Invasions of alien gammarid species and retreat of natives in the Vistula Lagoon (Baltic Sea, Poland)

During the last decades of the twentieth century, the alien gammarid species Gammarus tigrinus, Dikerogammarus haemobaphes, Pontogammarus robustoides and Obesogammarus crassus invaded the lower Vistula River and its deltaic, partly brackish regions. In brackish waters of the Vistula Lagoon the native Atlantic-boreal species Gammarus zaddachi and Gammarus duebeni have been replaced or at least outnumbered by the aliens. As compared to our earlier studies, through the years 1998–2004 we could observe nearly total decline of the native gammarid populations along the coasts of the Lagoon, and overdomination of the North-American G. tigrinus in most places. Possible reasons for the observed phenomena are e.g. increasing pollution and eutrophication of the Lagoon accompanied by competition between the native and the alien species.     

Mitochondrial DNA diversity and PCR-based sex determination of Irrawaddy dolphin (<Emphasis Type="Italic">Orcaella</Emphasis><Emphasis Type="Italic">brevirostris</Emphasis>) from Chilika Lagoon,India

Of the only known two Lagoon populations of Irrawaddy dolphins (Orcaella) in the world, one is residing in the Chilika Lagoon in Orissa state, India. In addition to accidental deaths in gill net fishery and mechanized boat operations, there has been exploitation of the species for their oil. Extreme patchy distribution and vulnerability to becoming entangled in fishing gear has made it a focus of conservation concern. Information on genetic diversity of populations has considerable potential for informing conservation plans. The present paper reports the first genetic study of O. brevirostris from Chilika Lagoon based on mtDNA sequencing and PCR-based sex identification from 11 individuals. Control region sequence comparison showed two haplotypes and cytochrome b a single haplotype in the Chilika population of the species. Phylogenetic analysis indicated distinct clades within the Asian samples, with the Indian population showing closest genetic proximity to the haplotypes from Thailand. Sex of the animal was determined by PCR-based method. It is important to continue to examine the population discreteness and genetic variation of Irrawaddy dolphin in Chilika Lagoon vis-à-vis its global geographic distribution for formulating the conservation plans of the species.     

Copepods as the first intermediate hosts of Ligula intestinalis L.: Parasite of bream Abramis brama L. in the Vistula Lagoon of the Baltic Sea

Seven copepod species (potential intermediate hosts of Ligula intestinalis L.) are recorded in the Vistula Lagoon. Megacyclops viridis (Jurine) and Diacyclops bicuspidatus (Claus) are dominant species among the Cyclopoida group and may be the main potential first intermediate host of L. intestinalis. Cytopoidae is unevenly distributed in the lagoon. The parts of the lagoon with high crustacean densities and high levels of bream infestation coincide. The peaks of Cyclopoidae abundance and the highest infestation of the bream by L. intestinalis were recorded in 1998–2000. This study shows that bream infestation in the Vistula Lagoon is directly connected with the presence of freshwater copepods (the first intermediate hosts of L. intestinalis), its abundance, and its spatial distribution over the lagoon area.     

Labidocera aestiva and L. scotti in Tamiahua Lagoon,Veracruz, Mexico

Labidocera aestiva and L. scotti were found in the Tamiahua Lagoon, Veracruz, Mexico. Fleminger (1957) found that the populations of these species may overlap geographically, although L. aestiva has affinity to the Carolinian province and L. scotti to the Caribbean province. This study describes the seasonal behavior and succession of this species in the Tamiahua Lagoon, a brackish water system with a high marine influence. A qualitative and quantitative analysis of samples was made in March, July, and September 1985 and January 1986. L. aestiva was found in temperatures below 26 °C in a wide salinity range. At temperatures above 26 °C and up to 32 °C, L. aestiva was present also with euryhaline character. In the Tamiahua Lagoon these two species did not overlap during this study. Both species are considered temporary inhabitants of this estuarine system in the Western Gulf of Mexico.     

Cytogenetic structure of Chironomus plumosus (L.) (Diptera, Chironomidae) population in regard to the trophic state of the Curonian Lagoon, Baltic Sea

It is shown that the cytogenetic structure of the Chironomus plumosus (L.) population in the Curonian Lagoon has not changed significantly over the last three decades. The existing cytogenetic structure supported not only population survival, but also its proliferation in new environmental conditions caused by an increase of the trophic status of the water body. The predominance of homozygotes pluB2.2 was marked in karyofund. Both the oxygen deficiency periodically occurring in the Curonian Lagoon and the fact that the population dwells at the periphery of the species areal in the Palearctic could be reasons for this phenomenon.     

