3.1 TOTAL CATCH
3.2 FISHING EFFORT, AND CATCH PER UNIT OF FISHING EFFORT
3.3 SIZE COMPOSITION
3.4 AGE COMPOSITION
Table 1 shows the catches of both sardinella species together (Sardinella aurita and S. maderensis) by country and statistical division, for the years 1956 till 1978 (1978 incomplete). The data show that until 1973, except for 1971, the Angolan catches contributed over 90 percent of the total landings. In 1975 and 1976, the Angolan landings were low, presumably due to reduced fishing related to the war conditions in the country.
The annual landings fluctuated around a fairly constant average level from 1956 till 1968, with relatively high catches in 1957 and 1964. Thereafter, catches were very high in 1969, 1971, 1972, 1973 and 1977. The high landings in 1971 and 1977 were due to additional fishing by foreign vessels, South Africa and USSR respectively, but those in 1969, 1972 and 1973 were obtained by the Angolan fleet in ICSEAF Division 1.2.
With respect to the reliability of the data, it should be noted that at least until 1972, the Angolan official statistics did not distinguish between Sardinella and Sardinops. Therefore, Campos Rosado (1973) in his estimates of the landings by species by division, had adopted the following procedure:
“The catch composition ........ was based on the previous knowledge of the dominant species caught in each division. Thus, it is known that “sardinha” in catches of southern Angola refers to Sardinops ocellata, and in central and northern Angola refers to both Sardinops aurita and S. maderensis, though the two sardinellas may sometimes be referred to by different common names (“sardinha lombuda” referring to S. aurita, and “sardinha palita” or “savelha” to S. maderensis). It was then decided to consider the nominal catches of “sardinha” in Divisions 1.1 and 1.2 as catches of sardinella, without aiming at distinguishing the two species, and the nominal catches of “sardinha” in Division 1.3 as catches of Sardinops ocellata, ........ but acknowledging that it includes an unknown but small proportion of sardinellas”.
Notwithstanding these observations, the USSR reports for 1977 a catch of 72 000 t of sardinella and 52 000 t of sardine in Division 1.3, and Angola reports a catch of 11 000 t of sardinella in that area in the same year. The difference between these data and the observations by Campos Rosado for Division 1.3 may be related with differences in fishing grounds or in fishing techniques and tactics, but may also suggest that the statistical data should not be considered as being very precise.
Table 2 shows the available data on the catches of both sardinella species together by month in the Angolan area. The data show considerable variation in the quantities landed by month and year, but with a general tendency each year for low catches in some of the months between June and September.
With respect to the Congolese data, it should be mentioned that there are good statistics of total catch for the industrial fisheries, but rough estimates only for the other fisheries. Because S. aurita fetches a higher price per unit weight than S. maderensis in Congo, the species are often sorted and complete statistics by species are available for the landings of the main industrial fishing company for the years until 1975; for 1976-1978 the species composition has been estimated from samples of the landings. These data are shown in Table 4.
Finally, Table 3 shows the quantities of sardinella landed in each division, together with the landings of other small pelagic species of the Congolese and Angolan purse seine fisheries. This table shows that with the exception of some of the earliest years for which sardinella catches have been reported, sardinella constituted by far the predominant part of the total pelagic catch in CECAF Division 34.3.6 and ICSEAF Divisions 1.1 and 1.2. It is striking that Sardinops ocellata in Division 1.3 shows high landings in 1969 and 1972, the same years in which sardinella shows high landings in Division 1.2. This puts some doubts on the species distinction.
Data on number of days at sea are available for the boats of the main Congolese industrial fishing company.
Table 4 shows the catches and the effort of these boats, and the calculated catch per boat per day at sea (uncorrected for changes in fishing power) for each of the two species of sardinella.
Tables 5a and 5b give the catch per boat per day fishing (uncorrected for changes in boat size) per month in each year, for each of the two sardinella species.
For the Angolan fleet the only information available is that on the number of boats, and their tonnage, in each of the statistical divisions for the years 1965-1972. Table 4 gives the total catch by division, the number of boats and their average tonnage, and the average catch per boat per year, uncorrected for the changes in tonnage.
Neither the Congolese catch per effort data, nor the Angolan ones, show any clear upward or downward trend, but both show large year-to-year fluctuations.
Particularly high catch rates have been obtained in the Angolan fishery in ICSEAF Division 1.2 in 1969 and 1972. These seem to coincide with the high catch rates of Sardinella aurita in the Congolese fishery in 1969/1970 and the exceptionally high rates in that fishery in 1972/1973, but no high catch rates were observed in these years in north Angola, ICSEAF Division 1.1 (Figure 2).
The Congolese catch rates of S. maderensis also fluctuate considerably, and more or less opposite to the fluctuations in the S. aurita catches.
Monthly data on the size composition of the catches of both S. aurita and S. maderensis are available for the Congolese purse seine fishery for the years 1964-1978. For the Angolan fishery, the available data are monthly size composition of S. maderensis for 1969 and 1970 (from Ghéno and Campos Rosado, 1972) and for part of 1974 (ICSEAF Sampling Bulletin), and monthly data of S. aurita for part of 1969 and 1970 (Ghéno and Campos Rosado, 1972).
These data are given in Appendix 3. Some features of the distribution are discussed in the section on migration (Section 6).
All data on length compositions refer to fork length, except perhaps the ICSEAF data for 1974 which may represent the total length.
The only data on age composition of the catches available to the Working Party were those given by Ghéno and Poinsard (1969). The authors mention the difficulties of age determination, especially in S. maderensis. For that species, the results (Appendix 4a) should be considered as very approximate only. The data on S. aurita have been obtained from scale readings, and are given in Appendix 4b. The latter data indicate a strong yearclass born in 1963.
