Composition, structure and distribution of the ichthyoplankton in a Mediterranean coastal lagoon

The species composition and assemblage structure of the ichthyoplankton from the Mar Menor Lagoon in south‐east Spain are given. The fish larvae were sorted from zooplankton samples collected at 20 stations with a plankton net (50 cm mouth diameter and 500 μm mesh) during 36 surveys between February and December 1997. A total of 39 575 fish larvae representing 14 families, 22 genera and 36 species were identified. Gobiidae was the most dominant family (77·0%) followed by Blenniidae (19·4%) and Atherinidae (1·3%). The most abundant species were Gobius niger and Gobius paganellus , which accounted for 42·7 and 19·3% of the total respectively. These species were followed in order of relative abundance by Pomatoschistus marmoratus (13·9%), Parablennius pilicornis (9·4%), Lipophrys pavo (7·7%), Atherina boyeri (1·3%) and Parablennius tentacularis (1·3%). The high species diversity (2·0–2·8 bits individual⁻¹ for the annual diversity spectra at each sampling station) reflected a diverse assemblage of species. The main commercial species in the lagoon (Sparidae and Mugilidae) were poorly represented among the ichthyoplankton and they probably enter the lagoon on the bottom as recruits. Chlorophyll a concentration in the water column was the main factor explaining the seasonal variation in larval abundance. Spatial distribution of larvae was related to hydrographical circulation patterns in the lagoon and the movement of marine‐spawned larvae through the channels connecting the lagoon with the Mediterranean Sea.     

Life history strategies of four small-size fishes in the Suez Canal, Egypt

Of 35 species collected from the shores of the Suez Canal and its lakes, five were abundant year round. Sihouettea aegyptia and Aphanius dispar are of Red Sea (warm water) origin, whereas Pomatoschistus marmoratus, Aphanius fasciatus and Atherina boyeri are Mediterranean species. S. aegyptia and A. dispar are distributed throughout the Suez system whereas A. fasciatus is restricted to the northern canal. P. marmoratus and A. boyeri have not spread southward beyond the Bitter Lakes. Salinity is the main limiting factor for the distribution of Mediterranean species. S. aegyptia and A. dispar are dominant in the Bitter Lakes (salinity 44‰), whereas P. marmoratus and A. boyeri are abundant in Timsah Lake (salinity 7·8–41·6‰). There was considerable interannual and monthly variation in the relative abundance of each species. The populations were dominated by a single age group, and life spans were no more than 2 years. Rapid growth was evident during the first spring in P. marmoratus and A. boyeri and during the first summer, early autumn in S. aegyptia and A. dispar . The relative abundance of each food item in the diet varied with fish size and season. S. aegyptia, P. marmoratus and A. dispar fed mostly on harpacticoid copepods, polychaetes, demersal eggs, diatoms and blue-green algae whereas A. boyeri fed mostly on planktonic copepods. The warm water species are summer spawners, whereas the temperate species are autumn-winter spawners.     

Phylogenetic relationships of Atherina hepsetus and Atherina boyeri (Pisces: Atherinidae) populations from Greece, based on mtDNA sequences

The genetic divergence and the phylogenetic relationships of six Atherina boyeri (freshwater and marine origin) and five Atherina hepsetus populations from Greece were investigated using partial sequence analysis of 12s rRNA, 16s rRNA and control region mtDNA segments. Three different well divergent groups were revealed; the first one includes A. boyeri populations living in the sea, the second includes A. boyeri populations living in the lakes and lagoons whereas the third one includes all A. hepsetus populations. Fifty-seven different haplotypes were detected among the populations studied. In all three mtDNA segments examined, sequence analysis revealed the existence of fixed haplotypic differences discriminating A. boyeri populations inhabiting the lagoon and the lakes from both the coastal A. boyeri and the A. hepsetus populations. The genetic divergence values estimated between coastal (marine) A. boyeri populations and those living in the lagoon and the lakes are of the same order of magnitude as those observed among coastal A. boyeri and A. hepsetus populations. The results obtained by different phylogenetic methods were identical. The deep sequence divergence with the fixed different haplotypes observed suggests the occurrence of a cryptic or sibling species within A. boyeri complex.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 151–161.     

