## 4 Discussion
Salinity may also play a role in the distribution of small and medium pelagic fishes, yet along the northern Mediterranean coastline, where the pelagic fishes are mostly abundant, salinity is greatly influenced by precipitation and riverine input, as well as by the inflow of Black Sea water in the Aegean Sea [66]. Thus, other processes including precipitation and runoff are also involved affecting salinity and in turn the distribution of small pelagic species [72]. Anchovy larvae have been reported to preferentially occupy coastal areas, which are areas that are often influenced by river plumes [77]. The effect of precipitation is stronger for pelagic fishes that are distributed along the coast (such as sardine and anchovy [78; 79]) and may also affect their catches [14]. Species with a more oceanic distribution such as the scombrids and swordfish are less impacted. In the NW Mediterranean, sardine and anchovy have been fluctuating in synchrony for over 30 years [70; 80] rather than alternating in high abundances, as globally observed for anchovy-sardine coexisting populations [81; 82]. Local environmental conditions, including river runoff, wind mixing, sea surface temperature and chlorophyll concentrations, influenced by climatic oscillations [80; 83] have been reported to control the fluctuations in abundance of these species in this area [14; 65; 84] and probably explain the high probability of occurrence for both species in the western Mediterranean. A regional index, the Western Mediterranean Oscillation index, which has been developed to explain the precipitation variability of the Iberian Peninsula [85], seems to represent well the suitable environmental conditions for sardine and anchovy in the west Mediterranean [80]. Furthermore, in the case of small pelagic fishes, the spawning areas and larval distributions are also highly related to environment and recruitment success, and they may determine adult abundance and affect spatial distribution. At the same time, inter-specific competition for resources may provide advantage for the species that has spawned earlier or is more abundant [86]. For example, when \begin{table}
\begin{tabular}{l l} \hline \hline
**Predictor** & **Friedman Rank** \\ \hline Longitude & 1.5 \\ Salinity & 2.625 \\ Temperature & 3 \\ Latitude & 4.625 \\ Distance to Coast & 7.25 \\ Dissolved Oxygen & 8.875 \\ Nitrate & 9.375 \\ Zonal Current & 9.75 \\ Eupbiotic Depth & 10 \\ Wave Height & 10 \\ Phosphate & 10.25 \\ Chlorophyll-a & 10.375 \\ Sechich Disk Depth & 10.875 \\ Distance to Major River & 11.375 \\ Meridional Current & 11.875 \\ Bathymetry & 14.375 \\ Substrate & 16.875 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Overall predictor importance among the eight commercial fish species ranked by Friedman Rank. outnumbered, round sardinella larvae are concentrated in areas where competition is minimized because the food availability would be higher [87, 88]. This behaviour is a characteristic of opportunistic and easy to adapt species [89], such as round sardinella. Similar results have been reported for the NW Mediterranean coast [87], with the less abundant round sardinella larvae occupying the less favourable for survival areas, in order to avoid potential competition with anchovy. Round sardinella larvae may be disadvantageous compared to anchovy, because their bathymetric distribution is limited to the upper 50m of the water column. Thus, they cannot feed on the deep chlorophyll maximum layer probably due to their inability to tolerate lower temperatures [90]. Finally, it is interesting to see what percentage of the Mediterranean Sea is covered by high probability occurrence for each species. Considering 80% and greater as high occurrence probability, following Figure 6, it was computed that anchovy covers 14.7% of the Mediterranean, sardine 17.8%, round sardinella 30.7%, Atlantic chub mackerel 2%, Atlantic mackerel 0.7%, picarel 82.3%, bluefin tuna 4% and swordfish 1.8%.