Ecology and fish catches in natural lakes of Benin,West Africa

Synopsis A preliminary study of the ecology and commercial fish catches was carried out in the Toho-Todougba, Ahouangan and Dati lakes (1500 ha) in southern Benin (West Africa) over a period of 18 consecutive months. Water quality, species richness, and the reproductive biology of the dominant species, Sarotherodon galilaeus, were examined. Unlike Lagoon Toho-Todougba, lakes Ahouangan and Dati are less favourable for fish production because of their high total iron content and their relative low pH. The study revealed the existence of 19 species belonging to eleven (11) families: 16 species in Lagoon Toho-Todougba,12 in Lake Ahouangan, and 7 in Lake Dati. Lakes Ahouangan and Dati had a relatively high faunal similarity whereas Lagoon Toho-Todougba exhibited a relatively low faunal similarity with the former systems. In Lagoon Toho-Todougba, six cichlid species were the most important component of the fishery: Sarotherodon galilaeus, Tilapia guineensis, T. zillii, T. mariae, Chromidotilapia guntheri, Hemichromis fasciatus. Three catfish species Chrysichthys auratus, Clarias agboyiensis, and Clarias lazera were harvested in low abundances. Some other fish, such as Polypterus senegalus senegalus, Protopterus annectens and Heterotis niloticus were captured sporadically, with H. niloticus appearing more consistently in catches than the others. Although not abundant, Gymnarchus niloticus and the African pike, Hepsetus odoe, were almost always present in the catches. Ctenopoma kingsleyae appeared only in Ahouangan. Some predatory species, such as Notopterus afer and Xenomystus nigri, are encountered only in lakes Ahouangan and Dati. In Lagoon Toho-Todougba, Sarotherodon galilaeus had a sex ratio (: ) of 0.49:1, and size at maturation was estimated as 12.3 cm TL. The spawning period extended from May to September with the peak occurring in July. Fecundity was correlated to log-body length (r = 0.74) and log-body weight (r = 0.76). Fish catches were estimated at 389 kg ha^–1 year^–1; about 73% of which was Sarotherodon galilaeus. The overexploitation of juvenile fish and the use of this lagoon for the irrigation of palm tree plantations have reduced fish recruitment and mean size.     

Population dynamics of alien gammarid species in the River Odra estuary

During the period of 1988–2000, three alien gammarid species, i.e. Gammarus tigrinus Sexton, 1939, Pontogammarus robustoides G. O. Sars, 1894, and Dikerogammarus haemobaphes (Eichwald, 1841) were recorded in the Odra estuary. This study, the first record of G. tigrinus and P. robustoides in Poland, focuses on the distribution, abundance, and biomass as well as on population structure of the three new species found in the coastal zone of the estuary. G. tigrinus and P. robustoides were first sampled in the Szczecin Lagoon (mid-part of the estuary) in 1988. The densities of both species were high from the time they were first recorded and exceeded 10 000 ind. m^–2, while the biomass was 25 and 140 g m^–2, respectively. G.tigrinus occurred at higher densities in northern and eastern parts of the Lagoon, while P. robustoides was particularly abundant in the south-eastern part, most heavily affected by River Odra discharge. In 1999, the third gammarid, D. haemobaphes, was recorded in the southern part of the estuary. Both in 1999 and 2000, the species was found in qualitative samples (dredge collections of Dreissena polymorpha) taken from the western branch of the river. As estimated from quantitative samples, densities and biomass in the eastern branch were rather low and did not exceed 150 ind. m^–2 and 2.7 g m^–2, respectively. The Szczecin Lagoon population of G. tigrinus produces at least two generations within a year: a summer one and an overwintering one. The latter is dominated by older and larger specimens. The species may reproduce in the Lagoon from April until November.     

The influence of rainfall variability on the species composition of a northern California salt marsh plant assemblage

Natural variability in the species composition of salt marsh plant assemblage was studied for 4 years (1986–90) at Bolinas Lagoon, California (USA). The study was conducted during a period in which little or no physical disturbance occurred in the marsh. During the study, Bolinas Lagoon experienced highly variable rainfall, both within and between years. In years with average or below average winter and spring rainfall, the cover of Salicornia virginica increased relative to that of the other species. During the one year with much higher than average spring rainfall, the cover of Salicornia declined and rare species increased in relative abundance. These patterns suggest that under typical marsh conditions, the plant assemblage experiences stress due to low availability of freshwater and high soil salinity. Under such conditions, the stress-tolerant Salicornia dominates the assemblage. If, however, there is abundant rainfall early in the growing season, the other species are released from stress and are able to increase in cover. The marsh of Bolinas Lagoon appears to be resistant to change and able to tolerate stress. Few studies have examined natural variability in species in undisturbed marshes and more of such studies must be made in order to understand whether or not marshes are in general resistant to change caused by rainfall variability.Abbreviations MLLW = mean lower low water     

