Anchovy on the rise: Investigating environmental drivers of recruitment strength in the northern Canary Current

Abstract

Since the mid-2010s, the abundance and recruitment of the European anchovy Engraulis encrasicolus has significantly increased off Western Iberia, leading to a 5-fold increase in anchovy catches. The potential environmental drivers impacting recruitment variability in anchovy in Atlantic Northwestern Iberian waters (NW Iberia) are unknown. Using data spanning 1999-2021, we identified regional changes in biological and physical factors most likely responsible for the persistent increased productivity of anchovy. Anchovy recruitment was strongest during periods with weak downwelling events (-500 to 0 m3 s-1 km-1), lower salinity (<35), and temperature between 15 and 17°C from April through June, months corresponding with annual peak spawning. Positive Winter North Atlantic Oscillation (NAOW) was also associated with years with strong anchovy recruitment. It is likely that local oceanographic features such as the Iberian Poleward Current and the Western Iberia Buoyant Plume contribute to a higher onshore retention of anchovy larvae, promoting life cycle closure and higher survival. The average lower salinity levels observed during spawning seasons since 2009 support this hypothesis. Moreover, random forest models suggested that years with relatively strong anchovy recruitment tended to be those with low abundance of European sardine Sardina pilchardus, suggesting that intra-guild processes such as foraging competition and egg predation are also important in establishing recruitment potential. We highlight future avenues of research needed to gain a mechanistic understanding of recruitment drivers of anchovy in this region to provide robust, science-based advice to managers and improve projections of the potential impacts of climate change.