Brackish Water Fish Research Articles

Hepatic microsporidiosis of mudskipper, Boleophthalmus dussumieri Valenciennes, 1837 (Perciformes: Gobiidae), due to Microgemma sp.

The present study reports a case of hepatic microsporidiosis caused by Microgemma sp. in brackishwater fish, Boleophthalmus dussumieri (Valenciennes, 1837) (n = 60), from thewest coast of India. An eight-month study from September 2017 to April 2018 revealed a prevalence of 11.7% for this parasite. The microsporidian showed tissue-specific infection and did not reveal any gross pathology in infected fish. Small whitish cysts containing microspores of size 0.3-0.5mm were observed in the liver of fish. The range of pyriform microsporidian spore size varied from 2.9-3.77×1.85-2.67µm. Scanning electron microscopy of the spores showed a distinct groove on the anterior end of the spore for polar tube extrusion. Polymerase chain reaction (PCR) amplification of the DNA extracted from the microsporidian-infected liver tissue using primers targeting small ribosomal subunit DNA (SSU rDNA) yielded ~ 1340bp amplicon and the genetic distance analysis showed a 0.2% variation with the reported M. tilanpasiri. Accordingly, in the phylogenetic tree, the present species of Microgemma clustered with M. tilanpasiri. Even though, the morphomeristic characters of the present Microgemma sp. was marginally different from the reported M. tilanpsasiri; the SSU rDNA showed considerably higher similarity with M. tilanpasiri. Thus, we report the species of Microgemma as Microgemma aff. tilanpasiri from a new host. This is the first report of a microsporidian from B. dussumieri and the first record of the genus Microgemma from India.

COMPARISON OF GROWTH RATE OF THREE CATFISH (Pangasius Hypopthalmus) WITH DIFFERENT KINDS OF FEED

<p>Feed is one factor that can support the development of fish farming is intensive and semi-intensive, both freshwater fish, brackish water fish, and sea water fish. While the feed required by the fish since the start of the size of the larvae (fry), up to the size of the parent. However, the feeding of the fish also can be creation to maximize growth. Fish growth is strongly influenced by the quality of the feed and therefore the need to do research, causes of a different kind of feed to seed the growth hormone of catfish. Here the research I did was observe the ratio of the growth rate of catfish that I give a different feed types among which the pellets, the remains of fish and leaves. The research of method used in this study is a quantitative method that is located in the home. And the observation time that I did was for 9 weeks. It turned out that the results shown by the fastest growth in the given fish feed pellets.</p>

Fish environmental RNA enables precise ecological surveys with high positive predictivity

Metabarcoding analysis using environmental DNA (eDNA) is increasingly being used for monitoring biota. However, knowledge regarding abundance of fish environmental RNA (eRNA) and its utility in ecological survey is limited. In this study, we aimed to perform eDNA/eRNA metabarcoding analyses of fishes using water samples from rivers in Japan. Sufficient amounts of eRNA from various species were present in the environmental water samples, which can support ecological survey based on eRNA metabarcoding. The sensitivity of eRNA was equivalent to that of eDNA; however, its positive predictivity was superior to that of eDNA. In addition, correlation with abundance in the ecological survey was higher for eRNA than for eDNA. Only eRNA (and the ratio of eRNA and eDNA) enabled distinguishing saltwater or brackish water fishes (false positives) that could be generated due to contamination from domestic wastewater containing their corpses or body parts or from bird feces. To the best of our knowledge, this is the first report of the possibility of eRNA to serve as a critical indicator of living biotic assemblages that actually inhabit sampling points.

Probiotics in Brackish Water Fish Farming: A Special Focus on Encapsulated Probiotics

In GMOs' age, pesticides, contaminants, and other anthropogenic practices move towards an environmentally sustainable solution. Aquaculture is one of the fastest-growing food sources connected with several challenges. Aquaculture industries are required to produce food with a better state of health and environmentally friendly. The encapsulation of probiotics in the aquatic feed addresses various problems as many probiotic organisms are shown to strengthen immunity, improve growth, survival, and reproduction of many fish species, including brackish water fish. By including certain probiotics as a food additive, the well-being of aquatic organisms can be enhanced. This review summarizes probiotics' inclusion in an encapsulated form in aquatic feed formulation for enhancing brackish water fish culture.

