A new species of Gobius (Perciformes: Gobiidae) from the Mediterranean Sea and the redescription of Gobius bucchichi

A new species of the gobiid genus Gobius (Gobiidae, Perciformes), Gobius incognitus sp. nov. is described from the Mediterranean Sea, and its most morphologically similar species Gobius bucchichi is redescribed. The new species is distinguished from its congeners by: scales in lateral series 51–59; predorsal scales 25–35; opercle scaled in adults with 10–16 scales present; pectoral fin with ray count 18–20 and free tips on upper rays well developed and on the first ray longer than two thirds of the entire ray length; pelvic disc complete and with well‐developed anterior membrane without lateral lobes; anterior oculoscapular canal with pore α at rear of orbit; oculoscapular row x¹ not extending forwards to pore β; suborbital row d discontinuous with large gap below suborbital rows 3 and 4; eye diameter 1·08–1·32 in snout length; by pigment rows on cheek and pigmentation on pectoral‐fin base.     

Aspects of the early life history of European hake from the central Adriatic

During early development, the left and right sagittae of European hake Merluccius merluccius showed dimorphism in both size and shape due to the different number and size of accessory primordia. Juvenile hake reached the total length ( L _T) of 15 cm in c. 1 year, with monthly growth rates ranging from 1·6 cm month^-1 in the third month of life to 1·1 cm month^-1 towards the end of the first year. Back-calculated hatch-date distribution indicated continuous spawning with a peak in summer and a second, less evident, peak in February–March. The presence of early demersal juveniles (16–30 mm L _T, c. 40 days old) very close to the Pomo pit area (Central Adriatic Sea) at c. 140 m depths indicates that the change from the pelagic to the demersal phase takes place at c. 40 days close to the area of concentration of juveniles. The daily-increment hypothesis was validated indirectly.     

Ecological and morphological characteristics of Ephelota gemmipara (Ciliophora,Suctoria), epibiontic on Eudendrium racemosum (Cnidaria,Hydrozoa) from the Adriatic Sea

The relationship between the suctorian Ephelota gemmipara and the large hydroid Eudendrium racemosum from the North Adriatic Sea has been studied over its full annual cycle. Ephelota gemmipara settles on the perisarc of the hydroid, usually close to the hydranths in order to exploit the hydroid's food discharges. The life cycle of E. gemmipara is influenced by temperature variations and by its relationship with the host. The hydroid shows an active phase in the summer, and it gets through the adverse winter season forming resting stages. In April, when temperature increases, the hydroid starts its active phase and it is colonized by suctorians. From May to September the suctorians produce multiple buds (swarmers) that detach from the parental cells to settle on an Eudendrium colony. The abundance of the suctorian peaks in September, with more than 1.2 million ind. m^?2. Their proliferation coincides with the maximal abundance of their host and the highest water temperatures. On the contrary, sexual reproduction and the encystment occur when the temperature and the abundance of E. racemosum decrease. Lastly, we also report the presence of symbionts such as bacteria and the parasitic protozoans Tachyblaston ephelotensis and Enigmocoma acinetarum.     

Shelter utilization by Gobius cruentatus and Thorogobius ephippiatus (Teleostei: Gobiidae)

Parameters of shelters utilized by Gobius cruentatus and Thorogobius ephippiatus were measured, in situ , using SCUBA. Both species exhibited non-random use of shelters, with T. ephippiatus , the smaller of the two species, utilizing significantly larger shelters than G. cruentatus . Interspecific size differences and competitive exclusion are not considered to be of major importance in the observed differential utilization of shelters. The size of shelters utilized by both species is suggested to be influenced by current velocities.     

A new record of Gobius jarosi (Teleostei,Gobiidae) from the Early Miocene of Poland with inference to paleogeography and palaeoecology of the Carpathian Basin

Abstract

Gobies (family Gobiidae) were in the past and now important components of marine ecosystems as an essential part of the food chain. However, the early fossil record of this group is relatively meager, with only scarce skeletal remains. The oldest known representative of the genus Gobius has been recently described from the Early Miocene of Czech Republic as Gobius jarosi P?ikryl & Reichenbacher, 2018. Here we present a detailed study of a well-preserved goby skeleton of the same age from the Harta locality (Poland). This specimen is assumed as belonging to Gobius jarosi based on its almost complete morphological and meristic identity with the type material from the Vá?any nad Litavou locality. Some aspects of the paleogeography and paleoecology of the Early Miocene fish assemblage from Harta with special reference to the Carpathian Basin are also discussed in this paper.     

