New records of deep-sea decapod crustaceans in the Turkish Mediterranean Sea (North Levant Sea)

A survey of the bathyal trawling grounds in the Gulf of Antalya (Turkish Mediterranean Sea) yielded 34 species of decapod crustaceans. Four species (Funchalia villosa, Plesionika acanthonotus, P. gigliolii, Monodaeus couchii) are recorded for the first time from the Levant Sea. The number of marine decapod species reported for Turkey rises to 265 and the number reported from the Turkish Mediterranean Sea to 211.     

Field studies of seahorse population density,structure and habitat use in a semi-closed north-eastern Mediterranean marine area (Stratoni,North Aegean Sea)

The present study was carried out in the marine area of Stratoni, Greece, where two seahorse species are present (Hippocampus hippocampus and Hippocampus guttulatus). Two surveys were conducted (September 2016 and May 2019) to gather information regarding seahorse species' abundance, distribution and habitat characteristics. Four different seahorse natural and artificial habitat types were identified. The results revealed that the presence of H. hippocampus was relatively high, especially at sites with artificial structures, whereas the presence of H. guttulatus was rare. Data collected can provide baseline information for future population assessments.     

A comparison of the deep-water demersal fish assemblages of the Rockall Trough and Porcupine Seabight, eastern North Atlantic: continental slope to rise

Fishery surveys of the continental slope to the west of the British Isles have shown quite marked differences between areas in both the proportion and abundance of marketable or potentially marketable species. In general, the northern slopes lying to the west of Scotland were considered to have a greater potential for exploitation than the southern slopes off Ireland. Subsequent detailed studies of a northern (Rockall Trough) and a southern slope area (Porcupine Seabight) sampled the demersal fish fauna using a Granton trawl fished on paired warps to depths of 1200 m, and a semi-balloon trawl fished on a single warp to depths of about 3000 m. The Granton trawl catches differed significantly between the two areas, especially at the greatest depths fished. The semi-balloon trawl catches did not differ between the areas. This slower trawl was poor at catching large, mobile species and efficient in the capture of the deep-waler eel Synaphobranchus kaupi. This eel was numerically dominant over the mid to lower slope and probably accounts for much of the similarity between areas at these depths.     

The diet of native and invasive fish species along the eastern Mediterranean coast (Osteichthyes)

The opening of the Suez Canal in 1869 enabled the invasion of more than 100 alien fish species into the Mediterranean. The aim of the present study was to compare the diet of native and alien fish species and to identify possibly shared food resources. We examined the diet composition of 13 of the most abundant fish species (6 alien, 7 native) on shallow soft bottom off southern Israel. All 13 species are omnivorous/carnivorous. The native fish exhibited a wider diversity of food types than the aliens. Alien fish prey upon and are preyed by native species as well as by other alien fish. A high level of diet overlap was found among some species, the aliens Saurida lessepsianus and Scomberomorus commerson overlapped with the native Synodus saurus; and the alien Nemipterus randalli with the native species Pagrus caeruleostictus, Lithognathus mormyrus and Pagellus erythrinus. The identified diet overlap is discussed, and the possibility of competitive interactions between these species is considered.     

长江口中华鲟自然保护区底层鱼类的群落结构特征

根据2004年8月、11月和2005年2月(Ⅰ年度)、2005年8月、11月和2006年2月、5月(Ⅱ年度)、2007年8月、11月和2008年2月和5月(Ⅲ年度)对长江口中华鲟自然保护区15个站位点的底拖网调查数据,对该水域的底层鱼类群落结构特征及时间和空间变化规律进行了分析。结果表明,调查中捕获底层鱼类42种,隶属于13目24科39属。底层鱼类的种类组成和群落结构进行聚类分析,15个站位聚合成两大类群,类群A位于南支北港和北港北沙近东滩水域,共出现20种底层鱼类,主要以淡水性和河口性鱼类为主;类群B位于北支和北港北沙近外海水域,共出现鱼类39种,主要以河口性和海洋性鱼类为主。ANOSIM和SIMPER分析表明底层鱼类群落结构不同季节间差异显著,造成这种趋势的主要原因可能是与棘头梅童鱼(Collichthys lucidus)和凤鲚(Coilia mystus)的繁殖和索饵洄游有关。     