Prevalence of Vibrio mimicus in Fish, Fishery Products, and Environment of South West Coast of Kerala, India.

Vibrio mimicus is a seafood-borne bacterium involved in incidences of human infections following consumption of raw or undercooked seafood. Regular monitoring of seafood for V.mimicus is necessary for risk assessment and to establish mitigation measures. During the period 2017-2020, a total of 250 samples comprising finfish, shellfish, water, ice, and sediment samples were collected from fish markets, fish landing centers, and fish farms in the Ernakulum district on the Southwest coast of Kerala, India. V. mimicus was isolated using enrichment in alkaline peptone water for 18 h followed by plating on thiosulfate citrate bile salts sucrose agar and then incubated at 37°C for 18-24 h. The presumptive V. mimicus isolates were confirmed by biochemical characterization and molecularly with vmh gene-specific for V. mimicus. The study revealed that the prevalence of V. mimicus is 5.6% in the total of samples screened. The highest occurrence was observed in brackish water fish (19%) followed by freshwater fish (18%) and marine fish (2%) samples. The study points out the risk of brackish water fishes as potential carriers of this pathogen. This requires preventive measures to mitigate health hazards associated with V. mimicus entering into the seafood production chain.

Susceptibility of orange chromide, Etroplus maculatus (Bloch, 1795) to experimental infection of Betanodavirus

Viral nervous necrosis (VNN), or viral encephalopathy and retinopathy caused by nervous necrosis virus (NNV), is an acute viral disease of fish, resulting in high mortality globally in cultured marine fish. The pathogen, Betanodavirus belonging to the family Nodaviridae, has been widely documented in both farmed and wild fish, besides in invertebrate species across the habitat barriers. However, cichlid fish, in particular Etroplus species, have a low susceptibility or resistance to this disease. The present study was undertaken to check the susceptibility of a brackishwater cichlid, orange chromide (Etroplus maculatus) through intramuscular injection and immersion challenge by NNV (RGNNV genotype). Intramuscular injection (10 μl) with NNV (105 viral particles ml−1) resulted in cumulative mortality of 50% at 15 days of post-infection (dpi), while immersion challenge in NNV spiked sea water (105 TCID50 ml−1) resulting in a mortality of 25% at 19 dpi. Unlike many marine fish which showed 100% mortality within 3–5 days, E. maculatus challenged through both the routes exhibited severe clinical symptoms for 2–3 weeks followed by a recovery stage and moderate level of mortality. Reverse transcription polymerase chain reaction (RT-PCR) tests on live fish sampled during the course of the experiment and the dead fish exhibiting symptoms in both challenge groups tested NNV-positive. Histological examination of fish in challenged groups showed VNN-specific lesions characterized by vacuolations in the brain and eye with more severe lesions in the injected group than the immersion group. In survived fish, no clinical sign was observed, but NNV could be detected by RT-PCR with moderate to severe vacuolations in the brain and eyes until 30 dpi. Despite the virus entering the body and triggering typical symptoms of VNN, the fish appeared to exhibit moderate resistance with a survival of 50–75%. The results indicate that E. maculatus could serve as a brackishwater fish model to study host-pathogen interaction and development of resistance for potential application in NNV-vaccine studies.

Biomethane Potential of Sludges from a Brackish Water Fish Hatchery

The development of intensive aquaculture is facing the challenge of the sustainable management of effluents. The reproductive sectors (i.e., hatcheries) mainly use water recirculation systems (RAS), which discharge a portion of wastewater. Anaerobic digestion (AD) could reduce the environmental impact of this waste stream while producing biogas. The study is focused on the biochemical methane potential (BMP) of brackish fish hatchery sludges. Wastewater was concentrated by microfiltration and sedimentation and thickened sludges were treated in a BMP system with different inoculum/substrate (I/S) volatile solids ratios (from 50:1 to no inoculum). The highest I/S ratio showed the highest BMP (564.2 NmL CH4/g VS), while different I/S ratios showed a decreasing trend (319.4 and 127.7 NmL CH4/g VS, for I/S = 30 and I/S = 3). In absence of inoculum BMP resulted of 62.2 NmL CH4/g VS. The kinetic analysis (modified Gompertz model) showed a good correlation with the experimental data, but with a long lag-phase duration (from 14.0 to 5.5 days) in particular with the highest I/S. AD applied to brackish water sludges can be a promising treatment with interesting methane productions. For a continuous, full-scale application further investigation on biomass adaptation to salinity and on retention times is needed. Further experimental tests are ongoing.

