Advection of continental water as an export mechanism for anchovy, Engraulis encrasicolus, larvae

Abstract

SUMMARY: The presence of a surface layer of a less saline water of continental influence (CIW) along the continental slope off the Catalan coast (NW Mediterranean) was observed in June 1995. This CIW was formed in the Gulf of Lions from Rhône runoff and carried by the current associated with the shelf-slope front. This study analyses the spatio-temporal behaviour of that water of continental influence in relation to the shelf-slope front, and its effect on the distribution of fish larvae, in particular the larvae of the anchovy, Engraulis encrasicolus. Displacements of the front are observed to follow an oscillation with a period of eight days and an amplitude of 10 km. Anchovy larvae were associated with the presence of CIW, whereas the oceanic species Hygophum benoiti appeared in the region of the slope when the front, and the associated CIW layer, moved close inshore during its oscillation. The size frequency distribution for the anchovy larvae trapped within the CIW suggests that the larvae had been spawned further north, near the Gulf of Lions. It is concluded not only that larvae were transported by the current but also that their development had taken place entirely inside the CIW. The possible benefit to the survival of anchovy larvae of being kept inside that water, though they have been carried far from their spawning areas, is discussed in the basis of fluorescence and microzooplankton data.

Patrones espacio-temporales de clorofila en el Mediterráneo Noroccidental derivados del sensor MERIS

“…At the peak of production (April), the COB is clearly visible though it loses strength offshore the city of Barcelona, at least at the surface, the absence or weakening of this frontal structure may facilitate shelf-slope exchanges at this latitude. In the same latitude, Sabatés et al, (2001) found a strip of low salinity water over the shelf-slope identified as continental influence water (CIW) which is enhanced by low wind speed and increasing thermal stratification (Sabatés et al, 2001). Results given for the CIW show that, firstly, this strip had the same speed of 25 km day -1 that has already been estimated for the NC (Castellón et al, 1990), and secondly its width offshore from Barcelona was about 15 km.…”

“…The reason why other studies (i.e. Estrada and Salat, 1989;Estrada 1991;Sabatés et al, 2001) did not find the low productive belt could be due to study areas which were further south (around 41ºN) where this belt is indiscernible or inexistent. Nevertheless, the oligotrophic influence of the north Mediterranean current was already observed in the Gulf of Lions (Gaudy et al, 2003).…”

“…The major difference between their CIW strip and our COB belt is that they found these waters to be highly productive while, in this study, the COB is characterised by the opposite condition. However, at certain months and off Barcelona, the COB is not so clear and may only partially support the findings of Sabatés et al, (2001) (e.g. March 2003 Fig.…”

Establishing the link between <em>Ostreopsis</em> cf.<em>ovata</em> blooms and human health impacts using ecology and epidemiology

“…Furthermore, water motion controlled by the major hydrodynamic patterns near the Catalan coast (see e.g. Sabatés et al 2001, and references there in), combined with the daily breeze regime and swell, would then cause the dilution or concentration of the Ostreopsis planktonic population. As for the epidemiological study in this Ostreopsis hot spot, the observed human cohort suffered a similar attack rate (81% of the studied cohort) to that of the previous reported outbreaks (Àlvarez et al 2005(Àlvarez et al , Àlvarez 2006(Àlvarez et al , Vila et al 2008).…”

Evidence for enhanced primary production resulting from relative vorticity induced upwelling in the Catalan Current

“…Still, a 1 m x 20 km slice through a zone with active upwelling over 30 days per year could inject 14 kg P. This would represent about 30% of the new production calculated by Estrada and Margalef (1988) for a 1 m wide band, approximately perpendicular to the coast, and some 200 km in length. Onshore-offshore distributions of larval fish have also been linked to topographically induced transport (Alvarez et al, 1996;Olivar et al, 1998;Sabatés et al, 2001). These motions and associated phytoplankton production might also explain the seasonal recruitment of fish larvae along the coast (Zika, 1999).…”