Analysis of genetic structure of the red shrimp <Emphasis Type="Italic">Aristeus antennatus</Emphasis> from the Western Mediterranean employing two mitochondrial regions

In this paper we addressed the phylogeographical genetic structure of the economically important red shrimp, Aristeus antennatus (Crustacea, Aristeidae) in the Western Mediterranean. Partial mitochondrial regions of the cytochrome c oxidase subunit I (514 bp) and ribosomal 16S subunit (547 bp) were sequenced in 137 individuals collected at three localities: Catalan Sea, Ligurian Sea and the southern Tyrrhenian Sea. Values of haplotypic diversity were h = 0.552–0.724, whereas those for nucleotide diversity were π = 0.0012–0.0026. Among-sample genetic diversity was not significant and no geographical patterns in the distribution of haplotypes were apparent. Results of the present study are consistent with a past population expansion that occurred <2,000 years ago. Despite the current fishing pressure, genetic variability appears to be sufficiently high to keep A. antennatus populations stable over time. Dispersal-related life history traits may account for the shallow genetic structure. Our results are not in contrast with the hypothesis of sustainability of Western Mediterranean red shrimp fisheries predicted on the basis of previously obtained biological results.     

Identification of deep-water pink shrimp abundance distribution patterns and nursery grounds in the eastern Mediterranean by means of generalized additive modelling

Generalized Additive Modelling (GAM) techniques were used to model the time series of abundance data of deep-water pink shrimp, collected during the MEDITS bottom trawl surveys carried out in the Greek seas from 1996 to 2006, as functions of the sampling location (longitude–latitude), depth and year. The life stages of the species were taken into account. All variables were highly significant, although latitude and depth had always the highest explanatory power. The total abundance was higher between 100 and 400 m of depth, with juveniles and adults being more abundant in the 100–200 m and 200–400 m depth strata, respectively. GAM prediction maps showed high abundance concentration areas for all life stages mainly in the Aegean Sea. The most important nursery ground identified was located in the Saronikos Gulf and a secondary in the Thracian Sea. Concerning the concentration areas of the adult specimens, they are located mainly in the Saronikos Gulf, the Thracian Sea, the Thermaikos Gulf, the Cretan Sea and the eastern part of the Aegean. Guest Editor: V. D. Valavanis Essential Fish Habitat Mapping in the Mediterranean     

Macrobenthic fauna of the Franz Josef Land archipelago

Benthic fauna of the deeper waters (50–320 m) of the Franz Josef Land archipelago sampled in August 1992 using standard western techniques is described and compared with earlier Russian studies of the archipelago. Three faunal assemblages are recognised at depth ranges between 50–150, 150–300, and >300 m depth. Their distributions are related to depth and to different water masses derived from a mixture of Barents Sea water entering from the south at intermediate depths (20–150 m), and Atlantic water from the north below 300 m. The recorded faunal diversity and biomass is as high as or higher than that from comparable Arctic and northern boreal areas. Comparisons are also made with a complimentary Russian survey in the same area using different techniques. The Russian work collected larger organisms most effectively, whereas the present work recorded the smaller taxa more efficiently. Russian surveys provide complementary data to western studies, but care must be taken when comparing studies as they reflect biases in sampling gear and scientific emphasis. These data intercalibrations are important as Russian archives contain a wealth of information that, if used correctly in association with western data sources, will be useful in environmental monitoring studies as human activities increase in the Eurasian Arctic. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Evidence of artisanal fishing impacts and depth refuge in assemblages of Fijian reef fish