Following the Mangroves: diversification in the banded lampeye Aplocheilichthys spilauchen (Duméril, 1861) (Cyprinodontiformes: Procatopodidae) along the Atlantic coast of Africa.

Available ecological information, an extensive distributional range, conflicting osteological data, and a proposed early Miocene origin provide the impetus for the present study which investigates genetic structuring, biogeographic, and phylogenetic relationships within the Aplocheilichthys spilauchen lineage. Through the analysis of the mitochondrial gene COI, species delimitation methods (ABGD, GB, GMYC, bPTP) were applied, recognizing 6–7 OTUs with absolute pairwise genetic distances ranging between 8 and 22%. The onset of diversification is estimated to be within the middle Miocene and both dispersal and vicariance-shaped A. spilauchen diversity and distribution, as suggested by time-calibrated and ancestral range reconstruction (S-DIVA) analyses. We report for the first time, a pattern of diversification within a lineage of brackish water fish that is concordant with the historical distribution of coastal mangroves forests, shaped by a series of historical events that likely affected forest cover since the middle Miocene (e.g. major climate shifts and sea-level fluctuations, onset of the modern Congo River outlet, increased volcanism in the Cameroon Volcanic Line).Supplementary informationThe online version of this article (doi:10.1007/s10750-020-04497-3) contains supplementary material, which is available to authorized users.

Spatio-temporal and host-dependent variations in prevalence and intensity of heterophyid (Digenea: Heterophyidae) metacercariae infection in brackishwater and freshwater fishes: a comparative study.

Studies on distribution of parasites are important to reveal the ecology of host-parasites interactions. The objective of the study was to compare the variations in heterophyid encysted metacercariae (EMC) infection in freshwater and brackishwater fish hosts and variation in parasitological descriptors of metacercariae infection during different seasons. The status of infection with heterophyid EMCs in the second intermediate host fishes from brackishand freshwater resources was investigated. Seasonal changes in the occurrence of EMCs in different fish hosts were monitored in a longitudinal field survey lasting 12 months from June 2018 to May 2019. Distribution of heterophyid EMCs was found varied in freshwater and brackishwater fishes with higher prevalence in brackishwater fish. There was a distinct seasonal trend in the prevalence of infection for all heterophyid EMCs in the brackishwater fish examined with high burden during summer. Thus variations in parasitic infection among hosts underpin the importance of parasites as an evolutionary or ecological force.

Consumer trend and fish distribution in fish markets in Batticaloa district, Eastern Sri Lanka

Fish distribution and consumption trends are varied among the people in Sri Lanka. A market and consumer study was conducted to identify the distribution of different fish species in the markets of the district. Moreover a pre-tested questionnaire was employed to collect information on fish consumption behavior and social and cultural factors influencing on fish consumption. Following the purposive sampling technique information were collected from 200 people who came to purchase fish from fish outlets. Results showed that 85% of the respondents consume fish as their major protein food and 25% people consumed fish for health purpose. However, all respondents mentioned that fish availability and distribution was the major constraints for consumption of their preferred type of fish. Among the respondents in urban area, approximately 45% of the respondents preferred seashore fishes (family: clupidae) and 40% preferred reef fishes (family:carangidae) and 15% consume fresh water fishes (family:cichlidae), but consumption depends on the availability of fish in the respective area and socio economical factors. Distribution of fish in markets showed variation in rural and urban markets. In this line, Shore fish and rock fishes have been distributed in 75% of the outlets in urban markets and 25% outlets had the brackish and fresh water fishes while in rural markets distribution of seafishes as 25% and 75% was brackish and fresh water fishes.

