Professional Fishermen Research Articles

How Much Hatchery-Reared Brown Trout Move in a Large, Deep Subalpine Lake? An Acoustic Telemetry Study

Fish movement into large, deep lakes has been rarely investigated due to the complexity and extent of such ecosystems. Among the different monitoring methods available, acoustic telemetry enables the study of the spatial ecology and behavior of aquatic organisms in lentic environments. In this study, the movement of 69 hatchery-reared adult brown trout (size 43–61 cm) marked with acoustic transmitters was monitored in the large and deep subalpine Lake Lugano (Switzerland and Italy). Trout were tracked for six consecutive months by seven acoustic receivers (March–August 2022), positioned in a non-overlapping array. Trout movement was reconstructed using R packages specific for acoustic telemetry (actel and RSP), which also allowed us to translate tracking information into utilization distribution (UD) areas for each fish. The effects of different environmental variables (rainfall, water discharge of the two main tributaries of Lake Lugano, atmospheric pressure, cloud coverage, and moon phases) on trout movement were tested, but none of these variables seemed to significantly correlate with fish movement. After release, most of the tagged fish exhibited reiterative movements during the initial month, with some maintaining this behavior throughout the entire study period. This spatial behavior can be particularly evident in hatchery-reared fish due to their aggressive and bold attitude. The association of these behavioral traits, shaped by domestication, could expose hatchery-reared fish to high risks and post-release mortality in the wild. Indeed, within a few months after the release, most of the tagged fish were no longer detected by the acoustic receivers. In addition, 26% of the total tagged fish were caught by recreational or professional fishermen.

Metabolomic and Lipidomic Tools for Tracing Fish Escapes from Aquaculture Facilities.

During adverse atmospheric events, enormous damage can occur at marine aquaculture facilities, as was the case during Storm Gloria in the southeastern Spanish Mediterranean in January 2020, with massive fish escapes. Fishes that escape were caught by professional fishermen. The objective of this study was to identify biomarkers in fish that enable differentiation among wild fish, escaped farm-raised fish, and farm-raised fish kept in aquaculture facilities until their slaughter. We focused on gilthead sea bream (Sparus aurata). We used nuclear magnetic resonance to search for possible biomarkers. We found that wild gilthead sea bream showed higher levels of taurine and trimethylamine-N-oxide (TMAO) in their muscle and higher levels of ω-3 fatty acids, whereas farm-escaped and farmed gilthead sea bream raised until slaughter exhibit higher levels of ω-6 fatty acids. From choline, carnitine, creatinine, betaine, or lecithin, trimethylamine (TMA) is synthesized in the intestine by the action of bacterial microflora. In the liver, TMA is oxidized to TMAO and transported to muscle cells. The identified biomarkers will improve the traceability of gilthead sea bream by distinguishing wild specimens from those raised in aquaculture.

Trypanorhynch cestode larvae parasitizing Hyporthodus niveatus (Valenciennes, 1828) (Actinopterygii) collected from fish markets in the municipality of Niterói, RJ, Brazil

This study is a continuation of the survey about helminths parasitizing the white grouper, Hyporthodus niveatus, a marine fish purchased from fish markets in the municipality of Niterói, Rio de Janeiro State, Brazil. Specifically, this study reports the results of an investigation concerning trypanorhynch cestodes parasitizing this host. A total of 20 fish specimens were caught by professional fishermen off the coast of Rio de Janeiro State. The fish were measured and necropsied, and their organs were investigated for trypanorhynch cestodes. A total of 13 H. niveatus were parasitized by 67 specimens of trypanorhynch cestode plerocerci that were found infecting the visceral serosa, stomach, intestine, and abdominal musculature. The taxonomic identification of these parasites was based on morphological and morphometric characters using bright-field and scanning electron microscopies. Five trypanorhynch species were identified: Pintneriella gymnorhynchoides, Grillotia (Christianella) carvajalregorum, Pterobothrium crassicolle, Callitetrarhynchus gracilis, and Callitetrarhynchus speciosus, and their parasitic indices were presented. This is the first report on the occurrence of P. gymnorhynchoides in the Western Atlantic Ocean. Apart from the repugnance, the presence of cestode plerocerci is worrisome because of the potential risk of allergic reactions, thereby reinforcing the hygienic-sanitary significance of monitoring these parasites.

