FISHERY BULLETIN: VOL, 74, NO. 4 



hatch 3 or 4 days after being spawned at temper- 

 atures from 15° to 19°C (Letaconnoux 1951), so 

 average age in our material should be 1.5 to 2 days. 

 Then, taking mean v as 10 cm/s we estimate that a 

 TrachurHs egg collected near the shelf edge was 

 probably spawned near the edge about 7 to 10 

 miles farther north. 



Maurolicua eggs (Figure 5E) were most abun- 

 dant just outside the shelf edge. Adults are meso- 

 pelagic fish of the continental slope (Maurin et 

 al. 1970; Hureau and Tortonese 1973) and pre- 

 sumably spawn there. We frequently found eggs 

 on the outer one-third of the shelf as well as on the 

 slope, which suggests some eastward transport. 

 The current meter data from arrays 3 and 4 show a 

 mean u about 10 cm/s to the east at 60 m. This 

 could account for the observed distribution if 

 MauroiicKs eggs occur at that depth and hatch in a 

 few days. Eggs of M.japonicus off Japan are most 

 abundant at 50 to 60 m (Nishimura 1957). This 

 species is considered synonymous with M. muel- 

 leri (Hureau and Tortonese 1973). 



Clupeoid larvae (Figure 5F) were abundant at 

 midshelf , on the outer shelf, and over the slope. In 

 general their distribution extended about 10 to 15 

 miles west of the eggs. Their average age probably 

 was 10 to 20 days more than that of the eggs. 

 Larvae of Sardina pilchardus and Engraulis 

 encrasicholus occur most commonly in the upper 

 25 m (Fage 1920). Thus the movement of 20-m 

 shelf water towards the west at about 0.9 nautical 

 mile/day generally explains the observed larval 

 distribution. This water movement is presumably 

 the Ekman transport, which provides a mechanism 

 for the coastal upwelling. 



Larvae of demersal fish (flatfish and sparids) 

 occurred mostly on the shelf as expected, but 

 occasionally on the slope. They were most common 

 in inshore waters where eggs and larvae of pelagic 

 species were scarce (Figure 5G, H). 



VERIFICATION FROM 

 COMMERCIAL FISH CATCHES 



From egg and larval evidence, the adult pelagic 

 fishes in the area and period of JOINT-I should 

 have been predominantly S. pilchardus and E. 

 encrasicholus, especially the former, on the shelf; 

 Trachunis, probably T. trachurus, at the shelf 

 edge; and the mesopelagic M. muelleri, on the 

 continental slope. Difi'erences in fecundity 

 between species could affect these findings, how- 

 ever, and other species could have been present but 



892 



not spawning. Commercial fish catches provide a 

 useful check on the results of the studies with eggs 

 and larvae. Some useful information of that type 

 was kindly provided by the Sea Fisheries Institute 

 of Gdynia, Poland. 



Polish pelagic (mid-water) trawlers of the Odra 

 Deep Sea Fishing Company fished just south of the 

 JOINT-I area at the end of March 1974. They 

 operated from lat. 20°40' to 21°00'N, between the 

 coast and shelf edge. Reported catches (tons/day) 

 of pelagic species were about 3.3 Trachurus spp., 

 6.5 Caranx rhonchus, and 0.2 Scomber japonicus. 

 Caranx rhonchus was the principal species within 

 the 50-m isobath, Trachurus the principal fish in 

 more offshore waters. During April, the trawlers 

 were located far north of the JOINT-I area 

 between lat. 23° and 27° N, where their catches 

 were predominantly Sardina pilchardus. 



The Polish research vessel Professor Siedlecki, 

 equipped for large-scale pelagic trawling, made 77 

 hauls between 13 May and 24 June, starting just 

 after JOINT-I. The hauls were made between lat. 

 20°16' and 25°01'N which includes the area of 

 JOINT-I. Hauls north of lat. 21°00' were all on the 

 continental shelf between the 35- and 70-m 

 isobaths and caught almost exclusively Sardina. 

 Hauls south of lat. 21°00' were made at the shelf 

 edge (100-m isobath) and caught almost exclu- 

 sively Trachurus or Sardina, usually Trachurus. 

 Klimaj (1971, 1973) summarized results of com- 

 mercial Polish trawling from 1965 to 1971 in a 

 small area (his area 22) which includes the area of 

 JOINT-I. The principal pelagic fishes taken from 

 March to May were Trachurus spp., Caranx 

 rhonchus, Scomber japonicus, and Pomatomus 

 saltatrix. Caranx rhonchus was common only in 

 March and P. saltatrix only in May. The other two 

 were important in all months, with Trachurus 

 generally much more abundant than Scomber. The 

 Trachurus would have been either T. trachurus or 

 T. trecae, which are not distinguished in the Polish 

 fishery. 



It was noted earlier that the principal spawning 

 seasons of Caranx and Scomber are respectively 

 later and earlier than the period of JOINT-I. The 

 spawning season of Pomatomus is also later 

 (references in Blackburn 1975). Thus these forms 

 could have occurred in the area and period of 

 JOINT-I although we did not recognize them in 

 the ichthyoplankton. Caranx rhonchus probably 

 did occur in March, especially inshore, and S. 

 japonicus may have occurred, although not in 

 great abundance. 



