Search

In order to recruit into adult populations juvenile fish must be able to find food, successfully compete with other organisms and avoid predation within a habitat, in other words they must be able to locate favourable and avoid detrimental conditions. Bio-chemical research into fish detection and discrimination between chemical cues is extensive, however whether olfactory mechanisms are critical in habitat selection and avoidance of detrimental conditions within the marine environment remains under-researched. Despite being one of the scientifically most explored seas, studies on the use of olfactory system in the selection of water masses of the Mediterranean fish species are absent. Using a chemical choice flume, the chemically mediated behaviour choices to distinct chemical cues (algae, seagrass, predator and conspecifics) of Symphodus ocellatus, a common Mediterranean fish, were investigated. In addition to the conventional analysis, which relies on the amount of the time spent in the specific water mass as the main indicator of preference, the behavioural response triggered by the detection of a particular cue was also examined, by analysing the mean and variance of speed of the individual fish movements, a complimentary approach previously not considered in the flume experiments. Bayesian statistical method was used to calculate both, proportion of time spent in the specific water mass, as well as to analyse the behavioural response of each individual within the specific water mass. In terms of the time spent, the flume trials conducted resulted in no significant fish selection preference or avoidance for any of the water masses tested, however varied speeds and number of burst speed movements were observed in a number of trials. When no olfactory stimulus was present, no change in behaviour was triggered. Thus, juvenile S. ocellatus undoubtedly has a capacity of change in behaviour to a complex array of olfactory stimuli, nevertheless the response in the flum

[EN] In this work we focus on the Alboran Sea (western Mediterranean) to relate wind field and ocean velocity variability with chlorophyll a (Chl a) behaviour, using a 2-km resolution, coupled 3D ocean circulation-NPZD model (ROMS). The analysis is done in three steps. First, we split the seasonal and residual contribution for the fields under study. Second, we calculate the corresponding empirical orthogonal functions (EOFs) for the seasonal and residual parts. Finally, we relate each pair of variables for both seasonal and residual contribution EOFs. The results reported here allow the links between wind and Chl a to be quantified. We explain these links in terms of the ocean velocity field acting as a driver of Chl a variability. The results show that, although the seasonal part of the Chl a field is modulated by the vertical velocity, the residual component is modulated by the horizontal velocity components. Vertical velocities are responsible, through coastal upwelling, for Chl a bloom enhancement, while horizontal velocities spread coastal Chl a surface blooms off-shore, [ES] En este trabajo nos centramos en el mar de Alborán (Mediterráneo Occidental) para relacionar los campos de velocidad del viento y del océano con la variabilidad de la clorofila a (Chl a), utilizando un modelo de circulación 3D-NPZD (ROMS-Fennel) con una resolución de 2 km. El análisis se realiza en tres pasos. En primer lugar, separamos la contribución estacional y el residuo para todos los campos de estudio. En segundo lugar, calculamos las correspondientes funciones ortogonales empíricas (EOFs) para las components estacionales y residuales. Por último, relacionamos cada par de variables para ambos, EOFs estacionales y residuales. Los resultados permiten la cuantificación de las relaciones entre el viento y la clorofila. Explicamos estas relaciones en términos del campo de velocidades del océano que actúa como motor de la variabilidad de la Chl a. Los resultados muestran que, aunque la parte estacional de campo Chl a es modulada por la velocidad vertical, la componente residual es modulada por las componentes de la velocidad horizontal. Las velocidades verticales son responsables, a través de la surgencia costera, de incrementar el valor de la proliferación de Chl a, mientras que las velocidades horizontales extienden estas proliferaciones costeras superficiales a mar abierto

Understanding the processes driving seabirds’ reproductive performance through trophic interactions requires the identification of seasonal pulses in marine productivity.We investigated the sequence of environmental and biological processes driving the reproductive phenology and performance of the storm petrel (Hydrobates pelagicus) in the Western Mediterranean. The enhanced light and nutrient availability at the onset of water stratification (late winter/early spring) resulted in annual consecutive peaks in relative abundance of phytoplankton, zooplankton and ichthyoplankton. The high energy-demanding period of egg production and chick rearing coincided with these successive pulses in food availability, pointing to a phenological adjustment to such seasonal patterns with important fitness consequences. Indeed, delayed reproduction with respect to the onset of water stratification resulted in both hatching and breeding failure. This pattern was observed at the population level, but also when confounding factors such as individuals’ age or experience were also accounted for.We provide the first evidence of oceanographic drivers leading to the optimal time-window for reproduction in an inshore seabird at southern European latitudes, along with a suitable framework for assessing the impact of environmentally driven changes in marine productivity patterns in seabird performance.

