Diel-depth distributions of fish larvae off the Balearic Islands (western Mediterranean) under two environmental scenarios

Final workshop IDEADOS: The wrapping up of the IDEADOS project, International Workshop on Environment, Ecosystems and Demersal Resources and fisheries, 14-16 November 2012, Palma de Mallorca, SpainPeer reviewe

2014-2021, 8 years without bottom-reaching deep water formation in the Western Mediterranean. Probably, the longest known period

Deep Water Formation (DWF) appeared almost regularly every year, during central winter months, in an area located offshore the Gulf of Lions in the NW Mediterranean Sea. Since the early 1960s, the processes involved in the DWF have been monitored, more or less intensively by regular hydrographic surveys or by moored instruments. It is worth noting the international efforts carried out in late 60s-early 70s by the so-called MEDOC Group to obtain a quite precise description of the whole process. Although the intensity of the DWF, as well as the amount of the newly formed Western Mediterranean Deep Water (WMDW), have shown high interanual variability, those years when the DWF was absent were exceptional, e.g. 1990, and those not reaching the bottom were scarce, e.g. 1997. Typically, they were years with almost no cold northerly winds during winter. By contrast, in some years the amount of newly formed WMDW was exceptional, e.g. 1987, and in some cases, an extra amount of this water came from dense shelf cascading, e.g. 1999. Moreover, in some years, the so-called variable Bottom Water, a slightly warm and salty layer, appeared near the bottom. It was a layer not thicker than 300 m, attributed to a large area affected by DWF which caused an extra amount of Levantine Intermediate Water (LIW) involved in the process, e.g. 1973. Other concomitant conditions that contributed to the DWF variability across the years was the presence of a blocking anticyclone in the Balearic Sea, that would play a role in intensifying the exposure of surface water to the northerlies, e.g. 1999. In winter 2005, all the factors contributing to an intense DWF process acted simultaneously, resulting in a new structure within the WMDW. The amount of newly formed WMDW, with higher density, T and S, was so extraordinary that affected the entire western Mediterranean basin, and it was identified as the Western Mediterranean Transition (WMT). The remnants of the WMDW previous to the WMT have been uplifted as to being available for a relevant contribution to the Mediterranean Outlfow Water (MOW) through the Gibraltar sill. After the WMT, the MOW showed both lower T and S than previously recorded up to around 2015, indicating that the old WMDW has been almost completely lost by leakage and diffusion. After the 2005 episode, the WMDW has evolved, changing its TS shape and increasing both T and S at the bottom, but still maintaining a deep layer with higher stratification than before 2005. In a previous work, we attributed the long period (2014-2018) without DWF to a combination of mild winters, the absence of the old WMDW, and the deep stratification. Such a process would be similar to the recovery of the Eastern Mediterranean Transient. In the present communication we incorporate 3 new years of data to the series, discuss the current situation and try to identify the requirements for a successful bottom-reaching DWF

The benthic communities of the Cap de Creus canyon

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Distribution and feeding dynamics of larval red mullet (Mullus barbatus) in the NW Mediterranean: the important role of cladocera

The feeding habits of Mullus barbatus larvae and the horizontal and vertical distribution of larvae and their dominant prey were studied in the NW Mediterranean during the summer oligotrophic period. The water column showed marked stratification with a deep chlorophyll maximum beneath the thermocline. Horizontal and vertical distribution of larvae showed good correspondence with that of cladocera, their preferential prey from 8 mm standard length. Both groups were restricted to the upper levels of the water column, above thermocline, and were very abundant in the southern area, associated with the low salinity waters from the Ebro river runoff. Prey items consumed by the smallest size classes of larvae <8 mm SL were dominated by copepod nauplii, then diet and prey selectivity shifted towards the cladoceran Evadne spp. The amount and mean size of ingested prey increased throughout development while niche breadth remained constant. This constancy in niche breadth implies that during development larvae shift to other niches, with the replacement of nauplii by cladocerans. Results suggest that M. barbatus larvae probably depend on energy derived from the microbial food web, via their feeding on cladocera, emphasizing the key trophic role of cladocera in this oligotrophic Sea

Comparative feeding patterns of early stages of mesopelagic fishes with vertical habitat partitioning