Diel and Seasonal Changes in the Structure of a Decapod (Crustacea: Decapoda) Community of Cymodocea nodosa from Southeastern Spain (West Mediterranean Sea)

The study of a decapod community in a Cymodocea nodosa meadow from Southeastern Spain (Western Mediterranean Sea) showed a stable structure, in which the families Hippolytidae, Processidae, Majidae and Portunidae were the most abundant and the species Hippolyte niezabitowskii dominated. The animal community was more numerous and diverse during the night, showing the existence of nychthemeral movements, which are essentially related to the trophic behaviour and shelter. In this way, many species increased their abundance as a result of an increasing activity and, also, of an influx of other species and specimens from adjacent sandy bottoms, such as Processa spp. (mainly P. modica) Sicyonia carinata, Liocarcinus spp. (mainly juveniles) and several species of hermit crabs, which were rare or absent during the day. All these changes produced modifications in the dominance curves and in the values of all ecological indices (richness, diversity and evenness). Monthly samples were grouped and ordered (MDS) by the factor “day–night”, which showed slight qualitative and quantitative differences (SIMPER, dissimilarity average of the factor day–night = 61.67). On the other hand, no global seasonal differences have been found (one way ANOSIM), but there was a significant level of similarity between winter and spring, while the summer samples were the most different. The differentiation of the summer 1999 can be attributed to a decrease in species abundance and richness, probably due to the dynamics of the decapod populations and the balance with predators (fishes), while that of the summer 2000, to an anomalous event: the massive proliferation of filamentous algae, mainly Ectocarpus s.l., which modified the environmental conditions.     

Zenopsis conchifera (Lowe, 1852) (Pisces, Actinopterygii, Zeidae): a new alien fish in the Mediterranean Sea

The first documented occurrence of a silvery John dory, Zenopsis conchifera , in the Mediterranean Sea is reported. A female (645 mm total length, 3296 g body mass) of Z. conchifera was caught in July 2006 by a commercial bottom trawler off the northern Tunisian coast (central Mediterranean Sea).     

The littoral fish community of the Lebanese rocky coast (eastern Mediterranean Sea) with emphasis on Red Sea immigrants

The organisation of the coastal rocky fish community of Lebanon was investigated for the first time, using visual censuses. A total of 62 fish species were recorded between the surface and 32 m depth, 8 species being Red Sea migrants. Species richness and fish abundance were positively correlated first with substrate complexity and second with depth. The trophic structure of the community was dominated by diurnal zooplanktivores (Chromis chromis, Oblada melanura and Spicara smaris) and mesocarnivores 1 (Coris julis and Thalassoma pavo), and did not vary significantly with depth. The Lessepsian migrants represented 13% of the species richness and 19% of the total abundance of individuals. They dominated among herbivores, nocturnal zooplanktivores and macrocarnivores. The Lessepsian Siganus luridus and S. rivulatus (Siganidae), Pempheris vanicolensis (Pempheridae) and Sargocentron rubrum (Holocentridae) were now among the most common fish species on the Lebanese rocky coast. Lessepsian fish species displayed either similar ecological niches in the Red Sea and in the Levantine basin (P. vanicolensis, S. rubrum) or an enlargement of their depth distribution towards deeper waters in their new environment (S. luridus, S. rivulatus). This study will serve as a baseline for future studies as eastern Mediterranean communities are subjected to a steady increase in Red Sea migrant species.     

