Article

Abundance and size structure of Thalassoma pavo (Pisces: Labridae) in the western Mediterranean Sea: Variability at different spatial scales

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Abstract

The present study was carried out during the summer of 1997 in three locations of the western Italian coast (La Spezia, Ligurian Sea; Ischia, central Tyrrhenian Sea; Ustica, southern Tyrrhenian Sea) to investigate variability in abundance and size structure of the labrid fish Thalassomapavo along a latitudinal gradient and over different spatial scales. Fish abundance and size were estimated by visual census in shallow rocky reefs. Significant differences were detected in average abundances of T.pavo (with and without the contribution of juveniles) among locations (separated by a distance of hundreds of kilometres from each other) and over the smallest scale examined (i.e. among sites located tens of metres from each other). However, most variability was explained considering the largest spatial scale associated with the latitudinal gradient. Average abundances generally decreased from the southern Tyrrhenian to the Ligurian Sea. In terms of frequency, juveniles (<5 cm total length (TL)) increased from north to south, while the largest fish (1610 and 115 cm) showed significantly higher densities at Ustica, followed by Ischia and La Spezia. Fish 615 cm long were significantly less abundant at La Spezia than at Ischia and Ustica, while those between 16 and 20 cm TL did not differ numerically among the three locations. The results of the present study provide suggestive evidence that factors acting on a geographical scale are likely to influence distribution patterns of the thermophilic fish T.pavo, although significant effects have been also observed at the smallest spatial scale examined. Climatic conditions (e.g. water temperature along the latitudinal gradient) and substrate features (e.g. macroalgal cover, physical complexity, slope) are thus likely to affect average abundances and size structures of T.pavo populations along the western Italian coast.

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... Understanding the origin of this T. pavo specimen requires a consideration of various biotic and abiotic factors that could influence the species's potential future establishment on the western (Italian) coast of the Middle Adriatic Sea. Firstly, T. pavo inhabits shallow rocky environments [2], where coralligenous reefs, animal biocenoses, and algal communities are well developed [14]. In this context, the Trabocchi Coast is an important monitoring site in the central western Adriatic, rich in rocky shorelines, bays, inlets, and submerged cliffs. ...
... On the other hand, instead, the northwestward ascent of eggs, larvae, or fish from the Apulian coasts should be less likely, given that, unlike the eastern Adriatic, where a northward expansion via the ESAC is plausible, the WAAC system could inhibit the movement from south to north. However, if more specimens were found, further research should be carried out to determine whether these populations are "true" reproductive populations or dependent on larval input from other regions, as observed in Liguria [2]. ...
... Wrasse larvae are known to disperse over vast distances, sometimes up to 1200 km offshore [40,41], confirming the species' potential for long-distance larval dispersal. The specimen observed on the Trabocchi reef measured approximately 8 cm in length, placing it within an intermediate size class as defined by Guidetti et al. [2]. Given its size and livery, it likely hatched in 2023. ...
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The Trabocchi Coast in the Chieti district of the mid-Adriatic (Italy) is one of the few rocky areas within the General Fisheries Commission GSA 17, alongside Mount Conero (Ancona 43°00′01″ N 13°52′13″ E) and the small San Nicola Rock (Ascoli Piceno; 43°32′0″ N 13°36′0″ E). This coastline is known for its biodiversity-rich bays, inlets, and submerged cliffs. Since 2015, annual biodiversity surveys have been conducted in the area, focusing on marine species richness and the identification of non-native species. In September 2024, a juvenile ornate wrasse (Thalassoma pavo) was documented for the first time in the middle Adriatic during an underwater visual survey at Trabocco Punta Torre, a key site along the Trabocchi Coast near artificial and biogenic reefs. This record extends the known distribution of T. pavo, a thermophilic species previously reported only along the southern Adriatic coast of Puglia. This is the first confirmed sighting on the middle and northern Adriatic coast of Italy. The discovery highlights the importance of ongoing biodiversity monitoring to track changes in marine ecosystems, particularly as the Adriatic Sea faces environmental shifts linked to climate warming. The presence of T. pavo in this area suggests the potential for the species to establish populations in previously uninhabited northern regions. Further research is needed to explore the role of biotic and abiotic factors—such as water temperature, current patterns, and habitat availability—in the survival and potential reproduction of T. pavo in the middle Adriatic. The observation contributes to the broader understanding of the meridionalization process in the Adriatic Sea, where rising water temperatures are facilitating the northward expansion of thermophilic species. Continuous monitoring is recommended to assess the long-term viability of T. pavo populations in the Adriatic Sea and better predict the impacts of ongoing climate change on marine biodiversity.
... Depuis 2013 Grouper's juveniles have a cryptic behavior and a preference for crevices, shelter availability being the determining factor for habitat suitability (La Mesa et al. 2002). They appear in shallow coastal waters, which makes them sensitive to littoral habitat degradation. ...
... Thalassoma pavo is a stenotherm species affiliated to warmer waters from southern parts of the Mediterranean. However, data from the last 20 years suggest a shift in its geographical range concomitant with global change and the warming of the Mediterranean (Guidetti et al., 2002;Milazzo et al., 2016). In the northern Mediterranean coasts, juveniles are still very rare and the detection of adult specimens is important data, as it indicates the shift of its expansion range towards the north. ...
... This stenotherm species is usually found on the southern Mediterranean coasts, in warmer waters. According to the maps presented in Guidetti et al. (2002) and Milazzo et al. (2016), the Gulf of Lion remain one of the last areas of the Mediterranean not populated by T. pavo. Generally T. pavo adults are the first to be observed colonizing a new area, followed by the juveniles (Figueiredo et al., 2005). ...
Thesis
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La perte d'habitat engendrée par l'artificialisation des côtes a de graves conséquences sur la biodiversité marine. Aussi, dans une optique de maintien de la biodiversité et des stocks de poissons, il peut s’avérer intéressant de restaurer certaines fonctions écologiques dans les zones anthropisées. Cette thèse avait pour objectif d’estimer le rôle potentiel des ports en tant qu’habitat pour les juvéniles de poissons côtiers et d’évaluer dans quelle mesure ce rôle peut être amélioré par le biais d’actions de restauration. Des expérimentations en aquarium ont permis d’estimer que le taux de survie des juvéniles sur des habitats artificiels utilisés à des fins de restauration était comparable à celui observé sur des roches. Une étude de la distribution spatiale des juvéniles à l’échelle d’un paysage sous-marin a ensuite montré que les ports pouvaient abriter des densités en juvéniles représentant de 50 à 90 % de celles retrouvées en milieu naturel. Les densités à l'intérieur des ports étaient cependant tributaires du type d’habitat considéré; les quais sans complexité structurale abritant les densités les plus faibles. Enfin, l'étude de cas concrets, a montré que la réhabilitation des ports pouvait significativement augmenter les densités de juvéniles à l’échelle de l’habitat, celles-ci pouvant atteindre des niveaux comparables au milieu naturel. Toutefois, ces bénéfices restaient faibles à l’échelle d’un port dans sa globalité. Ces travaux suggèrent un réel potentiel des infrastructures portuaires en tant qu’habitat juvénile alternatif, en particulier si des actions de restauration y sont entreprises. Cependant, pour plus d’efficacité, les projets de restauration devraient être menés à large échelle et utiliser une diversité d’habitats artificiels. La restauration écologique des ports peut ainsi être employée comme un outil complémentaire aux mesures de protection dans le cadre d’une gestion intégrée des zones côtières à l’échelle du paysage.
... As far as the geographic distribution in the Mediterranean Sea is concerned, C. julis is reported as fairly evenly distributed in the basin, without any evident latitudinal gradient (BINI, 1968;TO RTONESE, 1975). Thalassoma pavo, instead, is classically reported as more common along the southeastern coasts of the basin (BINI, 1968;TO RTONESE, 1975), which leads to consider this fish as a thermophilic species (see GUIDETTI et al., 2002). In the northernmost areas of the western basin, such as the Ligurian Sea, it was regarded as rare in the past (TO RTONESE, 1975). ...
... In recent years, nevertheless, T. pavo received an increasing attention due to its potential role as an indicator of climate changes. A number of studies have thus been carried out on its distribution patterns, ecological requirements, reproductive behaviour, recruitment and early mortality rates (VACCHI et al., 1999;SARA and UGOLINI, 2001;GUIDETTI, 2001GUIDETTI, , 2002GUIDETTI et al., 2002). ...
... In recent years, nevertheless, T. pavo received an increasing attention due to its potential role as an indicator of climate changes. A number of studies have thus been carried out on its distribution patterns, ecological requirements, reproductive behaviour, recruitment and early mortality rates (VACCHI et al., 1999;SARA and UGOLINI, 2001;GUIDETTI, 2001GUIDETTI, , 2002GUIDETTI et al., 2002). ...
Article
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Distribution patterns of two labrid fish, namely Coris julis and Thalassoma pavo, were assessed by visual census in autumn 2000 at four locations (with three sites per location), and at different depth levels (from 0 to about 30 m depth) in SE Apulia (SE Italy). Total abundance and juvenile density of T. pavo tended to be greater in shallow waters to about 10 m depth, in spite of some differences occur-red at the scale of sites. Conversely, C. julis showed low densities in waters shal-lower than 5 m, and higher values from 5 down to about 30 m depth. In the case of C. julis, differences in the pattern related to depth occurred at both the spatial sca-les examined (among locations and among sites within location). The patterns observed for the two species concerned both adult and juvenile fishes, which sug-gests the absence of evident ontogenetic shifts in habitat use during their life history. The results presented here suggest that the two species could segregate according to depth. T. pavo, due to its well known thermophily, could thus over-compete C. julis at very shallow depths where seawaters are warmer because of the seasonal thermocline (at least during the period of the year when sampling was performed). The patterns observed in this study may also provide useful informa-tion about the scenario that could take shape in areas of the NW Mediterranean, such as the Ligurian Sea, where T. pavo started increasing in abundance in the recent years.
... Moreover, a positive trend in the Mediterranean temperature has been recorded in the last 50 years, despite large cyclic fluctuations, with dramatic effects on water circulation (Vargas-Yáñez et al. 2008). As a result, some Mediterranean indigenous species with (sub)tropical affinities that were confined to the southern/eastern parts of the basin recently spread north-westward (Bianchi & Morri 1994, 2004Francour et al. 1994;Guidetti et al. 2002;Azzurro 2008). This is the case, for example, of the ornate wrasse Thalassoma pavo, a termophilic labrid fish that in the recent decades expanded its distribution range northwards (Guidetti et al. 2002). ...
... As a result, some Mediterranean indigenous species with (sub)tropical affinities that were confined to the southern/eastern parts of the basin recently spread north-westward (Bianchi & Morri 1994, 2004Francour et al. 1994;Guidetti et al. 2002;Azzurro 2008). This is the case, for example, of the ornate wrasse Thalassoma pavo, a termophilic labrid fish that in the recent decades expanded its distribution range northwards (Guidetti et al. 2002). This fish can be used as an indicator species to monitor water warming in the Mediterranean Sea (see Francour et al. 1994). ...
... A well-known example of a northward shift in the distribution of a fish species in the Mediterranean is the ornate wrasse T. pavo, a warm-water species quite common in the southern and eastern regions of the sea (Bianchi 2007 and reference therein). Likely in response to the ongoing warming of water, T. pavo expanded its geographic range up to the Ligurian Sea (Guidetti et al. 2002) and the north-eastern Adriatic Sea (Dulčić & Pallaoro 2002;Dulčić 2004), in about one decade. The northward expansion of T. pavo along the Adriatic coasts of Italy was not that striking. ...