First confirmed record of an established population of green swordtail (Xiphophorus hellerii Heckel, 1848) in Europe

The green swordtail (Xiphophorus hellerii) is a freshwater and brackish water fish native to North and Central America. It experiences wide human-traced introduction around the world, mostly due to aquarium release. Individuals of the green swordtail population from the warm spring with artificial origin located in Asparuhovo district, Bulgaria, were collected. The invasiveness screening tool for non-native freshwater fishes (FISK v2) calibrated for the Balkan region was used to assess potential invasion risk of the green swordtail to the coastal freshwater bodies of the Eastern Balkans. This study is the first confirmation on an existing self-sustained population of X. hellerii in Bulgaria and respectively in Europe. Climate change and the trend of warmer winters are prerequisites for the acclimatization of this species to the temperature out of the studied thermal spring. Therefore, the potential of the green swordtail to colonise new habitats is increasing with such facilitated acclimatization. We conclude that the green swordtail poses a high risk to become the next new invasive species in Southern Europe.

Seasonal abundance and diversity of finfish in a tropical estuary, Karwar, southwest coast of India

The spatial and seasonal variability in finfish availability in the tropical Kali Estuary, in Karwar was studied from January 2017- May 2019 at three stations. A total of 26 species belonging to 9 orders and 20 families were recorded from the Kali Estuary and the order Perciformes with 16 species dominated the group (62%) followed by order Mugilliformes and Pleuronectiformes (8%). Maximum abundance was observed during the pre-monsoon season in all the stations. Excluding Ambassis ambassis which was abundant in all the stations, Caranx ignobilis dominated in all the stations. Truly marine and estuarine species of fishes recorded dominated than the freshwater estuarine ones like Etroplus suratensis, Scatophagus argus, Aplocheilus lineatus. Number of species recorded at each station during the study ranged from 11 to 25 and it was significantly different between stations. The Shannon- Wiener diversity index ranged from 2.0 to 4.6, the minimum in station 1 and maximum in station 3. The seasonal analysis of diversity also showed minimum value during the monsoon season in station 1 and maximum value in station 3. The minimum value (2.2) of Margalef richness index was also recorded in Station 1 during monsoon season and maximum value (4.2) in Station 2. When comparing the relative abundance using Pielou’s evenness index (J’) the values were in the range of 0.92 to 0.99 which was closer to one, indicating evenness in distribution. There was similarity in species composition according to different seasons except for monsoon season in Station 1. The same pattern was also evident in the MDS plot where seasonal aggregation was observed between the stations. In addition to the diversity studies, the surveys also threw light on the abundance and seasonality of candidate species suitable for mariculture like C. ignobilis, Lutjanus spp., Etroplus spp., etc. Judicious exploitation of the species could help brackishwater fish farmers.

Some Spirurid Nematodes (Spirurida) from Freshwater and Brackish-Water Fishes in Okinawa Prefecture, Japan, with Descriptions of Two New Species.

Despite the fact that Okinawa Prefecture represents a very interesting subtropical region of Japan, its fauna of nematodes parasitizing fishes is still little-known. Therefore, new data are needed to recognize the species composition of these parasites in this zoogeographically remarkable region. Helminthological examinations of some freshwater and brackish-water fishes in Okinawa Prefecture carried out in the years 2010, 2016 and 2018, revealed two new and four insufficiently known species of spirurid nematodes (Spirurida), all gastrointestinal parasites. These were studied with the use of light and scanning electron microscopy. All nematode species recorded are described: Rhabdochonidae: Rhabdochona honshuensis Moravec et Nagasawa, 1989 from Glossogobius celebius (Valenciennes) (Gobiidae, Perciformes) (new host), Rhabdochona iriomotensis sp. nov. from Ophieleotris sp. (Eleotridae, Perciformes) and Rhabdochona sp. (only females) from Eleotris acanthopoma Bleeker and E. fusca (Forster) (both Eleotridae, Perciformes); Cystidicolidae: Spinitectus mirabilis sp. nov. from Kuhlia rupestris (Lacepède) (Kuhliidae, Perciformes) and Spinitectus sp. larvae from E. acanthopoma; and Camallanidae: Procamallanus (Spirocamallanus) sp. (fourth-stage larva) from Yongeichthys criniger (Valenciennes) (Gobiidae, Perciformes). Rhabdochona iriomotensis sp. nov. is very similar to R. honshuensis, but differs from it in the presence of well-developed ventral precloacal ridges. Spinitectus mirabilis sp. nov. differs from its congeners and all other cystidicolids in having eggs provided with both lateral swellings and polar filaments. In addition to the discovery of two new nematode species, Rhabdochona iriomotensis sp. nov. and Spinitectus mirabilis sp. nov., the findings of all other species represent new host and geographical records. Rhabdochona denudata honshuensis Moravec et Nagasawa, 1989 is elevated to the level of an independent species R. honshuensis.

