Transcript The management of small pelagic

The management of small
pelagics
The importance of small pelagics
Comprise the 1/3 of the total world landings
Comprise more than 50% of the total Mediterranean landings, while
Two species, anchovy and sardine, are the main target species
1200000
Total Catches of clupeoids in the Mediterranean and
Black Sea region
The main fisheries of small pelagics in the
Mediterranean are
 Purse seines
Trawls (mainly pelagic trawls,
prohibited in Greece)
Nets
Total Catches (mt)
1000000
800000
600000
Medit_clupeidae
Europ_Med_Clupeidae
400000
200000
0
1950
1956
1962
1968
1974
1980
Year
1986
1992
1998
2004
The importance of small pelagics
Small pelagics present a series of certain
characteristics that are very important for the
management of their resources
Present high abundances
Exhibit extended horizontal and vertical movements
Characterized by intermediate trophic level
Anchovy and sardine are characterized by short life span
(the bulk of individuals
found at sea are up to 3y old)
As a result their stocks present high annual variability in abundance
and age composition based on successful year recruitment.
Consequently their abundances are greatly affected by environmental
conditions
The importance of small pelagics
Comprise an important role in the energy flow of marine ecosystems,
linking plankton to top predators (wasp-waist control) thus consisting
“keystone” species in marine ecosystems
Upper TL (Bottom up
control)
Small pelagics
Lower TL (Top down control)
Consequently they are expected to be greatly affected by the climate
change
An effective management should be flexible depending on the
fluctuations of the stocks
Research areas/projects for an effective management of
small pelagics
1) Integrated assessment methods
The previous described characteristics raise a series of questions
regarding their assessment and the identification of the status of the
different stocks
The most effective monitoring programs are based on:
The in year monitoring of the stock by fisheries’ independent methods
(e.g. acoustics, DEPM).
The main drawback of these methods is the
difficulty to adopt reference points for the stock
Integrated assessment methods
This difficulty could be overcome by integrated assessment methods (e.g.
ICA, XSA)
 data obtained by fisheries e.g.
landings, ALK, Length frequency,
selectivity
integrated
 with the results from
fisheries independent
methods such as acoustics
or DEPM
In order to define reference
points, to obtain a more
effective diagnosis of the in
year status of the stocks
(e.g. SSB, abundance survey
indices at age, recruit
abundance, Z, E)
These methods are being applied in the Atlantic stocks and their
adaptation for the Mediterranean stocks will significantly improve the
management of small pelagics.
2) Determination and mapping of the spatial dynamics of small pelagics life
stages
High dependence of small pelagics due to their short life span from
the in year successful recruitment, which is strongly related to
environmental conditions, making them vulnerable to climate changes
For an effective management, the identification of geographical areas
that are important for the main life stages is crucial. These “critical
habitats” for the small pelagics are:
nursery areas
spawning areas
adults habitats
The spatial dynamics of the different life stages (i.e. their variability in
space and time) could imply the need for e.g. seasonal or temporal
closures of certain geographical areas
Identify the variability of the spatial occupation of preferential sites
across the years
mapping of the spatial dynamics
The identification of these areas could be achieved by:
• integrating existing and new knowledge on the distribution and
abundance of the species with
• satellite environmental data as well as
• field data.
This allows modeling and mapping of these “critical” spawning, juvenile
and adult habitats using advanced statistical analysis and GIS
techniques
Satellite data +
distribution of species
Regresion model : GAMs
2004
+
41o
40o
SST in oC
39o
38o
22o
23o
24o
25o
26o
27o
mapping of the spatial dynamics
By integrating knowledge of fish spatial distribution (based on existing
and new survey data) we can identify and use spatial indicators to
capture the variability of the spatial occupation of preferential sites
across the years and:
• Setting reference points useful for management or
• Constructing diagnostic tables where departures from reference
values may trigger alarm signals for the status of the stock in real time
3) Ecosystem approach of small pelagics’ fisheries management through
mass balance models
Small pelagic fish have a key role in pelagic ecosystems
• They are very abundant and control the biomass of both the lower
(zooplankton) and upper (top predators) trophic levels (“wasp-waist”)
• Their abundance and species composition is highly influenced by
environmental conditions
• Fisheries may substantially reduce the biomass of small pelagic fish also
affecting the other trophic levels (e.g. top predators)
Consequently effective management of small pelagic fish requires ecosystem
consideration.
Especially in the Mediterranean the multispecies nature of fisheries and the
high species richness raise the need for the application and improvement of
ecosystem approaches to fisheries management, with emphasis on the key –
role of small pelagics
This could be visualized by building “Mass Balance
Models”
Ecosystem approach of small pelagics’ fisheries management
The Ecosystem Approach could be very useful to:
• Assess the ecological role (e.g. trophic flows) of small pelagic fish
• Address different management scenarios and precautionary
measures
• Predict future changes in small pelagic fish abundance under specific
conditions (e.g. environmental conditions, levels of fishing effort) as
well as
• Investigate the effect of the adaptation of certain management
policies
Thank you for your attention!!