Seasonal abundance and reproduction of clausocalanid copepods in the northern Gulf of Aqaba (Red Sea)

Clausocalanid copepods dominate subtropical mesozooplanktoncommunities. Their life cycles, however, are generally unknown.Here, we follow the seasonal population development and reproductivebiology of Red Sea clausocalanids in the northern Gulf of Aqaba,between February 2002 and December 2003. Monthly vertical haulstaken with a Nansen net (200-µm mesh size) between 100m and the surface revealed four species, including a new record(Clausocalanus minor) for the area. Ctenocalanus vanus abundancespeaked during winter and spring, followed by Clausocalanus farranipeaking in spring and, additionally, in June 2003. In 2002,the abundance of Clausocalanus furcatus showed no distinct seasonaldevelopment of abundance, whereas in 2003, it reached high densitiesin January, July and November. Overall, C. vanus dominated theclausocalanid community during the first half of the year andC. furcatus during the second half of the year, whereas thepercentage of C. farrani remained fairly stable throughout bothyears. The correlation between the environmental parameters(temperature and chlorophyll a concentration) and the proportionof mature gonads was significant only between C. vanus and temperature.Incubation experiments showed that egg production rates variedbetween 0–3.3 and 1.8–9.2 eggs female^–1 day^–1in C. farrani and C. furcatus, respectively. Endoparasitismby dinoflagellates and the occurrence of intersexes were foundin all three species, with C. farrani being the most affected.