Stable isotopic analysis of stuffed specimens revealed the feeding habits of Oriental Storks Ciconia boyciana in Japan before their extinction in the wild

By 1971, the breeding populations of the oriental stork Ciconia boyciana in Japan had become extinct in wild. After long-term conservation efforts and breeding projects, Oriental Storks have been continuously reintroduced to the Toyooka Basin, their final habitat, since 2005. The restoration of shallow wetlands in river areas and paddy fields is urgently needed in the Toyooka Basin, because these areas represent the major foraging habitats for reintroduced Oriental Storks. However, limited information is available on their feeding habits prior to extinction in the wild and, thus, it is difficult to plan specific restoration targets for these foraging habitats. In the present study, we used stable isotopic analysis to compare the nutritional status of the reintroduced populations with that of the extinct populations using preserved (stuffed) specimens. The δ15N values in the extinct populations were higher than those of the reintroduced populations. The diet proportions of the extinct populations were calculated to be equally comprised of five prey items (brackish water fish, freshwater fish, amphibians, insects, and crustaceans), while the contribution of insects was remarkably higher than that of the other prey items in the reintroduced populations. We suggest that these stable isotopic trends and diet proportions reflect a decline in the trophic level of the reintroduced populations owing to the reduced prevalence of high-nutrient prey animals caused by the loss of healthy wetlands after the 1960s in the Toyooka Basin. To increase the abundance and diversity of natural prey species available to the reintroduced Oriental Storks in the Toyooka Basin, more eco-friendly paddy fields and restored wetlands are required in the current paddy and river areas, which would secure the continuity of these wetlands from sea areas to paddy areas using fishways. However, the sampling size of the extinct populations was limited and information about historical baseline changes in prey items was insufficient. Therefore, new approaches using reintroduced populations are required to plan future reintroduction projects for Oriental Storks.

Penyuluhan Teknologi Pembenihan Ikan Bandeng Untuk Mendorong Kemandirian Produksi Benih Ikan Bandeng Di Kabupaten Bima Provinsi Nusa Tenggara Barat

Milkfish (Chanos chanos Forskal) is one of the high economic value of brackish water fish and it has become the main commodity of brackish water fisheries for Bima Regency. Bima Bay was the center of milkfish production in Bima Regency with a pond area of around 1,612.16 Ha. Fishponds were spread in 3 (three) districts, namely Bolo sub-district covering 759.95 Ha, Woha sub-district covering 765.82 Ha, and Palibelo sub-district covering 86.39 Ha. As many as 11.41% of the total area of ponds used for milkfish enlargement throughout the year, while 88.59% used for milkfish enlargement and salt production alternately. The area of a pond was about 0.25-0.65 Ha using a stocking density of 4.000-6.000 milkfish fry/pond. The number of seeds needed for the Bima bay area was around 27.4 million per year. Even though milkfish hatchery technology has developed, the technology is not yet understood by milkfish farmers. Therefore, extension activities need to be carried out with the aim of increasing public understanding of seedling and quality of seedlings produced so that the independence of seed production in the future can be realized. Aquaculture Study Program of Vocational Program at Bima Regency of Mataram University conducted a counseling activity in Bima Regency in September 2019 with the theme is Milkfish Hatchery (Chanos chanos Forskal) Household Scale, Opportunities and Problems. It was attended by about 40 target communities, namely Milkfish Farmers in the Bima Bay area. Based on communication during counseling, there needs to be a demonstration plot for Milkfish Hatchery in Bima Regency as a place for training and learning related communities

