Hydrographic phenomena influencing early life stages of the Sicilian Channel anchovy

Abstract

The information collected from a European Union funded project on the ‘Distribution Biology and Biomass Estimates of the Sicilian Channel Anchovy (Engraulis encrasicolus)’ was used to analyse the linkage between the general circulation pattern of the Atlantic Ionian Stream (AIS) and the reproductive strategy of the Sicilian Channel anchovy. The main spawning ground is located in the NW region of the southern Sicilian coast. This region is a stable area of low current produced by the impingement towards the coast of the AIS and its bifurcation into two branches. The main branch heads towards the SE end of the Sicilian coast (Cape Passero) acting as a transport mechanism for the anchovy eggs and larvae. Along the AIS trajectory, there is a density front to the left of the current, facing downstream. This front is a consequence of the shoreward sloping of isopycnals that maintains the geostrophic flow, facilitating the mixing of deeper waters with surface layers and fertilization of coastal waters. The front enhances primary production assuring food availability for anchovy larvae during their advection by the AIS. The highest concentrations of larval anchovy were found off the SE Sicilian coast, in the area off Cape Passero. The greater average sizes of larvae found in this region, and their estimated age, support the evidence of advection by the AIS. The hydrographic features observed in this area, such as the existence of a well‐defined cyclonic vortex, implies the existence of upwelling in its centre, providing a suitable environment for sustained enhanced rates of primary production and allowing the larval population to maintain their relative position. This retention area is conceived as favourable for providing the necessary feeding conditions. The data acquired from a survey carried out to evaluate the anchovy recruitment strength confirm that larvae reach the juvenile stage in the south‐eastern coast of Sicily, since most of the young‐of‐the‐year anchovy were located in the Cape Passero region.

Forecasting ocean warming impacts on seabird demography: a case study on the European storm petrel

“…This latter situation probably coincides with unfavourable conditions in terms of prey availability in the Sicilian Channel. Although primary productivity at lower trophic levels may be increased by deep/ cool water upwelling enhancing the circulation of nutrients, negative SST anomalies may have a negative physiological influence, delaying fish development (Lafuente et al 2002). Studies on fish population in this area have shown that sardine and anchovy biomass are negatively correlated with the mean SST in periods corresponding to larval and juvenile growth, resulting in a reduction in recruitment success and thereby also population size (e.g.…”

“…Studies on fish population in this area have shown that sardine and anchovy biomass are negatively correlated with the mean SST in periods corresponding to larval and juvenile growth, resulting in a reduction in recruitment success and thereby also population size (e.g. Lafuente et al 2002). In particular, Marettimo storm petrel colonies are located at the western inlet of the Sicilian Channel, where the 2 large Mediterranean sub-basins meet, resulting in the bifurcations of the surface and intermediate-depth water transports (Pierini & Rubino 2001).…”

“…The area is characterized by seasonal wind-induced water movements, particularly in the spring period when winds from the north over the western basin and winds from the south-east over the the eastern basin meet, generating Ekman transport (Bakun & Agostini 2001). Geostrophic fronts in the area facilitate the pumping of nutrients from deep layers, and warm SSTs speed up the development of eggs and larvae (Lafuente et al 2002). When waters are colder, this process may be altered, affecting storm petrels whose diet depends on larval and juvenile stages of fishes (Albores-Barajas et al 2011).…”

Spatio-temporal behaviour of the deep chlorophyll maximum in Mediterranean Sea: Development of a stochastic model for picophytoplankton dynamics

“…Here we consider the Strait of Sicily, which is known to govern the exchanges between the eastern and western basins and is characterized by active mesoscale dynamics (Lermusiaux and Robinson, 2001), strongly influencing the ecology of phytoplankton communities. Moreover, the Strait of Sicily is a biologically rich area of the Mediterranean Sea with a key role in terms of fisheries (Lafuente et al, 2002;Cuttitta et al, 2003). The anchovy growth (along with phytoplankton biomass) in the Sicilian Channel resulted to be mainly explained by changes in the chlorophyll concentration, used as a phytoplankton biomass indicator (Basilone et al, 2004).…”

Relationship Patterns between Ichthyoplankton and Zooplankton: A Conceptual Model

“…In spite of the efforts of several international programs focused on the study of the biology of fish larvae (Miya, 1995;Noell, 2003), their assemblages (McGowen, 1993;Sanvicente-An˜orve et al, 1998) and relationship with the environment (Olivar, 1990;Lafuente et al, 2002), our current knowledge on the relationship between total abundance of fish larvae and zooplankton biomass (hereinafter termed Fl & Zoo) is still limited. Some authors have attempted to describe such a relationship (Ali Khan & Hempel, 1974;Loeb, 1979;Ciechomski & Sa´nchez, 1983;Cowan & Shaw, 1991;Rodrı´guez & Rubı´n, 1991), and some have restricted their interpretation to only one species of fish (Townsend, 1983;Cowan & Shaw, 1991).…”