Article
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Fish assemblages inhabiting shallow rocky reefs at six Italian marine protected areas (MPAs) were investigated to assess broad-scale patterns in assemblage structure, species richness and composition, and to evaluate the presence of a latitudinal gradient in the distribution pattern of a thermophilic fish, the ornate wrasse Thalassoma pavo. Fish abundance was estimated by visual censuses carried out within the integral reserve zones, within the 1–7 m depth range and during four sampling periods. Multivariate analyses revealed significant differences in the assemblage structure among MPAs, although patterns of variation changed considerably from time to time and they were not consistent with latitudinal or longitudinal gradient. Fish assemblages of Miramare (northern Adriatic) and those of the other MPAs clearly separated into two groups. Multivariate differences among MPAs mainly relied upon some relatively common species (e.g. Diplodus puntazzo and Muraena helena). Substantial contribution to these differences was also accounted for by T. pavo. Significant differences among MPAs were detected also in species richness and total density of fish, although the effect of MPA on species richness varied significantly from time to time. Both species richness and total density of fish at Miramare were always higher compared to the other MPAs, likely in relation to peculiar habitat characteristics. Density of T. pavo declined significantly from south to north, thus confirming the thermophily of this species. Present data point out the importance of monitoring marine fish diversity through long-term surveys across a wide spatial scale, in order to detect the early effects of water warming and to develop future plans of management and conservation.
... Length ( shift in its geographical range concomitant with global change and the warming of the Mediterranean (Guidetti et al., 2002;Milazzo et al., 2016). In the northern Mediterranean coasts, juveniles are still very rare and the detection of adult specimens is important data, as it indicates the shift of its expansion range towards the north. ...
... This stenotherm species is usually found on the southern Mediterranean coasts, in warmer waters. According to the maps presented in Guidetti et al. (2002) and Milazzo et al. (2016), the Gulf of Lion remain one of the last areas of the Mediterranean not populated by T. pavo. Generally T. pavo adults are the first to be observed colonizing a new area, followed by the juveniles (Figueiredo et al., 2005). ...
Article
Coastal nursery habitats are essential for the renewal of adult fish populations.We quantified the availability of a coastal nursery habitat (shallowheterogeneous rocky bottoms) and the spatial variability of its juvenile fish populations along 250 km of the Catalan coastline (France and Spain). Nurserieswere present in 27% of the coastline, but only 2% of thembenefited fromstrict protection status. For nine taxa characteristic of this habitat, total juvenile densities varied significantly between nursery sites along the coastline, with the highest densities being found on the northern sites. Recruitment level (i.e. a proxy of nursery value) was not explained by protection level, but itwas moderately and positively correlatedwith an anthropization index. Patterns of spatial variations were taxa-specific. Exceptional observations of four juveniles of the protected grouper Epinephelus marginatus were recorded. Our data on habitat availability and recruitment levels provides important informations which help to focus MPA management efforts.
... Within the Mediterranean Sea, C. julis was evenly distributed in coastal areas (Tortonese 1975), although more abundant in the northern and cooler waters (Quignard & Pras 1986). Instead, T. pavo was more common along the southern coast of the basin (Tortonese 1975; but see also Guidetti et al. 2002), although it has progressively expanded in the northernmost sectors over the last decades (Francour et al. 1994;Astraldi et al. 1995). ...
... Indeed, the results of the present study suggest that interesting changes might occur in locations where the density of T. pavo has recently increased (Francour et al. 1994;Vacchi et al. 1999;Guidetti et al. 2002; but see Bianchi 2007 for a review) and this may have some important ecological implications at community level such as composition shifts, habitat relocation of the competitive subordinate species, and alteration of the interspecific interactions. Interannual observations at these locations may be useful to clarify whether the northward expansion of T. pavo may lead to these expected changes, at least along steep rocky coasts. ...
Article
Changes in the shore topography (e.g. slope) occur at a scale of hundreds of meters in several locations in the Lusitanian and the Mediterranean Sea provinces. We tested whether differences in the bottom inclination might affect the vertical distribution patterns of two sympatric coastal labrid fishes, the rainbow wrasse Coris julis and the ornate wrasse Thalassoma pavo. Visual censuses were used to determine the distribution and abundance of these labrid species in high (≥30°) and low (≤3°) slope rocky substrates covered by brown macroalgae and at two different depths (shallow, 4–7 m, and deep 14–20 m). Pectoral fin aspect ratio was used as an estimate of swimming performance to potentially explain the patterns observed. Despite the intrinsic biogeographical differences in the overall density of T. pavo and C. julis, on steep coasts the ornate wrasse dominated in shallow waters, whereas the two species coexisted both in shallow and deeper depths on gentle slope coasts. These distribution patterns were consistent across locations, and fin aspect ratio was not a good predictor of between-habitat use for wrasses. We show that, under specific topographical conditions, the depth segregation pattern seems to be an interactive segregation (likely related to resource competition) rather than a result of selective segregation due to morphological differences in the pectoral fin. Significant ecological changes might occur in locations where the density of T. pavo has recently increased as a result of water warming.
... This stresses the importance of implementing rigorous experimental designs to investigate distribution patterns of marine species. Previous studies that employed proper experimental designs for examining spatial and/or temporal variability in fish were carried out in several areas of the world (e.g., Roberts, 1991; Levin, 1993; Levin et al, 1997; Gust et al., 2001 ), whereas similar investigations are fairly rare in the Mediterranean basin (Vigliola et al., 1998; Guidetti et al, 2002). As far as S. cretense is concerned, investigations have been carried out on social organisation and sexual patterns (De Girolamo et al, 1999; Azzurro & Andaloro, 2000), reproductive biology (Petrakis & Papaconstantinou, 1990), genetics (Bernardi et al, 2000), and growth rates (Potoschi et al, 2000 ), whereas no studies have specifically investigated its distribution patterns. ...
... Whether such an event could be conceived as an indirect indication of climatic changes (e.g., Mediterranean water warming; Astraldi et al., 1994) is effectively outside the aim of the present study. However, as changes in distribution patterns of marine species (including fishes) are considered to reflect changes in oceanographic-climatic conditions (Stephens et al., 1988), the northwards spreading of S. cretense (see also Guidetti & Boero, 2001, and Dulcic & Pallaoro, 2001), similarly to other thermophilic fishes (Bianchi & Morri, 1994; Francour et al., 1994; Vacchi et al, 1999; Guidetti et al., 2002), is worthy of attention and deserves specific research in the future. ...
Article
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Spatio‐temporal variability in the abundance of the parrotfish, Sparisoma cretense, was investigated along the SE Apulian rocky coast (SE Italy, Mediterranean Sea). Underwater visual census surveys were carried out in three different times (August 2000, March 2001 and May‐June 2001) at four locations between Otranto (Lower Adriatic) and S.M. di Leuca (Ionian Sea), at three sites at each location, and at four depth levels from the surface down to about 30 m. The species was never observed near the surface nor in the deepest zones, while it was more abundant at 12–15 m (mean ± SE: 0.69 ± 0.05 individuals 100 m‐2) than at 5–7 m depth (0.27 ± 0.04 ind. 100 m‐2). This general pattern was observed during all three sampling times and at each location surveyed. Significant differences in the abundance of S. cretense were detected among depths, locations and, to a lesser extent, among times, while no differences were observed among sites within locations. This study provides evidence that, besides a given variability over a spatial scale of kilometres (i.e., among locations), this fish lives exclusively between about 5 and 15 m depth, suggesting that it could have specific habitat requirements in terms of physical conditions (e.g., water temperature, wave action) and substrate features (e.g., benthic cover). In addition; taking into account that juvenile parrotfishes appeared for the first time in August 2000 along the coast of SE Apulia, where neither adults nor juveniles had been previously recorded, these data could support the hypothesis that S. cretense is establishing a true population in this region. The results presented here, in fact show that the low winter water temperature did not affect survivorship of this ther‐mophilous fish.
... In the first period of rapid warming (1985 to 1992), the rainbow wrasse Thalassoma pavo (Linnaeus 1758) started to be recorded regularly in the Ligurian Sea [35]; although not as abundant as it is in the southern sectors of the Mediterranean Sea [95], it is now established and reproduces successfully [96][97][98]. In the second period of rapid warming (1999 to 2006), Diplodus cervinus came to the Ligurian Sea and was subsequently established in localities of the western coast [36,98]; the present paper reports its first findings in eastern coast sites, a clue to its further range expansion. ...
Article
Global warming is causing poleward expansion of species ranges. Temperate seas, in particular , are undergoing a process known as 'tropicalisation', i.e., the combination of seawater warming and establishment of southern species. The Ligurian Sea is one of the coldest sectors of the Medi-terranean and has thus been characterized by a dearth of warm-temperate species and a comparative abundance of cold-temperate species. This paper uses a time series of sea surface temperature (SST) and new records of thermophilic fish species to reconsider the biogeography of the Ligurian Sea. SST has risen by about 0.7 °C on average between 1948 and 2023, but two phases may be distinguished: a cool one (ended in the mid-1980s) and a warm one (still ongoing); the latter phase shows alternating periods of rapid warming and comparatively stationary temperature. The arrival of thermophilic species coincided with the periods of rapid warming; some of these species were established in the subsequent stationary periods. Heatwaves and climate-related diseases associated with the periods of rapid warming have caused mass mortalities of autochthonous species. Our knowledge on the bio-geography of the Ligurian Sea was established during the cool phase; the present situation, however, calls for redefining the chorological spectrum of the Ligurian Sea biota.
... In the first period of rapid warming (1985 to 1992), the rainbow wrasse Thalassoma pavo (Linnaeus 1758) started to be recorded regularly in the Ligurian Sea [35]; although not as abundant as it is in the southern sectors of the Mediterranean Sea [95], it is now established and reproduces successfully [96][97][98]. In the second period of rapid warming (1999 to 2006), Diplodus cervinus came to the Ligurian Sea and was subsequently estab-lished in localities of the western coast [36,98]; the present paper reports its first findings in eastern coast sites, a clue to its further range expansion. ...
Article
Full-text available
Global warming is causing poleward expansion of species ranges. Temperate seas, in particular , are undergoing a process known as 'tropicalisation', i.e., the combination of seawater warming and establishment of southern species. The Ligurian Sea is one of the coldest sectors of the Medi-terranean and has thus been characterized by a dearth of warm-temperate species and a comparative abundance of cold-temperate species. This paper uses a time series of sea surface temperature (SST) and new records of thermophilic fish species to reconsider the biogeography of the Ligurian Sea. SST has risen by about 0.7 °C on average between 1948 and 2023, but two phases may be distinguished: a cool one (ended in the mid-1980s) and a warm one (still ongoing); the latter phase shows alternating periods of rapid warming and comparatively stationary temperature. The arrival of thermophilic species coincided with the periods of rapid warming; some of these species were established in the subsequent stationary periods. Heatwaves and climate-related diseases associated with the periods of rapid warming have caused mass mortalities of autochthonous species. Our knowledge on the bio-geography of the Ligurian Sea was established during the cool phase; the present situation, however, calls for redefining the chorological spectrum of the Ligurian Sea biota.
... However, most of them regarded fish fry of the species. It is known that T. pavo shows intense fluctuations at its distribution and those fluctuations are strongly related to the geographic position and to the state of reproduction period [69]. The species (T. ...
Article
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The Mediterranean Sea and its exceptional biodiversity suffer from non-indigenous (NIS) and invasive species. These result from Lessepsian migration and human activities. Species with the highest negative impact include Pterois miles, Lagocephalus sceleratus and Fistularia commersonii. The current study assessed the distribution and abundance of these three species in the Aegean and Ionian Seas in the context of the regional diversity of ichthyofauna. Using Scientific Diving and Visual Census, we focused on NIS fish fauna, and surveyed most of the areas where the occurrence or establishment of NIS had been documented. Emphasis was given to regions with limited available data. This study assessed the homogeneity of diversity and abundance of the fish species at the diving sites; assessed the most dominant species per region; and calculated relevant biodiversity indexes. Our results suggest that the south and east parts of the Aegean Sea are the most affected by the establishment of NIS. Samos Island is concluded to be an important region for the expansion of NIS to the northern parts of the Aegean Sea. Also, both the Saronikos Gulf and the whole area of the Peloponnese seem to have a pivotal role in the expansion of distribution of NIS from the east Mediterranean sub-basin to the west sub-basin. The genus Siganus seems to have very high abundances and population densities in certain areas, and therefore its establishment could have negative impacts in these regions. We conclude that scientific diving is not appropriate for monitoring the population status of L. sceleratus and we propose more appropriate methodologies such as the use of baited cameras and ROV’s to be used in the future.