Evaluation of therapeutic potential of selected antifungal chemicals and drugs against Aphanomyces invadans

Infection with Aphanomyces invadans is a serious disease affecting freshwater and brackishwater fish. Even after 50 years of its first occurrence, to date, there is no effective treatment for this disease. To develop an effective treatment against this disease, in the current study, we have evaluated the potential of six commonly used chemicals and drugs with known antifungal properties against different life-stages (zoospore production, germination of zoospores and growth of hyphae) of A. invadans. The chemicals namely formalin, potassium permanganate (KMnO4), hydrogen peroxide (H2O2), sodium thiosulphate (Na2S2O3) and drugs including amphotericin B and fluconazole were evaluated in a dose-dependent manner (0.1, 1.0, 5, 10 and 100 ppm) under in vitro conditions. Out of the chemicals tested, formalin could completely inhibit zoospore production and significantly inhibit germination of zoospores and growth of hyphae at 10 ppm, however, complete inhibition of zoospore germination and growth of hyphae could only be observed at 100 ppm. In the case of H2O2, there was significant inhibition of germination of zoospores and growth of hyphae at the highest concentration of 100 ppm, but it could not completely inhibit zoospore production, germination of zoospores and growth of hyphae. KMnO4 at the highest tested concentration (100 ppm), completely inhibited zoospore production and significantly inhibited germination of zoospores and growth of hyphae. Na2S2O3 was found to be ineffective against all the three life-stages of A. invadans even at the highest tested concentration of 100 ppm. Out of the two antifungal drugs, fluconazole could reduce the germination of zoospores and growth of hyphae significantly at a dose of 1 ppm. On the other hand, in the case of amphotericin B, significant inhibition of germination of zoospores and growth of hypahe was observed only at 100 ppm. Both drugs completely inhibited zoospore production only at 100 ppm. From the findings of the present study, it can be inferred that out of the six compounds, formalin and fluconazole have better anti-oomycete effects under in vitro conditions. The information generated would serve as a basis for developing treatment measures against infection with A. invadans in aquaculture ponds.

Biosafety, withdrawal and efficacy of anti-parasitic drug emamectin benzoate in Asian Seabass (Lates calcarifer)

Parasitic infestations are frequently reported in brackishwater fish. Hence, prevention and control strategy is paramount for successful brackishwater aquaculture. Emamectin benzoate (EMB) is found to be an effective in-feed treatment for controlling several ecto-parasites in fish. The objective of this study was to understand the biosafety, withdrawal and efficacy of EMB for use in brackishwater reared Asian Seabass (Lates calcarifer) under tropical climate. Biosafety was evaluated at doses of 0, 50, 250 and 500 μg kg−1 of fish body weight (BW) day−1 for 21 days. EMB was administered per os through coated pellet feed. Gross, haematological and histopathological observations were made and found that there were no biologically significant adverse changes between control and treated groups. Withdrawal period was estimated with similar experiment with same doses but for seven consecutive days. Samples were collected on 0th, 7th, 14th, 21st and 28th day of post-medication for QTRAP 4000 LC-MS/MS analysis. The data showed that the level of EMB in whole fish treated with 50, 250 and 500 μg kg−1 of fish BW day−1 were 21.0 ± 0.0, 142.4 ± 0.1 and 209.7 ± 0.1 parts per billion (ppb) on 0th day of withdrawal, respectively. These values were found drastically decreased on 7th day of withdrawal and reached undetectable level by 28th day. For assessing the environmental safety, acute immobilization test was conducted using 24 h old daphnid. The EC50 and LC50 values in daphnids were 107 and 160 times higher than the the treatment dose, respectively. Efficacy was tested with the therapeutic dose on Asian Seabass fingerlings infested with naturally sea louse (Caligus minimus). Medicated pellet feed was fed at 4% BW day−1 divided equally between three feedings. Efficacy trial showed that there was significant improvement in survival (92.0 ± 2.3%; P < .01), reduction in parasitic load (P < .05), percent efficacy (76.2%) and haematological parameters (P < .01; P < .05) on and after fifth day of treatment. Based on the results, it was concluded that there was an adequate margin of safety and 100% efficacy associated with administering EMB-medicated feed to Asian Seabass fingerlings at the proposed therapeutic treatment regimen of 50 μg of EMB kg−1 fish BW day−1 for seven consecutive days.