Stable carbon and nitrogen ratios in the sand smelt from a Mediterranean coastal area: feeding habits and effect of season and size

Enriched δ¹³C values (annual average – 11.2‰) suggest that in the study site (Stagnone di Marsala, Italy) the sand smelt Atherina boyeri exploited benthic prey throughout the year. In particular, Mysidacea and Isopoda seemed to dominate the diet. Stomach content data from the literature was in partial agreement with the present isotopic analysis suggesting that, while Mysidacea and Isopoda are exploited by A. boyeri , Copepoda Harpacticoida and Amphipoda are the dominant food items of the sand smelt diet. Several hypotheses are proposed to explain such partially different results from the two techniques. Both season and size influenced the δ¹³C and δ¹⁵N values of A. boyeri . Although throughout the sampling year, A. boyeri showed very enriched δ¹³C and δ¹⁵N values consistent with a diet based on benthic resources, it showed significant seasonal differences in both nitrogen and carbon isotope ratios. Such a finding suggests that the food preferences of A. boyeri undergo small seasonal differences, probably as a consequence of prey availability. Size also affected the isotopic composition of the sand-smelt indicating that this species shows ontogenetic diet shifts in the study site. Compared with other Mediterranean trophic data of the sand smelt these results substantiate the great adaptability of A. boyeri to the local environmental resources and its trophic plasticity.     

Dynamics of Kudoa camarguensis (myxosporean) infection in two gobiid species,Pomatoschistus microps and P. minutus (Teleostei: Pisces), in the Rhĵne River delta,France

The occurrence of the myxosporean parasite Kudoa camarguensis was surveyed monthly during 1997 in a brackish-water lagoon of the Rh?ne River delta (France). K. camarguensis was found on its typical host, Pomatoschistus microps, and on an additional host, P. minutus. Prevalence and mean abundance were higher in the typical host than in the additional host due to differences in the temporal occupancy of the lagoon by the 2 species. The temporal occurrence of this myxosporean parasite is discussed in relation to the migratory habits of P. minutus and the sedentary habits of P. microps.     

Environmental changes and zooplankton temporal and spatial variation in a disturbed Brazilian coastal lagoon.

The Imboassica lagoon, located in the Municipality of Macaé (RJ), is separated from the sea by a sand bar, and its surroundings are partially occupied by residential areas. This coastal lagoon has undergone environmental degradation due to sewage input and artificial sand bar openings. The temporal and spatial variation of environmental variables and zooplankton were studied monthly for four years. There were five artificial openings of the sand bar during the period of study, mostly in the rainy season. Besides osmotic changes, these events caused the drainage of the water of the lagoon into the sea, loss of total organic nitrogen, and an increase of total phosphorus. The zooplankton community of Imboassica lagoon included freshwater and marine taxa, holoplanktonic, meroplanktonic and nectobenthonic forms. Polychaeta, Bivalvia and Gastropoda larvae, and the taxa of Rotifera Hexarthra spp., Lecane bulla, Synchaeta bicornis, nauplii of Cyclopoida and Calanoida copepods were considered constant taxa. Distinct zooplankton assemblages were found during zooplankton spatial surveys in oligohaline and mesohaline conditions. The successful zooplankton populations were either favored by the disturbance of the sand bar opening, such as the veligers of the gastropod Heleobia australis, or capable of fast recovery after the closing of the sand bar, during the succession from a marine into an oligohaline environment, such as Hexarthra spp.. Such populations seemed well adapted to the stress conditions usually found in the lagoon due to osmotic changes, column mixing, nutrient input, and high fish predation pressure. Rare species in the community, such as Moina minuta, presented population increases all over the lagoon under oligohaline conditions.     