Intralocality Variation in Feeding Biomechanics and Prey Use in Archosargus probatocephalus (Teleostei,Sparidae), with Implications for the Ecomorphology of Fishes

Archosargus probatocephalusin a Florida estuary was investigated to explore intraspecific variation in prey utilization and jaw biomechanics. Volumetric contribution of major prey types and seven biomechanical features of the oral jaws that characterize prey-capture and processing performance were contrasted between two locations within the estuary. At Mosquito Lagoon, where A. probatocephalusinhabited mostly oyster beds, mangroves and salt marshes, fish consumed mostly thick-shelled bivalves, gastropods, crabs, and tubiculous polychaetes and amphipods. In contrast, conspecifics at Indian River Lagoon that inhabited mostly seagrass beds and algal turf consumed predominantly algae, seagrass, epiphytic invertebrates and small bivalves and gastropods. Difference in magnitude of durophagy between locations was associated with differences in oral-jaw biomechanics. Analyses of covariance indicated that A. probatocephalusat Mosquito Lagoon had more massive jaw muscles and bones, than conspecifics at Indian River Lagoon. Variations in lever ratios for jaw-opening and jaw-closing between locations were not significant. It is hypothesized that intralocality differences in food habits have induced the development of feeding morphologies that enhance the ability of A. probatocephalusto successfully exploit locally dominant prey resources within the estuary. Plasticity of the feeding mechanism of A. probatocephalusmay buffer the species from the adverse effects of settling on heterogeneous habitats that contain variable prey resources such as those found within estuaries.     

A Guide to Tropical Freshwater Zooplankton

The levels of Cu, Fe and Zn in water, sediment and Cynothrissa mento, a commercially important fish species, were investigated from April 2007 to March 2008 at three sites in Ologe Lagoon. Metal levels in the water column and C. mento were lower than the FAO/WHO drinking water and food safety limits. In most cases, metal concentrations were highest during the dry season and lowest in the wet season. Metal concentrations in sediment and C. mento varied significantly among the sampling stations, but in the water column only the levels of Fe and Zn differed significantly between stations. Concentrations of metals in C. mento were significantly affected by wet and dry seasons. The metal concentrations in Ologe Lagoon were lower than the values reported in some Nigerian water bodies. While the Ologe Lagoon system contains the heavy metals studied, their levels in the water, sediment and fish are still within acceptable limits.     

5. OBSERVATIONS FROM TRANSVAAL,NATAL, AND SOUTHERN RHODESIA

Pringle, J. S. &; Cooper, J. 1975. The Palaearctic wader population of Langebaan Lagoon. Ostrich 46:213-218.

Monthly counts of Palaearctic waders were made at high tide in three areas of Langebaan Lagoon, southwestern Cape, during 1973 and 1974. A total of sixteen species was observed. The five commonest species, in order of abundance, were Curlew Sandpiper Calidris ferruginea, Grey Plover Squalarola squatarola, Turnstone Arenaria interpres, Knot C. canutus and Sanderling C. alba. Together they formed 95,7% of the population counted. Waders arrived in September and departed in March and April. Overwintering populations of the commoner species were observed. Estimates of the total population size of the lagoon were 41 000–55 000 in summer and 10 500 in winter. These figures are of value for nature conservation and show that the lagoon is a wetland of international importance.     

Long-term studies on sex and size structures of the non-native crab Eriocheir sinensis from Polish coastal waters

The Chinese mitten crab Eriocheir sinensis is a non-native species that appeared in European waters more than 100 years ago. Size and sex structure as well as biological condition of populations of Eriocheir sinensis sampled annually between 1999–2014 from the eastern Baltic Sea coast (1999–2007 Gulf of Gdansk and 2008–2014 Vistula Lagoon, Poland) were analysed. Males were dominant over females, with a sex ratio of 1.6:1. Carapace width of all collected specimens (n?=?467) ranged from 33.3 to 89.1?mm and the mean values for specimens from Gulf of Gdansk and Vistula Lagoon were 62.4?±?8.1?mm (n?=?171) and 66.6?±?7.7?mm (n?=?296) respectively. There were no statistically significant differences in carapace width between males and females. It is important to note that there were no individuals with a carapace width less than 30?mm, which may indicate a lack of an established population of this species from the eastern Polish coast. The wet weight of all specimens ranged from 30.9 to 321.9?g and the mean values for all specimens from the Gulf of Gdansk and the Vistula Lagoon were 119.4?±?45.2?g (n?=?101) and 141.8?±?47.9?g (n?=?223), respectively. The wet weight of an individual was significantly correlated to carapace width and the exponent b reaching values close to 3 may indicate their good condition.     

