Temporal Dynamics of Jellyfish Pelagia noctiluca Stranded on the Mediterranean Coast of Morocco

Abstract

Seasonal dynamics of the scyphomedusa Pelagia noctiluca were studied along with their relation to certain environmental factors between the study period that extends from January 2018 to December 2019. During 2018, stranded individuals of P. noctiluca appeared throughout this year, but their high frequency was reported in the summer. While in contrast, P. noctiluca in 2019 was reported in a very low number only during the winter season and had not been detected in the other seasons of this year. The overall results revealed that the inter-annual variations in the abundance of jellyfish were not significantly (P<0.05) correlated with water temperature, relative humidity and atmospheric pressure. Our results showed easterly winds as a significant predictor of P. noctiluca strandings. The bell diameters of examined jellyfish ranged from 30 to 130 mm, with mean of 72 mm. Stranded mature jellyfish individuals as well as young ones were recorded throughout the year 2018. The size distribution indicated that P. noctiluca can reproduce all around the year, with its more intense activityduring the spring. The continuing presence of P. noctiluca in the Moroccan Mediterranean makes it necessary to set effective strategies in order to prevent and minimize their impact on economic activities.