Analysis of fish eggs and larvae collected in the region of the northern Benguela and Angola currents: preliminary results

摘要

Data on the ecology of ichthyoplankton in the northern Benguela Current, the Angola-Benguela Front and the Angola Current are scant. During Leg 3 of the BENEFIT research and training cruises in July-August 1999,2 fish eggs and larvae were collected using a 200-#mu#m meshed Bongo net, towed obliquely in the upper 200 m, between 9 and 23 deg S off Angola and Namibia (see Verheye et al. for details). Since many of the eggs and larvae have not yet been identified, they were pooled into a single group of 'unidentified species'. Although a more comprehensive analysis of the ichthyoplankton collections may change the results reported here to an unknown extent, our preliminary analysis nonetheless revealed some interesting findings, which are summarized below. Abundances of eggs and larvae given below are means +- 1 s.e. In total, 2943 fish larvae were sorted from the samples and of the 754 specimens identified so far, a total of 32 taxa were distinguished, distributed over 23 families. Myctophids were the most dominant family in all three regions, representing 12 percent of all larvae collected in the Angola Current, 19 percent in the AngolaBenguela Front and 22 percent in the northern Benguela. Gempylidae (including snoek larvae) ranked second most important (19 percent) in the northern Benguela, followed by Clupeidae (6 percent), Engraulidae (4 percent) and Carangidae (3 percent). The latter three groups were also found in the Angola-Benguela Front region in about the same proportions (5 percent, 2 percent and 4 percent, respectively), in addition to hake larvae (Merluccidae, 4 percent), but all these groups were absent in the samples from the Angola Current region. Other comparatively abundant groups (1-2 percent of total larval abundance) included Bathylagidae in the northern Benguela, Paralepididae and Photichthyidae in the frontal region, and Gonostomatidae and Scorpaenidae in Angola Current waters.