Spatial distribution of 0-group eel larvae (Anguilla sp.) in the Sargasso Sea

Abstract

Both Atlantic eel species (Anguilla anguilla and A. rostrata) were collected in the Sargasso Sea during the 1979 cruise of the F. R. V. "Anton Dohrn" and R. V. "Friedrich Heincke". A total of 3,097 0-group larvae were caught during 80 hauls using the Isaacs Kidd Midwater Trawl (55 hauls) and the 9-fold opening and closing net MOCNESS (25 hauls). 11 hauls of the MOCNESS indicated that the larvae showed a preference for the 150-175 m water depth during daytime and for the 50-75 m depth during night. The northern distribution limit seems to coincide with the "18 °C-water" at the sea surface. The Antilla current characterised by higher temperatures and salinities could have been the southern distribution limit. The north-easternmost occurrence of A. anguilla was noted at 50 ° W; the eastern distribution limit of this species could be farther east. The westernmost station at 69 ° W was positive for both species. A. anguilta, therefore, is very likely to occur beyond this area. The easternmost occurrence of A. rostrata was noted at 52°W though sporadic and with increasing abundance towards the west. At the western end of the network of stations the highest concentration of larvae from both species was recorded. Oceanographic investigations reveal that the distribution of the smaller larvae (size-groups < 7 mm and < 10 ram) almost coincides with the assumed spawning area.

Taxonomic studies on the 0-group eel larvae (Anguilla sp.) caught in the Sargasso Sea in 1979

“…This would imply that eggs of the same species are spawned in different water layers or sink to different depths with highly different temperatures. As, in the present material, very small specimens of both species came from the same hauls (Schoth & Tesch, 1982) this seems improbable. According to Blaxter (1969) there usually is a V-relation in changes of vertebrae with different temperatures, i.e.…”

“…Five specimens, longer than 30.0 mm (2 x 31.0 ram; 2 x 31.5 ram; 1 × 32.0 ram), have not been considered in the analysis; later on they turned out to be A. rostrata. For information on the station net in the Sargasso Sea, the geographical distribution of the larvae and the methods of fishing, see Schoth & Tesch (1982).…”

Studies on the small invertebrate plankton of the Sargasso Sea

“…It was originally attempted in the present study to assess this small zooplankton fraction in the Sargasso Sea as potential food supply for eel larvae. The spawning area of the American and European eel (Anguilla rostrata and A. anguilla) is located in the southern part of the Sargasso Sea, and recent studies by Schoth & Tesch (1982) have demonstrated that the youngest larvae occur mainly in this area. However, not one single food organism has yet been found in the guts of the eel larvae.…”

Species assemblages of leptocephali in the Sargasso Sea and Florida Current

“…The spawni.ng locations in the Sargasso Sea and the general distributions of the leptocephali of the American and European eels are relatively well known (Schmldt 1922, Schoth & Tesch 1982, Kleckner et al 1983, Boetius & Harding 1985, Tesch & Wegner 1990) in comparison to the other 12 families o' f anguilliform eels whose leptocephali are commonly found in the WNA. Some information is available on the distributions and diets of adult eels in the WNA (Bohlke & Chaplin 1968, Bohlke 1989), but little is known about the reproductive ecology of most marine eels, other than a few observations of apparent spawning migrations (Cohen & Dean 1970), reproductive behavior (Moyer & Zaiser 1982, Ferraris 1985, the presence of eggs and leptocephali (Castle & Robertson 1974) and gonadal morphology (Bohlke 1989, Fishelson 1992) In a few shelf species.…”