Nonaka et al.: Seasonal variation in larval fish assemblages off eastern Brazil 



771 



Larval fish composition and abundance 



A list of the family groups of fish larvae and their abun- 

 dance is given in Table 2. From the 45,614 larvae collected, 

 83 taxa (77 families and 6 orders) were identified. The 

 family Myctophidae was the most abundant, accounting 

 for more than 25% of the total catch on the three cruises. 



During the winter cruise, 58% of the total larvae taken 

 represented five families in decreasing order of abundance: 

 Myctophidae, Phosichthyidae, Sternoptychidae, Bregmac- 

 erotidae, and Serranidae, of which the first four belonged 

 to the mesopelagic fish group. 



The total number of lai-vae collected during the summer 

 cruise was twice as high as that of the other two cruises. 

 Myctophidae represented 27.6% of the total larvae, fol- 

 lowed by Scaridae (11.6% ), Sternoptychidae (8.2% ), Caran- 

 gidae (4.5%), and Phosichthyidae (4.2%). The following 

 nine families were collected only on the summer cruise; 

 Argentinidae, Clinnidae, Dactyloscopidae, Istiophoridae, 

 Caproidae, Macrorhamphosidae, Malacanthidae, Perco- 

 phidae and Symphysanodontidae, indicating that these 

 groups spawned only in summer. 



During the autumn cruise, the five most abundant fam- 

 ilies (Myctophidae, Scaridae, Gobiidae, Serranidae, and 

 Phosichthyidae) represented 58.7% of the total larvae 

 taken. Four families ( Elopidae, Notosudidae, Scombro- 

 labracidae, and Tripyterigiidae) were collected only in this 

 season, indicating that for these families spawning peaked 

 in autumn. 



Seasonal variation in abundance of fish groups 



In relation to habitat of adult fish groups, two dominant 

 fish groups were recognized in the sur\'ey area: meso- 

 pelagic fish and coral-reef-associated fish. Levels of 

 abundance of three families of mesopelagic fish larvae 

 (Myctophidae, Sternoptychidae, and Gonostomatidae) were 

 highest during the summer cruise (Fig. 4). For three other 

 families (Phosichthyidae, Bregmacerotidae, and Paralep- 

 ididae) levels of abundance were highest for the winter 

 cruise, decreased in summer, and were at a minimum 

 during the autumn cruise. The summer peak in abundance 

 for the myctophid Myctophum affine was outstandingly 

 high (Fig. 5). Five other species (Diaphus spp., Lepido- 



phanes guentheri, M. nitidulum. M. obtusirostre, and 

 Hygophum reinhardtii) were most abundant in summer, 

 but the seasonal differences were not pronounced. 



Figure 6 shows a seasonal variation in abundance of the 

 coral-reef-associated fish. Abundance of lai-val parrotfish 

 (Scaridae) was at a peak in summer, followed by autumn 

 and winter. The same trend was observed in six other fam- 

 ilies (Labridae, Holocentridae, Balistidae, Pomacanthidae, 

 Acanthuridae, and Pomacentridae). Levels of abundance 

 of larval grouper (Serranidae) were almost the same for 

 three seasons. For the family Gobiidae, a peak in larval 

 abundance was observed during the autumn cruise. 



Distribution patterns of fish larvae 



Distribution patterns of six species of Myctophidae among 

 each of the cruises are shown in Figure 7. Most of the Dia- 

 phus spp. larvae were collected at open ocean stations, but 

 also at some coastal stations between Vitoria and Cape 

 Frio on the winter and summer cruises. Larvae of Myc- 

 tophum affine, M. obtusirostre. M. nitidulum, L. guentheri, 

 and H. reinhardtii were found predominantly at open 

 ocean stations and some at the continental margin, but 

 a considerable number oi Myctophum affine larvae were 

 also found at coastal stations between Vitoria and Cape 

 Frio on the summer cruise (Fig. 7E). The presence of these 

 species along the coast coincided with the presence of the 

 coastal upwelling observed in this area (Fig. 3). 



Distribution patterns of the Gobiidae during the summer 

 and autumn cruises were similar, with higher density over 

 the Abrolhos Bank and seamount. Gobiid larvae during 

 the winter cruise were concentrated over the Abrolhos 

 Bank and only a small number of them were collected 

 at open ocean stations south of the bank (Fig. 8). The 

 distribution patterns of the parrotfish larvae (Scaridae) 

 were similar during all three cruises, with higher density 

 at open ocean stations. During the winter cruise the high- 

 est densities of grouper larvae (Serranidae) were found 

 around the Vitoria Channel, but the Abrolhos Bank sta- 

 tions also showed relatively high density. The stations 

 with the highest densities of grouper larvae during the 

 summer cruise were found along the shelf break and over 

 the seamount. The distribution pattern of grouper larvae 

 during the autumn cruise was different from the former 



