4. FISH DISTRIBUTION AND ABUNDANCE

As in previous reports the findings are presented for three categories of resources:

1. Pelagic fish type I: Clupeids e.g. sardinellas, sardin, anchovies

2. Pelagic fish type II: Other schooling pelagic fish such as horse mackerel, other carangids, scombrids, trichiurids, barracudas etc.

3. Demersal fish: Other than pelagic schooling fish such as hakes, sparids, sciaenids, catfishes, snappers etc.

One should note that the estimates of biomass presented are of a provisional nature. They are likely to be amended later when further information becomes available on the properties of the various species as acoustic targets.

Figures 7 through 10 show the distribution of the three categories of resources in the same acoustic density levels as used in previous reports.

For the southernmost area, the banks from Porto Alexandre to the border with Namibia, a special report covering the findings with regard to the pelagic resources has already been submitted. The Pelagic I category consisted of a relatively dense concentration of sardine over the inner part of the shelf outside Baia dos Tigres. The sardine area was surveyed twice and the resulting biomass estimates were 127 and 120 thousand tonnes. The size compositions showed modes of 23 cm and 27 cm, probably representing different age groups and the sardine was found to be in pre-spawning and active spawning condition.

The Pelagic II category was represented by horse mackerel distributed over most of the bank, but with areas of high density mostly just inside the shelf edge. The main part was identified as Trachurus capensis, but with parts of smaller catches in the north consisting of Trachurus trecae. The total biomass was estimated at about 220 000 tonnes. The size of the horse mackerel was small, mainly below 20 cm total length in contrast to Surveys 1 and II where nearly all the fish exceeded 20 cm. It thus seems likely that the small horse mackerel found in Survey III had recently been recruited from Namibia.

There was no heavy concentration of demersal fish on the bank, catches giving small and moderate amounts of Dentex and “capensis” hake.

The survey along the narrow shelf from Porto Alexandre to Benguela showed as previously only scarce resources, the main part identified as horse mackerel (T. trecae).

Between Benguela and Luanda sardinella was Found in some concentration only in a small area north of Pta do Morro. Most of the pelagic fish consisted of horse mackerel and some Trichiurus, but nowhere in heavy concentration.

Good concentrations of sardinellas were, however, found in several areas along the coast from Luanda northwards to Cabinda. South of the Congo most of these fish were large, and occurred predominantly in schools in the surface. The two species aurita and maderensis were found mixed and mostly in pre-spawning or spawning condition with a high fat content.

The Pelagic II category in the area from Luanda to Cabinda consisted mostly of horse mackerel (T. trecae) and Trichiurus lepturus south of Ambrizete. Further north this category of resource was scarce and represented in the catches by Trichiurus and Selene dorsalis.

The biomass estimates of the various resource categories by areas can be summarized as follows (thousand tonnes):

	Pel. I	Pel. II	Dem.	Total
Cunene to Porto Alexandre	120	220	40	380
Porto Alexandre - Benguela	-	60		60
Benguela - Luanda	100	130	30	260
Luanda - Cabinda	280	150	50	480
	500	560	120	1180

In these estimates account has been taken of the special condition factor of the Sardinellas which is thought to have effected the acoustic properties of these fish. The total biomass is about 200 thousand tonnes higher than during the second survey. This should be related to the occurrence of sardine in the south and the higher abundance of the capensis horse mackerel in this area. Otherwise the two sets of data demonstrate the northward shift especially of the Pelagic 1-resources.