Transcript Spanish Acoustic Surveys - Analysis of the Fish Pelagic Community

SPANISH ACOUSTIC
SURVEYS:
ANALYSIS OF THE FISH PELAGIC
COMMUNITY
M. Iglesias, M.B. Santos, C. Porteiro, M. Bernal,
F. Ramos, D. Oñate, A. Giráldez, E. Nogueira, N.
Díaz, P. Tugores, G.J Pierce & J. Miquel
• The Ecosystem Approach requires joined-up thinking in fisheries,
building from traditional framework of target species up to
communities, populations, ecosystems, and the interaction with
humans.
• In Spain, acoustic research surveys have traditionally been used to
evaluate and monitor the population of commercially important
pelagic fish species such as sardine (Sardina pilchardus) and
anchovy (Engraulis encrasicolus).
• These surveys have been carried out annually both in the
Mediterranean and Atlantic coasts since the 1980s collecting
acoustic and hydrographic data and lately also information on
distribution and abundance of top predators.
Four acoustic surveys are
carried out annually in Spain,
covering the shelf (20 to 200
m).
PELACUS spring, which was
developed to estimate the
spawning stock biomass
(SSB) of sardine in northern
waters (since 1986).
FRA NCE
Ca n ta b ri c S e a
PELACUS
spring
Tr am u n ta n a
A tla n tic
O ce a n
SP A IN
M
ed
ite
rr
an
ea
n
Se
a
P O R TU G A L
G u lf o f
C a d iz
A lb o ra n S e a
MO RO C CO
ARG E L IA
Four acoustic surveys are
carried out annually in Spain,
covering the shelf (20 to 200
m).
PELACUS spring, which was
developed to estimate the
spawning stock biomass
(SSB) of sardine in northern
waters (since 1986).
ECOCADIZ which started in
2004 to monitor SSB of
anchovy in the Gulf of Cadiz
FRA NCE
Ca n ta b ri c S e a
PELACUS
spring
Tr am u n ta n a
A tla n tic
O ce a n
SP A IN
M
ed
ite
rr
an
ea
n
Se
a
P O R TU G A L
G u lf o f
C a d iz
A lb o ra n S e a
ECOCADIZ
MO RO C CO
ARG E L IA
PELACUS
autumn
FRA NCE
Ca n ta b ri c S e a
PELACUS
spring
Tr am u n ta n a
A tla n tic
O ce a n
SP A IN
M
ed
ite
rr
an
ea
n
Se
a
P O R TU G A L
G u lf o f
C a d iz
A lb o ra n S e a
ECOCADIZ
MO RO C CO
ARG E L IA
Four acoustic surveys are
carried out annually in Spain,
covering the shelf (20 to 200
m).
PELACUS spring, which was
developed to estimate the
spawning stock biomass
(SSB) of sardine in northern
waters.
ECOCADIZ which started in
2004 to monitor SSB of
anchovy in the Gulf of Cadiz
PELACUS autumn which
started in 2006 to obtain an
index of the anchovy juvenile
stock in the Bay of Biscay.
PELACUS
autumn
FRA NCE
Ca n ta b ri c S e a
PELACUS
spring
Tr am u n ta n a
A tla n tic
O ce a n
G u lf o f
C a d iz
ed
ite
rr
an
ea
n
M
E
C
O
M
E
P O R TU G A L
Se
a
D
SP A IN
A lb o ra n S e a
ECOCADIZ
MO RO C CO
ARG E L IA
Four acoustic surveys are
carried out annually in Spain,
covering the shelf (20 to 200
m).
PELACUS spring, which was
developed to estimate the
spawning stock biomass
(SSB) of sardine in northern
waters (since 1990).
ECOCADIZ which started in
2004 to monitor SSB of
anchovy in the Gulf of Cadiz.
PELACUS autumn which
started in 2006 to obtain an
index of the anchovy juvenile
stock in the Bay of Biscay.
ECOMED,
which
was
implemented to obtain a
recruitment
index
for
anchovy in Mediterranean
waters (since 1990).
Material and Methods
Acoustic and biological sampling
-R/V
Thalassa (northern waters) and Cornide de Saavedra (Gulf of
Cadiz and Mediterranean).
- Echo-sounder at 38 kHz, calibrated prior to each survey (Foote et
al., 1987).
- Complementary frequencies (18, 70, 120 and 200 kHz).
Transects perpendicular to the coast and evenly spaced (4 – 8 nm),
constant speed (10 knots) from dusk till dawn.
-Pelagic trawls at daytime (Cantabrian coast and Gulf of Cadiz) or at
night (Mediterranean).
Material and Methods
Data processing
• Acoustic data is post-processed using SonarData Echoview©.
• Fish density integrated by nm and expressed in NASC (m2 x nm
2) (MacLennan et al., 2002).
• Energy split into species following their proportions in the trawls.
• Length frequency distributions are obtained for all fish species in
the trawl.
• Length-weight relationships are obtained for the main pelagic
species.
Material and Methods
Complementary data
•Sampling of fish communities (trawl stations)
•Hydrography and hydrodynamics (rosettes and CTD)
•Ichthyoplankton (Continuous Underwater Fish Egg Sampler) and
•Visual censuses of top predators (marine mammals and seabirds).
Results
There has been a decline in both abundance and distribution area of sardine in the
Cantabrian Sea. ..