Protection from fishing generally results in an increase in the abundance and biomass of species targeted by fisheries within marine reserve boundaries. Natural refuges such as depth may also protect such species, yet few studies in the Indo Pacific have investigated the effects of depth concomitant with marine reserves. We studied the effects of artisanal fishing and depth on reef fish assemblages in the Kubulau District of Vanua Levu Island, Fiji, using baited remote underwater stereo-video systems. Video samples were collected from shallow (5–8 m) and deep (25–30 m) sites inside and outside of a large old marine reserve (60.6 km², 13 years old) and a small new marine reserve (4.25 km², 4 years old). Species richness tended to be greater in the shallow waters of the large old reserve when compared to fished areas. In the deeper waters, species richness appeared to be comparable. The difference in shallow waters was driven by species targeted by fisheries, indicative of a depth refuge effect. In contrast, differences in the abundance composition of the fish assemblage existed between protected and fished areas for deep sites, but not shallow. Fish species targeted by local fisheries were 89% more abundant inside the large old reserve than surrounding fished areas, while non-targeted species were comparable. We observed no difference in the species richness or abundance of species targeted by fisheries inside and outside of the small new reserve. This study suggests that artisanal fishing impacts on the abundance and species richness of coral reef fish assemblages and effects of protection are more apparent with large reserves that have been established for a long period of time. Observed effects of protection also vary with depth, highlighting the importance of explicitly incorporating multiple depth strata in studies of marine reserves.     

Habitat discrimination of juvenile sardines in the Aegean Sea using remotely sensed environmental data

Despite the importance of the recruitment process for small pelagic fish and the high economic importance of European sardine (Sardina pilchardus, Walbaum 1792) in the Mediterranean Sea, knowledge on the distribution and environmental characteristics of its nursery grounds is very limited. In the present study, we used pelagic trawl data collected during 1995–2006 to explore the spatial distribution of sardine juveniles in the Aegean Sea in early summer. Based on sardine abundance per length class, a cluster analysis was initially used to define hauls dominated by juveniles. In a subsequent step, Discriminant Function Analysis (DFA) was applied to discriminate stations with high relative abundance of juveniles using satellite environmental data and bottom depth. The parameters contributing mostly to the discrimination of juvenile grounds were sea level anomaly, photosynthetically active radiation, sea surface temperature, chlorophyll-α and bottom depth. The classification functions of DFA were finally used to post classify unsampled areas in the Greek Seas and the Mediterranean Sea in order to map grounds that meet characteristic environmental conditions for young sardine. Such areas were mostly located inshore, in semi-closed productive areas and often in proximity to river mouths, a pattern that is generally supported by existing information. Guest editor: V. D. Valavanis Essential Fish Habitat Mapping in the Mediterranean     

Water mass and bathymetric characteristics of polar cod habitat along the continental shelf and slope of the Beaufort and Chukchi seas

Relatively little is known about the distribution of fish in deep water (>200 m) in the Beaufort Sea. Data collected by an Acoustic Doppler Current Profiler operated in the Chukchi and Beaufort seas in summer were examined for evidence of fish biomass detections between 18 and 400 m. The presence of fish in waters between 1 and 30 m was explored opportunistically with a non-scientific echo sounder. Evaluation of findings was enhanced by measurements of water column properties (temperature, salinity, fluorescence and transmissivity). Relatively small shoals of fish were detected on the Chukchi shelf and eastern Chukchi shelf break, and also on the Alaskan and Canadian Beaufort shelves in the upper 20 m (T = 2–5°C). Much larger shoals (putative polar cod) were detected within Atlantic Water along the Beaufort continental slope (250–350 m) and near the bottom of Barrow and Mackenzie canyons, where temperatures were above 0°C. A warm-water plume of Alaska Coastal Current water with high concentrations of phytoplankton, zooplankton, and fish was found extending along the shelf 300 km eastward of Barrow Canyon. In contrast to the warm surface and Atlantic Water layers, very few fish were found in colder, intermediate depth Pacific-origin water between them. The large biomass of fish in the Atlantic Water along the continental slope of the Chukchi and Beaufort seas represents previously undescribed polar cod habitat. It has important implications with regard to considerations of resource development in this area as well as understanding impacts of climate change.     

Response of Antarctic benthic communities to disturbance: first results from the artificial Benthic Disturbance Experiment on the eastern Weddell Sea Shelf, Antarctica

