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
• Main Authors: Labat, Jp, CUZINROUDY, J
• Other Authors: Station Zoologique de Villefranche, Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 1996
• Subjects: [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Meganyctiphanes norvegica
• Online Access: https://hal.archives-ouvertes.fr/hal-03479841; https://doi.org/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 0.052 mm day(-1) (1.56 mm 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(-1)). 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.