... The Adriatic Sea can undergo dramatic change in the lower part of its temperature ranges. In winter 2001, the Adriatic Sea experienced a period of abnormally low surface temperatures (from 9°C to freezing) that led to mass mortalities of sardines (Sardinella aurita) (Guidetti et al. 2002), with resulting alteration of the food webs. The Adriatic basin is also the site for deep-water formation, as a result of the bora winds associated with decreased temperatures, but recent studies have reported the shift of this water formation site towards the Aegean Sea by a phenomenon known as eastern-Mediterranean Transient (EMT), related mainly to climatic sea and atmosphere conditions (Hassoun et al. 2015). ...
... The Adriatic Sea can undergo dramatic change in the lower part of its temperature ranges. In winter 2001, the Adriatic Sea experienced a period of abnormally low surface temperatures (from 9°C to freezing) that led to mass mortalities of sardines (Sardinella aurita) (Guidetti et al. 2002), with resulting alteration of the food webs. The Adriatic Basin is also the site for deep-water formation, as a result of the bora winds associated with decreased temperatures, but recent studies have reported the shift of this water formation site towards the Aegean Sea by a phenomenon known as eastern-Mediterranean Transient (EMT), related mainly to climatic sea and atmosphere conditions (Hassoun et al. 2015). ...
Technical Report
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Balzan MV, Hassoun AER, Aroua N, Baldy V, Bou Dagher M, Branquinho C, Dutay J-C, El Bour M, Médail F, Mojtahid M, Morán-Ordóñez A, Roggero PP, Rossi Heras S, Schatz B, Vogiatzakis IN, Zaimes GN, Ziveri P 2020 Ecosystems. In: Climate and Environmental Change in the Mediterranean Basin – Current Situation and Risks for the Future. First Mediterranean Assessment Report [Cramer W, Guiot J, Marini K (eds.)] Union for the Mediterranean, Plan Bleu, UNEP/MAP, Marseille, France, pp. 323-468.
... The Adriatic Sea can undergo dramatic change in the lower part of its temperature ranges. In winter 2001, the Adriatic Sea experienced a period of abnormally low surface temperatures (from 9°C to freezing) that led to mass mortalities of sardines (Sardinella aurita) (Guidetti et al. 2002), with resulting alteration of the food webs. The Adriatic basin is also the site for deep-water formation, as a result of the bora winds associated with decreased temperatures, but recent studies have reported the shift of this water formation site towards the Aegean Sea by a phenomenon known as eastern-Mediterranean Transient (EMT), related mainly to climatic sea and atmosphere conditions (Hassoun et al. 2015). ...
Chapter
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Despite covering only 0.82% of the ocean’s surface, the Mediterranean Sea supports up to 18% of all known marine species, with 21% being listed as vulnerable and 11% as endangered. The acceler- ated spread of tropical non-indigenous species is leading to the “tropicalization” of Mediterranean fauna and flora as a result of warming and extreme heat waves since the 1990s. The acidification rate in the Mediterranean waters has ranged between 0.055 and 0.156 pH units since the pre-industrial period, affecting the marine trophic chain, from its primary producers (i.e., coccolithophores and fo- raminifera) to corals and coralline red algae. Projections for high emission scenarios show that endemic assemblages will be modified with numerous species becoming extinct in the mid 21st century and changes to the natural habitats of commercially valuable species, which would have many repercussions on marine ecosystem services such as tourism, fisheries, climate regulation, and ultimately on human health. Adaptation strategies to reduce environmental change impacts need effective mitigation policies and actions. They require anticipatory planning to enable them to tackle problems while they are still manageable. Given the diversity of each Mediterranean sub-basin, wider monitoring coverage is needed to strengthen our knowledge about the different adaptation processes that characterize and best suit each geographical zone. Adaptation implies the implementation of more sustainable fishing practices as well as reducing pollution from agricultural activity, sustainable tourism or developing more effective waste management. Marine protected areas can potentially have an insurance role if they are established in locations not particularly vulnerable to ocean acidification and climate change.
... The Adriatic Sea can undergo dramatic change in the lower part of its temperature ranges. In winter 2001, the Adriatic Sea experienced a period of abnormally low surface temperatures (from 9°C to freezing) that led to mass mortalities of sardines (Sardinella aurita) (Guidetti et al. 2002), with resulting alteration of the food webs. The Adriatic basin is also the site for deep-water formation, as a result of the bora winds associated with decreased temperatures, but recent studies have reported the shift of this water formation site towards the Aegean Sea by a phenomenon known as eastern-Mediterranean Transient (EMT), related mainly to climatic sea and atmosphere conditions (Hassoun et al. 2015). ...
Technical Report
Full-text available
Mediterranean Ecosystem report on Climate and Global changes. Balzan MV, Hassoun AER, Aroua N, Baldy V, Bou Dagher M, Branquinho C, Dutay J-C, El Bour M, Médail F, Mojtahid M, Morán-Ordóñez A, Roggero PP, Rossi Heras S, Schatz B, Vogiatzakis IN, Zaimes GN, Ziveri P 2020 Ecosystems. In: Climate and Environmental Change in the Mediterranean Basin – Current Situation and Risks for the Future. First Mediterranean Assessment Report [Cramer W, Guiot J, Marini K (eds.)] Union for the Mediterranean, Plan Bleu, UNEP/MAP, Marseille, France, 151pp, in press
... The Adriatic Sea can undergo dramatic change in the lower part of its temperature ranges. In winter 2001, the Adriatic Sea experienced a period of abnormally low surface temperatures (from 9°C to freezing) that led to mass mortalities of sardines (Sardinella aurita) (Guidetti et al. 2002), with resulting alteration of the food webs. The Adriatic basin is also the site for deep-water formation, as a result of the bora winds associated with decreased temperatures, but recent studies have reported the shift of this water formation site towards the Aegean Sea by a phenomenon known as eastern-Mediterranean Transient (EMT), related mainly to climatic sea and atmosphere conditions (Hassoun et al. 2015). ...
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Marine ecosystems: Despite covering only 0.82% of the ocean’s surface, the Mediterranean Sea supports up to 18% of all known marine species, with 21% being listed as vulnerable and 11% as endangered. The accelerated spread of tropical non-indigenous species is leading to the “tropicalization” of Mediterranean fauna and flora as a result of warming and extreme heat waves since the 1990s. The acidification rate in the Mediterranean waters has ranged between 0.055 and 0.156 pH units since the pre-industrial period, affecting the marine trophic chain, from its primary producers (i.e., coccolithophores and foraminifera) to corals and coralline red algae. Projections for high emission scenarios show that endemic assemblages will be modified with numerous species becoming extinct in the mid 21st century and changes to the natural habitats of commercially valuable species, which would have many repercussions on marine ecosystem services such as tourism, fisheries, climate regulation, and ultimately on human health. Adaptation strategies to reduce environmental change impacts need effective mitigation policies and actions. They require anticipatory planning to enable them to tackle problems while they are still manageable. Given the diversity of each Mediterranean sub-basin, wider monitoring coverage is needed to strengthen our knowledge about the different adaptation processes that characterize and best suit each geographical zone. Adaptation implies the implementation of more sustainable fishing practices as well as reducing pollution from agricultural activity, sustainable tourism or developing more effective waste management. Marine protected areas can potentially have an insurance role if they are established in locations not particularly vulnerable to ocean acidification and climate change. Coastal ecosystems: The coastal zone, i.e. the area in which the interaction between marine systems and the land dominate ecological and resource systems, is a hotspot of risks, especially in the south-eastern Mediterranean region. Alterations to coastal ecosystems (lagoons, deltas, salt marshes, etc.) due to climate change and human activities affect the flow of nutrients to the sea, the magnitude, timing and composition of potentially harmful/toxic plankton blooms. They also significantly increase the number and frequency of jellyfish outbreaks, and could have negative impacts on fisheries. 1.2 to 5% of seagrass meadows in the Mediterranean Sea, which represent 5 to 17% of the worldwide seagrass habitat, are lost each year. Among them, almost half of the surveyed Posidonia oceanica sites have suffered net density losses of over 20% in 10 years. As for fish, non-indigenous species and climate change cause local extinction. Projected temperature increases combined with a decrease in nutrient replenishment and ocean acidification, are expected to cause changes in plankton communities, negative impacts on fish, corals, seagrass meadows and propagation of non-indigenous species. Projected sea level rise will impact coastal wetlands deltas and lagoons. Extensive urbanization added to climate change is also expected to threaten coastal ecosystems, human health and well-being. A nexus approach is required when trying to establish adaptation methods for the entire Mediterranean, while taking into account ecosystem-based management, synergies and conflicts, integrating local knowledge and institutions. Suitable adaptation policies include reducing pollution runoff, both from agriculture and industry and waste management, and policies to limit or prevent acidification. Conservation planning and management should focus on cross-cutting approaches and building resilience between structural and functional connectivities of various fields. Terrestrial ecosystems: Biodiversity changes in the Mediterranean over the past 40 years have occurred more quickly and been more significant than in other regions of the world. Urbanization and the loss of grasslands are key factors of ecosystem degradation across the region. Since 1990, agricultural abandonment has led to a general increase in forest areas in the northern Mediterranean, while in the southern Mediterranean, ecosystems are still at risk of fragmentation or disappearance due to human pressure from clearing and cultivation, overexploitation of firewood and overgrazing. Drylands have significant biodiversity value, with many of the plants and animals highly adapted to water-limited conditions. They are undergoing an overall increase in response to climate change and extensive land abandonment. 48% of Mediterranean wetlands were lost between 1970 and 2013, with 36% of wetland-dependent animals in the Mediterranean threatened with extinction. Because of the reduction in river flows, 40% of fish species in Mediterranean rivers are endangered. Projections for the 21st century indicate drier climate and increased human pressure, with negative impacts on terrestrial biodiversity, forest productivity, burned areas, freshwater ecosystems and agrosystems. Future projections indicate that burnt areas can increase across the region by up to 40% in a 1.5°C warming scenario and up to 100% from current levels for 3°C warming at the end of the century. Mediterranean drylands will become drier and their extent is expected to increase across the region. Projections suggest decreased hydrological connectivity, increased concentration of pollutants during droughts, changes in biological communities as a result of harsher environmental conditions, and a decrease in biological processes such as nutrient uptake, primary production, and decomposition. Promotion of ‘climate-wise connectivity’ through permeability of the landscape matrix, dispersal corridors and habitat networks are key to facilitating upward the migration of lowland species to mountains in order to adapt to new climate change conditions. Promotion of mixedspecies forest stands and sylvicultural practices such as thinning, and management of understory can promote the adaption of Mediterranean forests to climate change. Promotion of the spatial heterogeneity of the landscape matrix can help reduce fire impacts. The preservation of the natural flow variability of Mediterranean rivers and streams and wide riparian areas, along with reductions in water demand are key to the adaptation of freshwater ecosystems to future climate change.
