BLACKBURN and NELLEN: EGGS AND LARVAE IN AN UPWELLING AREA 



identifications could have been made in some cases 

 but were not needed for this study. Clupeoids 

 predominated. Many clupeoids were small (about 5 

 to 10 mm) and had lost part of the intestine, 

 probably because of the repeated filtering of the 

 zooplankton. Clupeidae and Engraulidae were not 

 separately counted, but both families were well 

 represented. Preanal myomeres were counted in 

 randomly selected good clupeid specimens. These 

 counts ranged from 41 to 43, which agree with 

 Sardina pilchardus (Saville 1964). Comparable 

 ranges in two other west African clupeids, Sar- 

 dinella aurita Valenciennes and Sardinella eba 

 (Valenciennes), are respectively 38 to 41 and 35 to 

 38 (Conand and Fagetti 1971). These species were 

 looked for because Maigret (1972) found Sardin- 

 ella larvae near the area of JOINT-I in May. 

 Evidently they were absent or scarce in our ma- 

 terial. They were absent or scarce in the 1974 fish 

 catches reported to us. We conclude that our 

 clupeoid larvae were Sardina pilchardus and 

 Engraulis encrasicholus, like the clupeoid eggs. 

 Carangid larvae were scarce. Larvae in the last 

 line of Table 2 ("Others") were Merluccius, Cal- 

 lionymus, Paralepididae, and Anguilliformes 

 (leptocephali). 



Table 2 shows that Sardina dominated the egg 

 samples. It shows also that abundance of Sardina 

 eggs varied greatly during JOINT-I, which is 

 discussed later. 



SPATIAL DISTRIBUTION OF 

 EGGS AND LARVAE 



Figure 5B-H shows distribution and abundance 

 of the principal kinds of eggs and larvae identified, 

 during the whole period of cruise JOINT-I. All 

 positive hauls for each kind were charted and the 

 observed numbers per square meter were con- 

 toured without averaging. The purpose of Figure 5 

 is to show where maxima and minima occurred, 

 although some of them were more prominent at 

 those locations on some legs of the cruise than on 

 others. For example the midshelf maximum of 

 Sardina eggs was not prominent on Leg 2, when 

 eggs were scarce everywhere (cf. Tables 1, 2). We 

 were most interested in the pelagic species and 

 especially in their eggs, whose distributions should 

 be close to those of the adults. Furthermore, the 

 methods employed were more suitable for eggs 

 than larvae. Some larvae could have avoided the 

 nets, especially in daytime. 



Sardine and anchovy eggs were absent close 



inshore, most abundant on the continental shelf 

 between the 50- and 100-m isobaths, and occasion- 

 ally found just beyond the shelf edge (Figure 5B, 

 C). These eggs occur most abundantly in the 

 uppermost 25 m of the water column (Furnestin 

 and Furnestin 1959; Larraneta 1960; Demir 1963), 

 where temperatures on JOINT-I were about 16° to 

 17°C (Figures 2-4). The eggs take about 3 days to 

 hatch at such temperatures (Larraneta 1960; 

 Demir 1963), so their average age should be about 

 1.5 days. 



Six vertical arrays of current meters were 

 moored during JOINT-I (Figure 5A). No ichthyo- 

 plankton were collected near array number 6. The 

 other arrays operated for periods of about 20 days 

 (number 3) to 60 days (number 2). Means of the 

 meridional and zonal components of water 

 movement, v and u, are available for each current 

 meter during the period of operation (Pillsbury et 

 al. 1974). The top meter in each array was about 20 

 m below the surface. At this depth, mean v was 

 about 20 cm/s on the continental shelf (arrays 1 

 and 2) and 10 cm/s on the edge and slope (arrays 3, 

 4, and 5), towards the south. Mean u was about 2 

 cm/s towards the west, except at array 3 where it 

 had the same velocity towards the east. Thus, from 

 where it was spawned by the parent, a sardine or 

 anchovy egg of average age on the continental 

 shelf could have drifted about 14 nautical miles to 

 the south and 1.4 miles to the west. The movement 

 to the west is negligible for our purpose. The 

 coastline and isobaths run generally north and 

 south along this section of the coast, as do isopleths 

 of surface temperature and surface nitrate con- 

 centration (Voituriez et al. 1974; D. W. Stuart and 

 J. J. Walsh, pers. commun.). Thus the parent fish 

 probably occurred over the same bathymetry and 

 under the same environmental conditions as the 

 eggs did, but slightly farther north. 



Carangid eggs (Figure 5D) were found on the 

 outer half of the shelf, especially at the edge. 

 Kiliachenkova (1970) found eggs of Trachurus 

 trachurus distributed in exactly the same way in 

 the same area in November, December, and May. 

 The literature does not clearly show the vertical 

 distribution of the eggs of T. trachurus. Kilia- 

 chenkova (1970) found them abundant at the 

 surface. The eggs of the related T. symmetricus in 

 the California Current are most common at the 

 surface but fairly abundant down to 30 m, with 

 smaller numbers occurring deeper (Ahlstrom 

 1959). We, therefore, assume our eggs came mostly 

 from the top 30 m. Trachurus trachurus eggs 



891 