Larval retention plays a fundamental role in the persistence of coastal fish assemblages. Here, we examine larval fish distribution and abundance patterns in Palma Bay, a large (∼20 km) wind-driven microtidal bay in the southern coast of Mallorca (Spain, NW Mediterranean Sea). Larval fish assemblage structure in the bay were analyzed during July 2010 and interpreted in the context of the observed circulation patterns, adult habitat distribution and spawning traits. Acoustic Doppler Current Profiler (ADCP) observations showed the presence of retentive flow patterns in the middle of the bay enhancing local larval accumulation and self-recruitment. In consequence, larval abundances were higher in this central part of the bay (∼40 m depth, mean abundance 607.6 ± 383 ind. 10 m−2) than along the coastal fringe (<35 m 113.7 ± 91 ind. 10 m−2). Also, a multivariate predictive approach based on Redundancy Analysis (RDA) revealed differences between the larval fish assemblages in areas inside the bay, constituted by small pelagic and benthopelagic taxa (gobids, Chromis chromis and Serranus hepatus) and offshore larvae, mostly from meso and large pelagic fish. These larval fish assemblages were structured according to depth variations and zooplankton abundance, and remained relatively unmixed because of the circulation patterns in the mouth of the bay that uncouple its dynamics from alongshelf circulation. Even larvae of typically pelagic species that spawn close to the coast (Sardinella aurita, Auxis rochei) were associated with the retentive effect of the bay. Our study highlights the important role of coastal bays in the regulation of coastal fish population dynamics and as hotspots for the maintenance of diversity in the Mediterranean Sea

During the summer, the relative influence of resident Atlantic Waters (AW) and new AW largely drives the mesoscale dynamics around the Balearic Islands (NW Mediterranean). Two principal summer hydrographic scenarios were identified in the region, differentiated by the relative position of the density front between new and resident AW within the archipelago and its associated mesoscale activity. In this study, we investigated how those early summer mesoscale scenarios influence larval fish assemblages, by analyzing data from two cruises representative of these two scenarios (2004 and 2005). Redundancy analysis was used to assess the variance in the larval fish assemblage that could be significantly explained by the most parsimonious combination of available environmental variables in both years. While depth was the most important variable in explaining the larval fish assemblage structure variability observed under both scenarios, indicators of mesoscale activity (dynamic height, geostrophic velocity) contributed significantly to understanding the dynamics of the larval fish community. Mesoscale activity was higher in summer 2004, leading to higher larval fish abundances and zooplankton biomass and lower larval fish diversity than in the unusually warm summer 2005, which showed lower mesoscale activity. The larval assemblage dynamics are discussed in terms of extrinsic and species-specific factors.

The connectivity between the Gulf of Cadiz (northeastern Atlantic) and the Mediterranean Sea has been regarded as an interesting oceanographic and ecological issue, especially considering the missing knowledge on the processes at play in the Strait of Gibraltar. Moreover, the spatial and vertical dispersal of organisms in this highly dynamic system are poorly addressed, particularly for invertebrate larvae. Data on decapod larvae and ocean water masses were collected in three summer surveys along the Gulf of Cadiz and western Mediterranean Sea and were analysed to improve the knowledge about dispersal mechanisms and ecological connectivity in the area. Data revealed different spatial distributions for larvae of Sergia robusta, a common mesopelagic shrimp occurring in both basins. We suggest the reduced shelf width in the northern Alboran Sea coast as one of the promoters of the observed spatial distributions, as it accounts for the strong influence of offshore currents in the innershelf, resulting in a higher concentration of pelagic species. In the northern Gulf of Cadiz, the wider shelf and the complex hydrodynamic processes induce high water mixture, enhancing the along and cross-shore transport, and the occurrence of pelagic species in offshore areas. We hypothesized that the hydrological and hydrodynamic characteristics of each basin were the driven factors of the different distributions. However, factors as the origin of larvae, larval duration and migration behaviour seem to control the larval dispersal range that larvae can withstand to adequately settle and recruit to the adult populations.