... The warming of seawater recorded in recent decades (Bethoux et al., 1990;Vargas-Yáñez et al., 2008) is one of the direct consequences of climate change on the basin's marine ecosystems, which in turn is altering the biota (Boero et al., 2008;Calvo et al., 2011), including fish (Bianchi, 2007;Goren & Galil, 2005;Relini, 2010). In comparison with the global trend, the temperature increase of the NW Mediterranean has been particularly intense (Vargas-Yáñez et al., 2008), being in large part responsible for the remarkable changes reported in species distribution and abundance (Coll et al., 2010;Guidetti et al., 2002;Lloret et al., 2015;Sabatés et al., 2006;Villegas-Hernández et al., 2015). The observed decreasing abundance of "boreal-type", cold-water species and the simultaneous northwards diffusion of thermophilic taxa, once confined to the southern zone of the basin, is commonly known as "meridionalization" (Coll et al., 2010;Lloret et al., 2015). ...
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Among the thermophilic fishes that have become established in the north‐western Mediterranean as a consequence of sea warming, the yellowmouth barracuda (Sphyraena viridensis Cuvier, 1829) appears to be one of the most successful and abundant in the coastal rocky environment, having increasingly become the object of recreational and commercial exploitation in the study area. Lure‐fishing sessions were carried out from May 2016 to November 2018 in the Catalan Sea (NE Spain) at dawn and dusk, with the aim of providing new insight into the behavioural, spatial and feeding ecology and vulnerability to angling of this poorly known species. Generalized mixed‐effects linear models showed that S. viridensis is a crepuscular inshore dweller, whose vulnerability to angling is significantly influenced by solar and lunar light intensities, being highest in the pre‐spawn and spawning periods. Asymmetries between dawn and dusk activity patterns were detected, evidently related to a drop in aggressiveness at dusk following the spawning period. The simple study design adopted may be applied to other contexts, aiming to the recognition of several levels of fish vulnerability to angling.
... Reduced winter cooling and increased average temperature have allowed these southern species to establish and diffuse in the Ligurian Sea Bianchi et al. 2018a). The ornate wrasse Thalassoma pavo, for example, has been proved to reproduce in the Ligurian Sea (Vacchi et al. 1999(Vacchi et al. , 2001Sara et al. 2005), even if it does not reach population densities comparable to those observed in the warmer Tyrrhenian Sea (Guidetti et al. 2002). Several other fish species of southern origin are now to be considered as established in the Ligurian Sea, such as the zebra seabream Diplodus cervinus, the pearly razorfish Xyrichtys novacula, the Atlantic lizardfish Synodus saurus, the yellowmouth barracuda Sphyraena viridensis, the parrotfish Sparisoma cretense and the cryptobenthic Molly Miller combtooth blenny Scartella cristata (Parravicini et al. 2008;Bianchi et al. 2018a;Cattaneo-Vietti 2018). ...
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A rapid temperature increase in the 1980-90s has been accompanied by dramatic and unprecedented changes in the biota and communities of the Ligurian Sea. This review uses existing historical series (a few of which have been purposely updated) to assess extent and consequences of such changes. A number of warm-water species, previously absent or occasional in the comparatively cold Ligurian Sea, has recently established thanks to warmer winters. Occurrence among them of invasive alien species is causing concern because of their capacity of outcompeting autochthonous species. Summer heatwaves, on the other hand, caused mass mortalities in marine organisms, some of which found refuge at depth. New marine diseases appeared, as well as other dysfunctions such as the formation of mucilage aggregates that suffocated and entangled benthic organisms. Human pressures have combined with climate change to cause phase shifts (i.e., abrupt variations in species composition and community structure) in different habitats, such as the pelagic environment, seagrass meadows, rocky reefs, and marine caves. These phase shifts implied biotic homogenization, reduction of diversity, and dominance by invasive aliens, and may be detrimental to the resilience of Ligurian Sea ecosystems. Another phase of rapid warming has possibly started in the 2010s and there are clues pointing to a further series of biological changes, but data are too scarce to date for proper assessment. Only well addressed long-term studies will help understanding the future dynamics of Ligurian Sea ecosystems and their possibilities of recovery.
... This may further explain the discrepancies between adults and larvae abundances. For example, the Labrus and the Symphodus genera of the Labridae family are abundant over hard substrates throughout the French Mediterranean coast (Guidetti 2000, García-Charton & Pérez-Ruzafa 2001, Guidetti et al. 2002 and the fact that only 16 specimens were caught in the light-traps over the 27 800 larvae collected is evidence of their selectivity. The global absence of labrids in light-traps may be further attributed to the low mobility of their larvae, which have a short pelagic larval duration and do not undertake ontogenic migrations (Raventos & Macpherson 2005). ...
Article
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Most coastal fish species spend their early life stages in the pelagic environment, before settling in coastal habitats. The variability in the arrival of larvae to coastal habitats provide information on the species’ biology and recruitment potential. To explore the dynamics of larval fish supply to coastal habitats in the NW Mediterranean Sea, 13 sites were monitored using light-traps, from July 2012 to December 2015. Most variation in Catches Per Unit Effort (CPUE) among topographic basins and species were statistically significant for high (quantile 75%) and very high (quantile 90%) catches only. At year scale, CPUE displayed strong seasonality, and three main species assemblages were detected in late spring-early summer, summer and late autumn-early winter. At month scale, CPUE were higher around the new moon for all quantiles and temporally autocorrelated at a lag of about 28 days. Larval supply also varied spatially with site-specific associations, and with riverine influence. All together, these results confirm that the previously described patterns of larval supply observed in tropical and subtropical environments (e.g., the high variability at all spatial and temporal scales and the strong influence of the moon) also apply to Mediterranean fish assemblages. The larval supply in the NW Mediterranean Sea comes out as a solid candidate for monitoring the state of the marine ecosystems, highlighting the need to continue such time series.
... Most of the species recorded are now widespread in the wider Gulf of Genoa, although not all reach the densities commonly observed in the Southern Mediterranean (e.g. Guidetti et al., 2002). NIS, in particular, after the initial colonization in anthropized habitats, have recently also occupied natural habitats. ...
Article
Global warming is facilitating the poleward range expansion of plant and animal species. In the Mediterranean Sea, the concurrent temperature increase and abundance of (sub)tropical non-indigenous species (NIS) is leading to the so-called 'tropi-calization' of the Mediterranean Sea, which is dramatically evident in the southeastern sectors of the basin. At the same time, the colder northwestern sectors of the basin have been said to undergo a process of 'meridionalization', that is the establishment of warm-water native species (WWN) previously restricted to the southern sectors. The Gulf of Genoa (Ligurian Sea) is the northwestern reach for southern species of whatever origin in the Mediterranean. Recent (up to 2015) observations of NIS and WWN by diving have been collated to update previous similar inventories. In addition, the relative occurrences of both groups of southern species have been monitored by snorkelling between 2009 and 2015 in shallow rocky reefs at Genoa, and compared with the trend in air and sea surface temperatures. A total of 20 southern species (11 NIS and 9 WWN) was found. Two WWN (the zebra seabream Diplodus cervinus and the parrotfish Sparisoma cretense) and three NIS (the SW Atlantic sponge Paraleucilla magna, the Red Sea polychaete Branchiomma luctuosum, and the amphi-American and amphi-Atlantic crab Percnon gibbesi) are new records for the Ligurian Sea, whereas juveniles of the Indo-Pacific bluespotted cornetfish Fistularia commersonii have been found for the first time. While temperature has kept on increasing for the whole period, with 2014 and 2015 being the warmest years since at least 1950, the number of WWN increased linearly, that of NIS increased exponentially, contradicting the idea of meridionalization and supporting that of tropicalization even in the northern sectors of the Mediterranean basin.
... Therefore, higher abundances of the three species could be expected in the areas close to the source of transport, gradually declining in the inner part of the bay. Similar patterns were documented in the case of the Mediterranean wrasse, with a greater abundance of this species observed in the areas that were closer to the source of population 36 . High structural complexity and higher prey availability on reef habitats could be additional factors in explaining high abundance of G. hebraicum near the reef ridges. ...
Article
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Many fishes undergo ontogenetic habitat shifts to meet their energy and resource needs as they grow. Habitat resource partitioning and patterns of habitat connectivity between conspecific fishes at different life-history stages is a significant knowledge gap. Species distribution models were used to examine patterns in the relative abundance, individual biomass estimates and environmental niche associations of different life stages of three iconic West Australian fishes. Continuous predictive maps describing the spatial distribution of abundance and individual biomass of the study species were created as well predictive hotspot maps that identify possible areas for aggregation of individuals of similar life stages of multiple species (i.e. spawning grounds, fisheries refugia or nursery areas). The models and maps indicate that processes driving the abundance patterns could be different from the body size associated demographic processes throughout an individual’s life cycle. Incorporating life-history in the spatially explicit management plans can ensure that critical habitat of the vulnerable stages (e.g. juvenile fish, spawning stock) is included within proposed protected areas and can enhance connectivity between various functional areas (e.g. nursery areas and adult populations) which, in turn, can improve the abundance of targeted species as well as other fish species relying on healthy ecosystem functioning.
... Most of the species recorded are now widespread in the wider Gulf of Genoa, although not all reach the densities commonly observed in the Southern Mediterranean (e.g. Guidetti et al., 2002). NIS, in particular, after the initial colonization in anthropized habitats, have recently also occupied natural habitats. ...
... Most of the species recorded are now widespread in the wider Gulf of Genoa, although not all reach the densities commonly observed in the Southern Mediterranean (e.g. Guidetti et al., 2002). NIS, in particular, after the initial colonization in anthropized habitats, have recently also occupied natural habitats. ...
Article
Global warming is facilitating the poleward range expansion of plant and animal species. In the Mediterranean Sea, the concurrent temperature increase and abundance of (sub)tropical non-indigenous species (NIS) is leading to the so-called ‘tropicalization’ of the Mediterranean Sea, which is dramatically evident in the south-eastern sectors of the basin. At the same time, the colder north-western sectors of the basin have been said to undergo a process of ‘meridionalization’, that is the establishment of warm-water native species (WWN) previously restricted to the southern sectors. The Gulf of Genoa (Ligurian Sea) is the north-western reach for southern species of whatever origin in the Mediterranean. Recent (up to 2015) observations of NIS and WWN by diving have been collated to update previous similar inventories. In addition, the relative occurrences of both groups of southern species have been monitored by snorkelling between 2009 and 2015 in shallow rocky reefs at Genoa, and compared with the trend in air and sea surface temperatures. A total of 20 southern species (11 NIS and 9 WWN) was found. Two WWN (the zebra seabream Diplodus cervinus and the parrotfish Sparisoma cretense ) and three NIS (the SW Atlantic sponge Paraleucilla magna , the Red Sea polychaete Branchiomma luctuosum , and the amphi-American and amphi-Atlantic crab Percnon gibbesi ) are new records for the Ligurian Sea, whereas juveniles of the Indo-Pacific bluespotted cornetfish Fistularia commersonii have been found for the first time. While temperature has kept on increasing for the whole period, with 2014 and 2015 being the warmest years since at least 1950, the number of WWN increased linearly, that of NIS increased exponentially, contradicting the idea of meridionalization and supporting that of tropicalization even in the northern sectors of the Mediterranean basin.
... A specifi c study was addressed to Sphyraena sp.p. in order to clarify if native or alien species were involved (Relini and Orsi Relini, 1997). In the last decade in Italy several studies were dedicated to T. pavo (Vacchi et al., 1999;Guidetti, 2002;Guidetti et al., 2002;Sara et al., 2005) and Sparisoma cretense (Guidetti and Boero, 2001), mainly to study recruitment processes in the extended latitudinal range. ...