Fishery typology in sectors IV and V of the Ebrie lagoon in the department of Dabou (Ivory Coast)

Fishing is an essential activity for man because it provides him with food and income. Thus, it is important to ensure that it is practiced in a responsible and sustainable manner. The objective of this study is to collect information about fishing activities in the sectors IV and V of the Ebrie Lagoon in order to contribute to its sustainable management. Campaigns were carried out from August 2020 to July 2021 in nine villages with 152 fishermen. Data was collected using questionary submitted to fishing actors. Physical and online documents were also consulted. Results revealed that fishermen population was composed of 57.24% of Ivorians and 42.76% of non-Ivorians. The fishing activity was dominated by Ivorians (57.24%) of whom 46.05% were Adjoukuou. Professional and occasional fishermen were identified among both Ivorians and non-Ivorians. 40.23% of Ivorian professional fishermen practice only fishing and 44.83% of Ivorian professional fishermen were olso engaged in agriculture. The non-national professional fishermen practice only fishing (84.62% of no national professional group). Generally, fishermen were aged between 30 and 45 years for the Ivorians and more of 45 years for no national. Most of the fishermen had been to school, married and practiced the activity on their own funds. The fishing techniques used were individual (gillnets with smaller mesh than the standard mesh (45 mm), longlines, hawks, traps (net and mesh), bamboo traps, shrimp nets, lines, harpoons and brushwood pens). The low level of education of non-Ivorian fishermen and the sub-standard mesh sizes constituted a real obstacle to the sustainable management of fish resources. It is therefore important to monitor fishing activity in these sectors of the Ebrie lagoon in order to avoid any damage related to overexploitation.

Updating records of Squatina aculeata (Elasmobranchii: Squatiniformes: Squatinidae) in the Mediterranean Sea

Background. The decline of the populations of the three Critically Endangered species Squatina aculeata Cuvier, 1829, Squatina oculata Bonaparte, 1840, and Squatina squatina (Linnaeus, 1758) in the Mediterranean basin is mainly attributed to overexploitation by demersal fisheries, in particular bottom trawls, but also artisanal and recreational. The survey of their occurrence in the basin in parallel with the collection of biological information are essential in order to develop or improve conservation strategies. For that reason, the presently reported study aimed to enrich knowledge on today’s distribution and biology of one of the above-mentioned endangered species, S. aculeata. Materials and methods. Information on the incidental capture of twenty specimens of S. aculeata in various Mediterranean regions was provided between 2011 and 2020 by professional fishermen and citizen scientists. Thirteen specimens were identified through examination of photos taken directly on board, or at the fish market while seven specimens were deposited at scientific collections and studied in the laboratory. Sex, total length, and total weight were determined, whenever possible. The TW–TL relation was calculated and the stomach content of one specimen was examined. Results. The findings document the presence of this rare and endangered angelshark in the deep waters of a wide area of the Mediterranean covering six Geographical Subareas (GSAs) of the General Fisheries Commission for the Mediterranean (GFCM), from the west to the central and eastern sectors of the basin. The total length in 17 individuals ranged from 54 cm to 190 cm, the total weight in 12 individuals from 2100 g to 49 000 g. Fifteen specimens were caught by bottom trawlers, four by trammel nets, one with longline. Conclusion. The reported recent findings document the occurrence of S. aculeata in various Mediterranean areas, some of which lacked records for many years. A continuous survey on the occurrence of this endangered species is recommended in order to assess the actual status of its population, but also of huge importance is the improvement of fishermen education and awareness aimed at the protection of the species as well as the inflexible application of international recommendations and regulations both for the professional and non-professional or recreational fishery.