2007
2006
2005
2004
2003
#
#
Ortigueir a#
Cedeira
#
Bur ela
Viveiro
#
Ferr ol
Foz
#
#
Ribadeo
#
Pontedeume
#
#
A CORUÑA
Malpica
#
Betanzos
Luar ca
#
Cudiller o
#
GIJÓN
#
Villaviciosa
#
#
Ribadesella
#
#
#
Llanes
#
#
San Vicente
de la Barquera
#
SANTANDER
Santillana
Santoña
del Mar
Ber meo
BILBAO
1 - 100
101 - 350
351 - 650
651 - 1200
1201 - 2218
#
Muxía
Cabo F isterr a
#
#
Noia
Mur os
#
Villagarcía
de Arousa
#
#
#
PONTEVEDR A
Vigo
#
Baiona
A Guardia
#
#
#
#
Irún
#
Zumaia
SAN
SEBASTIÁN
Results
...and anchovy in Northern Mediterranean (Tramontana region).
Rosas
#
Blanes
#
BAR CELONA
#
TARR AGON A
#
San Carlos de la Rápita
#
Vinaroz
Torreblanc a
CASTELLÓN
#
#
#
El Puerto
#
VALEN CIA
2 - 10
11 - 60
61 - 120
121 - 350
351 - 544
#
Suec a
#
Gandía
#
2003
2004
2005
2006
2007
Results
Results from the 2007 surveys, when all main fish species were evaluated acoustically,
show that the most abundant species were:
- sardine (Sp), mackerel (Ss) and horse mackerel (Tt) in the northern waters
- anchovy (Ee), sardine and chub mackerel (Sc) in the Gulf of Cadiz
-sardine, anchovy, Mediterranean horse mackerel (Tm) and bogue (Bb) in the
Mediterranean.
PELACUS
Q
6
(10 ind)
B
(t)
TL
(cm)
ECOCADIZ
Q
6
(10 ind)
B
(t)
TL
(cm)
ECOMED
Q
6
(10 ind)
B
(t)
TL
(cm)
Sp
1 482
96 390
19.9
1 699
86 777
17.3
750
15 298
13.9
Ee
127
2 861
14.8
1 790
28 882
13.2
971
4 906
9.2
Ss
749
198 801
32.3
3
381
24.8
-
-
-
Sc
38
6 957
27.7
788
61530
20.8
10
2 593
30.6
Tt
243
31 962
24.7
47
2 425
17.7
11
448
16.8
Tp
33
2 147
19.5
109
3 853
15.7
23
1 690
21.0
Tm
-
-
-
24
1862
20.3
390
16 312
16.3
Bb
82
14 840
26.5
41
2 836
18.9
263
11 984
15.8
Sa
-
-
-
0
49
30.9
89
4 311
18.3
Mp
140
4 920
18.2
-
-
-
-
-
-
Ca
2 327
147 591
14.1
-
-
-
-
-
-
-
506 469
-
-
188 595
-
-
57 542
-
Species
Total
Results
The lowest fish biomass per squared nautical mile was estimated for the
Mediterranean.
In the Mediterranean, where the longer time series exists, there have been changes in
the relative proportion of target/non-target species in the survey. The Simpson´s index
indicates that species have become more evenly distributed .
100
S. aurita
80
B. boops
60
Trachurus spp.
Scomber spp.
40
E. encrasicolus
20
S. pilchardus
0
0.90
2003
2004
2005
2006
12000
2007
0.80
10000
0.70
0.60
8000
0.50
6000
Simpson´s index
Total abundance
0.40
0.30
4000
0.20
2000
0.10
0.00
0
2003
2004
2005
2006
2007
Discussion
Acoustic surveys constitute ideal platforms for the integrated monitoring of
pelagic communities and ecosystems. Data on abundance, distribution and
behavior of pelagic species can be collected systematically and geo-referenced,
at the same temporal and spatial scales as environmental data.
Historically, surveys monitored changes in abundance of commercially important
species. By collecting data on other components of the community we can
monitor changes at community level.
Fishing removes important amounts of small pelagic fish in Spanish waters and
this selective removal of species and in many cases size-classes can cause
changes in pelagic community structure and functioning (Pauly et al., 1998).
As we have shown, some of these changes have already taken place in the
abundance and distribution of some species both in northern and
Mediterranean Spanish waters, and the influence of fishing and environmental
changes should be assessed.
Discussion
In the Mediterranean, an oligotrophic environment, pelagic species are
becoming more evenly distributed and there is a substantial reduction in total
biomass.
Parallel changes can be observed in fisheries landings. Total fish landings have
decreased but number of exploited species is on the increase.
An increase in evenness implies a higher diversity, higher diversity in an
exploited ecosystem can be explained by the Intermediate Disturbance
Hypothesis (Huston, 1994) which states that disturbance (e.g. exploitation)
prevents competitive exclusion and therefore systems at intermediate levels of
disturbance possess highest diversity.
Future work
- Historical analysis of long time series of acoustic data to obtain estimates of
non-target species.
- Study the temporal and spatial dynamics of non-target species.
- Explore alternative biodiversity indexes and other ecosystem metrics to
monitor changes at ecosystem level in Spanish waters.
- Application of hydrodynamics - Nutrient Phytoplankton Zooplankton - fish
community coupled models to disentangle the effects of climate variability and
fisheries on the community.
Acknowledgements
We would like to thank all the crew and participants in the surveys.