胶州湾近岸浅水区鱼类群落结构及多样性

根据2009年3月-2010年2月在胶州湾西北部近岸浅水区进行的鱼类逐月定置网调查数据,采用生态多样性指数和多元统计分析等方法研究了该海域的鱼类群落结构及多样性特征.结果表明:调查共鉴定出44种鱼类,其中海洋性27种,河口性鱼类17种.鱼类种类组成与底层水温和盐度有密切关系.胶州湾近岸浅水区鱼类群落Margalef种类丰富度指数(R)变化范围为0.33-3.50,Shannon-Wiener多样性指数(H’)为0.42-2.25,Pielou均匀度指数(J’)为0.23-0.93.聚类分析(CLUSTER)和多维标度排序(MDS)分析表明,不同鱼类种类组成的各月份样品可划分为3个组分:水温较低的冬季组G1(12月-翌年4月)、水温次高的春秋季组G2(5-6月、10-11月)和水温最高的夏季组G3(7-9月).其中G1的典型种主要为尖海龙(Syngnathus acus)、方氏云鳚(Enedrias fangi)和玉筋鱼(Ammodytes personatus)等冷温性常栖类群种类,G2的主要典型种为鳀鱼(Engraulis japonicus)和尖海龙,G3的主要典型种为鲐鱼(Scomber japonicus)、细条天竺鱼(Apogonichthys lineatus)和普氏缰虾虎鱼(Amoya pflaumi)等洄游性鱼类.单因子相似性分析(ANOSIM)表明,3个月份组间鱼类群落结构差异显著,不同月份组间两两差异均显著.生物-环境分析(BIOENV)表明,底层水温是影响胶州湾近岸浅水区鱼类群落结构时间变化的主要环境因子.在胶州湾内近岸浅水区发现40余种幼鱼,但占优势的主要为低值鱼类,表明胶州湾的产卵、肥育场功能有所下降,应加强胶州湾近岸水域生态环境和渔业资源的保护及修复.     

Analysis of demersal fish assemblages off the Southern Tyrrhenian Sea (central Mediterranean)

Monitoring and management of Mediterranean trawling requires a multispecies and ecosystem-based approach. Over the last 20 years studies on diversity and distribution of fish communities have been carried out by ecologists and applied to different ecosystems. Until now, very little information has been available on the Southern Tyrrhenian Sea. The aim of this work is: to analyse the structure of fish demersal assemblages, on a temporal (10 years) and spatial scale using a multivariate approach; to analyse, across space and time, the pattern of biodiversity by means of univariate indices; to identify areas supporting high values of diversity and evenness by a Geographical Information System (GIS) method. The analysis of 249 hauls from ten trawl surveys carried out between depths of 30 and 750 m in the South Tyrrhenian Sea yielded a total of 164 fish species. Multidimensional scaling ordination showed four groups distributed according to the depth gradient: a coastal group (0–100 m depth), a group in the lower part of the continental shelf (101–200 m), an epibathyal group (201–500 m) and the last one derived from hauls made in the middleslope (501–800 m). There were no differences, between years, protected and unprotected areas and geographical sectors. The whole study area was characterised by diversity values which were quite heterogeneous. The persistence index was generally low. Results could be useful from an ecological point of view and for the management of fishery activities.     

Diversity of lacewing assemblages (Neuropterida:Neuroptera) in different forest habitats and agricultural areas in the East Mediterranean area of Turkey

The objectives of this study were to understand lacewing diversity patterns and the role of environmental factors in determining lacewing diversity in four habitat types: agricultural area (crops and orchards), pine forest (Pinus nigra Arnold and, Pinus brutia Ten), natural forest (cedar and willow‐oak), and mixed forest (beech and oak). Several diversity patterns were evaluated, including evenness and dominance, in the East Mediterranean area of Turkey by analyzing the abundance and species composition of lacewing assemblages using the Simpson and Shannon Diversity Indices. It was questioned whether these communities are structured according to environmental conditions such as altitude, temperature, rainfall, wind and humidity. This question was explored using generalized linear models (GLMs) and principal component analysis (PCA) to detect the effect of ecological parameters on the species composition of the lacewing assemblages. The data suggest that the species abundance, composition, and diversity of lacewings are affected by different forest and agricultural habitat types. Based on the results of the present study, it is recommended that the area of farmland under cultivation is decreased and the area of sustainably managed forest and agricultural land is increased in order to better protect lacewing diversity in the East Mediterranean area of Turkey.     

