4. ASSESSMENT OF RESOURCE POTENTIALS.

4.1 Review of the biomass estimates.

It is convenient to describe Angolas marine fish resources with reference to the environmental regime in which they are found. This gives the following groups:

Resources in the Benguela Current regime.

These are restricted to the shelf south of abt 15o S and their abundance in Angolan waters must be expected to show seasonal fluctuations with a maximum in southern winter - spring. The survey results indicate that such fluctuations took place during the period of investigations. The most important of these resources are the sardine, the Cape horse mackrel and the Cape hake.

In addition to the mean standinmg biomass over the year, their seasonal availability in Angolan waters will also be indicated.

Resources on the shelf in the Angola Current regime.

These have their main abundance on the shelf from abt. 15o S to Cabinda, but the distribution of many of the species extend somewhat to the south and north of these limits. The most important of the small pelagic fish are the round and flat sardinellas. Both of these species are also found off Congo and Gabon, but mostly as juvenile fish. The round sardinella may also occur in some abundance on the Baia dos Tigres Bank down to the border with Namibia. The Cunene horse mackerel is another common pelagic species. It was found in highest abundance between Benguela and Luanda, but the distribution ranges from northern Namibia to Gabon. This fish was caught both by mid water and bottom trawl, often together with other carangids, bumper, lookdown and scads and with hairtail and barracudas.

The demersal shelf fish consists of a higher number of commonly occurring species. Cape hake and large eyed dentex dominate south of Porto Alexandre. Farther north a commercially less interesting species, Brachydeuterus auritus, a smaller sized grunt dominate the demersal community along the whole shelf from Benguela to Cabinda. The commercially most interesting forms, seabreams, croakers, groupers and larger grunts represented about 25 per cent of the bottom fish biomass in Region 3, Benguela - Luanda and about 35 per cent in Region 4, Luanda-Cabinda.

Deep water resources along the slope, 200–600m.

In this regime of oxygen deficient low temperature water the most common fish species is the Benguela hake. It occurs in abundance on many locations in the depth range 300–500 m between Benguela and the Congo River. The greeneye is often caught in good quantities mostly in the depth range 200 – 400 m. Various species of deep sea shrimp inhabit this regime. The commercially most important are Parapenaeus longirostris which occurred from 180 – 500 m and Aristeus varidens found mostly in deeper waters 400 – 500 m. A small sized shrimp Nematocarcinus africanus was found in abundance between 300 and 600 m.

Other resources.

A brief remark should be added to draw attention to the fact that the programme did not cover all of Angolas fish resources. Large pelagic fish, tunas and billfishes could for methodical reasons not be covered. Oceanic squid was very incompletely explored in two visits to more offshore waters of the Benguela Current and observations of a certain abundance were made. The same species Todarodes sagitattus also formed part of the deep water catches. Another type of molluscs, clams was incidentally caught in a few of the trawl hauls. Finally one should recall that the extreme inshore waters of depths less than about 10 fathoms have not been covered.

Overview of biomass estimates.

Table 9 shows the estimates for the various types of small pelagic fish. The surveys demonstrated that the stocks shared with Namibia, sardine and Cape horse mackerel may occur in high abundance in southern Angola in the winter- spring period. With a mean standing biomass of 400 000 tons over the 1985 surveys the sardinellas form the most important resource. There is however some evidence of a declining biomass of these stocks in 1986. Together with other carangids, hairtails and barracudas the Cunene horse mackerel had an estimated standing biomass in 1985 of 280 000 tonnes.

The estimated biomass of all small pelagic fish taken together is close to 900 000 tonnes. No previous data exist on the standing biomass of these resources with which to make comparisons.

Table 10 shows the estimates of mean standing biomass over the period of the six surveys for the demersal shelf resources and the deep water slope resources. For the bottom fish on the shelf the total estimate is 230 000 tonnes of which close to 40 per cent can be classified as species and sizes of high market value. Of the deep water resources the estimated biomass of abt. 42 000 tonnes for Benguela hake between Lobito and the Congo river is about half the level estimated on the basis of the “Fiolent” survey in 1976, but their calculation was termed preliminary and a final results is not available

The estimate of the commercial shrimp stock of abt. 4 000 tons is also considerably lower than results from previous surveys. Thus the survey with the Cuban research vessel “Isla de Juventud” in 1976/77 gave estimates of the biomass of commercial shrimp in the area of abt. 10 000 tons. Reported catch rates from the fishery in this period are, however similar to those obtained now in our survey.