Comparative energy allocation in two sympatric, closely related gobies: the black goby Gobius niger and the grass goby Zosterisessor ophiocephalus

Seasonal energy allocation of lipid reserves into different body tissues was analysed comparatively in two sympatric, closely related gobies: the grass goby Zosterisessor ophiocephalus and the black goby Gobius niger . Lipid reserves were measured in liver, muscle and ovary and compared between the two species within a given sex and seasonal period (reproductive v . non-reproductive). Furthermore, temporal patterns of lipid reserves were investigated in the two species in relation to gonado-somatic and liver-somatic indices, as well as the relationship between size and lipid content. Results showed that the grass goby allocated more lipid reserves in reproduction while the black goby accumulated more reserves in liver and muscle, at a given size, although the temporal patterns of lipid accumulation and depletion were basically similar. Results are discussed in the light of life-history theories, taking into account both adaptation and evolutionary constraints.     

Cartography of littoral rocky-shore communities (CARLIT) as a tool for ecological quality assessment of coastal waters in the Eastern Adriatic Sea

Littoral cartography is a valuable tool which uses shallow water macroalgal communities for monitoring ecosystem health and water quality. Cartography of littoral rocky-shore communities (CARLIT) is a European Union Water Framework Directive-compliant monitoring method widely used in the Western Mediterranean Sea. This non-destructive method is based on a visual observation of the type and length of coast occupied by rocky-shore communities in the upper-sublittoral zone. Here we present the first wide-scale application of CARLIT in the Adriatic Sea. The reference values calculated specifically for the Croatian coast (Eastern Adriatic Sea) ensure accurate calculation of the ecological status. The measured ecological quality ratio values (EQR) show a good linear relation with the Land Uses Simplified Index (LUSI) and appropriately reflect an increase in nutrient concentrations. The results suggest that this method can be used as a reliable biomonitoring tool in the Eastern Adriatic Sea. This study highlighted that Cystoseira forests thrive in 39% of the surveyed coastline and 23% of the coastline seems to be subjected to overgrazing by sea urchins. Our results provide a spatially accurate information on the abundance of different upper-sublittoral communities and the associated ecological status, which can be used in future management plans for improving water quality.     

A comparison of circatidal rhythmicity and entrainment by hydrostatic pressure cycles in the rock goby, Gobius paganellus L. and the shanny, Lipophrys pholis (L.)

The intertidal teleosts Gobius paganellus and Lipophrys pholis show endogenous circatidal activity rhythms when recorded in constant conditions. Under these conditions, the rhythm of L. pholis is the more precise which may indicate stronger coupling between underlying circalunadian oscillators in this species. In G. pagunellus the inter-oscillator coupling may be weaker and this could enable a more subtle interpretation of tidal fluctuations than in L. pholis . The oscillators may, however, be fundamentally different in the two species; circalunadian in G. paganellus and circatidal in L. pholis .
When exposed to hydrostatic pressure cycles of tidal frequency both species responded pre- dominantly to increasing pressure, which suggests that in the wild they are likely to be most active on the rising tide. Hydrostatic pressure cycles are confirmed as a zeitgeber for both species by the successful entrainment of some individuals. The lack of entrainment of others impIies that additional zeitgebers are required for complete entrainment.     

First marine record of marble trout Salmo marmoratus

A specimen of marble trout Salmo marmoratus, of 955 mm total length (L_T) and weighing 10 220 g, was caught on 26 December 2008 by a commercial fisherman near the coast of Igrane (eastern Adriatic Sea). This represents the first marine record of this species.     

Racial differences in eggs and juveniles of Windermere charr, Salvelinus alpinus

At least four races of charr occur in Windermere, the largest natural lake in England: north basin and south basin autumn spawners, north basin and south basin spring spawners. This study examines racial differences between eggs and juveniles, and relates juvenile size and survival to egg size. There were no major differences between races for egg incubation times and the percentage of eggs hatching successfully, the latter being high (mean values 76–96%) with a negligible proportion of abnormal alevins (<0.8%). Although there were no significant differences in the lengths of the female parents, both eggs and alevins were significantly larger for the autumn spawners than the spring spawners. Size differences in alevins, especially live weight, were positively related to egg size but not female parent size. Mean percentage survival for juveniles attaining the independent feeding stage was higher for the progeny of autumn spawners (32%) than spring spawners (3%). Racial differences in the egg and alevin stages therefore appear to have a significant effect on subsequent survival, and could be ultimately responsible for the relatively small proportion of spring spawners (only 4–6%) in the Windermere population of charr.     

