The Mediterranean Sea is one of the world's hotspots for marine bio-invasions. Most invasions are first documented based on an initial record of occasional adult captures. However, reports of larval stages could indicate that there is an adult population that is reproducing and therefore well established in the area. The spread of the oriental shrimp, Palaemon macrodactylus, from its native estuarine waters of southeast Asia to new regions worldwide is well documented. We report the first record of this species in the Mediterranean based on the presence of its larval stages in plankton samples. Decapod larvae were collected in five offshore plankton surveys performed off the Balearic Islands (western Mediterranean), and zoeae III and VI of the oriental shrimp were found among them. Taking into account the duration of the successive developmental stages, and the hydrodynamic characteristics of the study area, these larvae were most probably spawned by adult populations not yet documented. The larvae were found in marine waters despite the fact that adults usually inhabit brackish waters. Our study is a good example of how plankton studies can help to detect larval stages of invasive species before the adult populations are detected. ; The research was carried out within the framework of the projects BALEARES (CTM 2009-07944 MAR) and IDEADOS (CTM2008-04489-C03-01), funded by the Spanish Plan R+D+i. Torres acknowledges pre-doctoral FPI Fellowship support from the Regional Government of the Balearic Islands, selected as part of an operational program co- financed by the Fondo Social Europeo. ; Peer Reviewed
Marine resources stewardships are progressively becoming more receptive to an effective incorporation of both ecosystem and environmental complexities into the analytical frameworks of fisheries assessment. Understanding and predicting marine fish production for spatially and demographically complex populations in changing environmental conditions is however still a difficult task. Indeed, fisheries assessment is mostly based on deterministic models that lack realistic parameterizations of the intricate biological and physical processes shaping recruitment, a cornerstone in population dynamics. We use here a large metapopulation of a harvested fish, the European hake (Merluccius merluccius), managed across transnational boundaries in the northwestern Mediterranean, to model fish recruitment dynamics in terms of physics‐dependent drivers related to dispersal and survival. The connectivity among nearby subpopulations is evaluated by simulating multi‐annual Lagrangian indices of larval retention, imports, and self‐recruitment. Along with a proxy of the regional hydroclimate influencing early life stages survival, we then statistically determine the relative contribution of dispersal and hydroclimate for recruitment across contiguous management units. We show that inter‐annual variability of recruitment is well reproduced by hydroclimatic influences and synthetic connectivity estimates. Self‐recruitment (i.e., the ratio of retained locally produced larvae to the total number of incoming larvae) is the most powerful metric as it integrates the roles of retained local recruits and immigrants from surrounding subpopulations and is able to capture circulation patterns affecting recruitment at the scale of management units. We also reveal that the climatic impact on recruitment is spatially structured at regional scale due to contrasting biophysical processes not related to dispersal. Self‐recruitment calculated for each management unit explains between 19% and 32.9% of the variance of recruitment variability, that is much larger than the one explained by spawning stock biomass alone, supporting an increase of consideration of connectivity processes into stocks assessment. By acknowledging the structural and ecological complexity of marine populations, this study provides the scientific basis to link spatial management and temporal assessment within large marine metapopulations. Our results suggest that fisheries management could be improved by combining information of physical oceanography (from observing systems and operational models), opening new opportunities such as the development of short‐term projections and dynamic spatial management. ; M. Hidalgo acknowledges support of two contracts funded by the Spanish national program "Ramon y Cajal" (RYC‐2015‐18646) and by the regional government of the Balearic Islands, the later co‐funded by the European Social Fund 2014‐2020. V. Rossi acknowledges support of a post‐doctoral 'Juan de la Cierva Incorporacion' fellowship (IJCI‐2014‐22343) provided by the Spanish MICINN and a networking grant through the HYDROGENCONNECT project funded by the French program MISTRALS ENVI‐Med. E. Ser‐Giacomi thanks French program "Investissements d'Avenir" (ANR‐10‐LABX‐54 MEMOLIFE and ANR‐11‐IDEX‐0001‐02 PSL Research University). This work was also supported by the Spanish National projects LAOP (CTM2015‐66407‐P) P. Monroy and E. Hernandez‐Garcia and CLIFISH (CTM2015‐66400‐C3‐1‐R) and to M. Hidalgo, B. Guijarro, and E. Massuti (AEI/FEDER, EU). P. Reglero and M. Hidalgo acknowledge funding of the H2020 PANDORA project (Nr. 773713). ; Peer reviewed