As mentioned under Section 3.1 above in terms of marine production system and certain ecological features the Angolan coast can be compared to the coastal area off north west Africa from Mauritania to Guinea. A survey largely similar to that for Angola was undertaken of these areas in 1981– 82. The estimates of mean standing biomass based on two surveys at different seasons covering the coast from Mauritania down to and including Guinea Bissau were as follows: small pelagic fish 1 230 000 tons, demersal fish 530 000 tons and balistes 540 000 tons. The comparable estimates for Angola is 900– 1 000 000 tons of pelagic fish depending on the seasonal availability of sardin and Cape horse mackerel, 320 000 tons of demersal fish and an insignificant amount of balistes. The standing biomass will of course be affected by the state of exploitation of the stocks and by natural stock fluctuations. The comparison indicates that the fish production in the two areas may be at a similar level apart from the balistes in the north. This stock is, however known to fluctuate considerably and its long term level is not known.

4.2 State of the resources and the management situation.

The standing biomass of fish stocks represents an important basis of resource information, but for an evaluation of their potential yields knowledge of their state of exploitation is also essential. The precision and reliability of yield assessments depends largely on the availability of good and detailed statistics of the fisheries and on biological knowledge of the species. Since fishery science and - management is in a developing stage in Angola our expectations to the precision of the assessments should not be too high.

It is also here convenient to consider the resources in their regime context. The resources of the Benguela current system are shared with Namibia and their assessment and management represent common problems. The Angola Current regime have resources which are exclusive for Angola or may be shared with the Congo and Gabon which to some minor extent is the case with the sardinellas.

The Benguela Current resources.

In the absence of an exclusive economic zone off Namibia the shelf there represents one of the few remaining coastal fishing regions of the world with open access for anyone to exploit. It is known as a high productive upwelling region. Most nations fishing there participate in the work of the International Commission for the Southeast Atlantic Fisheries, ICSEAF which acts as an advisory body on management. The technical work of the Commission is internationally appreciated. The management situation for most stocks which is the responsibility of the fishing countries themselves is, however not considered satisfactory, and this affects the stocks shared with Angola.

The sardine.

This stock has a potential yield of some 600 000 tons, but was depleted by overfishing in the early 1970's and the total stock which had a biomass exceeding 3 million tons has over a long periode of years been assessed at a level of one to two hundred thousand tons. The only responsible management would be a complete fishing ban over a number of years, but the Republic of South Africa maintains a fishery at a 50 000 tons level which keeps the spawning stock at a very low level and prevents a stock recovery. The main distributional area of the sardine is ICSEAF Division 1.4, but it extends into 1.3 and Angola as demonstrated by the presence of well over 120 000 tons off Baia dos Tigres in Survey 3. It is very likely that with a recovered stock, sardine would be available seasonally and in considerable quantities in southern Angola. Historical records of the Portuguese purse seine fishery in this area prior to the collapse of the sardine stocks shows that the species then represented a considerable part of the annual catch.

The survey also demonstrated the presence of anchovy in Region 1 although in small quantities. This stock has a similar distribution as that of the sardine and its abundance its abundance is also at a very low level as a result of overfishing by the South African purse seine fleet.

The Cape horse mackerel.

The abundance of and fishery on this stock increased greatly in the late 1970's possibly as a result of the collapse of the sardine, Catches exceeded 600 000 tons in 1982–83, but the latest ICSEAF recommendation is for a total allowable catch of 440 000 tons as a decline of the stock has been recorded. As shown by our surveys this species was abundant on the Baia dos Tigres bank in winter and spring 1985. The largest part of the 1985 catch of 435 000 tons of this stock was reported from Division 1.3, about half of which lies north of the Cunene river. No doubt part of this catch is taken in Angolan waters although non is reported. There is probably considerable confusion over the separation of the two species of horse mackerel in the catches in this area. The potential yield in Angolan waters of the Cape horse mackerel should be determined through an allocation between the two countries on the basis of long term observations of the stock distribution.

The Cape hake.

This species has a similar pattern of distributions as those mentioned above, but the surveys demonstrated the presence of only modest quantities in Region 1. The stock is, however overfished in Namibia. A recovery would result in increased availability in Angola and its abundance here should be monitored together with the other shared stocks.