The long-term benthic disturbance experiment (BENDEX) was started on the eastern Weddell Sea shelf off Austasen (Antarctica) during ‘Polarstern’ cruise ANT XXI/2 in December 2003 to simulate the impact of grounding icebergs on the seabed and follow the steps and timescales of recovery of disturbed benthos and demersal fish communities. Here, we report the basic approach and first results for this experimental field study. By means of 11 densely-placed hauls with a modified bottom trawl, a seabed area of approximately 100 × 1000 m was artificially scoured to inflict a similar damage to the benthic habitats as a grounding iceberg. Before the disturbance event and 11 days after it, the seafloor communities were sampled (invertebrate assemblages by multibox corers, the fish fauna by trawl hauls) and comparatively analyzed. Sediment texture and chemistry was not significantly altered by the heavy disturbance inflicted by repeated trawling, whereas the fauna was negatively affected. Invertebrate benthic biomass was drastically reduced by a factor of 10, while mean abundances were only slightly reduced. Demersal fish biomass and abundance were slightly but not significantly smaller after the disturbance. Effects of disturbance became more evident in the composition of the fish fauna, with Trematomus pennelli and T. hansoni being dominant at disturbed sites, whereas Chionodraco myersi was the dominant species in trawl catches from undisturbed stations.     

Patterns in species richness,species density,and evenness in groundfish assemblages on the continental slope of the U.S. Pacific coast

For many taxa, diversity, often measured as species richness, decreases with latitude. In this report patterns of diversity (species richness, species diversity, and evenness) in groundfish assemblages were investigated in relation to depth (200–1200 m) and latitude (33–47°N) on the continental slope of the U.S. Pacific coast. The data originated from the 1999–2002 upper continental slope groundfish surveys conducted by the National Marine Fisheries Service. When the data were pooled across depths, species density and evenness were found to decline with latitude. All three diversity measures declined with depth, with the lowest overall diversity in the 600- to 900-m depth range where longspine thornyhead Sebastolobus altivelis constituted close to 70% of the catch. When latitudinal gradients were examined within four depth zones (200–300 m, 400–500 m, 600–900 m, and 1000–1200 m) more complex patterns emerged. At depth species richness and evenness were inversely correlated with latitude as longspine thornyhead dominated catches to the north. However, in shallower areas of the slope, species richness and evenness were positively correlated with latitude. Latitudinal patterns of diversity in the deeper zones and when pooled across depths were positively correlated with temperature and broadly consistent with the Ambient Energy hypothesis discussed by Willig et al. [Annu Rev Ecol System 34:273–309 (2003)].     

Impacts of climate warming on the long-term dynamics of key fish species in 24 European lakes

Fish play a key role in the trophic dynamics of lakes. With climate warming, complex changes in fish assemblage structure may be expected owing to direct effects of temperature and indirect effects operating through eutrophication, water level changes, stratification and salinisation. We reviewed published and new long-term (10–100 years) fish data series from 24 European lakes (area: 0.04–5,648 km²; mean depth: 1–177 m; a north–south gradient from Sweden to Spain). Along with an annual temperature increase of about 0.15–0.3°C per decade profound changes have occurred in either fish assemblage composition, body size and/or age structure during recent decades and a shift towards higher dominance of eurythermal species. These shifts have occurred despite a reduction in nutrient loading in many of the lakes that should have benefited the larger-sized individuals and the fish species typically inhabiting cold-water, low-nutrient lakes. The cold-stenothermic Arctic charr has been particularly affected and its abundance has decreased in the majority of the lakes where its presence was recorded. The harvest of cool-stenothermal brown trout has decreased substantially in two southern lakes. Vendace, whitefish and smelt show a different response depending on lake depth and latitude. Perch has apparently been stimulated in the north, with stronger year classes in warm years, but its abundance has declined in the southern Lake Maggiore, Italy. Where introduced, roach seems to take advantage of the higher temperature after years of low population densities. Eurythermal species such as common bream, pike–perch and/or shad are apparently on the increase in several of the lakes. The response of fish to the warming has been surprisingly strong and fast in recent decades, making them ideal sentinels for detecting and documenting climate-induced modifications of freshwater ecosystems.     

