Transcript Illex argentinus

Remotely sensed spatial dynamics of the
Illex argentinus fishery, Southwest Atlantic
西南大西洋遙測阿根廷魷漁業
時空動態之研究
Claire M. Waluda ∗, Huw J. Griffiths, Paul G. Rodhouse
Fisheries Research 91 (2008) 196-202
Reporter: 凌子雅
Introduction
Atlantic
Ocean
22°S
54°S
Illex argentinus
Defence Meteorological Satellite Program-Operational Linescan System (DMSP-OLS)
http://www.daviddarling.info/encyclopedia/D/DMSP.html
> 300 kW
Objective
 This work examines inter-annual variability
in the distribution of the fishery over the
13-year period 1993-2005.
 The area occupied by the fleet is compared
with variability in catches over the same
period.
Materials and Methods
1. Data sources
 DMSP-OLS data
( Defence
Meteorological Satellite Program-Operational Linescan System data )
 Fishery data
2. Analyses
 Presence of fishing lights over the Patagonian shelf
 Inter-annual variability in the spatial distribution of
fishery
 Relationship between fished area and catch
DMSP-OLS data
Period: January to August 1993-2005
Time: 23:00 - 03:00 local time
Region: the Patagonian Shelf, Southwest Atlantic
Resolution: approximately 2.7 km
Images: 496 (five single-pass images per month)
National Geophysical Data Center (NGDC)
Geographical Information System (GIS)
DMSP-OLS data
•
Digital number (DN) values:
0 (no radiance) to 63 (saturated radiance)
•
DN value of ≥ 30
lights from vessels
lights reflected from the ocean surface
Fishery data
• Source:
from the Food and Agriculture Organization
(FAO)
• Period: 1993-2005
• Region: the Patagonian shelf
• Data: annual catch
Presence of fishing lights over
the Patagonian shelf
• This data composite was then used to identify
the extent of the fishery and the distribution
of areas of high and low fishing activity
during the period 1993-2005.
• The percentage frequency of occupation of
each grid cell calculated for the 13-year period
of the study.
Inter-annual variability in the spatial
distribution of fishery
PRIMER 5:
 inter-annual variability in the distribution of the
light-fishing fleet
Bray-Curtis similarities:
 distributional similarity between years
Hovmoller plot:
 fleet variability in the spatial extent and abundance
of the fleet over time and latitude
Relationship between fished area and catch
Regression analyses :
 examine relationships between annual
catch and the total fished area over the
period 1993-2005
Results
15%
13%
7%
Fig. 1. Distribution of fishing lights targeting Illex argentinus on the Patagonian Shelf,
Southwest Atlantic, obtained from the Defence Meteorological Satellite Program-Operational
Linescan System (DMSP-OLS) for the period 1993-2005. Legend indicates the number of years
in which fishing took place in each 2.7 km grid square.
15%
13%
7%
Fig. 1.
Fig. 2. Frequency of occupation (number of years that fishing occurred in each grid cell based
on 27 by 27 km grid cells) of the Patagonian shelf region by the I. argentinus light-fishing fleet,
1993-2005.
< 35%
50%
Fig. 3. Percentage inter-annual Bray-Curtis similarity of the geographic distribution
of fishing lights of the I. argentinus fleet on the Patagonian shelf, 1993-2005.
smaller
smaller
Fig. 1.
Fig. 4. Inter-annual variability in the latitudinal extent of the I. argentinus fishing fleet on the
Patagonian shelf (calculated as the proportion of the maximum lit area for each 27 km latitude
band; n = 90). Legend shows the percentage occupation of each latitudinal band by the fleet in
each year, 1993-2005.
19992001
log catch
area fished
2004
2005
Regression line
95% CI
Fig. 5. (a) Annual variability in catch (log tonnes; open circles, dashed line) and area fished (km2;
closed circles, solid line) for the period 1993-2005. (b) The area occupied by the fishery (km2) vs.
the total catch (log tonnes) for the corresponding year. (—) Regression line (R2 = 0.62); (- - -)
95% confidence intervals. (Regression equation: log catch = 4.02 + 0.000159×area fished (km2)).
Discussion
28%
Opportunistic
(Rodhouse and
• shelf break (200 m contour)
Nigmatullin, 1996)
• without a license
11% ~ 35% of the total stock
(FAO, 1994)
45°S
10% ~ 28% of the total lit area
47°S
80% of the total catch
33% of the total fished area
high productivity
(Ciechomski and Sanchez, 1983;
Bertolotti et al., 1996)
feeding aggregations of squid
Falkland current
(Waluda et al., 2001b; Sacau et al., 2005; Arkhipkin et al., 2006)
Fig. 1. Distribution of fishing lights targeting Illex argentinus on the Patagonian Shelf,
Southwest Atlantic, obtained from the Defence Meteorological Satellite Program-Operational
Linescan System (DMSP-OLS) for the period 1993-2005. Legend indicates the number of years
in which fishing took place in each 2.7 km grid square.
 most profitable fishery areas in any 1 year
< 35%
50%
Fig. 3. Percentage inter-annual Bray-Curtis similarity of the geographic distribution
of fishing lights of the I. argentinus fleet on the Patagonian shelf, 1993-2005.
Fig. 1. Distribution of fishing lights targeting Illex argentinus on the Patagonian Shelf,
Southwest Atlantic, obtained from the Defence Meteorological Satellite Program-Operational
Linescan System (DMSP-OLS) for the period 1993-2005. Legend indicates the number of years
in which fishing took place in each 2.7 km grid square.
smaller
log catch
area fished
smaller
Fig. 5. (a) Annual variability in catch (log tonnes) and
area fished (km2) for the period 1993-2005.
Fig. 4. Inter-annual variability in the latitudinal extent of the I. argentinus fishing fleet on the Patagonian shelf. Legend
shows the percentage occupation of each latitudinal band by the fleet in each year, 1993-2005.
 a reduction of squid in the southern part of the species range has the greatest effect
on the overall size of the fishery
 variability to the north of 47◦S had less overall effect on the reported catch
Illex argentinus
• thermal gradient regions occurring between
different water masses (Brunetti et al., 1998a; Waluda et al., 1999,
2001a,b; Bazzino et al., 2005; Sacau et al., 2005)
• feeding aggregations of squid occurring at
these fronts
• different depths dependent on water
temperature variability (Bazzino et al., 2005; Sacau et al., 2005)
variable distribution of the fleet over the 13
years
• Sea surface temperatures in the inferred hatching
region during June and July of 2003 and 2004 were
0.4 and 0.9◦C warmer than average, respectively
(over the period 1986-2005; BAS, unpublished
data), which may have partially contributed to the
reduced fishery yield during 2004 and 2005.
• Despite the very low catches in 2004 and 2005 the
fishery has recently shown some signs of recovery
with catches of over 85,000 tonnes recorded from
Falkland Islands waters in 2006.
 short-lived, fast growing (Rodhouse, 2001)
conclusion
 long-term monitoring of this highly variable squid fishery
Fig. 1. Distribution of fishing lights targeting Illex argentinus on the Patagonian Shelf,
Southwest Atlantic, obtained from the Defence Meteorological Satellite Program-Operational
Linescan System (DMSP-OLS) for the period 1993-2005. Legend indicates the number of years
in which fishing took place in each 2.7 km grid square.
Prospective
• I. argentinus is a major component of the
Patagonian shelf food web, it is vitally important
to manage the whole of the I. argentinus
population in the region.
• If this area is to be managed effectively, the
whole of the species range must be considered in
any stock management plan.
Thank you
for your attention!