Larval transport of Aristeus antennatus shrimp (Crustacea: Decapoda: Dendrobranchiata: Aristeidae) near the Palamós submarine canyon (NW Mediterranean Sea) linked to the North Balearic Front

Abstract

Marine fronts are oceanographic drivers for marine species dispersal, especially for their pelagic organisms like the larvae. Larvae can aggregate at the front and consequently have a limited dispersal, which in turn reduces the connectivity between marine populations. Due to the high variations in the ocean, the fronts also have annual changes (i.e., its formation period, gradient, and position), which have poorly-documented effects on larval retention. In the northwestern Mediterranean Sea, a surface density front is localized across a continental margin which is also indented by submarine canyons. There, an abundant population of the commercial deep-sea blue and red shrimp Aristeus antennatus (Crustacea: Decapoda: Dendrobranchiata: Aristeidae) inhabits the seafloor. Each summer, the shrimp offspring are released in pelagic deep-sea and access the superficial waters divided by the density front. In this study, we focused on the interannual variability of the density front influence on the larval transport of shrimps and its repercussions on the potential connectivity between shrimp populations at each front side. A particle-tracking model simulated the larval transport of A. antennatus in hydrodynamics of the northwestern Mediterranean Sea between the years 2006 and 2016. Larval drift distance and seawater density were correlated by 98%. Over the years 2006–2016, the front region retained 86% of larvae, but this rate yearly varied due to changes in density gradient and position of the front. For example, in 2010, 48% of larvae connected to zones south of the front when the density gradient was relatively low. In 2015, 99.2% of larvae were retained in the front region when the latitudinal front position and density gradient were relatively high. Interannual variability of the front position was potentially related to the strength and position of mesoscale circulation patterns. Our findings suggest that the larval retention on habitats favored by canyon productivity because of the front could explain the persistent abundance of A. antennatus population. This information is important to set or improve the fisheries management in zones with strong interannual hydrodynamic variability.