Distribution,abundance, and food habits of the snailfishLiparis tanakai in the Suo Sea,Seto Inland Sea

In order to examine the distribution, abundance, and food habits of the snailfish,Liparis tanakai, in the Suo Sea, western Seto Inland Sea of Japan, experimental fishing surveys were made using trawl nets on the night (1930–0340 h) of 26 May and 2 and 3 June, 1986. The study area was subdivided into 18 areas, each sampled by one trawl tow of 35 min duration. A total of 190 fish was collected during the surveys, and most fish (78.9%) were obtained from muddy substrata ranging in depth from 30 to 40 m at the middle area of the Suo Sea. The total length of the fish in the samples ranged from 72 to 273 mm. The overall length-frequency distribution formed a unimodal curve, the mode occurring at the class of 100–130 mm in total length. Of 151 fish examined, 146 (96.7%) had stomachs full of food, including a variety of small crustaceans and fish. Shrimps, especiallyCrangon affinis, ranked highest in importance in the diet ofL. tanakai. These biological data are compared with those of conspecifics from Sendai Bay, northern Honshu of Japan.     

Distribution and some features of biology of sea raven <Emphasis Type="Italic">Hemitripterus villosus</Emphasis> (Hemitripteridae) in the northwestern part of the Sea of Japan

On the basis of long-term (1981–2008) observations, it was shown that, in the northwestern part of the Sea of Japan, sea raven Hemitripterus villosus is a common species with low, but stable numbers and it is a part of elittoral ichthyocenoses. During the year it performs wintering, feeding, and spawning migrations within the shelf and the upper part of the continental slope occurring from almost the water’s edge to a depth of 550 m. Highest density of sea raven is observed in Peter the Great Bay and the lowest is observed off the coasts of northern Primorye. Maximum length of H. villosus in the northwestern part of the Sea of Japan reaches 57 cm, and the modal group of fish consists of fish with a length of 25–45 cm (75%). In Peter the Great Bay, in the summer period, individuals with a length of 11–50 cm feed mainly on mass fish species; the value of daily ration of H. villosus varies from 1.6 to 3.2% of body weight, averaging 2.5%. According to an expert estimate, the biomass of sea raven in the northwestern part of the Sea of Japan reaches 2000 t.     

Summer mesozooplankton distribution near Novaya Zemlya (eastern Barents Sea)

Regional variations in mesozooplankton composition, abundance and biomass were studied during a cruise in August 2006 near Novaya Zemlya Archipelago (eastern Barents Sea) using Juday net hauls from the bottom (or 100 m depth) to the surface. A comparison with multiannual literature values revealed that the mean temperature and salinity in the south and centre of the study area were similar to typical values, while temperature in the north was significantly higher. A total of 36 species and higher taxa were identified. Mesozooplankton abundance and biomass varied from 47 to 851 ind m⁻³ and from 5 to 74 mg dry weight m⁻³, respectively. Copepods dominated the mesozooplankton community, reaching 73–98% and 61–97% of the total abundance and biomass. Calanus finmarchicus and Oithona similis were the most abundant species at all stations. The biodiversities (Shannon indices) of the mesozooplankton community varied between stations from 1.10 to 2.46 (estimated from species abundances) and from 0.19 to 1.92 (estimated from species biomasses), averaging 1.93 ± 0.127 and 1.34 ± 0.151, respectively. Three groups at the 48% level of dissimilarity of species abundance were delineated by cluster analyses. The clusters differed significantly with respect to temperature and salinity. The total mesozooplankton abundance and biomass as well as quantitative parameters of most common taxa scaled negatively with temperature.     

Diversity of fish species in the trawl catches in the southeastern Barents Sea in 1980–2008

Analysis of trawl catches in the southeastern Barents Sea was performed for the period of 1980–2008. One lamprey and 48 fish species were defined, including 38 marine fish species, 8 anadromous and amphidromous species, and 1 freshwater species. The ichthyofauna of several areas of the southeastern Barents Sea was described (Cheshskaya Inlet, Pomorskiy Strait, southeastern Pechora Sea, Pechora Sea, Khaipudyrskaya Inlet and adjacent areas). Biodiversity indexes and Shannon Index were applied to describe the species diversity. Cluster analysis was applied to compare the species lists from different areas. Multiyear dynamics of ichthyofauna was studied. The tendency of geographical range expansion eastward was observed for boreal species.     