Larval retention plays a fundamental role in the persistence of coastal fish assemblages. Here, we examine larval fish distribution and abundance patterns in Palma Bay, a large (~20 km) wind-driven microtidal bay in the southern coast of Mallorca (Spain, NW Mediterranean Sea). Larval fish assemblage structure in the bay were analyzed during July 2010 and interpreted in the context of the observed circulation patterns, adult habitat distribution and spawning traits. Acoustic Doppler Current Profiler (ADCP) observations showed the presence of retentive flow patterns in the middle of the bay enhancing local larval accumulation and self-recruitment. In consequence, larval abundances were higher in this central part of the bay (~40 m depth, mean abundance 607.6 ± 383 ind. 10 m2) than along the coastal fringe (<35 m 113.7 ± 91 ind. 10 m2). Also, a multivariate predictive approach based on Redundancy Analysis (RDA) revealed differences between the larval fish assemblages in areas inside the bay, constituted by small pelagic and benthopelagic taxa (gobids, Chromis chromis and Serranus hepatus) and offshore larvae, mostly from meso and large pelagic fish. These larval fish assemblages were structured according to depth variations and zooplankton abundance, and remained relatively unmixed because of the circulation patterns in the mouth of the bay that uncouple its dynamics from alongshelf circulation. Even larvae of typically pelagic species that spawn close to the coast (Sardinella aurita, Auxis rochei) were associated with the retentive effect of the bay. Our study highlights the important role of coastal bays in the regulation of coastal fish population dynamics and as hotspots for the maintenance of diversity in the Mediterranean Sea.

During the summer, the relative influence of resident Atlantic Waters (AW) and new AW largely drives the mesoscale dynamics around the Balearic Islands (NW Mediterranean). Two principal summer hydrographic scenarios were identified in the region, differentiated by the relative position of the density front between new and resident AW within the archipelago and its associated mesoscale activity. In this study, we investigated how those early summer mesoscale scenarios influence larval fish assemblages, by analyzing data from two cruises representative of these two scenarios (2004 and 2005). Redundancy analysis was used to assess the variance in the larval fish assemblage that could be significantly explained by the most parsimonious combination of available environmental variables in both years. While depth was the most important variable in explaining the larval fish assemblage structure variability observed under both scenarios, indicators of mesoscale activity (dynamic height, geostrophic velocity) contributed significantly to understanding the dynamics of the larval fish community. Mesoscale activity was higher in summer 2004, leading to higher larval fish abundances and zooplankton biomass and lower larval fish diversity than in the unusually warm summer 2005, which showed lower mesoscale activity. The larval assemblage dynamics are discussed in terms of extrinsic and species-specific factors.

The inclusion of behavioral components in the analysis of a community can be of paramount importance in marine ecology. Diel (i.e., 24-h based), seasonal activity rhythms, or longer durational in behavioral responses can result in shifts in populations, and therefore on measurable abundances. Here, we review the value of developing cabled video observatory technology for the remote, long-term, and high-frequency monitoring of fish and their environments in coastal temperate areas. We provide details on the methodological requirements and constraints for the appropriate measurement of fish behavior over various seasonal scales (24 h, seasonal, annual) with camera systems mounted at fixed observatory locations. We highlight the importance of using marine sensors to simultaneously collect relevant environmental data in parallel to image data acquisition. Here we present multiparametric video, oceanographic, and meteorological data collected from the Mediterranean observatory platform, OBSEA (www.obsea.es; 20 m water depth). These data are reviewed in relation to ongoing and future developments of cabled observatory science. Two key approaches for the future improvement of cabled observatory technology are: (1) the application of Artificial Intelligence to aid in the analysis of increasingly large, complex, and highly interrelated biological and environmental data sets, and (2) the development of geographical observational networks to enable the reliable spatial analysis of observed populations over extended distances. © 2015, Springer International Publishing Switzerland

Rising levels of anthropogenic carbon dioxide in the atmosphere are acidifying the oceans and producing diverse and important effects on marine ecosystems, including the production of fatty acids (FAs) by primary producers and their transfer through food webs. FAs, particularly essential FAs, are necessary for normal structure and function in animals and influence composition and trophic structure of marine food webs. To test the effect of ocean acidification (OA) on the FA composition of fish, we conducted a replicated experiment in which larvae of the marine fish red drum (Sciaenops ocellatus) were reared under a climate change scenario of elevated CO levels (2100 matm) and under current control levels (400 matm). We found significantly higher whole-body levels of FAs, including nine of the 11 essential FAs, and altered relative proportions of FAs in the larvae reared under higher levels of CO. Consequences of this effect of OA could include alterations in performance and survival of fish larvae and transfer of FAs through food webs.

