Environmental drivers of sardine (Sardina pilchardus) in the Catalan Sea (NW Mediterranean Sea)

Abstract

In the area surrounding the Ebro Delta, similar to the rest of the northwestern Mediterranean Sea, the sardine (Sardina pilchardus), one of the most exploited small pelagic fishes, has suffered a decreasing trend in abundance and biomass in the last decade, with low values in evidence since 2007. The dependence of this species on environmental factors makes it vulnerable to environmental changes; consequently, the abundance of the species is highly variable. Using segmented regression, we evaluated the presence of discontinuities in the temporal pattern of the seasonally adjusted landings per unit effort (LPUE), which was used as a proxy of abundance, between 2000 and 2013. The results suggested a sudden increase in mid-2005, followed by a sharp decrease starting in 2006. A generalized additive mixed model (GAMM), incorporating the linear correlation structure, was used to identify relationships between the seasonally adjusted LPUE and trends of the Western Mediterranean Oscillation index (WeMOI), Sea Surface Temperature (SST), Salinity (SAL) and the Zonal and Meridional Currents (ZC and MC, respectively). The variance inflation factors (VIFs) were calculated between all environmental variables to avoid high-dimensional collinearities. The final GAMM, selected using the Akaike information criterion, indicated that positive WeMOI values, which favour the productivity of the area, along with SAL (at ca.38) and a northward-flowing MC, favoured LPUE. Our results, obtained by applying a method in which variation due to season, non-linearity, autocorrelation and collinearity of the covariates was taken into account, provided further evidence of the dependence of the sardine population upon specific hydrographic variables.

Current and Future Influence of Environmental Factors on Small Pelagic Fish Distributions in the Northwestern Mediterranean Sea

“…On the contrary, landings of sardine in both areas, and for anchovy in GSA07, presented a consistent negative relationship with salinity. Sardine aggregations tend to be higher in shallower areas characterized by lower salinitythat probably are less favorable for this species (Quattrocchi and Maynou, 2017). The negative relationship between salinity and anchovy seems to be correlated to the spawning success (Zorica et al, 2013), lower salinity values endorse the euryhaline condition of anchovies, indicating a connection between salinity fluctuations and their spawning.…”

The spawning strategy of European hake (Merluccius merluccius, L. 1758) across the Western and Central Mediterranean Sea

“…The presence in several Mediterranean areas of two reproduction peaks in winter and late summer could be explained by the corresponding biomass peaks in anchovy (in winter) and sardine (in late summer) (Patti et al, 2004;Giannoulaki et al, 2008;Martín et al, 2008;Tugores et al, 2011;Quattrocchi and Maynou, 2017). These species are the preferred preys of M. merluccius spawner females in Mediterranean Sea (Carpentieri et al, 2005).…”

“…Ferrer-Maza et al (2014) argued that the Mediterranean hake is capable to change its reproductive strategy and become an income breeder (the energy required for reproductive effort comes from concurrent feeding) during summer. The reason for this change could be the higher prey availability during the summer months in the Mediterranean (Bozzano et al, 1997;Martín et al, 2008;Quattrocchi and Maynou, 2017). These differences could demonstrate that hake is a plastic species with a highly adaptable breeding strategy according to the biotic and nonbiotic factors in each geographical area (Ferrer-Maza et al, 2014).…”

Year-round energy dynamics of sardine and anchovy in the north-western Mediterranean Sea

“…The two most important small pelagic fish in the Mediterranean Sea, in terms of biomass and commercial interest, are European anchovy (Engraulis encrasicolus, hereafter anchovy) and European pilchard (Sardina pilchardus, hereafter sardine) (Palomera et al, 2007). However, in recent decades, important changes in abundance, landings and biological features (such as growth and body condition) have been reported for both species in the north-western Mediterranean Sea (Brosset et al, 2017;Quattrocchi and Maynou, 2017). These changes have been partially attributed to variations in particular oceanographic parameters and increases in fishing pressure (Brosset et al, 2017;Coll et al, 2019;Saraux et al, 2019;Van Beveren et al, 2014).…”