Habitat selection and temporal abundance fluctuations of demersal cartilaginous species in the Aegean Sea (eastern Mediterranean)

Predicting the occurrence of keystone top predators in a multispecies marine environment, such as the Mediterranean Sea, can be of considerable value to the long-term sustainable development of the fishing industry and to the protection of biodiversity. We analysed fisheries independent scientific bottom trawl survey data of two of the most abundant cartilaginous fish species (Scyliorhinus canicula, Raja clavata) in the Aegean Sea covering an 11-year sampling period. The current findings revealed a declining trend in R. clavata and S. canicula abundance from the late '90 s until 2004. Habitats with the higher probability of finding cartilaginous fish present were those located in intermediate waters (depth: 200-400 m). The present results also indicated a preferential species' clustering in specific geographic and bathymetric regions of the Aegean Sea. Depth appeared to be one of the key determining factors for the selection of habitats for all species examined. With cartilaginous fish species being among the more biologically sensitive fish species taken in European marine fisheries, our findings, which are based on a standardized scientific survey, can contribute to the rational exploitation and management of their stocks by providing important information on temporal abundance trends and habitat preferences.     

Sea warming and fish distribution: the case of the small pelagic fish, Sardinella aurita, in the western Mediterranean

This study analyses the temporal and spatial changes in abundance and distribution of the warm water species round sardinella (Sardinella aurita) in the western Mediterranean over the last decades in relation to sea water temperature. In the western Mediterranean basin (1950–2003), a significant positive relationship was found between round sardinella landings and temperature anomalies. Along a latitudinal gradient off the Mediterranean Iberian coast (1989–2004), a gradual increase in species abundance was observed from south to north, with a certain time lag going northwards, associated with the increase in sea water temperature. The abundance of round sardinella in the two warmest and southernmost areas was positively and significantly correlated with sea surface temperature registered during the start of gonad maturation the previous year. In addition, the positive relationship established between water temperature and abundance of round sardinella in the coldest and northernmost study area demonstrates that there is a temperature limit for the distribution of this species in the western Mediterranean. In addition, this study analyses round sardinella larvae distribution and abundance in the summers of 2003 and 2004, and conducts a comparison with the situation 20 years ago (summer 1983). Results show a marked increase in larval abundance during the last decades and the present appearance of larvae in the northernmost study areas, where they did not occur 20 years ago. This indicates the successful reproduction of round sardinella in the northern part of the Mediterranean, where the species has expanded, confirming its establishment in the area.     

Bathymetric barriers promoting genetic structure in the deepwater demersal fish tusk (Brosme brosme)

Population structuring in the North Atlantic deepwater demersal fish tusk ( Brosme brosme ) was studied with microsatellite DNA analyses. Screening eight samples from across the range of the species for seven loci revealed low but significant genetic heterogeneity ( F _ST = 0.0014). Spatial genetic variability was only weakly related to geographical (Euclidean) distance between study sites or separation of study sites along the path of major ocean currents. Instead, we found a significant effect of habitat, indicated by significant differentiation between relatively closely spaced sites: Rockall, which is surrounded by very deep water (>1000 m), and the Mid-Atlantic Ridge, which is separated from the European slope by a deep ocean basin, were differentiated from relatively homogeneous sites across the Nordic Seas. Limited adult migration across bathymetric barriers in combination with limited intersite exchange of pelagic eggs and larvae due to site-specific circulatory retention or poor survival during drift phases across deep basins may be reducing gene flow. We regard these limitations to gene flow as the most likely mechanisms for the observed population structure in this demersal species. The results underscore the importance of habitat boundaries in marine species.     