温度和盐度对皱肋文蛤幼贝存活与生长的影响

在室内控制条件下,研究了不同海水温度和盐度对皱肋文蛤(Meretrix lyrata)幼贝存活与生长的影响。结果表明:皱肋文蛤幼贝适宜生存温度为12.2-35.6℃,最适生存温度为24-30℃;适宜生长温度为23.5-33.0℃,最适生长温度为27-30℃,属典型的南方滩涂贝类。皱肋文蛤幼贝适宜生存盐度为4.3-40.5,最适生存盐度为11-31;适宜生长盐度为17.1-33.4,最适生长盐度为19-23,属广盐性滩涂贝类。该贝低温和高温敏感起始点分别为21℃和33℃;低盐和高盐敏感起始点分别为9和33。皱肋文蛤幼贝对极端温、盐度具有一定的耐受力:在37℃下仍可保持6d,100%不死亡,在39、41℃下分别在3d和5d内全部死亡;在4、6、8、10、12℃下则可分别100%存活3、4、6、9、11d;在盐度为0、5、7、9时保持100%存活的时间分别为5、8、10、10d;在盐度为33、35、37、39时保持100%存活的时间分别为7、5、3、3d,盐度41时当天即出现死亡。     

Zooplankton community and hydrographical properties of the Neretva Channel (eastern Adriatic Sea)

Temporal and spatial variability of micro and mesozooplankton was studied in 1998 and 1999 at four stations in the Neretva Channel area influenced by the Neretva river and the open waters of the south Adriatic Sea. The area is orthophosphate limited, but an excessive accumulation of land derived nitrogen is prevented by phytoplankton uptake and the general circulation pattern. Microzooplankton was dominated by ciliates, with average abundances comparable to other Adriatic channel areas (122–543 ind. l⁻¹). Non-loricate ciliates (NLC) generally peaked in the warmer periods, but a winter increase was evident towards the inner part of the channel. Tintinnid abundances generally increased in autumn. A significant relationship with temperature was not recorded for either protozoan group. An inverse relationship between NLC and salinity might be indirectly caused by their preference for the food abundant surface layer. Mesozooplankton was dominated by copepods, with distinct summer maxima throughout the area and pronounced winter maxima of >10,000 ind. m⁻³ at the inner stations. The community was predominantly neritic but the open sea waters were important in structuring the mesozooplankton assemblage at all stations during the autumn–winter period. Although temperature regulated the seasonal dynamics of most metazoans and the species succession in the copepod community, small omnivorous copepods (Oncaea media complex, Oithona nana and Euterpina acutifrons) dominated regardless of the season. A trophic link between copepods and ciliates was evident in winter during low phytoplankton biomass.     

Releasing of the European sea bass Dicentrarchus labrax (Linnaeus) in the Adriatic Sea: Large-volume versus intensively cultured juveniles

The main goals of this project were to evaluate if artificial reefs are suitable sites for releasing hatchery-reared sea bass and if intensively and extensive large-volume cultured sea bass are suitable to be released into the wild for stock enhancement purposes. Large-volume cultured bass were reared in lower densities compared to intensively cultured ones and, when fry were about 90 days old, were transferred into external ponds connected to the channels of the surrounding marsh, where that they could integrate pellet food sources with live prey. Intensively cultured bass were fed for 55 days with Artemia salina (Linnaeus, 1758) and then with pellets. Underwater visual census (UVC) and fishing sampling were carried out to verify the presence of the tagged specimens at the artificial reef. A low mortality rate after tagging was observed and good tag retention was recorded. Individuals dead after tagging were statistically smaller than survivors. A total of 45 tagged bass (42 large-volume and 3 intensively cultured) were returned by fishers and 16 specimens were observed during UVC (15 large-volume and 1 intensively cultured). The majority of recaptured bass concentrated in the surroundings of river mouths and harbours suggesting that, after release, sea bass migrated towards shallower and brackish waters. Subsequently, as they grew, they came back towards deeper waters and tended to aggregate around artificial structures. Analysis of stomach contents of returned individuals confirmed their dependence on hard-substrate food items. The study provides evidence to support the suitability of large-volume juveniles for restocking purposes, due to their ability to prey on wild food and their endurance to the stress caused by release operations.     

Microplankton diversity indices as indicators of eutrophication in the northern adriatic sea

Phytoplankton community diversity indices are used to characterize the effects of eutrophication in the Northern Adriatic Sea. A derived Shannon diversity frequency spectrum provided a single biological quantification which allowed an interpretation of temporal and regional differences and which can also be used to evaluate future changes in species diversity. The data base comprised a 4+ year time series involving 300 taxa.     

Plectorhinchus mediterraneus from off north east Italy and Slovenia–the first records of fish of the family Haemulidae from the Adriatic Sea

The haemulid Plectorhinchus mediterraneus , previously unrecorded in the Adriatic Sea, has been found recently in the Gulf of Trieste, in Diga Rizzo, Italy, and near Piran, Slovenia.     