An electrophoretic study of the systematic relationships of some closely related goby species (Pisces, Gobiidae)

An electrophoretic study of genetic variation at 31 loci in each of nine closely related gobiid species was carried out in order to assess their systematic relationships. The species used were: Pomatoschistus canestrinii, P. lozanoi, P. marmoratus, P. microps, P. minutus, P. norvegkus, P. pictus, Knipowitschia caucasica, Neogobius melanostomus. Genetic distances ( D ) and identities ( I ) were calculated by Nei's method for all 36 pairwise comparisons and dendrograms were constructed.
The results show that the very similar and cross-fertile species pair, P. lozanoi and P. minutus , have the highest I value; P. norvegkus has high I values with both species. Pomatoschistus marmoratus and P. microps also display high genetic similarity with each other. The remaining Pomatoschistus species and Knipowitschia caucasica are broadly and moderately equidistant from each other and from the five species refferred to above, while Neogobius melanostomus is considerably more distant from all other species.
These findings essentially agree with the pattern of relationships established using classical taxonomic approaches. However, the observation that Knipowitschia caucasica is as similar to Pomatoschistus spp. as the latter are to each other suggests that the generic distinction of Knipowitschia could usefully be reconsidered.     

Genetic architecture of the marbled goby Pomatoschistus marmoratus (Perciformes, Gobiidae) in the Mediterranean Sea

The marbled goby Pomatoschistus marmoratus, a species inhabiting coastal Mediterranean lagoons, has been studied by measuring its mitochondrial DNA variation. This analysis revealed a Mediterranean west vs east split and, subsequently, an eastern differentiation among the Libyan-Tunisian Gulf, the Adriatic Sea and the Aegean Sea. The high cohesion between the samples collected in the vast area of western Mediterranean contrasts with the genetic mosaic of the more sub-structured eastern Mediterranean. This western homogeneity can not yet be fully explained even if a human-mediated migratory flow, due to a maritime traffic, has been posited. The pattern in the eastern basin revealed a genetic architecture possibly due to the non-migratory habit of the gobid. Within this perspective, the role of the Mediterranean lagoon habitat should be related to how much it amplifies the effects of historical (e.g. past sea-level changes) and environmental (e.g. present-day hydrographic regime) processes as regards the genetic structure of the inhabiting species.     

Environmental variables,habitat discontinuity and life history shaping the genetic structure of Pomatoschistus marmoratus

Coastal lagoons are semi-isolated ecosystems exposed to wide fluctuations of environmental conditions and showing habitat fragmentation. These features may play an important role in separating species into different populations, even at small spatial scales. In this study, we evaluate the concordance between mitochondrial (previous published data) and nuclear data analyzing the genetic variability of Pomatoschistus marmoratus in five localities, inside and outside the Mar Menor coastal lagoon (SE Spain) using eight microsatellites. High genetic diversity and similar levels of allele richness were observed across all loci and localities, although significant genic and genotypic differentiation was found between populations inside and outside the lagoon. In contrast to the F _ST values obtained from previous mitochondrial DNA analyses (control region), the microsatellite data exhibited significant differentiation among samples inside the Mar Menor and between lagoonal and marine samples. This pattern was corroborated using Cavalli-Sforza genetic distances. The habitat fragmentation inside the coastal lagoon and among lagoon and marine localities could be acting as a barrier to gene flow and contributing to the observed genetic structure. Our results from generalized additive models point a significant link between extreme lagoonal environmental conditions (mainly maximum salinity) and P. marmoratus genetic composition. Thereby, these environmental features could be also acting on genetic structure of coastal lagoon populations of P. marmoratus favoring their genetic divergence. The mating strategy of P. marmoratus could be also influencing our results obtained from mitochondrial and nuclear DNA. Therefore, a special consideration must be done in the selection of the DNA markers depending on the reproductive strategy of the species.     