Genetic identification and insights into the ecology of Contracaecum rudolphii A and C. rudolphii B (Nematoda: Anisakidae) from cormorants and fish of aquatic ecosystems of Central Italy.

Contracaecum rudolphii (s. l.) is a complex of sibling species of anisakid nematodes having the fish-eating birds belonging to the Family Phalacrocoracidae as final hosts. The great cormorant Phalacrocorax carbo sinensis is parasitized by C. rudolphii A and C. rudolphii B. Adults and L4 specimens of C. rudolphii (s. l.) (N = 3282) were collected in cormorants from brackish and freshwater ecosystems of Central Italy. Third-stage larvae of Contracaecum (N = 882) were obtained from the fish species Dicentrarchus labrax, Anguilla anguilla, Aphanius fasciatus, Atherina boyeri, Leuciscus cephalus, Barbus barbus, and Carassius carassius captured in the same geographical areas of cormorants' standings. Contracaecum rudolphii A and C. rudolphii B were identified by a multilocus genetic approach: allozymes, sequences analysis of the mtDNA cox2, and ITS region of rDNA gene loci. Differential distribution of the two parasite species was observed in different aquatic environments. Contracaecum rudolphii B outnumbered C. rudolphii A in wintering cormorants from freshwater ecosystems; the opposite trend was found in cormorants from brackish water. Analogously, C. rudolphii A larvae were more prevalent in brackish water fish, while C. rudolphii B larvae were found infecting only freshwater fish. The findings seem to confirm that C. rudolphii A and C. rudolphii B would have a life-cycle adapted to brackish and freshwater environments, respectively. A differential feeding behavior of wintering cormorants, the ecology of the infected fish species, and abiotic factors related to early stages of the parasites are supposed to maintain the distinctiveness of the two parasite species' life cycles in the two different aquatic ecosystems.

Bioaccumulation of heavy metal lead (Pb) in different tissues of brackish water fish Mugil cephalus (Linnaeus, 1758)

Bioaccumulation of heavy metal lead (Pb) in different tissues of brackish water fish Mugil cephalus (Linnaeus, 1758)

Changes in Fish Assemblages after Dike Construction in the Saemangeum Area

In the Saemangeum area, construction of a dike began in 1991 and was completed in 2006; desalination is currently being conducted. In order to investigate the influence of dike construction on fish assemblages, we analyzed the changes in fish assemblages using fish monitoring data accumulated before, during, and after construction of the Saemangeum Dike. Analysis of changes in the salinity of the Saemangeum Reservoir between 1997 and 2014 revealed that the overall salinity decreased, and this pattern became evident after completion of the dike. Long-term changes in fish assemblages were also confirmed in freshwater areas (Mankyeong and Dongjin Rivers) and the Saemangeum Reservoir. In freshwater areas, different fish assemblages were collected before and after dike construction according to NMDS analysis, and the proportion of freshwater fish continuously increased during analysis of ecological types. In the Saemangeum Reservoir, differences in fish assemblages were observed before, during, and after dike construction (PERMANOVA, F = 2.5325, P = 0.017). Moreover, the numbers of families and species decreased during dike construction; in terms of species composition, the proportion of brackish water fish increased, while that of marine fish decreased. Currently, a salinity gradient exists in the Saemangeum area between the rivers and the dike, and the M1-3 and D1-3 sites were classified as freshwater sites. Desalination is expected to increase freshwater areas in the future; as the change will happen over a very long period of time, differentiated management plans for each site of the Saemangeum area should be implemented through continuous monitoring.