... According to the projected rise of seawater temperature along the Mediterranean coast, the cool-water fish is predicted to be displaced from a larger portion of the basin in the near future and will be further displaced by the end of this century, whereas the warm-water fish is predicted to be even dominant at deeper depths in a large portion of the Eastern Mediterranean coast. Not surprisingly, the warm-water Thalassoma pavo has received increasing attention in the last decades because of its potential role as indicator of climate change (Guidetti, 2002; Guidetti et al., 2002; Bianchi, 2007; Lejeusne et al., 2010; Coll et al., 2010 ). The coolwater Coris julis seemed to show a more uniform distribution inside the Mediterranean, but in recent years an increased frequency of occurrence of the cool-water wrasse in northern Croatia and Slovenia and the first record in the coolest part of the Northern Adriatic have been reported (Piron et al., 2007 ). ...
... For example, Labridae display a complex phototaxis behaviour [245] and their abundance is clearly underestimated by light-traps [246]. Labridae are observed in the Bay of Villefranche-sur-Mer and in the region [247]; larval stages can be collected in the bay using plankton nets (pers. data). ...
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La majorité des espèces de poissons côtiers a un cycle de vie comprenant une phase juvénile et adulte démersale et une phase larvaire pélagique. Cette seconde phase représente l’unique opportunité de dispersion pour de nombreuses espèces mais est soumise à une forte mortalité. Aujourd’hui, il est toujours délicat de prédire la connectivité entre les populations car tous les processus influençant la survie et le transport des larves durant leur phase pélagique ne sont pas encore décrits. Les larves de poissons possèdent des capacités comportementales non-négligeables (de nage, d’orientation, etc.) qui pourraient leur permettre de contrôler leur dispersion au cours de leur épisode pélagique. Cependant, les observations in situ de ces comportements ont principalement été faites en milieu tropical. Elles sont nettement plus rares en milieu tempéré, notamment chez les poissons Perciformes. Dans cette thèse, nous cherchons à décrire l’écologie et les capacités comportementales des larves de poissons en Mer Méditerranée Nord-Occidentale, un milieu tempéré où elles n’ont pas encore été décrites.La première partie de cette thèse vise à décrire la distribution des jeunes stades larvaires le long d’un transect côte-large traversant un front hydrologique. Nous nous intéressons également à leurs comportements de migration nycthémérale et d’évitement des prédateurs. La méthode d’imagerie utilisée pour décrire leur distribution à microéchelle génèrant des quantités de données considérables, nous avons développé une méthode de classification automatique pour accélérer le traitement de ce type de données. La seconde partie se concentre sur la phase d’installation, c’est-à-dire lorsque les larves arrivent à la côte à la fin de leur phase pélagique. Nous avons suivi l’arrivée des larves à la côte afin de déterminer les périodes d’installation des différentes espèces ainsi que les facteurs influençant leur arrivée. Nous avons également testé in situ les capacités d’orientation des espèces les plus abondantes, en se focalisant sur les mécanismes d’orientation à large échelle. En laboratoire, nous avons mesuré les vitesses de nage de plusieurs espèces, incluant celles testées pour l’orientation. Nous avons ensuite implémenté ces comportements observés dans un modèle biophysique afin de tester leur l’influence combinée sur le taux d’installation. Pour finir, nous discutons de l’influence que peut avoir le comportement sur la survie des larves de poissons tout au long de la phase pélagique, ainsi que de l’importance de sa prise en compte dans les modèles de dispersion.
... For example, Labridae display a complex phototaxis behaviour [245] and their abundance is clearly underestimated by light-traps [246]. Labridae are observed in the Bay of Villefranche-sur-Mer and in the region [247]; larval stages can be collected in the bay using plankton nets (pers. data). ...
Thesis
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RÉSUMÉ : La majorité des espèces de poissons côtiers a un cycle de vie comprenant une phase juvénile et adulte démersale et une phase larvaire pélagique. Cette seconde phase représente l’unique opportunité de dispersion pour de nombreuses espèces mais est soumise à une forte mortalité. Aujourd’hui, il est toujours délicat de prédire la connectivité entre les populations car tous les processus influençant la survie et le transport des larves durant leur phase pélagique ne sont pas encore décrits. Les larves de poissons possèdent des capacités comportementales non-négligeables (de nage, d’orientation, etc.) qui pourraient leur permettre de contrôler leur dispersion au cours de leur épisode pélagique. Cependant, les observations in situ de ces comportements ont principalement été faites en milieu tropical. Elles sont nettement plus rares en milieu tempéré, notamment chez les poissons Perciformes. Dans cette thèse, nous cherchons à décrire l’écologie et les capacités comportementales des larves de poissons en Mer Méditerranée Nord-Occidentale, un milieu tempéré où elles n’ont pas encore été décrites. La première partie de cette thèse vise à décrire la distribution des jeunes stades larvaires le long d’un transect côte-large traversant un front hydrologique. Nous nous intéressons également à leurs comportements de migration nycthémérale et d’évitement des prédateurs. La méthode d’imagerie utilisée pour décrire leur distribution à microéchelle génèrant des quantités de données considérables, nous avons développé une méthode de classification automatique pour accélérer le traitement de ce type de données. La seconde partie se concentre sur la phase d’installation, c’est-à-dire lorsque les larves arrivent à la côte à la fin de leur phase pélagique. Nous avons suivi l’arrivée des larves à la côte afin de déterminer les périodes d’installation des différentes espèces ainsi que les facteurs influençant leur arrivée. Nous avons également testé in situ les capacités d’orientation des espèces les plus abondantes, en se focalisant sur les mécanismes d’orientation à large échelle. En laboratoire, nous avons mesuré les vitesses de nage de plusieurs espèces, incluant celles testées pour l’orientation. Nous avons ensuite implémenté ces comportements observés dans un modèle biophysique afin de tester leur influence combinée sur le taux d’installation. Pour finir, nous discutons de l’influence que peut avoir le comportement sur la survie des larves de poissons tout au long de la phase pélagique, ainsi que de l’importance de sa prise en compte dans les modèles de dispersion. ABSTRACT: Most coastal fish species have a bipartite life history, with a demersal phase as juvenile and adult and a pelagic larval phase. Dispersal is often limited to this pelagic phase, which is also the phase experiencing the highest mortality rates. Predicting the connectivity between populations remains difficult because not all processes determining larval fish survival and transport during the pelagic phase are understood. Besides the environmental conditions that may influence the journey of fish larvae in the open ocean, these tiny organisms possess high behavioural abilities (swimming, orientating, etc.) that have the potential to shape their dispersal. However, the vast majority of in situ observations of these behaviours have been conducted in tropical environments and very little data exists on temperate Perciformes fish larvae. In this dissertation, we aim to describe the ecology and behavioural abilities of fish larvae from the Mediterranean Sea, a temperate environment where they have never been studied. The first part of this dissertation describes the distribution of young fish larvae along an inshore-offshore transect crossing an hydrological front. We also describe their diel vertical migration and predatoravoidance behaviour. The high-frequency imaging techniques used to capture their distribution at miscroscale generated huge amount of data. It lead us to modify an automatic classification method to reduce the time required to processes these kind of data. The second part focuses on the settlement phase, when fish larvae come back to the coast at the end of their pelagic journey. To shed light on the factors influencing the settlement process, we monitored the supply of fish larvae to a coastal habitat, on a weekly basis for three years and at higher frequency over shorter periods of time. Additionally, we tested the in situ orientation abilities of the most abundant species, focusing on large scale orientation mechanisms. In the laboratory, we measured the swimming speeds of several species, including the ones tested for orientation. Then, we implemented these observed behaviours in a biophysical model to explore their combined influence on settlement rate. To finish, we discuss on how larval fish behaviour may influence survival throughout the pelagic larval phase and insist on the importance of considering behaviour to improve larval dispersal models.
... Pombo et al. (2005); 3Mourad (1999);4 Dulcic et al. (2000);5 Gordoa et al. (2000); 6 Alonso-Fernández et al. (2011); 7 Fishbase; 8 Raposeiro-Azevedo and Azevedo (2009); 9Raventós and Macpherson (2005a); 10 Raventós (2009); 11Pallaoro and Jardas (2003);12 Ghorbel et al. (2002);13 Guidetti et al. (2002);14 Hotos et al. (2000);15 Reñones et al. (2004);16 Dulcic and Kraljevic (1995);17 Grau et al. (2009); 18 Tserpes and Tsimenides (2001); 19 García-Diaz et al., 1997; 20 Tuset et al. (2005); 21 Monteiro et al. (2006); 22 El-Agamy et al. (2004); 23 Morales-Nin and Moranta (1997); 24Loir et al., 2001; 25 Pajuelo and Lorenzo (2001);26 Pajuelo et al. (2003);27 Pajuelo et al. (2008);28 Gordoa and Molí (1997);29 Mouine et al. (2007);30 Gonçalves et al. (2002);31 Lorenzo et al. (2002);32 Pallaoro et al. (1998);33 Criscoli et al. (2006);34 Pajuelo and Lorenzo (1998) and35 Allam et al. (2004). ...
... Sardina pilchardus and Engraulis encrasicholus (Palomera et al., 2007). In general, these studies often described temporal changes in population density at a different life phases (see also Raventos and Macpherson, 2005;Guidetti, 2002;Guidetti et al., 2002), with no study analysing the relationship among the phases conforming the entire life cycle of the population. ...
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The influence of distinct demographic factors on determining population size in a littoral nesting fish (Symphodus roissali) was studied. Differences in the overall abundances were studied at three sites in the NW Mediterranean Sea for three years, to examine whether: 1) the adult population determined the number of successful nests; 2) the number of successful nests determined recruitment levels; 3) recruitment levels were subsequently related to the number of young of the year (YOY) joining the population after the recruitment period; and 4) the YOY value determined the size of the year class 1 cohort in the following year's adult reproductive population. The results show that there was a significant relationship between the number of spawners and the number of successful nests. However, the number of successful nests does not always correlate well with recruitment level. Furthermore, recruitment levels are not good indicators of the Young of the Year (measured three months after settlement) in number joining the populations, though YOY in number was related to the strength of the year class joining the adult reproductive population the following year. Therefore, the magnitude of the recruitment and probably the size of the adult population did not determine the year-class strength in S. roissali.
... Control and treatment pellets were presented to pairs of Mediterranean wrasses Thalassoma pavo. The ornate wrasse T. pavo is a labrid fish inhabiting shallow rocky bottoms in the Mediterranean Sea (Guidetti et al., 2002). It is a generalist carnivore with a tendency to omnivory (Kabasakal, 2001). ...
Article
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The palatability of organic chemical extracts from ten of the most abundant sponge species along the Israeli (shallow) coast, eastern Mediterranean Sea (Axinella sp., Axinella polypoides, Chondrilla nucula, Ircinia sp., Psammocinia sp. 1, Psammocinia sp. 2, Psammocinia sp. 3, Psammocinia sp. 4, Sarcotragus sp. and Tetilla sp.) was tested. To examine the generality of the phenomenon, it was evaluated with two types of potential predators, a fish and a gastropod. It was determined that the extracts of only two species (Psammocinia sp. 1 and Psammocinia sp. 3) deterred feeding of the omnivorous ornate Mediterranean wrasse Thalassoma pavo. On the other hand, extracts of five other sponges (Chondrilla nucula, Axinella sp., Ircinia sp., Sarcotragus sp. and Psammocinia sp. 2) were non-palatable to the omnivorous gastropod Strombus persicus (the extracts that deterred the fish did not deter the gastropod and vice versa). We also determined the capacity of extracts from six Red Sea sponges to deter T. pavo, and compared it with these extracts' effect on the Red Sea wrasse T. klunzingeri. All the extracts that deterred the Red Sea wrasse (from Amphimedon chloros, Crella cyatophora, Negombata magnifica and Theonella swinhoei) were also non-palatable to the Mediterranean wrasse. In addition to these four species, also Diacarnus erythraenus deterred Thalassoma pavo while being palatable to T. klunzingeri, whereas food pellets with extracts of Niphates rowi were eaten by both wrasse species.
