Geoscience Reference
In-Depth Information
35
30
25
20
15
10
5
0
10
0
10
2
10
3
10
4
10
1
Sampling effort
Figure 2
Sampling effort curve: y-axis represents the cumulative number of prey
species as a function of sampling effort for each of the 10 most common fish species.
The number of new prey species is still growing even after a sampling of more than
1000 individuals for some species.
Sampling sites were located at Tarfia (36
57
0
30
00
N-6
10
0
37
00
W), in the oligo-
haline estuarine region (mean
8.8
NTU, nephelometer turbidity units), Esparraguera (36
54
0
6
00
N-6
16
0
12
00
W), in
the mesohaline
SE salinity
¼
3.7
0.3 and turbidity
¼
74.9
estuarine
region (mean
SE salinity
¼
8.5
0.8
and
7.2 NTU), and Bonanza (36
52
0
2
00
N-6
20
0
53
00
W),
turbidity
¼
69.3
in the
polyhaline region (mean
5.2
NTU), situated at 32, 20 and 8 km, respectively, from the river's mouth,
with all sampling sites approximately being 3 m in depth at low tide. The
temperature was spatially homogeneous throughout the estuary (mean
SE salinity
¼
19.9
1.5 and turbidity
¼
42.3
SE
0.8
C at Tarfia and Bonanza, respectively)
but with amarked seasonal variation (mean
temperature
¼
19.4
0.8 and 19.3
SE temperature
¼
10.5
0.18 and
0.25
C in January and August, respectively).
27.1
2. Predator Stomach Content and Estimation of Predator-Prey
Abundance
Stomach contents and estimations of abundance in the three stations were
collected from February 1998 to January 1999 (12 months) following
the periodicity associated with the lunar cycle (
Bald ´ and Drake, 2002;
