Plan
The survey coverages
Since the International Indian Ocean Expedition (IIOE, 1959-65), which produced abundant data on the oceanographic and biological environment, the seas off North East Somalia have been known to belong to the high productive areas of the world in terms of primary and secondary production, due to the seasonal upwelling occurring in the area.
Even though direct data on fish resources were missing, it was assumed that the area could hold considerable fish resources.
Based on the findings from IIOE, a joint programme between the Norwegian Agency for International Development (NORAD) and the Food and Agriculture Organisation of the United Nations (FAO) was set up to investigate the fish resources of the Arabian Sea. In the period from January 1975 to November 1976 the R/V “Dr. Fridtjof Nansen” carried out five coverages of the coastal waters from Pakistan to Somalia. Based on the acoustic data collected during these surveys, the fish resources of Somalia were estimated to the average level of 570 thousand tonnes for the small pelagic fish and 400 thousand tonnes for demersal fish, making it one of the most productive areas in the Indian Ocean. The dominating part of the pelagic stock was located between Ras Hafun and Ras Asir, which is also the center of the upwelling system.
During the years 1983-84 the vessel returned to the region under the UNDP/FAO programme GLO/82/001 “Survey and identification of World Marine Resources”, with the purpose of investigating the high productive regions located during the 1975-76 surveys. In agreement with the Ministry of Fisheries in Mogadishu two coverages of the region between Ras Asir and Ras Mabber were planned for February and August 1984.
The main objectives of these surveys were to update the previous findings and provide more detailed information on the state of the resources with a more intensive sampling programme than during the earlier surveys.
The level of the small pelagic resources was to be assessed by acoustic surveys, while the demersal resources were to be estimated by concurrent trawl surveys. In addition, one hydrographical section was to be worked out in order to evaluate the strength of the upwelling system. The acoustic data, combined with the trawl sampling programme, would also provide information on species distribution and composition of the fish community in the region.
Preliminary cruise reports have been issued shortly after the two, surveys and the present report is a final summary report, based on the results from these two surveys and on knowledge from previous work.
The participating staff is listed in Annex I and information on the instruments and gear used, are given in Annex II.
Figures 1a, b show the cruise tracks and stations worked during the two surveys. The operational characteristics of the surveys are summarized in Table 1.
The average distance between the main acoustic transects was 10 nm and the shelf was usually surveyed from 15 m bottom depth out to the 200 m depth limit, which was well into the continental slope. Areas of less than 15 m depth represent a very small fraction of the shelf in the region and the survey grid practically covered the whole shelf. During the second survey the work started in the south and the survey net was laid in an oblique pattern northwards. This was done to minimize the effect of the waves generated by the strong SW-monsoon, still prevailing in the area.
Estimates of survey intensity are also shown in Table 1, given as ratios between nautical miles steamed and 100 nm2 covered during the three surveys. Survey intensities for the R/V “Dr. Fridtjof Nansen” usually range between 5-40 nm/nm2 The latest coverages in Somalia thus belong to the more intensive worked out.
Figure 1a. Cruise track and stations worked during the two surveys.
Figure 1b. Cruise track and stations worked during the two surveys.
Table 1. Operational features of the surveys.
|
SURVEY |
REGION |
DATES |
SHELF AREA nm2 |
DISTANCE (nm) TRAVELLED IN SURVEY AREA |
SURVEY INTENSITY nm/nm2 |
NUM. OF FISHING STATIONS |
NUM. OF HYDROGRAPHIC STATIONS |
|
|
I |
Alula- |
|||||||
|
|
4.3 |
150 |
32 |
.21 |
0 |
0 |
||
|
|
Ras Asir |
|||||||
|
Ras Asir- |
28.3-2.3 |
|
|
|
|
|
||
|
|
& |
1920 |
480 |
.25 |
13 |
5 |
||
|
|
Ras Hafun |
4.3 |
|
|
|
|
|
|
|
Ras Hafun |
||||||||
|
|
2.3-4.3 |
1570 |
380 |
.24 |
9 |
4 |
||
|
|
Ras Mabber |
|||||||
|
II |
Alula- |
26.8 |
|
|
|
|
|
|
|
|
& |
150 |
69 |
.46 |
0 |
0 |
||
|
|
Ras Asir |
31.8 |
|
|
|
|
|
|
|
Ras Asir- |
26.8 |
|
|
|
|
|
||
|
|
& |
1920 |
570 |
.28 |
18 |
4 |
||
|
|
Ras Hafun |
28-31.8 |
|
|
|
|
|
|
|
Ras Hafun- |
||||||||
|
|
27-28.8 |
1570 |
314 |
.20 |
7 |
0 |
||
|
|
Ras Mabber |
|||||||
