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

The deep-sea red and blue shrimp Aristeus antennatus is a commercially valuable species for Spanish fishing harbors of the northwestern Mediterranean Sea. Since 2012, some fishermen of the deep-sea shrimp follow a local management plan which restricts fishing in certain areas to sustain the resource. However, little is known about the dispersal of larvae; specifically, it is not known how far larvae can be transported from spawning areas and if there could be mixing of larvae from different fishing grounds. The objective of this study was to estimate the spawning sites of larvae that were collected on a field campaign in 2016, evaluate uncertainty related to model parameterizations, and determine if collected larvae could have come from the restricted fishing areas. Using a 3-dimensional coupled hydrodynamic and Lagrangian transport model, the spawning sites of the larvae were estimated by backwards simulation of larval trajectories from the sampling stations. The backtracked larvae were assigned temperature-dependent stage durations based on a literature review of similar species. Simulated larvae were released from the sampling locations and then were backtracked to spawning sites, with median distances from starting to ending locations of 11 and 38 km when minimum and maximum Pelagic Larval Durations were implemented, respectively. Uncertainty analysis of backward trajectories showed that distance estimates could vary by as much as 27 and 3 km due to differences in how simulated Pelagic Larval Durations and turbulent mixing were parameterized. Of the 35 sampling stations from which larvae were backtracked to fishing grounds, 13 were tracked back to multiple fishing grounds, suggesting that mixing of larvae from different fishing grounds does occur. These results support the idea of multiple connectivities between subpopulations of the A. antennatus and may help inform regional management plans.