Matching an Old Marine Paradigm: Limitless Connectivity in a Deep-Water Fish over a Large Distance

Abstract

Investigations of population structuring in wild species are fundamental to complete the bigger picture defining their ecological and biological roles in the marine realm, to estimate their recovery capacity triggered by human disturbance and implement more efficient management strategies for fishery resources. The Blackspot Seabream (Pagellus bogaraveo, Brünnich 1768) is a commercially valuable deep-water fish highly exploited over past decades. Considering its exploitation status, deepening the knowledge of intraspecific variability, genetic diversity, and differentiation using high-performing molecular markers is considered an important step for a more effective stock assessment and fishery management. With one of the largest efforts conceived of and completed by countries overlooking the Atlantic and Mediterranean coasts in recent years, a total of 320 individuals were collected from different fishing grounds in the Mediterranean Sea and Atlantic Ocean and analysed using 29 microsatellite loci. We applied multiple statistical approaches to investigate the species' connectivity and population structure across most of its described distribution area. Considering the incomplete knowledge regarding the migratory behaviour of adults, here we suggest the importance of egg and larval dispersal in sustaining the observed genetic connectivity on such a large geographical scale.

Keywords: Blackspot Seabream; Pagellus bogaraveo; connectivity; fishery resource; microsatellite; population structure.

Figure 1

Map of geographical distribution of the sample analysed. Geographical coordinates are available only for the MEDITS-2018 (red dots) and MEDITS-2019 (green dots) samples. Refer to Table 1 for location codes. Location codes refer to landing ports. Sources (basemap): Esri, GEBCO, NOAA, National Geographic, DeLorme, HERE, Geonames.org, and other contributors. Maps were created using ArcMap™ (version 10.8) software of ArcGIS (https://www.arcgis.com/, accessed on 16 January 2023). ArcGIS^® and ArcMap™ are the intellectual property of Esri and are used herein under license.

Figure 2

(a) Result of DAPC analysis performed on 14 locations. (b) Result of DAPC analysis performed on 6 macro-areas.

Figure 3

Summary plot of the STRUCTURE analysis from K = 2 to K = 5. Each individual is represented by a single vertical line on the x-axis. Coloured segments represent the membership of individuals in the population clusters. Results are shown for the 14 locations using 14 microsatellite loci.