Biological parameters and current status of European eel (Anguilla anguillaLinnaeus, 1758) from Asi River, Northeastern Mediterranean region, Turkey

The biological characteristics of eels from the Asi River, Turkey, were assessed between December 2017 and November 2018. Eels were sampled monthly using fyke nets (operated by professional fishermen), yielding a total of 509 specimens. Total length and weight were measured, sex, age and maturity stages (silver or yellow eel) were determined. Catch Per Unit Effort (CPUE) was calculated for both biomass per unit effort and numbers caught on a monthly and annual basis. The length-weight relationships (LWRs) of silver and yellow eel was W = 0.009*TL3.22 (n = 262) and W = 0.0106*L3.09 (n = 247), respectively. The age of the sampled fish ranged from year class II to VI. Von Bertalanffy growth parameters were estimated as L∞=69.25 cm, K = 0.43 1/year, t0= −0.41 and phi prime index (ǿ)= 3.31 for all samples. The overall eel fishing mortality rate (F) was 0.31 year-1, and the exploitation and survival rates of silver stage eels were estimated with 30% and 39%, respectively.

Giant otter diet differs between habitats and from fisheries offtake in a large Neotropical floodplain

Abstract Giant otters Pteronura brasiliensis are semiaquatic mammals that mainly eat fish, the abundance of which is affected by seasonal flooding and habitat structure. The piscivorous habits of giant otters lead to negative human perception and conflicts with fisheries. We compared giant otter feeding habits between seasons and habitats in the Southern Pantanal, Brazil, by analyzing feces collected between September 2008 and June 2011.We investigated whether habitat and season affected P. brasiliensis diet composition and prey size. We calculated the frequency of occurrence, relative frequency, and overlap of fish species eaten by giant otters and caught by fishermen. The giant otters had a more diverse assemblage of fish prey than the offtake in the fisheries. We did not find strong seasonality in otter diets, but diet composition and prey size differed between rivers and lakes. The giant otter diet had higher overlap with the offtake of sport than with professional fishermen. Although the otters’ piscivorous diet often leads to negative perceptions by humans, the low overlap between otter diet and species taken in local fisheries suggests that otters have little effect on the commercial fishery. These results indicate that educational programs could be used to reduce perceived conflict between giant otters and fishermen.

Characteristics of illegal inland fishing according to the opinions of Polish fisheries guards

Abstract Poaching is still a great problem in Poland. Officers of the fisheries guard from three regions in northeast Poland rich in natural inland waters were surveyed. The most frequent type of poaching encountered by the officers was that practised by recreational fishers using rods (ranking of 4.4 points on a scale of 0–5) followed by poaching stemming from poverty or unemployment (3.4 points), and poaching by professional fishermen was ranked the lowest (1.5 points). Organized poaching was identified as the most dangerous for ichthyofauna (42% of responses), followed by poaching by recreational fishers (28%) and poaching stemming from poverty or unemployment (23%). According to the officers surveyed, the species that were targeted by poachers most frequently were the predators: pike, Esox lucius (98% of responses), European eel, Anguilla anguilla, pikeperch, Sander lucioperca and perch, Perca fluviatilis.

Noise exposure and effects on hearing in Brazilian fishermen.

Several health conditions among professional fishermen have been reported. Among the risks to the health of fishermen, it should be noted that high noise levels cause hearing loss and general health problems. to investigate the effects of exposure to occupational noise on hearing in professional fishermen at the main large-scale commercial fishing center in Brazil. A cross-sectional study, 466 Brazilian commercial fishermen participated in the study, all males, ages range 18-67 years. A total of 15 vessels were included in the study. The first phase involved assessment of the sound pressure levels (SPLs) in the vessels, the second phase involved the use of a questionnaire and audiological assessment. Most compartments registered SPLs greater than 80 dBA and the noisiest compartment was the engine-room, where the vessel pilot works. Among the fishermen, tinnitus was the most commonly reported symptom (48.63%). A higher prevalence of hearing loss was observed in engine-room keepers. Longer the length of time in service, and consequently, exposure to noise (in years), were associated with higher auditory thresholds. the tolerance limits to noise exposure were exceeded according to legislation. Fishing activities are associated with noise-induced hearing loss, with the risk increasing with the length of service.