It was hypothesized that the survival and growth strategies of herring Clupea harengus, displaying a flexible reproductive activity, are adapted to coping with longer periods of prey deprivation (i.e. more variable prey availability), in contrast to cod Gadus morhua, which are adapted to match growth and survival at high prey concentrations. Experimental larval growth and survival data for the two naturally co-occurring species reared either in separate tanks or in combination are presented to test this hypothesis. Natural zooplankton was supplied either ad libitum or in a periodically restricted manner to mimic natural suboptimal conditions. Periodically restricted feeding significantly reduced initial growth of G. morhua larvae co-reared with C. harengus, while no such initial effect was seen for co-reared C. harengus. Overall survival of G. morhua was higher when reared together with C. harengus (32 v. 24%), while C. harengus had higher survival without the presence of G. morhua (59 v. 44%), indicating that both species were affected by higher densities of G. morhua larvae. Furthermore, the final survival in G. morhua was inversely related to average final size, while in C. harengus an opposite trend was observed. How potential behavioural interactions may drive the present results are discussed and contended that a better insight into field vital rates may be gained from further exploration of co-rearing experiments.

We show the application of a Spatially-Explicit Individual-Based Model (SEIBM) to understand the recruitment process of European anchovy. The SEIBM is applied to simulate the effects of inter-annual variability in parental population spawning behavior and intensity, and ocean dynamics, on the dispersal of eggs and larvae from the spawning area in the Gulf of Lions (GoL) towards the coastal nursery areas in the GoL and Catalan Sea (northwestern Mediterranean Sea). For each of seven years (2003-2009), we initialize the SEIBM with the real positions of anchovy eggs during the spawning peak, from an acoustics-derived eggs production model. We analyze the effect of spawners' distribution, timing of spawning, and oceanographic conditions on the connectivity patterns, growth, dispersal distance and late-larval recruitment (14 mm larva recruits, R14) patterns. The area of influence of the Rhône river plume was identified as having a high probability of larval recruitment success (64%), but up to 36% of R14 larvae end up in the Catalan Coast. We demonstrate that the spatial paths of larvae differ dramatically from year to year, and suggest potential offshore nursery grounds. We showed that our simulations are coherent with existing recruitment proxies and therefore open new possibilities for fisheries management

The European anchovy fishery in the Gulf of Cádiz (ICES Division IXa South) is largely influenced by age-0 individuals. Knowledge of young of the year growth dynamics is crucial for management, yet data on daily growth are lacking in the area. Linking growth patterns to the environment requires information on habitat occupancy through ontogeny of the fish that reach the fishery, as anchovy use different areas of the Gulf and the Guadalquivir Estuary through development. We describe the growth dynamics of age-0 anchovy through otolith microstructure analysis, and couple these data with data on microchemical signals in the otoliths to shed light into habitat use and growth dynamics in the area. Age-0 anchovy captured in September, 2011 in the Gulf ranged from 3 to 6 months old for similar sizes, with average growth rates varying twofold. Individual non-linear growth curves showed that maximum otolith growth was positively correlated with the date of spawning, which in turn was negatively correlated with the time to reach maximum growth. There was no correlation between growth parameters and body length or condition (Fulton K) at capture. The strontium:calcium (Sr/Ca) and magnesium:calcium (Mg/Ca) ratios were significantly lower at the edge of the otolith (approximately the age of capture) than at ages corresponding to larval and early juveniles (<60 days old), but values fell within typical estuarine-dwelling species. The barium:calcium ratio (Ba/Ca) increased significantly in the edge of the otolith, which possibly resulted from residency in highly productive coastal waters or from ontogenetic effects. The variance in otolith elemental ratios was larger at otolith back-calculated ages around 50 days old, age which coincides with the presumed closer dependence of estuarine waters. Our data are a first step towards understanding the contribution of the estuarine system to the fishery of anchovy in the Gulf. The limitations of the approach and future steps are discussed

All demersal fish with planktonic larvae settle at some point early in life, generally around the transformation from larvae to juveniles or soon after. Sampling pre-settlement or very young, settled fish is challenging due to spatial concretions within the habitat and the pulsed, rapid nature of the settlement process. There is a lack of robust sampling methods, but information on the settlement, which represents a mortality bottleneck, is crucial for the follow-up of populations for fisheries and conservation purposes. Empirical evaluation of sampling methods focusing on settling fish has not been conducted in temperate habitats. Here, we compare six different sampling methods to collect pre- and post-settlement stages of fish and determine the best combination of techniques to utilise in Posidonia oceanica, an endemic Mediterranean seagrass that provides a key nursery habitat for coastal fish. We used three types of pelagic nets (bongo net, neuston net and ring net), two types of light-traps (Quatrefoil and Ecocean CARE®) to sample pre-settled stages and a low-impact epibenthic trawl for recent settlers. Our results show a significantly different size-spectrum for each method, with a continuous range of sizes from 2 mm to 200 mm. The smallest sizes were collected by the bongo net, followed by the ring net, the neuston net, the Quatrefoil, the Ecocean and finally the epibenthic trawl. Our results suggest that an appropriate strategy for collecting and estimating the abundance of key littoral fish species around settlement size is the combination of the Ecocean light trap and the epibenthic trawl.

