Estimating the spawning locations of the deep-sea red and blue shrimp Aristeus antennatus (Crustacea: Decapoda) in the northwestern Mediterranean Sea with a backtracking larval transport model

Abstract

The deep-sea red and blue shrimp Aristeus antennatus is a commercially valuable species that occurs in the northwestern Mediterranean Sea where ripe females have been found in fishing areas. In the Palam´os harbor, a local management plan restricts fishing in certain locations to sustain the resource. However, little is known about the dispersal of larvae; specifically, it is not known how far larvae are transported from spawning locations and if there could be mixing of larvae between different fishing areas. The objective of this study was to estimate the spawning sites of larvae collected at 35 sampling stations, evaluate uncertainty in the estimates, and determine if larvae could be exchanged between fishing areas. The spawning sites of larvae were estimated by backward simulation of larval trajectories using a 3-dimensional coupled hydrodynamic and Lagrangian transport model. The backtracked larvae were assigned temperature-dependent stage durations based on a literature review of similar species. Results of model simulations indicated that the median distances from sampling to spawning locations were 11 and 38 km when shortest and longest pelagic durations (PD) were implemented, respectively. Sensitivity studies of backward trajectories showed that distance estimates could vary by as much as 27, 3, and 8 km due to differences in simulated PD, sub-grid-scale turbulence, and advection, respectively. Larvae from 13 of the 35 sampling stations were tracked back to multiple fishing grounds, suggesting that mixing of larvae from different fishing areas could occur. For example, for the sampling stations within the restricted area of Palam´os, 35% of simulated larvae came from the restricted area itself, and 0.9% and 10% of larvae came from neighboring areas to the north and south, respectively. These results suggest that larval transport may connect subpopulations of A. antennatus across different fishing areas, an idea that may help inform regional management plans.