PRODUCTION FACTORS OF AN ARTISANAL FISHERY ON A MANMADE LAKE IN COTE D’IVOIRE

Fisheries management involves, among other things, knowledge of the actors and the catching gear used. These data are generally absent in the fisheries of Côte d'Ivoire. However, there is a strong fishing activity. To lead this study, surveys were conducted among fishermen and fishery administrators. The study of fishing activity in the area of Dioulabougou (Côte d’Ivoire, West Africa) in the district of Bouaflé done from November 2013 to February 2014 identified 88 fishermen. This population is composed of ivorians (39.77%) and foreigners (60.23%). The fishing activity is led by malians (Bambara ethnic group): 34.1%. Baoulé ethnic group (29.54% of ivorian fishermen) is the greatest ethnic group of ivorians. Two categories of fishermen stand in the fishing activity. We registered professional fishermen whose job is only fishing (84.1%) and professionals with another activity (4.5%). The fishing activity in Dioulabougou is dominated by adult aged more than 45 years (48%). Fishermen are predominantly illiterate at 42.04%. The fishing techniques used at Dioulabougou are conical fishing baskets (mesh and trunk of ronier), bamboo-traps, gillnets, bottom lines and shore seines. The illiterate situation of fishermen isa serious matter for sustainable management on fish’s resources.

Challenges to reconcile conservation and exploitation of the threatened Anguilla anguilla (Linnaeus, 1758) in Santo André lagoon (Portugal)

The adoption of the EC Regulation 1100/2007 for the recovery of the European eel required EU member states to implement and periodically report on their Eel Management Plans (EMPs) with the goal of achieving at least 40% of the silver eel escapement relative to the best estimate of escapement that would have existed if no anthropogenic influences had impacted the stock. The specific measures to achieve such a goal have spurred a harsh debate among the different stakeholders with the need to mediate among multiple conflicting interests. In this investigation the study of the dynamics of the eel fishery in the Santo André Lagoon, a small-scale fishery in the southwest of Portugal, is presented. Through the description of the management structure, the analysis of 40 years of catch and effort data, and the analysis of socio-economic data, the existing enforcement and the way forward is discussed. Day-to-day logbooks of catch and effort data from five professional fishermen, for two fishing seasons (that is, 2011/2012 and 2016/2017), and surveys to the community, were used to independently estimate total harvest and income of the eel fishery in Santo André Lagoon, and the perception of the fishermen toward regulation and management. The results showed that both catch per unit effort and fishing yield increased during the study period and now ranges between 68 and 169 kg/ha, with eel fishing making a significant fraction of the fishermen's revenue. Although the existing regulation does not satisfy the fishing community, their disagreement decreased during the studied period. The analysis of the fisheries management in the lagoon and its impact on eel harvesting and, on the stock, revealed opportunities to adjust the set of regulations enforced at the national level under the Portuguese EMP to the specific context of the Santo André Lagoon. Specifically, a co-management approach would promote legitimacy and contribute to a better acceptance of the regulations by the fishing community.

Fish exploitation in medieval and early modern Switzerland: Evidence from the ichthyoarchaeological record and historical sources

AbstractIn Switzerland, fish played a substantial role in people's diets both in medieval times and in the early modern period. In this paper, we present an overview of ichthyoarchaeological data from 20 years of research, mainly from the northern and eastern regions of Switzerland. The integration of results of faunal analyses from 20 archaeological sites, and the study of historical sources provided information on different modes of fish exploitation during these periods. This study shows that the fish remains from archaeological sites correspond with the descriptions in the written records: Both sources point to local fisheries within Swiss freshwater systems. These fisheries were strongly regulated and often selective. Large freshwater fish of high quality was mainly caught by professional fishermen and eaten by the aristocratic and clerical classes, whereas small or young specimens were caught by all social classes even though their catch was strongly restricted. Furthermore, both sources provide evidence for an inland freshwater fish trade of selected species and for the import of herring and suggest the practice of different freshwater fish cultivation methods.

