The population of mysid Neomysis integer (Leach 1814) was studied in the Galgenweel, a brackish pond situated on the left bank of the Westerschelde near the city of Antwerp (Belgium). This study covers the population dynamics of N. integer involving density, biomass, population structure, growth, fecundity and secondary production and also briefly investigates its diet quantitatively and qualitatively. Fortnightly samples were collected from 18 December 1992 to 16 December 1993. The Bhattacharya method was applied to the length-frequency data for detection and separation of cohorts. Growth was described both by a generalized von Bertalanffy function and by a von Bertalanffy function incorporating seasonal oscillations in growth. Secondary production was estimated for each cohort using the size-frequency method. The food items consumed by Neomysis integer in months of February, May, July and November were briefly described quantitatively and qualitatively. The density and biomass of Neomysis integer fluctuate seasonally. The lower densities and biomass were recorded during winter and peak densities and biomass in summer and autumn. Neomysis integer produced three generation per year. The overwintering generation lived from autumn till spring of the following year , the spring generation, which was born in spring, lived for about three months, while the summer generation lived from summer until early winter of the same year. The three generations showed differences in their biology (e.g. density, growth, size at maturity and production). The overwintering generation accounts for more than half of total production. Within cohort, the females lived longer, reached a bigger size and showed higher production than the males. The food items consumed by Neomysis integer varied seasonally and consisted mainly of unidentifiable detritus, while other items were remains of calanoid copepods, sediment part, pollen and macrophyte detritus. In May, most of the stomach contents of the N. integer consisted of pollen and cladoceran. |
