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3.4 Comparison of ocean potentials

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
(106 km2)

Potential 1
(106 t)

Productivity 1
(t/km2)

Potential 2
(106 t)

Productivity 2
(t/km2)

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
(106 km2)

Potential 1
(106 t)

Productivity 1
(t/km2)

Potential 2
(106 t)

Productivity 2
(t/km2)

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




When the estimated potential obtained for the three oceans and the Mediterranean separately is considered in relation to shelf area (Figure 34) and in relation to surface area (Figure 35), the relationship is remarkably consistent although there are only four data points (the world totals are plotted for comparison, but these are not independent points). This result would tend to indicate that, while the results for each region have to be considered with caution and the Indian Ocean figures do appear high, the overall picture is generally coherent.

Figure 34. Relationship between ocean fishery potential and shelf area for two estimates of potential (see Table 7)

Figure 35. Relationship between ocean fishery potential and surface area for two estimates of potential (see Table 7)

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
(106 km2)

Recent
landings
(106 t)

Recent
productivity
(t/km2)

Potential 1
(106 t)

Potential
productivity 1
(t/km2)

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
(106 km2)

Recent
landings
(106 t)

Recent
productivity
(t/km2)

Potential 1
(106 t)

Potential
productivity 1
(t/km2)

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


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