... increasing excitement seemed to act as starter for spawning just like the courtship does during pair mating. The populations recorded in the Ligurian Sea are newly established (Sara & Ugolini, 2001) and as a result less abundant than southern populations (Guidetti et al., 2002 and references therein). During the reproductive season, however, many individuals that live solitary during the winter gather together in shallow water, so population density rises to numbers approaching those recorded in southern regions. ...
Article
Reproduction of newly established populations of the warm-water Atlantic Mediterranean wrasse Thalassoma pavo is here reported for the first time in the Ligurian Sea, and mating behaviour is described in detail. The reproductive season (May to October) may be divided in three stages: (1) pre-mating (mid-May to the end of June), during which terminal-phase (TP) males establish territories and start courting females; (2) mating (end of June to the end of August), with a mean frequency of up to one spawning event ind−1 h−1; and (3) post-mating (September to mid-October), when TP males remained inside territories but no spawning events were recorded. Mating followed two distinct modalities: pair spawning and group spawning, the latter replacing the former when population density exceeded 10 ind 100 m−2. Four phases have been distinguished in both modalities: (1) approach (pair) or gathering (group), to establish the contact between potential partners; (2) acceptance (pair) or priming (group), in which partners establish a common behavioural pattern; (3) ascent to near the sea surface; and (4) spawning. The saddled sea-bream Oblada melanura has been seen to predate intensively on the large cloud of sexual products released by groups.
... The present finding also represents the northernmost record of this species and provides further evidence of the ongoing trend of northward expansion of thermophilic organisms in the Mediterranean Sea (Bianchi & Morri, 1994; Astraldi et al., 1995; Guidetti et al., 2002), where more than 50 fish species, of both exotic and native origin, were recently recorded northwards with respect to their previous distribution (Azzurro, 2008). This phenomenon of geographical expansion encompasses a variety of thermophilic organisms, including macroalgae, plankton, invertebrates and fish (Bianchi, 2007) and it is widely considered as one of the Fig. 2 ...
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The record of several individuals of the African hind Cephalopholis taeniops from Lampedusa Island (Italy) is here reported, with discussion on the biogeographical importance of the Sicily channel as a crossroad for exotic fish of Atlantic and Indo-pacific origin.
... Another possible factor affecting body shape variation in geographical space, which remains to be investigated in future studies, is the variation of biological communities in geographical space. In particular, T. pavo, being more markedly thermophilic, is assumed to outcompete C. julis in shallow waters ( Guidetti & D'Ambrosio, 2004) and the abundance of T. pavo has been shown to decrease at northern sites ( Guidetti et al., 2002). It is therefore possible that the extent of the competition between C. julis and T. pavo varies with temperature in geographical space and that this competition drives, at least in part, the morphological variation observed in C. julis. ...
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... Distribution patterns of marine species, however, are well known to change in space (e.g. across latitudinal gradients) and time (e.g. from year to year), also considering the implications of current climate change in the Mediterranean Sea (Astraldi et al. 1995; Guidetti et al. 2002a; Bianchi & Morri 2003; Guidetti & Dulcic 2007; Nykjaer 2009). There is thus the need to widen the spatio-temporal scales for the assessment of distribution patterns of juvenile stages of many coastal fishes to see whether or not the information coming from the NW Mediterranean Sea is coherent at a larger scale. ...
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Recent studies suggest that the lithological properties of hard substrates play an important role in influencing the diversity and structure of marine assemblages involving macroalgae, sessile organisms and vagile animals like heterobranchs gastropods and fishes. The present study aims at exploring whether the influence of different substrates (limestone vs granite) could drive the occurrence of different vagile groups (crustacean decapods, echinoderms and fishes). The study was carried out at the "Tavolara-Punta Coda Cavallo" Marine Protected Area (NE Sardinia, Mediterranean Sea) where substrates of different lithology, namely granites and limestones, occur on a local spatial scale. The diversity and the abundance of 16 vagile species (four crustaceans, seven echinoderms and five fishes) were investigated by the analysis of photographs (2352 images) collected in 20 sites (10 limestones and 10 granites), between 30 and 50 m depth. Statistical analyses showed a clear-cut separation between the assemblages assessed on the two lithological substrate types, with assemblages on granites that were tightly grouped and those on limestones more dispersed. The total species richness did not significantly vary between limestones and granites. Galathea strigosa and Marthasterias glacialis were exclusively recorded on granites, while Palinurus elephas, Scyllarides latus, Arbacia lixula, Ophidiaster ophidianus and Serranus scriba were exclusively found on limestones. The observed patterns could be partially explained by multiple factors related to lithology: i) the different availability of preferred food sources, potentially influenced by substrate type; ii) the site geomorphology, that could provide different dens and refuges (in terms of quantity and types of shelters) suitable for different species; iii) the colour of different substrates enhancing the mimicry of different species according to their livery and camouflage ability. Our and literature data suggest that the substrate type in rocky reefs could interact with other environmental factors (i.e., light intensity related to depth) in shaping the structure of rocky-reef assemblages.
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Fish communities are an important cultural, recreational and commercial resource that also have an important role in the functioning of marine ecosystems. Around the world fish assemblages are experiencing pressures from anthropogenic activities, and marine spatial planning is being established to mitigate these impacts and assist with biodiversity conservation. Information about how fish assemblages are structured across a range of spatial scales which encompass variations in physical, biotic and environmental parameters will assist marine spatial planning and management. We investigated differences in reef fish assemblage composition over three reef lines across an inshore to offshore gradient (3–23 m depth) at two marine reserves (70 km apart) in the Perth metropolitan region, Western Australia. There were significant increases in the number of individuals, species richness, and relative abundance of fish species across the shallow shelf depth gradient in the two locations. There were distinct fish assemblages associated with each reef line, correlated to depth and distance from shore. The differences across the shelf gradient, even over this small depth range, were greater than the differences between the two locations. These findings have implications for marine spatial management and the design of marine reserves that aim to conserve biodiversity. It may be most appropriate for such marine reserves to encompass a wide depth gradient, rather than a large longshore area. At the very least, cross and longshore patterns in fish assemblages should be taken into consideration and used to guide spatial management plans for biodiversity conservation.
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In the last 20–30 years, the temperature of the Mediterranean Sea has increased and global warming is allowing the establishment of tropical-affinity species into more temperate zones. Sessile communities are particularly useful as a baseline for ecological monitoring; however, a lack of historical data series exists for sessile marine organisms without commercial interest. Hydroids are ubiquitous components of the benthic sessile fauna on rocky shores and have been used as bio-indicators of environmental conditions. In this study on the benthic hydroid assemblages of the Chafarinas Islands (Alboran Sea, South-Western Mediterranean), we characterized the hydroid assemblages, identified the bathymetric gradients, and compared them with a previous study carried out in 1991. Hydroid assemblages showed a significant difference both between year and among depths. Furthermore, eight species not present in 1991 were found, including two possible new species and the tropical and subtropical species Sertularia marginata. Due to its strategic position at the entrance of the Mediterranean and the existence of previous data on hydroid assemblages, the Chafarinas Islands are proposed as a possible monitoring point for entrance of Atlantic tropical species into the Mediterranean Sea.
Chapter
The Mediterranean Sea is a biodiversity hotspot containing between 15,000 and 20,000 marine species, nearly a quarter of which are endemic. The causes of the high Mediterranean biodiversity lie primarily in the turbulent geological history of the basin during the Tertiary and in the dramatic climatic fluctuations of the Quaternary. Both induced a rate of environmental change, and hence species occurrence, which acted as a 'biodiversity pump'. As a result, species with different biogeographic origins and affinities are found in the basin. A background of warm-temperate Atlantic-Mediterranean species, representing half of the biota, and the endemics are flanked by both boreal and subtropical species. Although the Mediterranean Sea as a whole constitutes a distinctive province of the Atlantic-Mediterranean biogeographic region, a great variety of climatic and hydrologic situations is found in its fairly isolated sub-basins. Thus, a dozen different biogeographic sectors can be recognized: 1) Alboran Sea; 2) Algeria and north Tunisia coasts; 3) Tyrrhenian Sea; 4) Balearic Sea to Sardinia Sea; 5) Gulf of Lions and Ligurian Sea; 6) northern Adriatic Sea; 7) central Adriatic Sea; 8) southern Adriatic Sea; 9) Ionian Sea; 10) Levant Sea; 11) southern Aegean Sea; 12) northern Aegean Sea; the micro-sector of the Straits of Messina can be added. The high Mediterranean biodiversity is presently threatened by the combined action of anthropogenic impacts, introduction of alien species, and climate change. Mediterranean Sea ecosystems are modified at increasingly fast rate, which constitutes an unprecedented phenomenon because of the overwhelming influence of humans, a driver of change not present in the geological past. Humans are modifying the climate through increased carbon dioxide emission, which also causes sea water acidification, and directly altering biodiversity through the deliberate or involuntary introduction of alien species. The present-day Mediterranean is a primary stage for the Anthropocene, the dynamics of human populations being a major factor in the future of its biodiversity. Mediterranean
Chapter
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The Mediterranean Sea is a biodiversity hotspot containing between 15,000 and 20,000 marine species, nearly a quarter of which are endemic. The causes of the high Mediterranean biodiversity lie primarily in the turbulent geological history of the basin during the Tertiary and in the dramatic climatic fluctuations of the Quaternary. Both induced a rate of environmental change, and hence species occurrence, which acted as a 'biodiversity pump'. As a result, species with different biogeographic origins and affinities are found in the basin. A background of warm-temperate Atlantic-Mediterranean species, representing half of the biota, and the endemics are flanked by both boreal and subtropical species. Although the Mediterranean Sea as a whole constitutes a distinctive province of the Atlantic-Mediterranean biogeographic region, a great variety of climatic and hydrologic situations is found in its fairly isolated sub-basins. Thus, a dozen different biogeographic sectors can be recognized: 1) Alboran Sea; 2) Algeria and north Tunisia coasts; 3) Tyrrhenian Sea; 4) Balearic Sea to Sardinia Sea; 5) Gulf of Lion and Ligurian Sea; 6) northern Adriatic Sea; 7) central Adriatic Sea; 8) southern Adriatic Sea; 9) Ionian Sea; 10) Levant Sea; 11) southern Aegean Sea; 12) northern Aegean Sea; the micro-sector of the Straits of Messina can be added. The high Mediterranean biodiversity is presently threatened by the combined action of anthropogenic impacts, introduction of alien species, and climate change. Mediterranean Sea ecosystems are modified at an increasingly fast rate. This constitutes an unprecedented phenomenon because of the overwhelming influence of humans, a driver of change not present in the geological past. Humans are modifying the climate through increased carbon dioxide emission, which also causes seawater acidification, and directly altering biodiversity through the deliberate or involuntary introduction of alien species. The present-day Mediterranean is a primary stage for the Anthropocene, the dynamics of human populations being a major factor in the future of its biodiversity. Mediterranean ecosystems must become closely managed =new commons', where natural and socio-economic components are integrated. A complex scenario is emerging, both undetermined and unpredictable. Changes that occurred in the past, before the Anthropocene, are of little help in understanding the future of Mediterranean biodiversity. Three tools, combined, can help to predict and manage change: MPA networks, adoption of field models, and long-term monitoring.