The European anchovy fishery in the Gulf of Cádiz (ICES Division IXa South) is largely influenced by age-0 individuals. Knowledge of young of the year growth dynamics is crucial for management, yet data on daily growth are lacking in the area. Linking growth patterns to the environment requires information on habitat occupancy through ontogeny of the fish that reach the fishery, as anchovy use different areas of the Gulf and the Guadalquivir Estuary through development. We describe the growth dynamics of age-0 anchovy through otolith microstructure analysis, and couple these data with data on microchemical signals in the otoliths to shed light into habitat use and growth dynamics in the area. Age-0 anchovy captured in September, 2011 in the Gulf ranged from 3 to 6 months old for similar sizes, with average growth rates varying twofold. Individual non-linear growth curves showed that maximum otolith growth was positively correlated with the date of spawning, which in turn was negatively correlated with the time to reach maximum growth. There was no correlation between growth parameters and body length or condition (Fulton K) at capture. The strontium:calcium (Sr/Ca) and magnesium:calcium (Mg/Ca) ratios were significantly lower at the edge of the otolith (approximately the age of capture) than at ages corresponding to larval and early juveniles (<60 days old), but values fell within typical estuarine-dwelling species. The barium:calcium ratio (Ba/Ca) increased significantly in the edge of the otolith, which possibly resulted from residency in highly productive coastal waters or from ontogenetic effects. The variance in otolith elemental ratios was larger at otolith back-calculated ages around 50 days old, age which coincides with the presumed closer dependence of estuarine waters. Our data are a first step towards understanding the contribution of the estuarine system to the fishery of anchovy in the Gulf. The limitations of the approach and future steps are discussed

The eastward current at the Strait of Gibraltar (the Atlantic Jet) fertilizes the southwestern Mediterranean and it is the responsible for the comparatively high fish landing of this region. However, we demonstrate in this communication that the high kinetic energy of this current negatively impacts the recruitment of anchovy owing to the advection and dispersion of larvae and post-larvae. The inhibitory effect of kinetic energy on anchovy landings is not a transient but a persistent state. Only an exceptional combination of events can release anchovy recruitment from this inhibition to create landing outbreaks. As such, the dynamics of anchovy in the Alborán Sea is more akin to a pest than to a standard fishery. We disentangle here what are these events and their high sensitivity to climatic fluctuations.

The Alboran basin is one of the most productive areas of the Mediterranean Sea and supports an anchovy fishery with a history of remarkably variable landings. Past and present anchovy recruitment levels are highly sensitive to changes in the strength and direction of the incoming jet of Atlantic waters, which modulate the hydrographic features of the basin. Here, we analyze plausible consequences for the anchovy fisheries in the region based on a projected physical scenario for the end of the century obtained using a coupled hydrological-biogeochemical model. Our model predicts a substantial increase in horizontal water velocity and a negligible change in the associated biological production, which likely indicates reductions in anchovy stock, catches and revenues. Alternative policies are analyzed here for the economic scenario that is expected to emerge under future conditions of oceanographic features, pelagic ecosystem dynamics and anchovy landings in the Alboran Sea. © 2013 Elsevier B.V.

When gene flow is limited and harvesting is intensive, fishing may alter life histories and favour trait combinations that collectively reduce adult body size. However, empirical evidence of downsizing of adults in small-bodied coastal fish is still scarce, in part due to the lack of knowledge about the selective nature of certain fishing gears, such as recreational angling, and the difficulties in estimating the dispersion of pelagic early-life stages. Using the small-bodied sedentary coastal marine fish Serranus scriba as a model, we first empirically show that recreational angling selects for life-history traits (i.e. increased reproductive investment) that promote downsizing of adults. Second, using Lagrangian particle dispersion modelling, we show how local hydrodynamics generates patterns of limited connectivity and the emergence of meta-population structure. Finally, the life histories presently observed in isolated populations of S. scriba that experienced differential fishing pressure matched expectations of fishing-induced downsizing of adult body size. Body size is an important trait in aquatic food webs, and evolutionary downsizing might have unforeseen consequences. From a precautionary perspective, maintaining the metapopulation structure and the full range of genotypes inherent in them is important, even for smallbodied, geographically restricted fish species that are mainly harvested by recreational anglers. © Inter-Research 2014.