Transcript Ecosystem monitoring and indicators

Ecosystem monitoring
and indicators
Valerie Allain
SPC- OFP
Ecosystem Monitoring and Analyses
WHAT DO THE TEXTS SAY?
During the past few decades implementation of an
Ecosystem Approach to Fisheries Management
(EAFM) has been promoted.
The FAO Code of conduct for Responsible fisheries
states that fisheries management should ensure
the conservation not only of target species, but
also sympatric non-target species.
This resolution is now explicit in most Regional
Fisheries Management Organisation (RFMO)
conventions including the Western and Central
Pacific Fisheries Commission (WCPFC).
The WCPFC convention also states that:
- improved knowledge should be acquired for
marine ecosystems and populations of non-target,
associated and dependent species
- the impacts of natural factors and human
activities should be assessed
- monitoring should be continued or implemented
- and conservation and management measures and
recommendations should be adopted.
WHERE ARE WE AT?
In single-species management measures based
on stock assessment models such as FMSY can
guide management decision.
Analogous indices for non-target species and
ecosystem are needed to implement EAFM
These indices are needed to assess overall
ecosystem status, the impacts of human
activities, and environmental variation
They are in a nascent stage of development
INTERNATIONAL WORKSHOP
International workshop on opportunities for
Ecosystem Approaches to Fisheries Management in
the Pacific Ocean tuna fisheries
SPC, Noumea
28 March –1 April 2011
During the workshop, scientific information
available from RFMOs and the main scientific
organizations were synthesized into 14
presentations which included:
-time series of catches (target and non-target),
effort
-length-frequencies
-observer data
-potential ecosystem metrics
-information on trophic structure and mid-trophic
levels
-ecosystem models assimilating these data.
SOME RESULTS AND INDICATORS
DEMONSTRATING CHANGES IN
THE ECOSYSTEM
Time-series analyses showed changes in ecosystem
structure in the central North Pacific subtropical
pelagic ecosystem.
At the base of the ecosystem, cholorophyll data
demonstrated that oligotrophic centers of the
subtropical gyres in the Pacific have expanded in
area by 2-4%/yr over the past decade.
Polovina
At the top of the ecosystem, time-series of
observer and logbook data from the Hawaii-based
longline fishery showed an increase in catch rates
of mid-trophic fishes concurrent with the declines
in catch rates of apex predators
Polovina
Decadal-scale diet shift in
yellowfin tuna in the
Eastern Pacific
Set
Locations
Olson
1990
s2000
s
Mean proportion W (± 95%CI)
During the intervening decade, a suite of epipelagic
fishes declined from dietary dominance and were
largely replaced by mesopelagic fishes and
cephalopods
0.50
1992-1994 Dieg
Diet composition
composition
Dietcomposition
composition
2003-2005 Diet
0.40
0.30
0.20
0.10
0.00
Olson
Auxis spp.
Jumbo squid
Mesopel. fishes
Epipel. fishes
Calculation of
ecosystem
indicators based on
Ecopath models
including trophic
structure
Griffiths
6
Lg. sharks
Swordfish
Bigeye
tuna
Striped
Marlin
Yellowfin
tuna
5
Lg. Mesopelagic
Fishes
Juv.
Swordfish
Juv. Bigeye
tuna
Blue
Marlin
Med. Scombrids
& Dolphinfish
Albacore
Tuna
Trophic level
Opah
4
Med. Mesopelagic
fishes
Juv. Yellowfin
tuna
Pelagic Triggerfishes
& Pufferfishes
Small Clupeids
& Engraulids
3
Black
Marlin
Short-billed
Spearfish
Lancetfish
Skipjack
tuna
Sm. Scombrids
& Carangids
Blue
shark
Mackerel
sharks
Toothed
whales
Hammerhead
sharks
Lg. Mesopelagic
squids
Epipelagic
squids
Southern
Bluefin tuna
Med. Mesopelagic
squids
Sm. Mesopelagic
squids
Sea
birds
Sm. Mesopelagic
fishes
Micronekton
fishes
Mesopelagic
crustaceans
Epipelagic
Beloniform fishes
Leatherback
turtle
2
1
Griffiths
Juv. Southern
Bluefin tuna
Sunfish
Green sea
turtle
Epipelagic
zooplankton
Gelatinous
zooplankton
Primary
producers
Detritus
Mesopelagic
zooplankton
Ecosystem indicators – Structural indices
• Degree (number of direct connections to
other species)
• Betweenness centrality
• Closest centrality
• Topological importance
Griffiths
Ecosystem indicators – Functional indices
• Community importance (CI)
• Community Longevity Support (CLS)
• Interaction Strength Index (ISI)
• ‘Keystone’ index or ‘Keystoneness’
– The relative importance of a species
• Trophic level of the catch
• Fishing-in-balance index (FiB)
• Mixed Trophic Impact
Griffiths
SOME CONCLUSIONS
• Food-web models can produce various
indicators particularly relevant to EAFM.
• However the validity of the results is highly
dependent upon the extent to which the
model represents the system.
• Better ecosystem (food web) models are
needed (spatially-explicit) with good speciesand regionally-specific data and calibration to
reliable long time series.
• Research on pelagic food webs is progressing
and stomach contents analyses are still
necessary (monitoring indicator prey species).
• There is no panacea or “silver bullet” for
ecosystem indicators
• “Of the many hundreds of potential indicators
that exist or have been proposed, it is not yet
clear which ones achieve this purpose.” (Fulton
et al. 2004)
• A combination of indices will be required to
capture the range of intricate changes in an
ecosystem
• Ecosystem indicators should always be
interpreted along with fishing and
environmental indicators
• Local expertise with extended knowledge of the
ecosystem functioning is critical for identifying
data bias and for separating fishing from
environmental effects
Future Opportunities and Priorities
1. Complete a basin wide ocean monitoring
system to support EAFM across the pelagic
tropical and subtropical Pacific Ocean.
Extended observer coverage can provide a
spatially explicit catch time-series of target and
non-target species and operational level
information. Would supply comprehensive
catch information for the upper trophic levels
for inclusion in ecosystem models as well as
species-specific analyses.
2. Detailed ecological analyses of observer data
available in the region should be
implemented to understand the influence of
environmental and fishing effects and to
identify potential changes in the upper
trophic levels.
3. Comparison of trophic models would be
highly beneficial to ascertain the degree of
difference in the function and structure of
the ecosystems described across the Pacific
Ocean.
This comparison would assist in developing a
candidate list of indices that could potentially
be used by fisheries managers to assess the
status of the Pacific Ocean ecosystems and
the differential traits of Pacific Ocean marine
food webs.
4. These models would also benefit from time
series of the composition and biomass
estimates of mid-trophic level organisms.
Enhanced collection of data on these
organisms through standardised acoustic
surveys should be encouraged. Predatory
fishes are also effective ‘biological samplers’ of
this forage and the expanding temporal and
spatial coverage of observers across the Pacific
Ocean provides an opportunity for the
systematic sampling of mid-trophic levels via
the stomach contents.
5. Analyses to identify dynamic oceanographic
biomes are an immediate priority. Subsequent
analysis to associate these biomes with tuna
size patterns, growth rates, bycatch
composition, diet composition, fat content and
stable isotope signatures would provide the
spatial template necessary for future sampling
programs.