The fish assemblage on a coralligenous shallow shelf off the Mediterranean coast of northern Israel

The fish assemblage on the shallow coralligenous shelf (16-30m depth) off Haifa, Israel was sampled using trammel nets throughout a period of 1 year. Complementary data were obtained via underwater censuses of fish on an artificial reef established later in the sampling area. Fortythree species of fish were sampled by trammel nets, 79% of which were observed also during the underwater censuses. Although fish of Red Sea origin constituted only 11.6% of the species composition in the net samples, they contributed 46.2% of the fish abundance and 40.6% of the biomass in these samples. This was supported by the finding that species of Red Sea origin contributed 64% of the abundance of large fish counted on the artificial reef. Siganus luridas, S. rivulatus and Sargocentron rubrum are the main contributors in number and biomass among fish of Red Sea origin. It is suggested that the biogenic rocky bottom of this area contains several components which are similar to biogenic habitats favoured by these benthic species in the Red Sea; this may explain the high abundance of these species in the studied area.     

Temporal Variations in Fine Sand Assemblages in the North Aegean Sea (Eastern Mediterranean)

Two sites were selected in the North Aegean Sea for the study of shallow fine sand assemblages, which are poorly known in the Eastern Mediterranean. The biomonitoring of these sites can provide useful information on the impact of human activities on the macrofaunal and meiofaunal composition of these assemblages. In order to examine this impact, sampling took place in five different periods between 2000 and 2001. The qualitative and quantitative compositions of the communities at the two sites showed certain differences, mostly between the sites and the year of sampling rather than between sampling periods, which would be the expected outcome. The communities seem to be affected by a combination of the human activities with the particular hydrodynamics of the studied sites.     

The meiofaunal community structure of a Mediterranean lagoon (Gialova lagoon, Ionian Sea)

The higher taxonomic structure of a meiofaunal community was investigated in an Eastern Mediterranean lagoon (Gialova lagoon, Ionian Sea). Seven stations were sampled on a seasonal basis during 1995–1996. Stations within the lagoon were found to support a maximum of 14 meiofaunal taxa with densities ranging from 17 to over 2000 individuals per 10 cm². Nematodes were not always the most abundant taxa, although they dominated about half of the total 28 samples. Uni- and multivariate analyses were employed to study the community structure. The distribution pattern of the meiofaunal community varied both across the lagoon and over the seasons. On the basis of the spatial differences a meiofaunal coenocline, correlated with the degree of isolation, was observed, composed of mainly two zones: one defined by the area close to the marine channel and the other the more isolated area in the inner lagoon. Meiofaunal distribution pattern was not clearly correlated to one environmental variable, but rather to many, and spatial and seasonal effects could be seen. Received: 2 March 1999 / Received in revised form: 6 December 1999 / Accepted: 9 December 1999     

Spatial patterns and GIS habitat modelling of fish in two French Mediterranean coastal areas

The spring and summer distribution of adults and larval fish stages of Sparids and Scorpaenids was studied in two sites in the western Mediterranean. Fish adults and larvae of those two taxa were identified and sorted according to their life stages in order to study their distribution and develop suitable habitat maps. Study areas were located on French coastal waters, the “Côte Bleue” Marine Park (CBMP) has an east-west orientation with substratum dominated by Posidonia beds and the Marine Reserve of Cerbère-Banyuls (MRCB) runs north–south and is dominated by rocky substrates. Generalised Additive Models (GAM) combined with Geographic Information System (GIS), were used to model the suitable habitats for fish larvae and adults. During spring months, waters exhibit low Sea Surface Temperatures (SST), low Photosynthetically Active Radiation (PAR), high values of Sea Surface Chlorophyll-a concentration (Chl-a), and mostly negative values of Sea Level Anomaly (SLA) indicating anticyclonic eddies. During summer months, waters have higher values of SST, lower values of Chl-a and positive values of SLA indicating cyclonic eddies. The results revealed different environmental responses in the distribution of fish adults and larvae in the CBMP and MRCB. Suitable habitats for adult were mainly dependent on the substrate types (Posidonia meadows and sand) and they were found close to the coast, whereas fish larvae were dependent on environmental cues (Chl-a, SLA, SST) with a sparse spatial distribution.