The spatial distribution of anchovy and sardine in the northern Aegean Sea in relation to hydrographic regimes (original) (raw)
Related papers
Environmental drivers of the anchovy/sardine complex in the Eastern Mediterranean
Hydrobiologia, 2011
The anchovy/sardine complex is an important fishery resource in some of the largest upwelling systems in the world. Synchronous, but out of phase, fluctuations of the two species in distant parts of the oceans have prompted a number of studies dedicated to determining the phenomena, atmospheric and oceanic, responsible for the observed synchronicity and the Guest editors: Graham J. Pierce, Vasilis D. Valavanis, M. Begoña Santos & Julio M. Portela / Marine Ecosystems and Sustainability Electronic supplementary material The online version of this article (
Hydrobiologia, 2008
Acoustic and satellite environmental data as well as bathymetry data were used to model the presence of anchovy, Engraulis encrasicolus during early summer in the northern Aegean Sea (Eastern Mediterranean). Generalized Additive Models (GAMs) were used for modelling and subsequently applied in a predictive mode to identify those areas in the Greek Seas and the entire Mediterranean basin that could support species' presence. Model results were evaluated with the estimation of Receiver Operating Characteristic (ROC)-plots as well as qualitatively, based on (a) acoustic data from concurrent studies in certain areas of the northern Aegean Sea that were not included in the estimation of the GAM model and (b) historical acoustic data from the central Aegean and Ionian Seas. Mapping the estimated environmental conditions in the Mediterranean basin indicated areas that generally agree with the known distribution grounds of anchovy, such as the straits of Sicily and coastal waters of Tunisia, areas in the Tyrrhenian Sea, the Adriatic Sea, the Gulf of Lions and the Catalan Sea.
Fisheries Oceanography, 2012
Identification of the potential habitat of European anchovy (Engraulis encrasicolus) at different life stages in relation to environmental conditions is an interesting subject from both ecological and management points of view. For this purpose, acoustic data from different seasons and different parts of the Mediterranean Sea along with satellite environmental and bathymetry data were modelled using generalized additive models. Similarly, egg distribution data from summer ichthyoplankton surveys were used to model potential spawning habitat. Selected models were used to produce maps presenting the probability of anchovy presence (adults, juveniles and eggs) in the entire Mediterranean basin, as a measure of habitat adequacy. Bottom depth and sea surface chlorophyll concentration were the variables found important in all models. Potential anchovy habitats were located over the continental shelf for all life stages examined. An expansion of the potential habitat from the peak spawning (early summer) to the late spawning season (early autumn) was observed. However, the most suitable areas for the presence of anchovy spawners seem to maintain the same size between seasons. Potential juvenile habitats were associated with highly productive inshore waters, being less extended and closer to coast during winter than late autumn. Potential spawning habitat in June and July based on ichthyoplankton surveys overlapped but were wider in extent compared with adult potential habitat from acoustics in the same season. Similarities and dissimilarities between the anchovy habitats as well as comparisons with sardine habitats in the oligotrophic Mediterranean Sea and other ecosystems with higher productivity are discussed.
2010
Information integrated from different parts of the Mediterranean was used in order to model the spatial and temporal variability of the distribution grounds of anchovy at different life stages. Acoustic data from the Aegean Sea (Eastern Mediterranean), the Adriatic Sea and the Sicily Channel (Central Mediterranean), the Spanish waters and the Gulf of Lions (Western Mediterranean) have been analyzed along with satellite environmental and bathymetry data to model the spatial distribution of adult anchovy during summer and early autumn and the spatial distribution of juvenile anchovy during late autumn and winter. Similarly, egg distribution data from summer surveys were used to model the potential spawning habitat of anchovy in June and July. Generalized Additive Models were applied in a presence/absence approach. Selected models were used to produce potential habitat maps for the entire Mediterranean basin for each year and period, indicating areas presenting the highest probability of supporting the presence of anchovy adults, juveniles and spawning grounds. The temporal stability of these areas was examined. Bottom depth and productivity were 1 the most important parameters found in all models. An expansion of anchovy adult habitat area was observed from summer to early autumn in all study regions. Potential juvenile grounds were identified within the continental shelf in association to high productivity waters, presenting a more extended distribution towards deeper waters in late autumn and moving to more inshore waters in winter. Potential spawning grounds presented a high degree of overlapping between June and July, being more extended compared to the adult grounds in summer.
