Twenty- year trends of Centropages typicus (Copepoda, Calanoida) reproduction, feeding, population abundance and structure in the Gulf of Naples (Western Mediterranean Sea)

Centropages typicus is a temperate calanoid copepod occurring in Atlantic and Mediterranean coastal waters, where its reproductive biology and population dynamics are well-known. C. typicus has also been suggested as a key species for monitoring the impact of environmental changes on copepod secondary production. The aim of this study is to investigate the seasonal and interannual reproductive (egg production and egg hatching success) and feeding (fecal pellet production) traits, population abundance and structure (sex ratio) of C. typicus over a 20-year period at the Long-Term Ecological Research site MareChiara (LTER-MC) in the Gulf of Naples (Central Tyrrhenian Sea, Western Mediterranean Sea), identifying specific trends and patterns. At a seasonal scale, egg production and hatching success were tightly linked with maxima in February-March, driving the juvenile and adult springtime population peaks but showing a poor correlation with phytoplankton abundance, pointing to an omnivorous diet. At a multiannual scale, an observed decrease in the population is backed up by a reduction in egg production, despite an increase in hatching success. The results of this study provide new elements to comprehend the links between C. typicus functional traits, population dynamics, and environmental factors and highlight the importance of running LTER series to monitor the trends in natural environments.