Population dynamics of the krill Meganyctiphanes norvegica (M. Sars, 1857) (Crustacea: Euphausiacea) in the Ligurian Sea (NW Mediterranean Sea). Size structure, growth and mortality modelling

• Published in: Journal of plankton research 1996-12, Vol.18 (12), p.2295-2312
• Main Authors: Labat, J.Ph, Cuzin-Roudy, J.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Animals; Biological and medical sciences; Demecology; Earth Sciences; Fundamental and applied biological sciences. Psychology; Marine; Meganyctiphanes norvegica; Oceanography; Protozoa. Invertebrata; Sciences of the Universe
• ISSN: 0142-7873; 1464-3774
• DOI: 10.1093/plankt/18.12.2295

The seasonal abundance, population structure and dynamics of the euphausiid Meganyctiphanes norvegica were studied from samples taken year round in the NW Mediterranean Sea. Length-frequency distributions were generally bimodal: the first mode was interpreted as the born-in-the-year cohort (0+) and the second as a combination of the older age classes (1+). To describe growth, a bilinear function provides the best fit. A growth rate of 0.052mm day−1 (1.56mm month−1 was calculated for the first part of the growth function and 0.0034 mm day−1 for the second part. A negative exponential mortality function was fitted, giving a mortality rate of 0.0034 day−1 (1.25 year A numerical simulation of the size structure of the Ligurian population was performed and the validity of the model was checked using a multifactorial analysis. The demographic characteristics of the Ligurian population were compared to those of other areas and were interpreted as a functional adaptation of M.norvegica to the southern part of the geographical distribution of the species.