Role of deep sponge grounds in the Mediterranean Sea: a case study in southern Italy

The Mediterranean spongofauna is relatively well-known for habitats shallower than 100 m, but, differently from oceanic basins, information upon diversity and functional role of sponge grounds inhabiting deep environments is much more fragmentary. Aims of this article are to characterize through ROV image analysis the population structure of the sponge assemblages found in two deep habitats of the Mediterranean Sea and to test their structuring role, mainly focusing on the demosponges Pachastrella monilifera Schmidt, 1868 and Poecillastra compressa (Bowerbank, 1866). In both study sites, the two target sponge species constitute a mixed assemblage. In the Amendolara Bank (Ionian Sea), where P. compressa is the most abundant species, sponges extend on a peculiar tabular bedrock between 120 and 180 m depth with an average total abundance of 7.3 ± 1.1 specimens m⁻² (approximately 230 gWW m⁻² of biomass). In contrast, the deeper assemblage of Bari Canyon (average total abundance 10.0 ± 0.7 specimens m⁻², approximately 315 gWW m⁻² of biomass), located in the southwestern Adriatic Sea between 380 and 500 m depth, is dominated by P. monilifera mixed with living colonies of the scleractinian Madrepora oculata Linnaeus, 1758, the latter showing a total biomass comparable to that of sponges (386 gWW m⁻²). Due to their erect growth habit, these sponges contribute to create complex three-dimensional habitats in otherwise homogenous environments exposed to high sedimentation rates and attract numerous species of mobile invertebrates (mainly echinoderms) and fish. Sponges themselves may represent a secondary substrate for a specialized associated fauna, such zoanthids. As demonstrated in oceanic environments sponge beds support also in the Mediterranean Sea locally rich biodiversity levels. Sponges emerge also as important elements of benthic–pelagic coupling in these deep habitats. In fact, while exploiting the suspended organic matter, about 20% of the Bari sponge assemblage is also severely affected by cidarid sea urchin grazing, responsible to cause visible damages to the sponge tissues (an average of 12.1 ± 1.8 gWW of individual biomass removed by grazing). Hence, in deep-sea ecosystems, not only the coral habitats, but also the grounds of massive sponges represent important biodiversity reservoirs and contribute to the trophic recycling of organic matter.     

Phase shift to algal dominated communities at mesophotic depths associated with lionfish (<Emphasis Type="Italic">Pterois volitans</Emphasis>) invasion on a Bahamian coral reef

Mesophotic coral reefs (30–150 m) have been assumed to be physically and biologically connected to their shallow-water counterparts, and thus may serve as refugia for important taxonomic groups such as corals, sponges, and fish. The recent invasion of the Indo–Pacific lionfish (Pterois volitans) onto shallow reefs of the Caribbean and Bahamas has had significant, negative, effects on shallow coral reef fish populations. In the Bahamas, lionfish have extended their habitat range into mesophotic depths down to 91 m where they have reduced the diversity of several important fish guilds, including herbivores. A phase shift to an algal dominated (>50% benthic cover) community occurred simultaneously with the loss of herbivores to a depth of 61 m and caused a significant decline in corals and sponges at mesophotic depths. The effects of this invasive lionfish on mesophotic coral reefs and the subsequent changes in benthic community structure could not be explained by coral bleaching, overfishing, hurricanes, or disease independently or in combination. The significant ecological effects of the lionfish invasion into mesophotic depths of coral reefs casts doubt on whether these communities have the resilience to recover themselves or contribute to the recovery of their shallow water counterparts as refugia for key coral reef taxa.     

Distribution of polar cod and age-0 fish in the U.S. Beaufort Sea

Little is known about species composition, distribution, and abundance of pelagic fish in the U.S. portion of the Beaufort Sea continental shelf and slope. To inventory the community and describe pelagic fish distributions relative to water characteristics, a systematic survey was conducted in August 2008. Acoustics (38 kHz), midwater trawling, and CTD casts were used to sample water depths from 20 to 500 m. Age-1+ polar cod (Boreogadus saida) was the dominant fish species, with peak densities of 155,000 # ha⁻¹ at bottom depths of 100–350 m. Age-0 fish (polar cod, sculpin (Cottidae family), and eelblenny (Lumpenus sp.)), dominated the pelagic biomass at bottom depths between 20 and 75 m, with peak densities of 160,000 # ha⁻¹, but were also found in surface waters at bottom depths >75 m. Age-1+ polar cod were associated with cold, saline waters likely of Chukchi Sea origin and mirrored published foraging distributions for beluga whales (Delphinapterus leucas). Conversely, age-0 fish were found in warm, fresher water, likely of ice melt and/or riverine origin, throughout the study area. This study provides a necessary baseline for the development of Arctic assessment surveys and management plans for polar cod.     