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Distribution patterns of epibenthic assemblages, sea urchins and fishes were assessed in NE Sardinia (Mediterranean Sea) in shallow (4 to 7 m depth) rocky habitats with 2 rock-type substrates, i.e. limestone and granite, to examine possible differences related to the mineralogical composition of rocks. Sessile organisms and sea urchins were sampled in situ within quadrats. Fishes were assessed by visual census transects. Sessile epibenthic assemblages significantly differed between granite and lime- stone substrates, and the number of epibenthic sessile taxa was greater on limestone. Average cover of the algae mat (unidentified mixture of filamentous and mucilaginous algae) was significantly greater on granite than limestone, while no significant differences were detected in total cover or in the average cover of the remaining most common epibenthic taxa. Densities of sea urchins (i.e. Paracentrotus lividus and Arbacia lixula) did not differ between the 2 rock types. Fish assemblages were significantly differ- ent between granite and limestone rock substrates. Labrids of the genus Symphodus and Serranus scriba were more abundant on granite, whereas Serranus cabrilla, Parablennius rouxi, Gobius bucchichi and Thalassoma pavo showed greater densities on limestone. Sarpa salpa (the most important herbivorous fish in the Mediterranean sublittoral) did not show any significant difference between granite and lime- stone substrates. These results suggest that rock type may have the potential to influence marine as- semblages, probably through direct effects on epibenthic organisms (e.g. the presence of quartz and sub- strate texture, both related to the mineralogical features of rocks), and indirect effects on fishes (e.g. the influence of the structure of the epibenthic cover). These results suggest a possible role of the miner- alogical composition of rocks in 'bottom-up' processes influencing marine assemblages in shallow sub- littoral rocky habitats in the Mediterranean, where direct effects on sessile organisms (e.g. macroalgae) may cascade up through the entire community and affect higher trophic levels (e.g. carnivorous fishes). However, extensive experimental work is needed before drawing any conclusion about the specific processes determining the patterns we observed.
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Post-settlement events can significantly alter the density distribution of settlers and subsequently the adult population structure. The temporal and inter-annual variability of settlement and the effects of mortality on recruitment were investigated across 2 years in the vicini-ties of Cabo de Palos–Islas Hormigas Marine Reserve by visual census and light trap sampling. Settlement was seasonal with greater species richness and abundance in summer. Although temporal synchronization was observed between larval supply and settlement, densities of settlers could not be predicted from post-larval abundances. Tim-ing of settlement was consistent between years but with high inter-annual variation in abundance. High mortality (*80 %) and general decoupling between post-larval and settlement stages suggest that early mortality is driving such patterns. Nevertheless, indications of habitat-mediated mortality were found for benthic species such as Sympho-dus and Diplodus, highlighting the importance of habitat in shaping population demography.
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The sociology and habits of recreational anglers on the Island of Majorca (western Mediterranean) were evaluated using telephone and on-site surveys, as well as fishing logbooks and recreational fishing competitions. The recreational fishery is one of the island's main leisure activities, 5.14% of the population (37 265 people) participating. Enthusiasts tend to be mainly middle class (most anglers own boats moored at marinas), middle-aged males (90% male, mean age 46 ± 2 years). The most popular fishing method is from a boat (62.9%), followed by fishing from shore (32.4%), and spearfishing (3.6%). The mean time spent fishing is 3.86 ± 0.03 h d-1, and more than one type of gear (mean 1.27 ± 0.21) is used simultaneously by a single angler. The frequency of fishing is 4-6 times per month, mainly on holidays and weekends, increasing in summer. The activity has a sizeable impact on the coastal fauna, with diverse catches of at least 1209.25 t year-1 (about 615 000 fishing outings year-1). Thus, the amount of carbon extracted annually is at least 137.34 kg C km-2 year-1, and the recreational fishery removes about 31% of production at trophic level 4. Although these are gross estimates and more detailed study of the effect on trophic level and local production is needed, the values do highlight the pressure the recreational fishery exerts on coastal fish communities. Assuming that this level of exploitation is common to north-shore Mediterranean countries, there may be cause for concern about sustainable exploitation in the recreational fishery, and the effectiveness of current protection measures is discussed. Despite the limitations of the study, recreational fisheries clearly should be taken into account when considering measures for fisheries management. Moreover, fishing has considerable social import, and the benefits must be taken into account when investments to protect exploited resources are being contemplated.
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Habitat destruction is a major cause of its fragmentation. Since the 1960’s, human pressure on seashores, especially along the Gulf of Lion has induced lots of fragmented habitats. Destruction is not the predominant factor for this fragmentation, but the large-scale installation of coastal artificial rocks which creates new habitats. This study investigated on the role of these structures compared to natural areas (lagoons, rocky shores) to maintain fish populations more south, on the rocky coast. The white seabream, infeodated to these rocky areas, is the biological model used. Scuba diving visual census of adults and juveniles, direct tagging and otolith microchemistry were performed to better understand these dynamics. Coastal artificial habitats have to be considered as important nursery areas. Depending on the year, densities of juveniles are 30 to 109 times higher than those observed on natural habitats, either on the rocky coast or in the lagoon. Such differences could be explained by the presence of only two main groups of adults along the French Catalan coast. The first would supply the coastal artificial rocks and be located at cap Leucate. The second, in the reserve of Cerbère-Banyuls, would export juveniles to the Spanish coast following the dominant north-south current. Moreover, the lagoon has lost its nursery function to the benefit of the artificial coastal habitats. Our results also show the connectivity during the adult phase between these coastal structures and the natural rocky areas. 20% of white seabreams which had settled on the artificial habitats, left for the rocky coast, mainly in spring and autumn. We also presume that one third of the seabreams living there are those that had settled on the artificial habitats of the sandy coast. This study underlies the importance presumably of major role played by these artificial habitats to the maintenance and expansion of populations of white seabream in the Catalan coast. The results are possibly a snapshot of the population dynamics in the Gulf of Lion. Habitat fragmentation has a positive effect in this case. It could be the origin of emergence of new species on the coast of Languedoc-Roussillon like the zebra seabream, Diplodus cervinus and the common dentex, Dentex dentex.
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Describes a long-term study of the independent effects of, and the interactions among, two sources of temporal variation (seasonal and annual) and two sources of spatial variation for a rocky intertidal community in the northern Gulf of California. The sources of spatial variation were: 1) microspatial effects due to the foraging patterns of a common predatory snail (Acanthina angelica) and 2) macrospatial effects due to differences among sites. Results showed highly significant temporal and spatial effects for all members of the sessile community (barnacles, mussels, algae) and for limpets over the 8-yr study period. There were also highly significant season × space interactions for all sessile members of the community, which probably resulted from seasonal settlement by the sessile members of the community, and aestivation by the predator. There were highly significant year × space effects as well as year × season × space effects for most species. These latter interactions can be understood as an amplification of seasonal and spatial effects due to the largely unpredictable differences among years. Most of the variation in percentage cover of barnacles and a brown encrusting alga was due to year and season effects. Competition and predation by Acanthina are relatively more important in controlling the distributions and local abundances of barnacles and encrusting algae. Unpredictable differences among years in settlement are more important in controlling the local population densities of mussels and limpets. -from Authors
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The purpose of this study, was to assess the importance of pre-and post-settlement processes in the temperate reef fish Tautogolabrus adspersus at multiple spatial scales and in 2 distinct regions, Newfoundland, Canada, and the Gulf of Maine, USA. We examined a total of 20 sites (separated by 100 to 1000 m) nested within 10 locations (separated by ca 10 km). Greater numbers of adult fish were observed in Newfoundland than in the Gulf of Maine; however, higher abundances of newly recruited fish occurred in the Gulf of Maine. An experiment in which we provided standardized habitats in both regions also revealed that recruitment was higher in the Gulf of Maine than Newfoundland. In the Gulf of Maine, variation in the densities of adults and newly recruited fish was most pronounced among sites, but in Newfoundland we detected pronounced variability at both the site and location scales. Algal height was not associated with among-site variability in the abundances of recruits or adults. Algal coverage, however, was an important predictor of variability of fish abundance in the Gulf of Maine but not in Newfoundland. The age structure of Newfoundland populations suggests that strong recruitment years are rare, while in the Gulf of Maine the age structure is consistent with the expectation of declining abundance with age. Our data suggest that pre-settlement processes are not of primary importance to cunner populations in the Gulf of Maine. Rather, we hypothesize that habitat-related differences in post-settlement processes are the most significant factors affecting these populations. However, in Newfoundland the evidence gathered thus far supports the hypothesis that episodic settlement is responsible for much of the variation in population size in this region.
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Analyses of spatial pattern in populations and assemblages along distinct environmental gradients are common in ecology. Few studies have examined whether these patterns are consistent at a hierarchy of spatial scales, despite increasing evidence indicating that spatial variability is not scale independent. In this study I have investigated the general model that much of the variation on rocky sea shores occurs across the vertical gradient, unless major physical attributes of the habitat change. This model was contrasted with 2 alternative models that incorporate patchiness at different scales: either vertical variation is larger than horizontal variability at small but not at large scales of horizontal spatial variability or there is no characteristic scale at which vertical variation is larger than horizontal variability. In order to distinguish among these alternatives, I compared variability in abundance of organisms across heights on the shore on rocky coasts in the north-west Mediterranean, with estimates of horizontal variability obtained at different scales, ranging from the scale of the patch (among quadrats 10s of cm apart) up to the regional scale (among shores 100s of km apart). Results indicated that vertical and horizontal variability were comparable in magnitude at the smallest spatial scale, while horizontal variability was generally larger when measured at scales of 100s to 1000s of m. When multivariate patterns in the structure of assemblages were examined, there was more vertical than along-shore variation at small (10s to 100s of cm) but not at large (> 1000s of m) spatial scales. Univariate and multivariate analyses also revealed that much of the horizontal variation was among quadrats 10s of cm apart. These results indicated that any description of spatial pattern in abundance for organisms living on rocky sea shores in the NW Mediterranean must contemplate both vertical and horizontal sources of variation, regardless of the scale investigated. It is concluded that failure to recognise the importance of sources of variation other that those expressed by the most obvious gradients detracts from potentially important causal processes hindering progress in ecological understanding.
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Juvenile settlement of 3 sparid fish species, Diplodus puntazzo, Diplodus sargus and Diplodus vulgaris, was studied over 3 yr at 20 stations located at 5 sites in the NW Mediterranean Sea: 1 site in Spain (Girona), 2 in France (Banyuls and Marseille) and 2 in Italy (Portofino and Elba). When all sites and years were combined, 71% of the settlers recorded belonged to D. vulgaris, 25 % to D. sargus and 4% to D. puntazzo. Settlement was seasonal, with D. sargus settling in May-June, D. puntazzo in October-November, and D, vulgaris in 2 pulses, the first in November-December and the second in January-February. Settlement intensity varied spatially, temporally, and among species. At a small spatial scale (within site), settlement intensity varied between stations and particularly between years. At a large spatial scale (among sites), settlement intensity varied among sites, with Marseille and Girona generally experiencing higher settlement than other sites. No difference in settlement intensity was observed between protected and unprotected areas. The settlement of D. sargus was higher in 1994 than in 1993 and 1995 at all sites, suggesting the influence of meso-scale hydroclimatic conditions on the settlement success of this species. The settlement of D. vulgaris was higher in 1993 in the western part of the NW Mediterranean, and in 1994 in the eastern part. No consistent spatial trend over time was seen for D, puntazzo. Thus, settlement intensity of Diplodus species to nearshore habitats in the NW Mediterranean exhibited high year-to-year variations at both local and regional scales.
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Population dynamics and post‐settlement mortality of the ornate wrasse, Thalassoma pavo, were studied by visual censuses from July 1997 to December 1998 at the Island of Ischia (Gulf of Naples, western Mediterranean). The size classes best represented throughout the year encompassed specimens from 9 to 17 cm in length, chiefly females and, to a lesser extent, terminal phase males. Fish longer than 18 cm (mainly terminal phase males) were rare during the winter‐spring period, while they slightly increased in abundance from July‐August to November. Newly settled T. pavo juveniles, which display distinct livery patterns from adults, arrived in late August‐early September, reaching settlement abundance peaks in mid‐September, both in 1997 and 1998. During the first year of study, juveniles survived the winter period and were recruited into the adult population, whereas the following year they completely disappeared during November. Due to the well‐known thermophily of the studied species, the significantly higher post‐settlement mortality rate estimated for 1998, in comparison with the 1997 value, was attributed to the unusual decrease of surface water temperature occurring in November 1998. The results reported here suggest that density‐independent mechanisms such as fluctuating abiotic conditions could be more important in affecting the population dynamics of T. pavo than density‐dependent biotic interactions.
