Biology Reference
In-Depth Information
Table 1
.
Types of driftnet used by the artisan fishing fleet in the Amazonian estuary.
Mesh size in centimeters (cm), length of net (ft) and net thread gauge (TG) in
millimeters (mm) are displayed. Single-threaded (S)
and multi-threaded nets are included.
Net Type
Target Species
Mesh(cm)
Length(ft)
TG(mm)
Serrera
Scombridae
5-10
400-1.000
60 (S)
Douradera
Brachyplatystoma flavicans
Brachyplatystoma vaillantii
14-20
400-3.500
23-35 (M)
Pescadera
Arius parkeri
Cynoscion acoupa
16-22
400-3.500
36-48 (M)
Tiburonera
Sharks
40
1.500-2.000
96 (M)
Fishing Vessel Characteristics and Size of Fishing Crew
Fishing vessel characteristics and crew size varied greatly among fishing vessels both
between and within strata. The average values for vessel length, engine power, hole capacity
and crew size were all greater in stratum one compared to stratum two. Of course differences
between strata were artificially created by the experimental design. In stratum one, vessel
length varied from 6 to 11.8 m (
n
= 145,
x
= 8.9 m, ± 1.26 m), engine horse power between
9 and 160 (mode =18 HP) and, the hole capacity varied from 0.2 to 9 tons of ice (
x
=4.9 t ±
1.83 t). Fishing crew size varied from 2 and 7 men (mode = 4 men) and fishing nets were
between 400 and 2,500 ft long (
x
=750 ft ±308.65 ft) in stratum one.
Length of vessel in stratum two ranged between 12 and 32 m (
n
= 44,
x
= 14.9 m, ± 3.57
m). Their engine horse power and hole capacity ranged from 18 and 230 (mode =69 HP) and
from 1.5 to 35 tones (
x
= 12.4 t ± 6.51 t) respectively. The size of fishing crew (4 -12 men;
mode = 8 men) and length of nets used (900 - 3,500 ft;
x
= 2027.5 ft ±508.31 ft) also varied
greatly in stratum two.
Method of Fishing
.
Gillnets were released in the water from the bow, with the aid of a
power engine and in the same direction of the wind and tide. A fisherman released the net
while another fisherman set the float line to determine at which depth the net would do its
work. After drifting for 5 to 6 h, during the tidal period, the net was pulled in by a fisherman,
while a second fisherman pulled out the fish from the net, and a third fisherman gathered the
net and coiled the line.
Fishing capacity and fishing effort
.
The estimated variable, number of fishermen,
presented the best correlation coefficient with fish capture (
n
= 927;
r
= 0.888;
r
2
= 0.789;
P
<0,05). Fishing effort units were defined as netting time divided by number of
fishermen.
There was a significant correlation between capture and fishing effort measures, however, the
determination coefficient (
r
2
) for each stratum was low. This implies that there were other
factors acting in the capture which were not being considered.
Fishing trip
.
During the first sampling period (oct/96 to mar/97) 440 fishing trips were
registered (350 in stratum one and 90 in stratum two). In the second period of sampling
(Jan/99 to sept/01) 927 fishing trips were registered (590 in stratum one and 337 in stratum
two). The distribution of fishing trips across months and years is displayed in Table 2.
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