A new species of Pomatoschistus (Teleostei,Gobiidae): the Mediterranean's smallest marine fish

The new sand goby species Pomatoschistus nanus (Teleostei: Gobiidae) is described from the northern coast of the Levantine Sea (eastern Mediterranean Sea) based on both morphological and DNA barcoding data. The new species is the smallest fish in the Mediterranean Sea and may be distinguished from congeners by the following features: predorsal area, first dorsal‐fin base and breast naked; δ‐pore missing; anterior point of the suborbital row b not reaching level of posterior point of suborbital row d; slightly emarginated caudal fin and nape coloration pattern. DNA barcode data clearly discriminate Pomatoschistus spp. in the neighbour‐joining tree with an average of 17·7% interspecific K2P distance. The most closely related taxon to P. nanus sp. nov. is Pomatoschistus bathi and the most distantly related is Pomatoschistus tortonesei with 11·9 and 21·9% K2P distances respectively. Morphometric and genetic data are also provided for Pomatoschistus bathi.     

Weight‐length relationships for five fish species from a temperate coastal lagoon of southern Europe

The weight‐length relationships (WLR) were estimated for five fish species of Ria Formosa, a coastal lagoon in southern Portugal. WLRs for Gobius couchi, Pomatoschistus microps and Parablennius pilicornis were determined for the first time ever and for Gobius cruentatus for the first time for the southern European Atlantic coast.     

Environmental factors influencing the gobiid assemblage of a Mediterranean Lagoon: Empirical evidence from a long-term study

A severe freshwater inflow during our long-term ichthyological study of the brackish Vaccarès lagoon (1993–1998) helped us to assess the impact of sudden environmental changes on the specific biomass composition of the gobiid population and the catches per unit effort of the black goby Gobius niger, the common goby Pomatoschistus microps and the sand goby P. minutus. In 1993, the composition of the Gobiid fish assemblage of the Vaccarès lagoon was dominated by the black goby (63%) and finally evolved to an assemblage dominated by the common goby (80%). The black goby disappeared from the Vaccarès lagoon 2 years after the inflow, whereas catches of the common goby increased significantly after the environmental changes and reached maximum values in 1998. Catches of sand goby did not seem to be affected by environmental changes and depended on the communication between sea and lagoon. This study showed that evolution of an ecosystem after environmental changes is linked to the reaction that species developed to face perturbations.     

Sperm adaptation in relation to salinity in three goby species

In externally fertilizing species, the gametes of both males and females are exposed to the influences of the environment into which they are released. Sperm are sensitive to abiotic factors such as salinity, but they are also affected by biotic factors such as sperm competition. In this study, the authors compared the performance of sperm of three goby species, the painted goby, Pomatoschistus pictus, the two-spotted goby, Pomatoschistus flavescens, and the sand goby, Pomatoschistus minutus. These species differ in their distributions, with painted goby having the narrowest salinity range and sand goby the widest. Moreover, data from paternity show that the two-spotted goby experiences the least sperm competition, whereas in the sand goby sperm competition is ubiquitous. The authors took sperm samples from dissected males and exposed them to high salinity water (31 PSU) representing the North Sea and low salinity water (6 PSU) representing the brackish Baltic Sea Proper. They then used computer-assisted sperm analysis to measure the proportion of motile sperm and sperm swimming speed 10 min and 20 h after sperm activation. The authors found that sperm performance depended on salinity, but there seemed to be no relationship to the species' geographical distribution in relation to salinity range. The species differed in the proportion of motile sperm, but there was no significant decrease in sperm motility during 20 h. The sand goby was the only species with motile sperm after 72 h.     

