1,721,030 research outputs found
Modelli di distribuzione dell’habitat per la gestione di specie lagunari di interesse alieutico e conservazionistico
No full textLa ricerca condotta ha come scopo quello di sviluppare modelli di distribuzione spaziale di specie animali e vegetali in ambienti lagunari del Nord Adriatico (laguna di Venezia e Sacca di Goro), e di valutarne le possibili implicazioni come strumenti per la gestione e la conservazione degli habitat lagunari. Questa tipologia di modelli si basa sulla quantificazione delle relazioni esistenti tra la presenza di una specie e i parametri ambientali che influiscono sulla sua distribuzione. Sono stati sviluppati modelli per alcune specie nectoniche, che utilizzano gli habitat lagunari come aree di nursery, una specie bentonica di grande importanza per la pesca lagunare e alcune specie fitobentoniche di particolare interesse dal punto di vista conservazionistico. L’applicazione dei modelli sviluppati alle mappe dei parametri ambientali ha permesso di ottenere rappresentazioni spazialmente esplicite della distribuzione potenziale delle specie studiate. Tali applicazioni sono proposte come strumento utilizzabile nelle fasi decisionali della gestione dell’ambiente lagunare, della pesca e della tutela di specie di interesse conservazionistico
IMPLEMENTATION OF THE HABITAT FISH BIO-INDICATOR IN TWO WATER BODIES OF THE VENICE LAGOON: THE ROLE OF SEASONAL AND ENVIRONMENTAL VARIABILITY IN THE ASSESSMENT OF ECOLOGICAL STATUS OF FISH FAUNA
Full text linkUnder the Water Framework Directive (WFD; Dir. 2000/60/EC), fish are one of the Biological Quality Elements that need to be taken into account when evaluating the Ecological Status of transitional water bodies. The Habitat Fish Bio-Indicator (HFBI), a multi-metric index composed of six descriptors based on functional traits of fish assemblages, was recently developed to assess Italian transitional waters. In this study, HFBI was applied, following the national application protocol, to two water bodies in the Venice lagoon featuring different water and sediment physco-chemical properties and habitat distribution. The analysis highlighted that, in addition to seasonality, environmental variability along confinement gradients and presence and extent of seagrass meadows strongly influence the six metrics, the HFBI score and the subsequent assessment outcome. The selection of number and location of sampling sites must then be based on environmental characteristic and variability found within each water body, and is therefore a crucial step in the evaluation of Ecological Status in transitional water ecosystems
Climate impact on Italian fisheries (Mediterranean Sea)
Full text linkGlobal warming is increasingly affecting marine ecosystems and ecological services they provide. One of the major consequences is a shift in species geographical distribution, which may affect resources availability to fisheries. We computed the mean temperature of the catch (MTC) for Italian catches from 1972 to 2012 to test if an increase of warmer-water species against colder-water ones was observed. We further analysed the relationship among MTC, landings, fishing effort and climatic factors through a Linear Mixed Models approach. Global MTC increased at a rate of 0.12 _C per decade. Though, by considering the influence of sea surface temperature (SST), a strongest increase (0.31 _C) was estimated in southernmost areas, while in the northernmost basin (Northern Adriatic Sea) a decrease of 0.14 _C was observed. SST resulted the most relevant driver, and the relationship between MTC and SST showed a high spatial variability both in terms of strength and sign, being positively stronger in southernmost areas while negative in the northernmost basin. The result is probably underestimated since several psychrophilous and thermophilous species were not included in the analysis. However, it seems that a change towards warmer-water species has already occurred in Italian marine ecosystems. Conversely, total landings temporal dynamics seem mostly driven by changes in fishing effort rather than by MTC and climatic factors. Consequently, fishery management strategies need to focalize primarily on fishing effort reduction, in order to reduce the pressure on the stocks while increasing their resilience to other stressors, among which global warmin
Boat-induced pressure does not influence breeding site selection of a vulnerable fish species in a highly anthropized coastal area
No full textThe brown meagre (Sciaena umbra) is a vulnerable vocal fish species that may be affected by boat noise. The breeding site distribution along the anthropized Venice sea inlets was investigated, by using the species' chorusing activity as a proxy of spawning. Passive acoustic campaigns were repeated at 40 listening points distributed within the three inlets during three-time windows in both summer 2019 and 2020. The role of temporal, morphological, and hydrodynamic variables explaining the observed distribution patterns was evaluated using a GLM approach, considering also human-induced pressures among the candidate predictors. The GLM analysis indicates a higher probability of recording S. umbra chorus after sunset in deeper areas of the inlets, characterized by low water current, while the underwater noise overlapping the species' hearing range and boat abundance did not play any role. This suggests that the species' breeding site choice in the inlets was not influences by boat-induced pressure
Habitat distribution model for European flounder juveniles in the Venice lagoon