Juvenile migration of the exclusively pelagic cyprinid,Gnathopogon caerulescens (Honmoroko) in Lake Biwa,Central Japan

Migration of wild and cultivated juvenile honmoroko Gnathopogon caerulescens of from the spawning and nursery areas in Lake Biwa were investigated, both in the Ibanaiko Lagoon and its outlet to Daido River, using beam‐trawl surveys in 2013 and 2014. The study demonstrated migration of G. caerulescens from a nursery lagoon toward Lake Biwa after the juvenile stage. These findings appear to be the first direct evidence for migration of an exclusively pelagic cyprinid species from a littoral nursery to a pelagic adult habitat in a large deep lake.     

Structure and diversity of fishes in a freshwater and coastal subtropical lagoon

This study examined the fish communities of Peri Lagoon in southern Brazil to aid in the development of an effective management plan because the area is under threat from human activities. Sampling of fish fauna, ichthyoplankton and limnological data were compared between sites, differing by habitat type and characteristics such as depth, substratum composition and vegetation type. Results were significantly related to site, with the highest diversity and abundance recorded at shallow vegetated sites. A total of 14 fish species were recorded throughout the lagoon, with the most abundant being Hyphessobrycon luetkenii. Of the 14 species, half were sampled at their larval stage, suggesting a healthy and protected system. Significantly more larvae and eggs were collected during colder months (autumn to winter) and at sites closer to stream flow, possibly owing to increased food sources and habitat protection. This study highlights the importance of Peri Lagoon as a nursery ground for a wide range of fish species, providing essential information for incorporation into the future protection of fish stocks throughout Brazil.     

Population dynamics of potentially harmful algal blooms in Bizerte Lagoon,Tunisia

The population dynamics of potentially harmful phytoplankton in the semi-closed, coastal Bizerte Lagoon, Tunisia, in the south-western Mediterranean, were examined from November 2007 to February 2009 at six sampling stations, three situated in areas of mussel and oyster farming. The harmful species monitored included the potential producers of amnesic shellfish poisoning (Pseudo-nitzschia spp.), paralytic shellfish poisoning (Alexandrium spp.), diarrheic shellfish poisoning (Dinophysis spp. and Prorocentrum spp.), ichthyotoxins (Cochlodinium polykrikoides, Akashiwo sanguinea and Karenia mikimotoi), yessotoxins (Gonyaulax spinifera) and the discolouration of water (Neoceratium lineatum and Protoperidinium sp.). These were numerically dominated by potentially toxic species of the diatom genus Pseudo-nitzschia, which were present year-round at all stations. Prorocentrum spp., Dinophysis spp. and Neoceratium lineatum were the most abundant and recurrent harmful dinoflagellates, exhibiting their highest densities at the shellfish farming stations. Alexandrium spp. bloomed only on one occasion, reaching its highest densities at a shellfish farming station. Canonical correspondence analyses revealed significant relationships between the harmful phytoplankton species monitored and the environmental conditions. The widespread distribution of harmful phytoplankton in Bizerte Lagoon, with the permanent presence of Pseudo-nitzschia spp. and the high frequency of dinoflagellate blooms in the shellfish areas, suggests a potential risk of shellfish poisoning events in the region.     

Bottom Communities of Nyivo Lagoon (Northeastern Sakhalin)

Clasterization of benthic stations by biomass of common species using an index of coenotic similarities allowed us to distinguish three communities of macrophytobenthos (Zostera marina + Z. japonica, Zostera japonica, and Potamogeton pectinatus) and eight macrozoobenthos communities (Macoma balthica, Limnodrilus hoffmeisteri + Anisogammarus tiuschovi, Spio filicornis + Archaeomysis grebnitzkii, Kamaka kuthae, Glyptotendipes paripes, Neomysis awatschensis + Dolielinotus moskvitini, Neomysis mirabilis, and Anisogammarus tiuschovi + Littorina sitkana + Crangon septemspinosa). The bulk of the bottom surface is occupied by a community of Zostera marina + Macoma balthica with the mean biomass of the dominating species reaching 0.3–1386.6 and 573.9 g/m², respectively. Specific geomorphologic and hydrologic features, as well as the presence of many estuarine areas in Nyivo Lagoon, provide conditions for numerous different fresh-and brackish water communities and variations of them. However, bottom communities cannot be clearly separated into mostly freshwater and mostly brackish communities, which is the case for Pil'tun Lagoon, a well studied lagoon in eastern Sakhalin. Several decades of timber rafting in the Tym' River has had a significant effect on bottom biota and the communities of Nyivo Lagoon. Considering the well-known negative effects of phenol and its derivatives on benthic biota and communities derived during timber decomposition, the sources of pollution of the natural environment in the lagoons of eastern Sakhalin must be evaluated and differentiated.     

