Search results for "POPULATION"
showing 10 items of 9945 documents
Seascape connectivity of European anchovy in the Central Mediterranean Sea revealed by weighted Lagrangian backtracking and bio-energetic modelling
2020
AbstractEcological connectivity is one of the most important processes that shape marine populations and ecosystems, determining their distribution, persistence, and productivity. Here we use the synergy of Lagrangian back-trajectories, otolith-derived ages of larvae, and satellite-based chlorophyll-a to identify spawning areas of European anchovy from ichthyoplanktonic data, collected in the Strait of Sicily (Central Mediterranean Sea), i.e., the crucial channel in between the European and African continents. We obtain new evidence of ecosystem connectivity between North Africa and recruitment regions off the southern European coasts. We assess this result by using bio-energetic modeling, …
Exploring connectivity between spawning and nursery areas ofMullus barbatus(L., 1758) in the Mediterranean through a dispersal model
2017
Connectivity between spawning and nursery areas plays a major role in determining the spatial structure of fish populations and the boundaries of stock units. Here, the potential effects of surface current on a red mullet population in the Central Mediterranean were simulated using a physical oceanographic model. Red mullet larvae were represented as Lagrangian drifters released in known spawning areas of the Strait of Sicily (SoS), which represents one of the most productive demersal fishing-grounds of the Mediterranean. To consider the effect of inter-annual variability of oceanographic patterns, numerical simulations were performed for the spawning seasons from 1999 to 2012. The main goa…
Nanism (dwarfism) in fish: a comparison between red mullet Mullus barbatus from the southeastern and the central Mediterranean
2007
The gradient of environmental conditions from west to east in the Mediterranean results in very low primary productivity in the eastern area of this sea. This impoverishment is expressed also in higher trophic levels and has been accounted for by several faunistic phenomena. One of these is 'Levantine nanism' (dwarfism); this is characterized by smaller body size of specimens in the Levantine basin compared with conspecifics in the western Mediterranean. Nanism has been hypothesized for various taxonomic groups in the Mediterranean, but no quantitative study has yet been carried out to confirm it. In the present study male and female red mullet Mullus barbatus from trawl surveys carried out…
Man-made garbage pollution on the Mediterranean coastline
1991
Abstract Measurements of persistent litter on 13 beaches in Spain, Italy (Sicily), Turkey, Cyprus and Israel between 1988 and 1989 show that plastic items are the most abundant in the litter composition, followed by wood, metal and glass items. Remnants of fishing gear are rather rare. It appears that the quantity of litter on a beach is inversely related to its geographical distance to a population center and directly related to the number of visitors frequenting it. Seasonal fluctuations in coastal litter are caused by storm waves which wash the litter landward, leaving the beach clean during winter, and by bathers who pollute it during summer. Based on the nature of the garbage, there ar…
Discrimination of fish populations using parasites: Random Forests on a ‘predictable’ host-parasite system
2010
SUMMARYWe address the effect of spatial scale and temporal variation on model generality when forming predictive models for fish assignment using a new data mining approach, Random Forests (RF), to variable biological markers (parasite community data). Models were implemented for a fish host-parasite system sampled along the Mediterranean and Atlantic coasts of Spain and were validated using independent datasets. We considered 2 basic classification problems in evaluating the importance of variations in parasite infracommunities for assignment of individual fish to their populations of origin: multiclass (2–5 population models, using 2 seasonal replicates from each of the populations) and 2…
Effects of marine noise pollution on Mediterranean fishes and invertebrates: A review.
2020
International audience; Marine noise pollution (MNP) can cause a multitude of impacts on many organisms, but information is often scattered and general outcomes difficult to assess. We have reviewed the literature on MNP impacts on Mediterranean fish and invertebrates. Both chronic and acute MNP produced by various human activities - e.g. maritime traffic, pile driving, air guns - were found to cause detectable effects on intra-specific communication, vital processes, physiology, behavioral patterns, health status and survival. These effects on individuals can extend to inducing population- and ecosystem-wide alterations, especially when MNP impacts functionally important species, such as k…
Assessing cetacean surveys throughout the Mediterranean Sea: a gap analysis in environmental space
2018
Heterogeneous data collection in the marine environment has led to large gaps in our knowledge of marine species distributions. To fill these gaps, models calibrated on existing data may be used to predict species distributions in unsampled areas, given that available data are sufficiently representative. Our objective was to evaluate the feasibility of mapping cetacean densities across the entire Mediterranean Sea using models calibrated on available survey data and various environmental covariates. We aggregated 302,481 km of line transect survey effort conducted in the Mediterranean Sea within the past 20 years by many organisations. Survey coverage was highly heterogeneous geographicall…
From glacial refugia to hydrological microrefugia: Factors and processes driving the persistence of the climate relict tree Zelkova sicula
2021
Abstract With only two tiny populations, the climate relict Zelkova sicula (Sicily, Italy) is one of the rarest trees in the world. It also represents the most marginal member of genus Zelkova that was widespread in the broadleaved forests thriving in warm–temperate climates throughout Eurasia until the Last Glacial Age. Occurring at the westernmost range of the genus under typical Mediterranean climate, the micro‐topographic settings have always appeared crucial for the survival of this relict. However, the factors and processes actually involved in its persistence in the current refugia, as well as the response of similar relict trees in arid environments, are poorly understood worldwide.…
Sporadic nesting reveals long distance colonisation in the philopatric loggerhead sea turtle (Caretta caretta)
2018
The colonisation of new suitable habitats is crucial for species survival at evolutionary scale under changing environmental conditions. However, colonisation potential may be limited by philopatry that facilitates exploiting successful habitats across generations. We examine the mechanisms of long distance dispersal of the philopatric loggerhead sea turtle (Caretta caretta) by analysing 40 sporadic nesting events in the western Mediterranean. The analysis of a fragment of the mitochondrial DNA and 7 microsatellites of 121 samples from 18 of these nesting events revealed that these nests were colonising events associated with juveniles from distant populations feeding in nearby foraging gro…
Assessing geographical variation on whistle acoustic structure of three Mediterranean populations of common bottlenose dolphin (Tursiops truncatus)
2017
Whistles are acoustic signals produced particularly during social interactions. Here, we compare whistles by bottlenose dolphins from three Mediterranean areas (Croatia, Sicily and Sardinia) to investigate the presence of acoustic divergence and to discuss the possible causes of variability. Whistle parameters differ significantly between populations, but PCA highlights that the majority of variability is due to a limited number of frequency parameters. Cluster and DFA show that the Croatian population is acoustically divergent from the western populations of Sicily and Sardinia. This divergence could be consistent with geographical isolation, and a possible genetic differentiation between …