No full textIn order to identify nursery habitats for Platichthys flesus in the Venice lagoon we developed a generalized additive model relating juvenile flounder's distribution to environmental variables. A field survey was conducted between March 2004 and June 2005 and between February and October 2008 in the central and Northern sub-basins of the lagoon. Each station was sampled by means of a beach seine net and characterized collecting the main chemico-physical variables, such as water temperature, salinity, turbidity, dissolved oxygen content and bottom grain size. Main winds fetches were also considered, and estimated in a GIS environment. A logistic model was fitted, and evaluated on an independent dataset. The response curves allowed to identify the role of the environmental parameters in explaining the distribution of the juvenile flounder: turbidity, salinity and sand content revealed to be the most important factors, showing the preference for mesohaline turbid waters together with a low sand content of the sediment. The application of this model to continuous surfaces of the environmental variables allowed the creation of potential habitat distribution maps. In this way it has been possible to recognize several areas covering a key role for the juveniles of flounder, located mainly in the inner part of the lagoon. © 2009 Elsevier B.V. All rights reserved
Small creeks in a big lagoon: The importance of marginal habitats forfish populations
Full text linkTemperate transitional water systems, as in the case of the Venice Lagoon, are characterised by many different shallow-water habitats. The availability of trophic resources and the low predator pressure make salt marshes one of the most important habitats for many fish species, both resident and marine migrant, but several anthropogenic pressures, erosion and relative sea level rise in particular, are causing a significant loss of this habitat. A part from natural habitats, in many small islands of the Venice lagoon, artificial creeks of different size and morphology are present, once used in traditional aquaculture activities or built up as defence lines. Aims of this study is to analyse and compare the structure and composition of fish communities inhabiting small-sized creeks, considering both the natural and artificial ones, in order to evaluate the ecological importance of these marginal habitats for fish populations. A particular attention was given to artificial sites, assessing their ecological value as alternative refuge habitats to natural salt marsh creeks. One year samplings conducted in four sites (two natural salt marshes and two artificial creeks) allowed to describe the local fish communities, which comprised 20 species overall. The analysis of how water parameters and habitat structure influenced the fish communities showed the importance of the connection between small creeks and the open lagoon, but also the refuge function offered by confined systems. High abundances of resident fish species listed in the Annex II of the Habitat Directive were observed and juveniles of eight species of marine migrant fish were found, some of which are of economic importance. This study underlined the presence of significant densities of juvenile marine migrant and lagoon resident fish species in the two artificial habitats. Actually, species richness and density resulted to be, in some cases, higher than in natural salt marsh systems. Results of this study emphasize the ecological importance of these marginal habitats for many fish species, of both conservation and economic importance Thus a proper management and restoration strategy of these sites is needed to maintain their functionality and to buffer the disappearance of natural salt marshes
Influence of Seascape on Coastal Lagoon Fisheries: the Role of Habitat Mosaic in the Venice Lagoon
Full text linkFisheries are a staple human activity supported by coastal lagoons. Together with water quality and trophic status, lagoon
morphology is acknowledged as one of the main ecological drivers of fishery yields; however, the role of lagoon seascape
structure is still poorly understood. This paper investigates how morphological variables, habitat distribution and seascape
diversity and complexity affect yields of artisanal fishery performed with fyke nets in the Venice Lagoon (northern Adriatic
Sea, Italy). Two spatial scales were considered in the analysis, with water quality parameters (temperature, salinity, dissolved
oxygen, turbidity, water residence times, N, P and chlorophyll-a concentrations) being measured at a fine, fyke-net scale and
morphological (average bottom elevation and sediment grain size) and habitat features (habitat proportion, diversity and
complexity) being measured at a broader, seascape scale. Generalised linear mixed models were employed to model 8 years
of nekton and green crab catches, disentangling the role of broad-scale morphology and seascape from that of fine-scale
water quality. Broad-scale variables clearly influenced fishery target species. Among them, lagoon residents were associated
with specific morphological and habitat characteristics, while marine migrants showed a stronger link with overall habitat
diversity and complexity. This evidence emphasises how artisanal fishery in the Venice Lagoon relies on the conservation
of morphological and habitat heterogeneity. Moreover, it highlights how habitat restoration performed at the seascape level
should also be taken into account, in addition to controlling hydrology and water quality, when managing fishery resources
in coastal lagoons
First record of adult specimens of the Oriental shrimp Palaemon macrodactylus Rathbun, 1902 in the Venice Lagoon (north Adriatic Sea, Italy)
Full text linkThe first record of adult Oriental shrimps Palaemon macrodactylus Rathbun, 1902 in the Venice Lagoon (north Adriatic Sea) is presented based on six specimens collected in a shallow water habitat during May 2012. The record is discussed in the context of the widespread distribution of the species, taking into account the possible ways of introduction and the possible consequences of the presence of P. macrodactylus in the Venice Lagoon
Ocean Color products supporting the assessment of good environmental status: development of a spatial distribution model for the seagrass Posidonia oceanica (L.) Delile, 1813.