Seasonal dynamics of genus Alexandrium (potentially toxic dinoflagellate) in the lagoon of Bizerte (North of Tunisia) and controls by the abiotic factors

Some species of the genus Alexandrium are known as potential producers of saxitoxin, a neurotoxin that causes the paralytic shellfish poisoning (PSP) syndrome. Blooming of these species, especially in shellfish farms can affect the aquaculture production and harm human health. Seasonal dynamics of Alexandrium spp. abundance in relationship to environmental factors was investigated from November 2007 to February 2009 at six stations in the Bizerte lagoon, an important shellfish farming area situated in SW Mediterranean. The sampling stations represented different hydrological and trophic conditions: one station TJ (Tinja) is affected by the river plume; two stations (Chaara [Ch] and Canal [Ca]) are influenced by marine inflow (particularly in summer), industrial and urban effluents; and the three other stations (Menzel Abdelrahmen [MA], Menzel Jemil [MJ] and Douaouda [Do]) are located close to shellfish farms. Cell abundance of Alexandrium spp. varied among stations and months. Species of this genus showed a sporadic appearance, but they reached high concentration (0.67-7 × 10(5)cells L(-1)). Maximal cell density was detected in autumn (November 2007; station MA), at salinity of 37.5, temperature of 16 °C and NH(4)(+) level of 55.45 μM. During this month, Alexandrium spp. abundance accounted for a large fraction (61%) of the harmful phytoplankton. The statistical analysis revealed that Alexandrium concentrations were positively correlated with N:P ratio and NH4+ levels. Thus, the eutrophic waters of the lagoon favour the growth of Alexandrium, which seemed to have preference for N-nutrient loading from antrophogenic activities, as ammonium. Blooms of these potential harmful algae may constitute a potential threat in this coastal lagoon of the southern Mediterranean. Consequently, it is necessary to be well vigilant and to do regular monitoring of Alexandrium species.     

Feeding patterns of the dominant benthic and demersal fish community in a temperate estuary

The diet and feeding relationships of the 12 most abundant benthic and demersal fish species of the Mondego Estuary, Portugal, were studied between June 2003 and May 2006. Fishes were caught during the night using a 2 m beam trawl. The stomach contents were analysed for prey identification, counting and weighing. According to prey importance in diets, three main feeding guilds were identified: (1) invertebrate feeders, (2) invertebrate and fish feeders and (3) plankton and invertebrate feeders. Besides these main feeding guilds, some fishes also presented fractions of algae and zooplankton in their stomach contents. The most abundant prey items were macroinvertebrates, with several polychaetes ( Nephtys spp., Capitellidae, Spionidae and Eunicidae), Corophium spp. and Crangon crangon among the dominant prey. Pomatoschistus spp. were the most preyed on fishes. Several fish species showed a tendency for a specialized diet, but almost all also showed some degree of opportunistic feeding by preying on other food resources. High diet overlap was found between some fish species, yet exploitative competition could not be concluded.     

Red List of macrofaunal benthic invertebrates of the Wadden Sea

Parasites were observed in medium- and small-sized fish taken from the discards of a commercial shrimper during seven different cruises in the tidal channels of the North Frisian Wadden Sea (Süderaue, North Sea) from April to September 1991. In total, 442 fish comprising four species (Sprattus sprattus, Hyperoplus lanceolatus, Ammodytes tobianus, Pomatoschistus minutus) were investigated. The parasite fauna consisted of 22 species. The parasite community structure of the 4 hosts was compared. The diet of the hosts seemed to be the main factor determining the structure of the parasite community. Other factors could not be assessed. Eight species of parasites occurred as larval stages. This indicated that fish were intermediate or paratenic hosts in their life cycle. The nematodeHysterothylacium sp. (Anisakidae) and the digeneanCryptocotyle lingua (Heterophyidea) were the dominant parasites, reaching their highest prevalence and density in sprat and sand eel. Sprat and sand eel play a very important role in parasite transmission to predacious fish and seabirds.     