The Angola Current resources.

The sardinellas.

There are no reliable assessments of the sardinella stocks in Angola, but some suggestions have been presented of likely potentials of between 150 and 170 thousand tons. Reported catches had a peak of 240 000 tonnes in 1978 declining to 160 000 tons in 1981. Since then the catches have been reported as abt. 180, 150, 200, 210 thousand tons from 1982 to 1985. A correction of the 1985 catch may raise this to nearly 240 thousand tonnes. Compared with our assessment of a 1985 standing biomass of 400 thousand tons a catch of about half that amount indicates a very high rate of exploitation. This would be the case even if we choose our highest estimate of 500 thousand tons as a true stock level. The trend of decline of biomass observed and the reduced juvenile component in the stocks in 1986 should also be considered as a sign of a too high fishing pressure on these stocks.

The Cunene horse mackerel and associated species.

There is no previous assessment available for these stocks. ICSEAF reports the highest part of the catch of Cunene horse mackerel from Division 1.3, but it is uncertain whether this may include some Cape horse mackerel. The reported total catches for the Cunene species in 1984 and 1985 were 75 thousand tons and 78 thousand tons respectively (Source CIP). Together with other carangids the catch level is 80 thousand tonnes which should be related to our estimate of standing biomass of 280 thousand tons.

This indicates a fairly moderate rate of exploitation. There was no trend of decline in the biomass estimates over the survey periode although they fluctuated considerably. The size compositions indicated widespread and maintained recruitment.

The demersal shelf resources.

These consist of biologically widely different groups and assessments of their state of exploitation is further complicated by incomplete or unavaiable statistics of their catch. Nearly 40 per cent of the standing biomass of 230 thousand tons represent commercially interesting species. Good catch rates were obtained in many areas, often with large sized fish and it seems unlikely that these resources are fully utilized in Angolan waters under the present conditions. If more details statistics becomes available the survey data can be utilized to provide a better analysis.

The deep water resources on the slope.

Some confusion exists over the history of fishery for the Benguela hake as the data reported in FAO's Yearbook of Fishery Statistics are widely different from those of ICSEAF. Confiding in the latter catches were 23 and 21 thousand tons in 1977 and 1978, but has since then been reported as between 0 and 6 thousand tons. The 1977 and 1978 catches apparently caused a sharp decline of catch rates. It must be assumed that the recent high effort in the shrimp fishery causes a considerable by- catch of hake. In the absence of information on the by-catch level it is difficult to assess the state of the stock. On the basis of our estimate of a standing biomass of abt. 40 thousand tons a preliminary assessment of the potential of the stock would be a total annual yield of 10 thousand tons including the by catch. The yield will, however to a large extent depend on the proportion of juveniles caught.

The fishery for the commercial deep sea shrimp species has a long history. Starting in 1967 the catches increased to abt 8 thousand tons by 1972 and reached 11 and 10 thousand tons in 1975 and 1976 respectively. After a disruption the 1985 catch is of the same high level. A recent assessment published by FAO (Fish. Techn.Paper, 178 Rev.1) indicate a potential yield of 8 – 10 thousand tons for these stocks. Improved assessments should be attempted based on detailed catch data by species and biological sampling. Our surveys gave about the same catch rates as those of the commercial fishery, but the patchy distribution of the shrimps complicates biomass estimates.

A review of the resources covered by the investigations with comments on their state of exploitation and potentials is as follows:

As overall conclusions one could say that there are significant potentials for increases of Angolas yield from the resources shared with Naimbia, particularly of sardine, if improved management brings about a recovery of these stocks. There is furthermore probably some potential for increased catches from the Cunene horse mackerel and the other carangids, the hairtails and the barracudas. And there is a potential for increased catches from at least some of the demersal groups of fishes. The catches of the Benguela hake can probably be increased depending upon the level of this species in the by catches of the shrimp fisheries. The deep water shrimp stocks are probably fully utilized and the sardinellas are overexploited and the fishing intensity on these stocks should be reduced.

Apart from this, one should note that there are considerable resources in Angolan waters of presently non commercial types of fish which should be considered as a possible source of raw material for cheap fish products for internal consumption in Angola. The demersal shelf- and deep water slope resources include about 170 thousand tons of “other” fish and these contain species of high quality fish flesh such as greeneyes and Brachydeuterus auritus in significant quantities.