No full textPosidonia oceanica (L.) Delile, 1813 is a seagrass species endemic to the Mediterranean Sea, which is considered as one of the key habitats of the coastal areas. This species forms large meadows sensitive to several anthropogenic pressures, that can be regarded as indicators of environment quality in coastal environments and its distributional patterns should be take into account when evaluating the Environmental Status following the Ecosystem approach promoted by the Mediterranean Action Plan of UNEP and the EU Marine Strategy Framework Directive (2008/56/EC). The aim of this study was to develop a Species Distribution Model for P. oceanica, to be applied to the whole Mediterranean North African coast, in order to obtain an estimation of the potential distribution of this species in the region to be considered as an indicator for the assessment of good Environmental Status. As the study area is a data-poor zone with regard to seagrass distribution (i.e. only for some areas detailed distribution maps are available), the Species Distribution Model (SDM) was calibrated using high resolution data from 5 Mediterranean sites, located in Italy and Spain and validated using available data from the North African coast. Usually, when developing SDMs species occupancy data is available at coarser resolution than the information of environmental variables, and thus has to be downscaled at the appropriate grain to be coupled to the environmental conditions. Tackling the case of P. oceanica we had to face the opposite problem: the quality (in terms of resolution) of the information on seagrass distribution is generally very high compared to the environmental data available over large scale in marine domains (e.g. global bathymetry data). The high resolution application and the model transfer (from calibration areas to North African coast) was possible taking advantage of Ocean Color products: the probability of presence of the species in a given area was modelled using a binomial generalized linear model as a function of the bathymetry and some water characteristics mainly obtained from satellite data. Full resolution (c.a. 300m) Medium Resolution Imaging Spectrometer (MERIS) sensor imagery have been processed in order to extract a set of environmental variables to be coupled to seagrass distribution in the areas used to calibrate the model and for the whole North Africa coast (i.e. model application area). For the period 2003-2011 we processed data of: 1) the diffuse attenuation coefficient 2) coloured dissolved organic matter 3) Particle backscatter at 443nm; 4) Euphotic depth, estimated considering the coefficient of extinction of light; 5) Euphotic depth/ depth ratio, combining the estimation of euphotic depth with the bathymetry. Other variables have been resampled at MERIS full resolution, like data obtained from Moderate Resolution Imaging Spectroradiometer (MODIS; Sea Surface Temperature and Photosynthetically Available Radiation) or by model simulation (e.g. water salinity). The fitted model suggests that water transparency plays a major role, but also other variables, such as salinity and photosynthetically available radiation at surface, are important at larger spatial scales in explaining meadows distribution. The availability of high resolution time-series of input data allowed us to apply the validated model to the whole NA coast. Using model predictions to identify areas with suitable conditions for P. oceanica, it was possible to develop an indicator of potential habitat use and to define baseline reference conditions, necessary for the assessment of Good Environmental Status in Mediterranean coastal waters. This work shows how the Ocean and Land Colour Instrument (OLCI) within the Sentinel-3 mission can be exploited - thanks to the way opened by MERIS - to carry out the operational monitoring needed for the implementation of the UNEP MAP and EU MSFD Ecosystem Approach to the integrated management of land, water and living resources
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