As stressed in relation to Table 5, the statistical power of the present analysis is weak and attempts should be made to validate or reject the results using external information. As the assessments were made independently for each ocean, it would seem useful to compare them. For each ocean (Atlantic, Pacific, Indian, and Mediterranean plus Black Sea) we compared the potential shown in Table 5 with the shelf area (between 0 and 200 meters) estimated using GIS (Table 7). The data by major fishing area show a fairly large variability as would be expected from their diverse characteristics due to such features as upwelling and river inputs. Better elements of comparison might be needed based on a typology of fishing regions.
Table 7: Fisheries production potential in relation to shelf area and surface area calculated using data at different levels of aggregation. (1) Sum of the potentials calculated separately for all the FAO major fishing areas. (2) Potential calculated for ocean aggregates. (3) Potential calculated for world marine aggregates.
Ocean |
Shelf area |
Potential 1 |
Productivity 1 |
Potential 2 |
Productivity 2 |
Atlantic |
8.64 |
26.1 |
3.0 |
21.4 |
2.5 |
Mediterranean |
0.91 |
2.2 |
2.4 |
2.2 |
2.4 |
Indian |
4.62 |
22.7 |
4.9 |
22.7 |
4.9 |
Pacific |
13.49 |
74.1 |
5.5 |
54.3 |
4.0 |
TOTAL (1 & 2) |
27.66 |
125.1 |
4.5 |
100.6 |
3.6 |
TOTAL (3) |
27.66 |
82.1 |
3.0 |
|
|
Ocean |
Surface area |
Potential 1 |
Productivity 1 |
Potential 2 |
Productivity 2 |
Atlantic |
85.2 |
26.1 |
0.31 |
21.4 |
0.25 |
Mediterranean |
3.0 |
2.2 |
0.73 |
2.2 |
0.73 |
Indian |
60.1 |
22.7 |
0.38 |
22.7 |
0.38 |
Pacific |
168.1 |
74.1 |
0.44 |
54.3 |
0.32 |
TOTAL (1 & 2) |
316.4 |
125.1 |
0.40 |
100.6 |
0.32 |
TOTAL (3) |
316.4 |
82.1 |
0.26 |
|
|
In terms of potential, the estimate for the Indian Ocean (which, with 23 million tonnes is about 16 million tonnes higher than the present production) is surprisingly high although it does not appear widely out of line with other oceans in terms of productivity per unit shelf area and per unit surface area (Table 7). The apparent deficit in pelagics in the Indian Ocean (Figure 6) which is tentatively explained by Bakun (1996) in terms of hydrographic conditions, might indicate that an important biomass of small pelagics is underexploited; this deficit however, amounts only to about 1-2.4 million tonnes, and does not explain the large difference between current production and estimated potential. There is probably potential for development of myctophid fisheries and some other offshore small pelagic species, but it is not at all obvious which resources could provide the large gains in yield implied by the estimate of potential which may be unrealistically high.
The Indian Ocean is essentially a tropical ocean, and a comparison of the tropical sectors10 of the oceans in terms of present and potential productivity (data from Table 6) shows that recent productivity for the Indian Ocean is low, whether in terms of shelf area or surface area, whereas estimated potential productivity estimates lie between those of the Pacific and the Atlantic in terms of shelf area but higher than both in terms of surface area (Table 8).
10 These areas are the Western Central, Eastern Central, Southwest and Southeast Atlantic; the Western Central, Eastern Central, Southwest and Southeast Pacific; and the Western and Eastern Indian Ocean.Table 8: Comparison of recent landings and estimated potential production per shelf area and per surface area for tropical waters.
|
Shelf area |
Recent |
Recent |
Potential 1 |
Potential |
Atlantic tropical |
4.6 |
8.8 |
1.91 |
10.6 |
2.3 |
Pacific tropical |
8.4 |
25.9 |
3.08 |
43.6 |
5.2 |
Indian |
4.6 |
6.9 |
1.49 |
22.7 |
4.9 |
Mediterranean |
0.9 |
1.6 |
1.76 |
2.2 |
2.4 |
|
Surface area |
Recent |
Recent |
Potential 1 |
Potential |
Atlantic tropical |
64.7 |
8.8 |
0.14 |
10.6 |
0.16 |
Pacific tropical |
139.0 |
25.9 |
0.19 |
43.6 |
0.31 |
Indian |
60.1 |
6.9 |
0.11 |
22.7 |
0.38 |
Mediterranean |
3.0 |
1.6 |
0.53 |
2.2 |
0.73 |