Temporal variability of the ichthyofauna in a Northern Aegean coastal lagoon (Greece). Influence of environmental factors

The ichtyofauna of the Porto-Lagos Lagoon in northern Greece was sampled over 17 months, using a bag-seine net, to investigate factors influencing species seasonal composition and abundance. Of the 35 resident, migrant and straggler species caught, representing 22 families, the most numerically dominant species were Atherina boyeri (46.4% of total catch), which today is the most economically important species, followed by Pomatoschistus marmoratus (28% of total catch) and Aphanius fasciatus (9.1% of total catch). Mugilidae and Sparidae were the most diverse families. According to various diversity indices, the lagoon’s ichthyofauna was found to be most diverse in May 1990; taxonomic spread however, as shown by the taxonomic distinctness index (Δ*), was lowest in July 1990, when the greatest monthly water temperature range was observed (13.5 °C). Overall fish relative abundance was positively correlated with the maximum monthly water temperature (r²=0.32, p < 0.05). The NMDS and cluster analysis performed on the bag seine catches showed four groupings, based mainly on the life history of the species. The main group consisted of all the resident species of the lagoon and four mugilid species that were present throughout most of the sampling period. The second group consisted of marine migrant species that spent a short period of their life in the lagoon. Marine migrants and one marine straggler that were found once or twice formed the third group, while the fourth group consisted of species with casual presence. The importance of Porto-Lagos Lagoon as nursery and feeding area for marine species was confirmed by the catch of young individuals of several marine species.     

The occurrence of potentially toxic dinoflagellates and diatoms in a subtropical lagoon, the Indian River Lagoon, Florida, USA

The occurrence of potentially toxic phytoplankton species was examined over a 5-year period in a region of the Indian River Lagoon in Florida that has recently been subject to ecologically significant events, putatively related to algal toxins. The results of the study reveal a significant presence of two species of phytoplankton that have been shown to be toxic in Florida or other regions of world, the dinoflagellate Pyrodinium bahamense var. bahamense and the diatom Pseudo-nitzschia pseudodelicatissima. Concentrations of the former species reached 638,000 cells l⁻¹ and concentrations of the latter reached 23.9 million cells l⁻¹. In addition, the abundance of one of these species, P. bahamense var. bahamense appears to have increased over the 5-year study period from 1997 to 2002. It may be hypothesized that rainfall events following a regional drought period resulted in a flushing of bioavailable phosphorus and nitrogen into the Indian River Lagoon that stimulated P. bahamense var. bahamense blooms. The significance of these results is discussed within the context of the ecology of this flow-restricted lagoon.     

Length–weight relationships of three estuarine species in the Comacchio Lagoon,Po River delta,Italy

The length–weight relationships (LWRs) for three native fish species of the Comacchio Lagoon (northwestern Adriatic Sea, Italy) were determined. The species Zosterisessor ophiocephalus (Pallas, 1814), Pomatoschistus canestrini (Ninni, 1883) and Knipowitschia panizzae (Verga, 1841), were sampled monthly from 2010 to 2014. Both P. canestrini and K. panizzae are listed as protected species in the Habitat Directive and the Berne Convention and there is no information on their LWRs in FishBase.     

DIVERSITY AND MORPHOLOGY OF SKELETONEMA SPECIES IN SOUTHERN BRAZIL,SOUTHWESTERN ATLANTIC OCEAN1

We examined the morphology of Skeletonema species occurring in coastal waters of southern Brazil, on the basis of LM, SEM, and TEM analyses of six isolated strains and of 13 field samples from the Patos Lagoon estuary and the adjacent Cassino Beach. We concluded that the genus Skeletonema is highly diverse in coastal waters of southern Brazil, with the occurrence of four confirmed species: S. costatum, S. pseudocostatum, S. potamos, and S. tropicum. In addition, EM details must still be provided for S. menzelii, and genetic studies should be conducted to confirm the identity of S. cf. grethae and S. subsalsum. The high diversity in this geographic area can be attributed to the proximity of the Subtropical Convergence and to the freshwater ecosystems of Patos Lagoon and La Plata River that favor the presence of warm‐, cold‐, and brackish‐water species.