Genetic Divergence Among Marine and Lagoon Atherina boyeri Populations in Greece Using mtDNA Analysis

Genetic differentiation and phylogenetic relationships among 15 Atherina boyeri populations from several marine and lagoon or lake sites in Greece were investigated using mtDNA analysis. PCR-RFLP analysis of 12s, 16s rRNA genes and D-loop revealed 23 haplotypes. All the lake or lagoon populations, as well as the Kymi and Kalymnos populations that originated from sites with lagoonlike environmental conditions, showed haplotypes 1-6, clearly distinguishable from the marine populations, which exhibited types 7-23. The genetic divergence values estimated between the lagoon and the marine populations ranged from 5.55 to 10.45%. The high genetic differentiation observed between these two types of populations is also highlighted by the dendrograms obtained using UPGMA and maximum parsimony methods.     

Life history traits of Pomatoschistus minutus in the Rhône Delta, France

Life history traits and migratory status of the Sand goby Pomatoschistus minutus were investigated in a brackish lagoon of the Rhône river Delta (Mediterranean Sea, south of France).     

The Lagoon at Caroline/Millennium Atoll,Republic of Kiribati: Natural History of a Nearly Pristine Ecosystem

A series of surveys were carried out to characterize the physical and biological parameters of the Millennium Atoll lagoon during a research expedition in April of 2009. Millennium is a remote coral atoll in the Central Pacific belonging to the Republic of Kiribati, and a member of the Southern Line Islands chain. The atoll is among the few remaining coral reef ecosystems that are relatively pristine. The lagoon is highly enclosed, and was characterized by reticulate patch and line reefs throughout the center of the lagoon as well as perimeter reefs around the rim of the atoll. The depth reached a maximum of 33.3 m in the central region of the lagoon, and averaged between 8.8 and 13.7 m in most of the pools. The deepest areas were found to harbor large platforms of Favia matthaii, which presumably provided a base upon which the dominant corals (Acropora spp.) grew to form the reticulate reef structure. The benthic algal communities consisted mainly of crustose coralline algae (CCA), microfilamentous turf algae and isolated patches of Halimeda spp. and Caulerpa spp. Fish species richness in the lagoon was half of that observed on the adjacent fore reef. The lagoon is likely an important nursery habitat for a number of important fisheries species including the blacktip reef shark and Napoleon wrasse, which are heavily exploited elsewhere around the world but were common in the lagoon at Millennium. The lagoon also supports an abundance of giant clams (Tridacna maxima). Millennium lagoon provides an excellent reference of a relatively undisturbed coral atoll. As with most coral reefs around the world, the lagoon communities of Millennium may be threatened by climate change and associated warming, acidification and sea level rise, as well as sporadic local resource exploitation which is difficult to monitor and enforce because of the atoll''s remote location. While the remote nature of Millennium has allowed it to remain one of the few nearly pristine coral reef ecosystems in the world, it is imperative that this ecosystem receives protection so that it may survive for future generations.     

An electrophoretic investigation of populations of Atherina boyeri Risso, 1810 and A. presbyter Cuvier, 1829 (Teleostei: Atherinidae): genetic evidence in support of the two species

The data obtained using electrophoresis strongly support the specific status of Atherina boyeri Risso, 1810 and A. presbyfer Cuvier, 1829, and thuscontradict the recently proposedsynonymyof the two species. Four populations of A. boyeri and six populations of A. presbyter were assayed for 11 enzymes and general protein using muscle and liver extracts. Eight of the 11 enzymes were shown to be polymorphic at the 95% level. Sixteen loci, encoding 40 putative alleles were consistently resolved in all 10 populations.
The two species were fixed for different alleles at the EST-3 locus. At the G3PDH locus. with the exception of two heterozygotes, all individuals of each species were also homozygous for different alleles. At the PGM locus the common allele was unique to each species.
The mean Nei's genetic distance ( ), over all loci, calculated between populations of A. boyeri (= 0.10 ± 0.06); between populations of A. presbyter ( = 0.02 0.02) and between populations of A. boyeri and A. presbyter ( = 0.42 0.09) indicated the separateness of the two species.
UPGMA cluster analysis based on genetic distances produced a dendrogram whose principal dichotomy resulted in the formation of two clusters. The ordination of populations in the UPGMA cluster analysis strongly reflected the geographic distribution of populations in both species.