimating stock parameters
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Stock assessment/yield curves usually done to
estimate optimum catches and fishing
effortHowever, yield curves 1. often require
more data than are available 2. may result in
optimistic estimates of yield/effort3. are less
useful in multispecies fisheries
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Yield curves can be drawn with minimal inputs
eg unexploited biomass population growth rate,
r
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Yield curves are less useful in multispecies
fisheries (less abundant species may be
overfished at overall fmey)
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One notable exception is a multispecies curve
based on AREA rather than TIME
Each point on graph represents mean catch per
area for different villages (with fishing
grounds that are similar ecologically)If 15
people per hectare represents the optimum fishing
effort, many village fishing grounds are
overexploited
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But, even if optimum effort yield can be
estimated, how can it be used?In many coastal
(particularly subsistence) fisheries,it is
difficult to control both ? the amount of
fishing done, and ? the quantity of fish
caughtALSO an EAF precautionary approach
suggests that the conservation of fish stocks
must be given priority over the optimisation of
fish catches.
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Conventional controls are used in the absence of
assessment examples Input controls on
fishing egsize limits widely used (even if
poorly enforced)gear controls eg banning of
SCUBA to catch lobsters Output controls on fish
caught egquotas quota on trochus in Cook
Islands set at 30-40 of stock (between 80 and
110 mm). this is good example of safe
precautionary limits applied in the absence of
formal stock assessment
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Non-target species are a world concern (here
discards are given as of total catch from FAO)
However, no trawls or dredges in PICs (except for
prawns in PNG)and tuna longlining not relevant
to coastal fisheries
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However, some issues withfish fences and
loosely-hung gill nets which are unselective
(and ghost fish when abandoned). In some PICs,
restrictions on number and mesh sizes
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Ecosystem issues include direct impactsby
damaging fishing methods (inc. dynamite
poisons).
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We must accept thattraditional fishing methods
can also cause damageGleaning on reef flats
Communal fish drives across reefsBreaking of
coral to catch small fish Use of plant-derived
fish poisonsIn the past, these methods caused
less damageONLY because fewer people were
involved.
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Global concern over selective removal of
speciesthat disrupt ecosystems (by affecting
predators prey)
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Commercial fisheries often target species from
one trophic level. However, artisanal fishers
target speciesfrom many different trophic
levels. and this may beless disruptive to
ecosystems.
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But there is no doubt that the removal of some
species will affect coral reef ecosystems.2
examples from the literature - the removal of .
? Parrotfishes will allow algae to grow and
smother corals. ? Triggerfishes etc will allows
urchin populations to increase and erode corals
faster than they can grow.
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Environmental issuesMany non-fisheries
activities have the potential to impact marine
ecosystems and fisheries.
Which ones are important in Pacific islands?
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Environmental impacts in PICsfrom questionnaires
0no effect 50moderate 100severe
Siltation, garbage dumps, nutrients result in
major impacts
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Siltation in coastal watersSources - forestry,
land-clearing, development, mining?Results -
smothered corals decreasing depths in lagoons
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Excessive nutrients in coastal watersSources -
human stock sewage, fertilizers?Results -
eutrophic conditions (high bacteria/low O2)
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Eutrophic conditions are associated with- fish
kills (caused by low O2 ), excessive plant
growth ? corals in lagoons replaced by
seagrasses ? abrasion of corals (eg by
Sargassum).
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Excessive nutrients result in high abundance of
dinoflagellates and harmful algal blooms (HABs)
including those responsible for ciguatera.
Toxins produced by some dinoflagellates (eg
Karenia spp) produce airbourne toxins causing
asthma-like symptoms in people - eg Cook
Islands.47 of all countries reported some
increase in HABs
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Key points are that ?Many of the
environmental issues that impact coastal
ecosystems(forestry, development, sewage systems
etc) are beyond the control of government
fisheries agencies. AND ? Controls on fishing and
ecosystems are difficult to apply (and
especially enforce)in rural fishing communities.
