A Snapshot of the Tropical Tuna Purse Seine Large-Scale Fishing ...
A Snapshot of the Tropical Tuna Purse Seine Large-Scale Fishing ... A Snapshot of the Tropical Tuna Purse Seine Large-Scale Fishing ...
3.2.2 FHV vs FCC The relationship between FHV (m 3 ) and FCC (tonnes) was linear (Figure 3): FHV=1.2269*FCC (n=230, R 2 =0.91) Figure 3. Relationship between FHV (m 3 ) and FCC (tonnes). 3.2.3 FHV vs LOA The relationship between FHV (m 3 ) and LOA (m) followed a function of the form (Figure 4): FHV = 0.472*LOA 1.873 (n=506, R 2 =0.78) There is also considerable variability in this relationship. The correlation between FHV and LOA is not as strong as that between GRT and LOA, or between FHV and FCC. There is a group of vessels in the 30-40 m size range that appear to be outliers, though this possibility could not be confirmed using the available data. 6
Figure 4. Relationship between between FHV (m 3 ) and LOA (m). 3.2.4 FHV vs GRT The relationship between FHV (m 3 ) and GRT (tonnes) followed a linear relationship (Figure 5): FHV = 524.44+0.6733*GRT (n=324, R 2 =0.60) For the smaller vessels, some of the data seem to follow a relationship through the origin (which is logical) while others do not. There is not enough data available to identify erroneous records. Figure 5. Relationship between between FHV (m 3 ) and GRT (t). 3.3 Filling in missing values Taking into consideration the goodness of fit of the various relationships in Section 3.2, the following approach was taken to fill missing values in the database, aiming to estimate FHV for all vessels that did not have this information: 1. Fill in LOA: If GRT is available, then use the GRT-LOA relationship in Section 3.2.1 (this was done for 281 vessels). Otherwise, set LOA to average LOA for other vessels of the same Flag (this was done for 6 vessels). 2. Fill in FHV: If FCC available, use the FHV-FCC relationship from Section 3.2.2 (this was done for 276 vessels). Otherwise, use FHV-LOA relationship from Section 3.2.3 (this was done for 839 vessels). 3.4 The global tuna purse seine fleet We estimated that 1,664 purse seine vessels were authorized to fish for tunas at the end of 2011. Using largely extrapolated data, we estimate that these vessels have a combined 7
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3.2.2 FHV vs FCC<br />
The relationship between FHV (m 3 ) and FCC (tonnes) was linear (Figure 3):<br />
FHV=1.2269*FCC (n=230, R 2 =0.91)<br />
Figure 3. Relationship between FHV (m 3 ) and FCC (tonnes).<br />
3.2.3 FHV vs LOA<br />
The relationship between FHV (m 3 ) and LOA (m) followed a function <strong>of</strong> <strong>the</strong> form<br />
(Figure 4):<br />
FHV = 0.472*LOA 1.873 (n=506, R 2 =0.78)<br />
There is also considerable variability in this relationship. The correlation between FHV<br />
and LOA is not as strong as that between GRT and LOA, or between FHV and FCC. There<br />
is a group <strong>of</strong> vessels in <strong>the</strong> 30-40 m size range that appear to be outliers, though this<br />
possibility could not be confirmed using <strong>the</strong> available data.<br />
6
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