Long-term changes in Krill biomass and distribution in the Barents Sea: are the changes mainly related to capelin stock size and temperature conditions?

Krill plays a significant role in the Barents Sea ecosystem, providing energy transport between different trophic levels. The current paper presents the results of a long-term study (1980–2009) based on pelagic trawl catches from August to September. Our investigations show that the krill species were distributed widely in the Barents Sea and that the largest krill concentrations were restricted to the west-central and eastern parts of the Barents Sea. The current paper presents the relative biomass indices, and the estimates must be interpreted as minimum biomass. The mean annual krill biomass was estimated to be 22 million tonnes in wet weight, with the highest values being as much as 48 million tonnes. Capelin is the largest pelagic stock, and in some years, their biomass can amount to 4–7 million tonnes, which can impose high predation pressure on krill. When their biomass is high, capelin may consume close to 26 million tonnes annually. The predation from pelagic (herring and blue whiting) and bottom (cod and haddock) fish species was much lower, being 9 and 1 million tonnes, respectively. A negative relationship between krill biomass and capelin stock size above 74°N was observed during the study period. However, during the last decade, the krill biomass has increased despite heavy predation from capelin in some years. A positive significant linear relationship between the mean annual Kola temperature and the krill biomass seems to indicate that the recent warming conditions have favourable impacts on the krill populations in the Barents Sea.     

Discrimination of the redfish (Sebastes mentella) stock components in the Irminger Sea and adjacent waters based on meristics,morphometry and biological characteristics

Redfish Sebastes mentella samples were collected in 2004 and 2005 during commercial cruises to the Irminger Sea on board the Polish vessel M/T ‘Wiesbaden’. Ichthyological studies included length and weight measurements, sex, gonad maturity stages and age determinations. Meristic and morphometric measurements were performed on digital images of the redfish. Comparison of the pelagic redfish from the northeastern (depths deeper than 500 m) and southwestern (depths shallower than 500 m) fishing grounds of the Irminger Sea indicates a number of differences including spatial and vertical distribution, ambient temperature, length and age composition. Moreover, 12 morphometric and 4 meristic characters differed significantly between fish samples from these two areas. Results of Cluster Analysis showed the clear grouping of samples into that of the ‘oceanic’ component (depth 300–450 m) and the ‘deep sea’ component (depth 550–800 m). These results were confirmed by Principal Component Analysis, which revealed the separation of samples into two catch depth groups. The share of fish allocated by Discriminant Analysis into the pelagic ‘deep sea’ component in the northeastern area was nearly 92%, while the ‘oceanic’ component was dominant in the southwestern area and comprised more than 88% of the fish. Cluster and Principal Component analyses suggest that the ‘oceanic’ component is a more homogeneous group than the ‘deep sea’ component. These results support the management units recently established by ICES.     

Copepod communities off Franz Josef Land (northern Barents Sea) in late summer of 2006 and 2007

Copepods are considered to be the main component of the Arctic marine zooplankton. We examined the copepod distribution and diversity off Franz Josef Land (northern Barents Sea) in August 2006 and 2007. A total of 18 and 14 copepod taxa were identified from the sampling layers (100–0 m or bottom–0 m) in 2006 and in 2007, respectively. There were no significant differences in the total copepod abundance between the years (means ± SE: 118,503 ± 24,115 individuals m⁻² in 2006 vs. 113,932 ± 28,564 individuals m⁻² in 2007). However, the copepod biomass in 2006 (4,518 ± 1,091 mg C m⁻²) exceeded clearly the value in 2007 (1,253 ± 217 mg C m⁻²). The copepod community showed low species richness and diversity in both years (Simpson index D: 0.34 and 0.38, respectively). Biomass of the large and small copepod species strongly decreased from 2006 to 2007. The total abundance of copepods was negatively correlated with water temperature in 2006 and positively correlated with salinity in 2007. The patchiness in copepod distribution was associated with local hydrography and temperature conditions.