Male Deep-Sea Shrimps Aristeus antennatus at Fishing Grounds: Growth and First Evaluation of Recruitment by Multilocus Genotyping

The population biology of the deep-sea shrimp Aristeus antennatus, as with other exploited demersal species, is usually studied using data from fishery statistics. Such statistical analyses have shown female-biased sex ratios during the spawning season in this species. Because the abundance of males increases at greater depths that are not exploited by fisheries (virgin grounds), knowledge on their recruitment is limited. Here, the growth and recruitment of A. antennatus males at fishing grounds was evaluated. This was achieved by integrating information on previously identified breeding behaviours and by tracing the young-of-year cohort through genotyping at 10 microsatellite loci. Using a codend and a codend cover with distinct meshed windows, four groups of males were collected in winter and in a subsequent spawning summer season. Summer collections were mostly composed of pre-adult males, reaching sizes that are to be expected from the growth of winter juveniles; however, many specimens also originated from nearby grounds. This result indicates the horizontal dispersal of male juveniles via intermediate and deep oceanographic currents. Such dispersal complements passive larval dispersal in surface waters, and contributes to the weak genetic divergence among regional fishing grounds. These features could be shared by other deep-sea crustacean and fish species, and should be considered for the sustainable exploitation of demersal fisheries.

Genetic analyses reveal temporal stability and connectivity pattern in blue and red shrimp Aristeus antennatus populations

Temporal variability of the genetic structure and connectivity patterns of the blue and red shrimp Aristeus antennatus in the seven most important fishing grounds of the Western Mediterranean Sea, were assessed using twelve microsatellite loci during 2 consecutive years (2016 and 2017), in a total of 1403 adult individuals. A high level of geographical connectivity among groups was observed in the two studied years. In fact, no significant geographical differentiation was found in 2016 (FST = 0.0018, p > 0.05), whereas it was indicated in 2017 (FST = 0.0025, p < 0.05). This small divergence in 2017 was not attributed to the distance among locations nor to the effect of the Ibiza Channel. Significant allele frequency changes were found at local level between the 2 years (FCT = 0.0006, p < 0.05), mainly due to Blanes’ fishing ground. Larval dispersal from the North to the South through the main superficial current supports the high level of connectivity pattern found. The temporal genetic instability detected in the Blanes’ fishing ground could be explained by oceanographic temporary features. Our findings evidence only one biological unit in the study region and establish the baseline for an inter-federal management plan of A. antennatus.