13 pages, 7 figures, 4 tablesThe present study analysed the trophic ecology of the early developmental stages of four species of mesopelagic fish, the myctophids Ceratoscopelus maderensis, Hygophum benoiti and Benthosema glaciale and the sternoptychid Argyropelecus hemigymnus. These species display different morphological traits and a segregated vertical distribution throughout the water column. The study was conducted off Mallorca Island (39° N, 3° E) in the western Mediterranean, during the summer stratification period. The results indicated that feeding patterns of myctophid larvae were strictly diurnal, while in A. hemigymnus larvae, day and night feeding occurred. In the transformation stage of C. maderensis, B. glaciale and A. hemigymnus, day and night feeding was evidenced. The feeding incidence during the larval stages was low, increasing in the transformation stages, and being particularly high for A. hemigymnus. Although an increasing tendency in size and number of ingested prey was observed, the trophic niche breadth did not indicate a trophic specialization in any of the species analysed. Gut content analysis determined that diet composition was very similar among the four species, with the different developmental stages of copepods being the dominant prey throughout the early larval development. Nevertheless, in transformation stages of C. maderensis and H. benoiti, other preys, like ostracods, become important contributors to the diet. Despite the important physical and biological structuring of the water column, no differences in feeding success were observed for larvae occurring in the layers of higher biological productionThis research was funded by project CTM2008-04489-C03Peer Reviewe

Els peixos en un escenari de canvi global: la importància dels primers estadis del cicle vital per a la conservació de les poblacions naturals

3 pages, 2 figures[EN] The early life history of fish is the period that elapses from spawning to recruitment into the adult population (Figure 1). These early stages –eggs and larvae– are a key component in the fish life cycle because their survival success determines both short- and long-term variations in population abundance. Most marine fishes produce thousands to millions of pelagic eggs, which in a few days hatch into larvae that spend weeks to months in the plankton. Fish larvae are characterized by their small size (a few mm to ca. 2 cm), transparency and limited swimming skills, and they display amazing shapes that differ greatly from those of adults (Figure 2). During the planktonic period, fish larvae interact with other planktonic organisms as both predators and prey (Figure 1): feeding upon small prey such as juvenile stages of copepods and, in turn, being preyed on by larger nektonic and planktonic organisms such as jellyfish. […][ES] Las primeras etapas del ciclo vital de los peces comprenden el periodo desde la puesta hasta el reclutamiento a la población adulta (figura 1). La supervivencia de estos estadios tempranos del desarrollo, los huevos y las larvas, determina las variaciones, a corto y largo plazo, en la abundancia de sus poblaciones. La mayoría de peces marinos producen entre miles y millones de huevos pelágicos que en pocos días eclosionan dando lugar a larvas que pasan desde semanas a unos pocos meses en la comunidad planctónica. Las larvas de peces se caracterizan por su pequeño tamaño (entre pocos mm y unos 2 cm), su transparencia, una limitada capacidad natatoria, y una morfología, en ocasiones sorprendente, que difiere notablemente de la de los adultos (figura 2). Durante el periodo planctónico, las larvas interactúan con otros organismos del plancton, siendo tanto depredadores como presas (figura 1). Las larvas de peces se alimentan de organismos de pequeño tamaño, como estadios juveniles de copépodos (pequeños crustáceos), y, a su vez, son presa de otras especies más grandes que viven también en el medio pelágico, como las medusas. […][CAT] Les primeres etapes del cicle vital dels peixos comprenen el període des de la posta fins al reclutament a la població adulta (figura 1). La supervivència d’aquests estadis inicials del desenvolupament, els ous i les larves, determina les variacions, a curt i llarg termini, en l’abundància de les seves poblacions. La majoria de peixos marins produeixen entre milers i milions d’ous pelàgics que en pocs dies eclosionen i donen lloc a larves que passen des d’unes setmanes fins a uns pocs mesos en la comunitat planctònica. Les larves de peixos es caracteritzen per tenir una mida petita (de pocs mm a 2 cm), la seva transparència, una limitada capacitat natatòria, i una morfologia, a vegades sorprenent, que difereix notablement de la dels adults (figura 2). Durant el període planctònic, les larves interactuen amb altres organismes del plàncton, sent tant depredadors com preses (figura 1). Les larves de peixos s’alimenten d’organismes de mida petita, com per exemple estadis juvenils de copèpodes (petits crustacis), i, al seu torn, són presa d’altres espècies més grans que viuen també en el medi pelàgic, com les meduses. […]Peer reviewe

Six consecutive years (and adding) without Deep (>2000 m) Water Formation in the NW Mediterranean Sea

12th HyMeX Workshop, 20-23 May 2019, Split, Croati

Micronekton groups contributing to the night scattering layers in the Western Mediterranean

40th CIESM Congress: The largest Forum on Mediterranean and Black Sea Research, 28 October - 1 November 2013, Marseille, France.-- 1 page, 1 figureIn the present study the biomass and numerical contribution of micronekton organisms responsible of the night Scattering Layers of the upper water column were investigated. Relative abundance in weight and number of individuals of the different groups collected using midwater trawls performed concurrently with the detection of the scattering layers by echosounders are presentedPeer Reviewe