Population dynamics of the copepod invader Oithona davisae in the Black Sea

Abstract

During 2013–2016 in Sevastopol Bay, seasonal and interannual dynamics of the population density, age and sex composition,fecundity, and mortality of males and females of O. davisae were studied. A maximum population number (up to 554 ind × 103 m–3) wasregistered at the end of summer–end of autumn. In this period, the nauplii and early copepodite stages constituted up to 95% of the O.davisae population. During 1–2.5 cold winter–spring months, the population consisted only of females, who were not numerous. Thephase of latent population development was recorded from April until July-August, with a high share of ovigerous females, maximumclutch size, and high egg production rate but low population density, which may be due to predator pressure from lobate ctenophores.The average share of adult males amounted to 32% at the end of spring and 27% at the beginning of winter, while the share of dead malesreached maximum values (20.7%) during the winter degradation period for the population. On the basis of the studied successions of thepopulation’s developmental stages, from ovigerous females through nauplii and early copepodites to adults, the number of generationsproduced by O. davisae during the reproductive period (10–11) was determined.