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The Mediterranean parrotfish Sparisoma cretense is reported for the first time along the south-eastern coasts of Apulia (Ionian Sea, south-east Italy). Only juvenile specimens of S. cretense were observed during visual census surveys carried out in late August 2000, whereas adults were never observed in, or reported from, this region. Juvenile parrotfish were 3–4-cm long (TL), with a light-grey livery, pale-yellow heads and marked yellow margins around the eyes. They were recorded at 5–15 m depth, whereas they were absent near the surface (0–2 m depth) and in deeper areas (25–28 m depth). The possibility that climatic changes occurring in the Mediterranean basin (i.e. water warming) would be involved in the spreading of S. cretense outside its typical distribution range is discussed.
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Populations of three species of juvenile Sparidae ( Diplodus puntazzo , Diplodus sargus and Diplodus vulgaris ) were sampled at different spatial scales in the north-western Mediterranean Sea over two years to follow growth after settlement. Length–frequency distributions were collected each week for periods of six months following the arrival of off-shore larvae in inshore habitats. Data were collected by underwater visual census along permanent transects. Growth rate measured as the slope of the linear relationship between mean size and time varied between species. Diplodus puntazzo (0.160 mm d ⁻¹ ) and D. vulgaris (0.202 mm d ⁻¹ ), which are settling in winter experienced slower growth than D. sargus (0.567 mm d ⁻¹ ) which settles in summer. It is concluded that the difference was in part due to water temperature. Analysis of growth rate within each species also revealed significant differences among sites probably related to the currents and the water mass temperatures.
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The authors are biologists specializing in benthos or ichthyofauna survey. They have worked in marine protected areas or in other littoral zones of the Mediterranean Sea for a long time. The use of SCUBA diving as a sampling method allows them a great knowledge of the benthos and ichthyofauna. Charles-Francois Boudouresque is vice-chairman of the Benthos Committee of the CIESM, and chairman of the scientific committees of the National Park of Port-Cros and of the Natural Regional Park of Corsica (marine reserve of Scandola). The other authors are members of these scientific committees.
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It is argued that the problem of pattern and scale is the central problem in ecology, unifying population biology and ecosystems science, and marrying basic and applied ecology. Applied challenges, such as the prediction of the ecological causes and consequences of global climate change, require the interfacing of phenomena that occur on very different scales of space, time, and ecological organization. Furthermore, there is no single natural scale at which ecological phenomena should be studied; systems generally show characteristic variability on a range of spatial, temporal, and organizational scales. The observer imposes a perceptual bias, a filter through which the system is viewed. This has fundamental evolutionary significance, since every organism is an "observer" of the environment, and life history adaptations such as dispersal and dormancy alter the perceptual scales of the species, and the observed variability. It likewise has fundamental significance for our own study of ecological systems, since the patterns that are unique to any range of scales will have unique causes and biological consequences. The key to prediction and understanding lies in the elucidation of mechanisms underlying observed patterns. Typically, these mechanisms operate at different scales than those on which the patterns are observed; in some cases, the patterns must be understood as emerging form the collective behaviors of large ensembles of smaller scale units. In other cases, the pattern is imposed by larger scale constraints. Examination of such phenomena requires the study of how pattern and variability change with the scale of description, and the development of laws for simplification, aggregation, and scaling. Examples are given from the marine and terrestrial literatures.
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We present a model of community regulation that incorporates the effects of abiotic disturbance, predation, competition, and recruitment density. We assume that mobile organisms (i.e., consumers) are more strongly affected by environmental stress than are sessile organisms and that food-web complexity decreases with increasing stress. The model makes three predictions under conditions of high recruitment. First, in stressful environments, consumers have no effect because they are absent or inactive, and competition for space is prevented. Both mobile and sessile organisms are regulated directly by environmental stress. Second, in moderate environments, consumers are still ineffective, but sessile organisms are less affected by stress and frequently attain high densities, leading to competition for space. Finally, in benign environments, consumers prevent competition for space unless the prey can escape a predation bottleneck and reach a high abundance. A reduction in recruitment density reduces the import...
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Quantitative information about spatial patterns in subtidal hard substrate assemblages is scant. Such information is necessary to understand the responses to anthropogenic disturbances in these habitats. Along the coast of Apulia (Southern Italy), the collection of the European date mussel Lithophaga lithophaga is a strong source of disturbance: harvesting is carried out by demolition of the rocky substrate and causes epibiota disappearance. A hierarchical sampling design was used to quantify the spatial variability of subtidal epibenthic assemblages and the extent of rock damage due to L. lithophaga harvesting along 360 km of rocky coasts in Apulia. The surveyed coast was divided into 8 adjacent sectors, and replicate samples were taken by visual inspection at each of the 3 sites nested in each sector. Multivariate analyses indicated that assemblages differed consistently with spatial scale, variability being higher at the largest scale. However, variability among sites within each sector was also detected. Patchiness (i.e., average similarity among quadrats) was consistent among sectors. Some species were identified as 'important' in characterising and/or differentiating sectors. The pattern of distribution of these species as well as total cover and number of species were analysed by analysis of variance. Results recorded a considerable source of variation at site level. Damage by L. lithophaga fishing was shown to be extremely widespread. A humped relationship between patchiness and disturbances by L. lithophaga fisheries was obtained. In particular, patchi- ness at a small scale was highest at 'intermediate' levels of damage, because disturbance produces patches of different size and/or age, leading to 'mosaic' landscapes of epibenthic assemblages.
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This book presents an in-depth discussion of the biological and ecological geography of the oceans. It synthesizes locally restricted studies of the ocean to generate a global geography of the vast marine world. Based on patterns of algal ecology, the book divides the ocean into four primary compartments, which are then subdivided into secondary compartments. *Includes color insert of the latest in satellite imagery showing the world's oceans, their similarities and differences *Revised and updated to reflect the latest in oceanographic research *Ideal for anyone interested in understanding ocean ecology -- accessible and informative.
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Pronounced spatial variation in recruitment occurs in many marine invertebrate and fish populations and is thought to be critical to the demography of these species. In this study I examined the importance of habitat structure and the presence of conspecific residents to spatial variation in larval settlement and recruitment in a temperate fish Tautogolabrus adspersus. I define settlement as the movement of individuals from the water column to the benthic habitat, while I refer to recruitment as numbers of individuals surviving some arbitrary period of time after settlement. Experiments in which standard habitats were stocked with conspecifics showed that resident conspecifics were not an important factor contributing to small-scale variability in recruitment. Further correlative analyses demonstrated that large-scale variation in recruitment could not be explained by variability in older age classes. By contrast, manipulations of macroalgal structure within a kelp bed demonstrated that recruitment was significantly higher in habitats with a dense understory of foliose and filamentous algae than in habitats with only crustose algae. Understory algae varied in their pattern of disperison among sites, and the dispersion of fish matched that of the plants. In order to determine the effects of differences in patterns of algal dispersion on the demography of associated T. adspersus populations, I used experimental habitat units to manipulate patterns of dispersion. Settlement was significantly greater to randomly placed versus clumped habitats; however, no differences in recruitment between random and clumped habitats were detected. Because recruitment is a function of the numbers of settlers minus the subsequent loss of settlers, rates of mortality or migration must have been higher in the randomly placed habitats. These results are counter to the current paradigm for reef fishes which suggests that larval settlement is the crucial demographic process producing variability in population abundance. In this experiment patterns of settlement were modified by varying the patch structure of the habitat.
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Spatial pattern of the fish assemblage inhabiting a littoral rocky reef was examined in relation with its habitat, by means of spatial (correlograms, Mantel tests) and regression (GLM, RDA) analysis techniques. Several biological variables showed an aggregated spatial pattern, although with different patch sizes −180 m for total abundance and ∼400 to 500 m for species richness. Habitat complexity, as measured by rugosity, number of medium-sized boulders and verticality, and Posidonia cover showed a small-scale spatial pattern (with a patch size of ∼120 to 200 m), while the alternation of rock (covered or not by Posidonia) and sand, and also wind exposure, showed a larger scale aggregation (400–500 m). Regarding the relationship among biological and environmental variables on a small spatial scale (101 m), the 17 more frequent species showed significant, and usually linear relationships, with descriptors either of complexity, heterogeneity, or both, while habitat structure accounts for a important portion (12–40%, depending on the analysis) of the observed variability in fish assemblage structure. Therefore, spatial structure of biological data would be determined, to some extent, by that of habitat. Habitat heterogeneity of rocky substrate seems to promote species richness in the studied area, so that each bottom type (patches of sand, clumps of Posidonia) embedded in the rocky matrix would provide specific resources for more or less specialized species. For its part, habitat complexity favors at the same time a higher number of species and higher abundances. Habitat structure is thus likely to drive a large part of spatial variability in the distribution and abundance of Mediterranean rocky reef fishes, especially when abundance is assessed on small spatial scales. We argue that knowledge about this “natural” variability can help to separate the influence of habitat from other sources of variation, such as the effect of protection from fisheries.
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Environmental disturbances can alter the variability of assemblages of organisms in impacted sites compared to control sites. It has therefore been proposed that increased variability might be an important feature of stressed populations. Increased variability may be due to changes in the population structure of individual species or changes in the suite of species. In this study, spatial variances of shallow subtidal assemblages of organisms inhabiting vertical cliff-faces were compared among two control locations and one location that had for many years been exposed to the discharge of sewage. These assemblages covered nearly all available space on the substratum and consisted primarily of encrusting and foliose macro-algae and numerous filterfeeding animals, such as ascidians, sponges and bryozoans. Mean differences in abundances between these locations were investigated using Beyond BACI designs. In addition, these locations were used to examine the model that assemblages are more variable in disturbed than undisturbed environments and to try to distinguish differences in variability due to differences in the population structure of individual species from that due to changes in species composition.
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Research over the past decade shows that fish populations on coral reefs can vary enormously, both spatially and temporally. Nonetheless, predictable patterns in structure are present at both small and regional scales. These have usually been interpreted as resulting from processes acting after settlement of fishes from the plankton. However, current research now suggests that planktonic processes could also result in deterministic patterns of community structure.
Habitatanspruche und abundanzen vonThalassoma pavo (Teleostei, Labridae) bei Kreta, Griechenland. Zeitschrift fu« r Fishkunde
  • F Velte
Velte, F., 1998. Habitatanspruche und abundanzen vonThalassoma pavo (Teleostei, Labridae) bei Kreta, Griechenland. Zeitschrift fu« r Fishkunde, Solingen, 2, 47^58.
Recent naturalization of the warmwater wrasse Thalassoma pavo (Pisces, Osteichthyes) in the Ligurian Sea
  • G Sara
  • U Ugolini
Sara, G. & Ugolini, U., 2001. Recent naturalization of the warmwater wrasse Thalassoma pavo (Pisces, Osteichthyes) in the Ligurian Sea. Atti dell' Associazione Italiana di Oceanologia e Limnologia, 14, 249^258.
Osteichthyes. Pesci ossei (parte seconda)
  • E Tortonese
Tortonese, E., 1975. Osteichthyes. Pesci ossei (parte seconda). Fauna d'Italia (vol. XI). Bologna: Calderini Editore.
Mediterranean and Atlantic ¢sh guide. Frankfurt: IKAN Unterwasserarchiv
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Debelius, H., 1999. Mediterranean and Atlantic ¢sh guide. Frankfurt: IKAN Unterwasserarchiv.
Underwater Guide Madeira
  • P Wirtz
Wirtz, P., 1994. Underwater Guide Madeira, Canary Islands, Azores. Fish. Stuttgart: Verlag Stephanie Naglschmid.