2012
Identification of the potential habitat of European anchovy (Engraulis encrasicolus) at different life stages in relation to environmental conditions is an interesting subject from both ecological and management points of view. For this purpose, acoustic data from different seasons and different parts of the Mediterranean Sea along with satellite environmental and bathymetry data were modelled using generalized additive models. Similarly, egg distribution data from summer ichthyoplankton surveys were used to model potential spawning habitat. Selected models were used to produce maps presenting the probability of anchovy presence (adults, juveniles and eggs) in the entire Mediterranean basin, as a measure of habitat adequacy. Bottom depth and sea surface chlorophyll concentration were the variables found important in all models. Potential anchovy habitats were located over the continental shelf for all life stages examined. An expansion of the potential habitat from the peak spawning (early summer) to the late spawning season (early autumn) was observed. However, the most suitable areas for the presence of anchovy spawners seem to maintain the same size between seasons. Potential juvenile habitats were associated with highly productive inshore waters, being less extended and closer to coast during winter than late autumn. Potential spawning habitat in June and July based on ichthyoplankton surveys overlapped but were wider in extent compared with adult potential habitat from acoustics in the same season. Similarities and dissimilarities between the anchovy habitats as well as comparisons with sardine habitats in the oligotrophic Mediterranean Sea and other ecosystems with higher productivity are discussed.
Trophodynamics of anchovy in a non-upwelling system: direct comparison with sardine
Anchovies and sardines hold a very important position in pelagic ecosystems and are usually found in species pairs, exhibiting fluctuations in abundance. In upwelling systems, alternations in small pelagic fish have been hypothesized to be, at least partly, trophically mediated. In non-upwelling areas, direct comparisons of sardine and anchovy trophodynamics are lacking, which represents an impediment to our understanding of forage fish interactions. In the present study, we analyzed the diel feeding periodicity, daily ration and diet composition of anchovy Engraulis encrasicolus in a coastal area of the eastern Mediterranean. Τhe anchovy feeding parameters and diet compositions were then compared with published data on sardine Sardina pilchardus, captured in the same set of pelagic trawl hauls and analyzed using identical methods. Both anchovy and sardine foraged in daytime in summer, and mainly at night in winter. Their feeding intensities per daily sampling time were highly correlated. In both species, daily consumption was significantly and similarly related to fish size and per capita food availability. In terms of dietary carbon, intraspecific dietary differences between juveniles and adults were insignificant. Copepods (especially large ones) were the main energy source for both species. In contrast to adult sardines, anchovies did not consume phytoplankton, and ingested large prey (including decapod larvae) more frequently. Both species broadened their trophic niche in summer; dietary differences between the stratification and mixing periods mostly reflected corresponding changes in prey availability in the field. The strong size-based partitioning of plankton resources described for anchovy and sardine in upwelling systems was not corroborated in the Mediterranean Sea.
In the Atlantic Ocean, small pelagic fish occasionally execute long distance migrations before they become adults. However, in the Mediterranean Sea, the populations of the most common small pelagic fish, anchovy and sardine, seem to be generally more confined to relatively small areas. Particularly in the NW Mediterranean, local environmental conditions, such as mesoscale events, wind forcing or river run-offs, can contribute to shaping the dispersal patterns of fishes, especially in their early life stages. Intrinsic factors such as dietary preferences, swimming abilities or feeding behavior can also play an essential role in the distribution of the populations in the region. Some studies have been done in the NW Mediterranean in order to elucidate which factors are playing the main roles in the dispersal and in the ecology of anchovy and sardine larvae and juveniles. Nevertheless, a holistic evaluation of all the potential attributes conditioning the distribution of early life history anchovy and sardine is lacking. It is therefore necessary to clearly highlight the most determinant biological and environmental features for the dispersion of the early life stages of anchovy and sardine in the NW Mediterranean. This review of the state-of-the-art in the distribution and the trophic ecology of the larvae and juveniles of these populations, pointing out the main methods utilized, will also help to identify some of the major gaps of knowledge and discrepancies that might conduce to future research.