Population structure and accumulation of lipids in the ctenophore Mertensia ovum

We studied the abundance, length-frequency distribution and body composition (lipid accumulation) of the ctenophore Mertensia ovum in Kongsfjorden, Svalbard (79°N) between May 2001 and April 2002. The highest abundances were found during summer in the outer and middle areas of the fjord, possibly caused by the concentration of advected zooplankton. Polymodal length-frequencies indicated a life span of 2 years, with 0, 1 and 2-groups being present in summer. Total lipid for a standardized animal decreased from May to August, and increased to the highest level in September. Relative lipid content was always highest in the 0-group, probably reflecting reduction of lipid levels due to increased energy costs during reproduction for the older age groups. Lipids probably are used to fuel prolonged reproduction from May to August until spawning ends by September. The overwintering age groups (0 and 1) subsequently build up lipid reserves for the next years’ spawning.