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There is, therefore, a need to extend the
management base for EAF to include ? Fishing
communities that have Vested interest in
sustainable seafood stocks Knowledge of threats
solutions Traditional control (often) of adjacent
coastlines. ? Other government agencies that
have Responsibility for many non-fisheries
activities that affect marine ecosystems.Many
communities and non-fisheries agencies are
already contributing to solutions in EAF issues
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Example of community input Problem
Availability of cheap underwater torches allowed
spearing of sleeping fish at night Result -
large breeding fish removed- devastated fish
stocks Solution - method banned by some villages
under CBFM
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Example of environmental agency input into
EAF Problem Uncontrolled coastal
developmentResult Increase in silt loss of
fish habitatsSolution Environmental impact
assessments (EIAs)required before each new
project or development - must include government
projects main offenders? (eg habitat loss -
over 25 of wetlands in Tutuila in A.Samoa)
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How can the management base be extended?
Perhaps management advisory committees (?)with
members from Fishing communities? Environmental
agencies? Other relevant government
agencies? NGOs with environmental interests? SPC
is working in this area commendable example in
Marshall Islands fisheries are managed by
representatives from fisheries, environment,
education etc
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A consultative process is needed to identify and
give priority to important issues- score
1(minor impact) to 4 (extreme impact) in columns
2 and 3)
Issue Consequence to local area Consequence to entire ecosystem Total impact(column 2 times col.3)
Rubbish dumps near coast 4 2 8
Siltation of lagoonsetc. 2 3 6
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For each priority issue - set objectives, targets
and propose management actions
Objective Target and limit Indicator Management actions
To maintain the spawning stock at level at which the risk of stock collapse is minimised. Target 11 fish per100 m2 Limit 6 fish per100 m2 Density from underwater visual census surveys a) Enforce size limitsb) Reduce fishing effortc) Impose closed seasons
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The indicator (abundance of mature individuals)
can be plotted over time.Example - indicator
drops below limit in year 7and triggers strong
management actions eg reduce fishing effort,
closed seasons etc
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EAF objectives can be also be devised for
ecological, economic and social issues.One
objective covering both biological and ecosystem
issues relates to protecting some part of an
entire ecosystem from exploitation.Marine
Protected Areas (MPAs) are widely used to
address this objective.MPAs are a moderate to
very high priority in 86 of all countries
surveyed.
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MPAs may protect stocks from the effects of
environmental fluctuations.
? fluctuations may cause an exploited stock to
crash - to drop below the number required to
successfully reproduce (Allee effect) ?a pool of
individuals in an MPA may avoid this
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In MPAs larvae settle within its boundaries (self
recruitment) or disperse within an
envelope.Juveniles and adults may spillover
from MPA.
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In conclusion ? The view of fisheries managers
is that non-fisheries activities are affecting
ecosystems and fish stocks. ? Many countries
regard communities as key stakeholders (many
have implemented CBFM with SPC assistance).To
implement EAF, this emphasises the need to
involve ? relevant government Agencies ?
fishing communities Much work is being done by
SPC to involve both. Also, a regional meeting
was proposed (in 2003) to involve
representatives from environment as well as
fisheries agencies.
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Exercise on EAF based on figure below.- break
into 4 groups (Advisory panels)to do this
exercise)
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1) Possible causes of environmental
degradationExamine illustration and list issues
and possible causes(Siltation and eutrophication
are priority issues)
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2) How could impacts be reduced and
controlled?Propose actions/controls that would
reduce impacts on marine ecosystems
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3. How could effects be assessed? set objectives
the expected resulttargets limits
desirable undesirable positionsindicators a
measurable indication of performance
Objective(example) Target and limit Indicator Managementactions
To reduce levels of TBT in sea to a level that does not affect marine life. Target 6? ppm Limit 11? ppm Concentration of TBT in sea water.
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Effects of actions could be monitoredbased on
the use of indicators and reference levels.
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4. Additional management actionslist management
actions in increasing order of severity
Objective(example) Target and limit Indicator Management actions
To reduce levels of TBT in sea to a level that does not affect marine life. Target 6? ppm Limit 11? ppm Concentration of TBT in sea water. a) Ban use of TBT on local boatsb) Ban foreign vessels using TBT
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In example Year 0 - local use of TBT
bannedYear 4 entry of foreign vessels using
TBT banned