Diet and feeding strategy of thornback ray Raja clavata

The diet and feeding strategy of thornback ray Raja clavata, from the eastern-central Adriatic Sea, were investigated. Stomach contents of 428 specimens, total length (L(T) ) of 14·0-75·1 cm, were collected from commercial bottom trawls. The prey items identified in the stomachs belong to eight major groups: Cephalopoda, Polychaeta, Stomatopoda, Decapoda (Natantia and Reptantia), Mysidacea, Isopoda, Amphipoda and Teleostei. Decapods were the most important prey (index of relative important, %I(RI) ,= 72·8) followed by teleosts (%I(RI) = 20·4), whereas other prey groups were only occasionally ingested. Small-sized individuals (<25 cm L(T) ) fed primarily on small crustaceans (mysids and amphipods), whereas large-sized specimens consumed larger prey, such as decapods, cephalopods and teleosts. Diet composition showed little seasonal variation; decapods were the most important prey in all seasons. There was high dietary similarity between sampling locations. The percentage of empty stomachs did not differ significantly among size classes and seasons. In terms of composition by species, the diet of R. clavata was characterized by a variety of rare or unimportant prey. As a result, R. clavata could be considered a generalist predator.     

Some distributional characteristics of small zooplankton at two stations in the Otranto Strait (Eastern Mediterranean)

The qualitative composition, numerical abundance and vertical distribution of protozoan and microcopepod communities were studied in the Otranto Strait at two stations during five cruises from August 1986 to May 1990. The samples were collected with a plankton net of 53-m mesh size equipped with a closing system in six or seven vertical layers. The principal component analysis (PCA) was used to analyse the spatial and temporal variability of small zooplanktonic assemblages. Data are presented for 36 species of radiolarians, 46 tintinnines and for 22 oncaeid copepods. Differences between the eastern shore and the western shore were not significant, according to the PC analysis of the total density values for all assemblages. However, on the basis of the distribution of PC loadings, it was possible to distinguish three vertical layers whose variability contributes in different amounts to the total variability in the small zooplankton community at both stations. The water masses have crucial significance for the spatial and seasonal distribution of all assemblages. Each type of water mass is connected by the presence of characteristic species.     

Effects of changes in seagrass shoot density and leaf height on the abundance of juveniles of Acentrogobius pflaumii in a Zostera marina bed

The effects of changes in the structural complexity of a seagrass (Zostera marina) habitat on the density of juveniles of the streaked goby, Acentrogobius pflaumii, were investigated by field experimentation at Moroiso Bay, Miura Peninsula, Japan. The experimental design, which included seven treatments plus a control, included reduction of seagrass shoot densities and leaf heights as well as complete removal of seagrass. Throughout the study period, juvenile densities remained similar among the experimental quadrats, including the completely cleared quadrat. On the other hand, juveniles did not appear over the bare sandy substratum surrounding the experimental seagrass bed. Within the bed, prey densities were high, being similar among the experimental quadrats, whereas prey were relatively scarce over the surrounding bare substratum. This result suggested that streaked goby juveniles were not attracted to the structure of the Zostera bed per se and that their distribution patterns may be determined by other factors, such as prey availability. Received: September 25, 2000 / Revised: November 22, 2000 / Accepted: January 16, 2001     

Nutrient (N,P, Si) fluxes between marine sediments and water column in coastal and open Adriatic

Nutrient benthic fluxes, as well as sediment phosphorus concentration at the open sea and coastal water stations of the Central and South Adriatic were studied during 1997–98. The fluxes were in the ranges: 0.16–2.67 mmol m^–2 d^–1 (silicate); –0.031–0.164 mmol m^–2 d^–1 (phosphate); –0.51–2.03 mmol m^–2 d^–1 (ammonia); and –1.32–1.62 mmol m^–2 d^–1 (nitrate + nitrite). Silicate flux showed a gradient from the coastal area to the open sea. Ammonia was the main nitrogen species in the flux at the estuary and bay stations, while the sum of nitrate and nitrite was predominant at the open sea stations. Relationships between phosphate and ammonia fluxes (r = 0.699, p<0.01) as well as phosphate and silicate (r = 0.529, p<0.01) were established.     

Chorotypes of seaweeds from the western Mediterranean Sea and the Adriatic Sea: An analysis based on the genera Audouinella (Rhodophyta), Cystoseira (Phaeophyceae) and Cladophora (Chlorophyta)

The aim of the present paper is to identify the possible existence of groups of species in the genera Audouinella (Rhodophyta), Cystoseira (Phaeophyceae) and Cladophora (Chloropyta) with significantly similar distribution patterns (chorotypes), in the western Mediterranean Sea and the Adriatic Sea. Of the 98 species studied, 59 were grouped into 11 chorotypes, whereas 39 species remained ungrouped. Thirty‐eight species were included in a generalist chorotype, whereas 6 chorotypes were monospecific. The relationships with the environmental factors that could explain the chorotypes are discussed.