Monitoring uncommon and non-indigenous fishes in Italian waters: One year of results for the AlienFish project

Results of the AlienFish project – monitoring and study of rare and non-indigenous fish species in Italian waters – collected through citizen science in 2018 are here reported. Overall, 36 observations of 21 fish species belonging to 17 families were provided from the central and southern sectors of Italian seas. Our findings highlight the effectiveness of involving sea users in the detection of fish species of both indigenous and non-indigenous origin. Professional fishermen were particularly effective in providing information on rare deep-water and open-water fishes.

Expansion history of the blue crab (Callinectes sapidus Rathbun, 1896) in the Eastern Iberian Peninsula (Western Mediterranean Sea).

Expansion history of the blue crab (Callinectes sapidus Rathbun, 1896) in the Eastern Iberian Peninsula (Western Mediterranean Sea).

The Global Repercussions of the 1947 Symposium on Fish Populations in Toronto: Scientific Networks and the Over-fishing Question

A relatively small, contentious, and long-forgotten meeting, the 1947 Symposium on Fish Populations, had enormous and decades-long repercussions for global fisheries policies. Convened in Toronto by Archibald Gowanlock Huntsman, former director of the Atlantic Biological Station, it drew together leading North American fisheries biologists and professional fishermen. By exposing the lack of agreement on, or understanding of, the nature of overfishing, this meeting made it difficult for later scientists to challenge pro-industry fisheries policies. The published proceedings, in-demand by a tight network of fisheries scientists across North America and the North Atlantic, guaranteed this meeting’s disproportionate and unfortunate impact.

Characterization of artisanal fishery in a coastal area of the Strait of Sicily (Mediterranean Sea): Evaluation of legal and IUU fishing

The present study analyses the artisanal fishery of Sciacca (Mediterranean Sea) through the investigation of fishing activities, resources and yields, in order to characterize for the first time one of the most important traditional coastal activities of the area. Further, the study evaluates the incidence of illegal artisanal fishing, this being one of the major threats to the good management of fishery. Landing surveys and interviews with professional fishermen (i.e. those operating on vessels provided with a fishing licence) were carried out from May 2006 to April 2007 in order to record catches, type of fishing gear used and fishing areas. At the same time, illegal artisanal fishing vessels – i.e. vessels without a licence whose catch is illegally sold in local markets – were also monitored. The artisanal fishery of Sciacca is multi-specific, exploring various resources with different techniques. The most used gear by both professional and illegal fishing vessels throughout the study period was the trammel net. Other less frequently used gear has seasonal use related to source availability, and some is mainly or exclusively used by one or the other category of fishing vessels. Overlapping between professional and illegal fishing vessels emerged in the exploitation of some fishing areas, mainly coastal (within 3 nautical miles). A strong competition between the two categories for commercial resources was highlighted. The present study reports for the first time data on professional and illegal artisanal fishing in one of the most important Sicilian fisheries.

Recorded captures of American lobster (Homarus americanus) in Swedish waters and an observation of predation on the European lobster (Homarus gammarus)

The intentional or unintentional release of American lobsters (Homarus americanus), imported through the European seafood trade, has resulted in findings of H. americanus in European waters. A total of 36 specimens was recorded within a smaller area, halfway along the Swedish west coast, between 2008 and 2016. The lobsters were caught by both recreational and professional fishermen and delivered to the Institute of Marine Research in Lysekil, where species identification, measurements, and genetic sampling were performed. Twenty-five of these lobsters were caught inside the sill of the Gullmar Fjord, most of them close to Lysekil harbor, where escapes from an illegal holding is suspected. Six females had eggs, which in two cases were hybrids. While there is no evidence to suggest that a population has been established in the Gullmar Fjord or elsewhere in Swedish waters, serious concerns must be raised regarding the possible consequences for the native species. An American lobster has for the first time been filmed eating a killed European lobster (Homarus gammarus) in Swedish waters.

Percepção dos atores sociais do turismo sobre o pulso de inundação do Pantanal (MT)

O Pantanal é a maior planície de inundação contínua do planeta. O ciclo periódico de seca e cheia, chamado de pulso de inundação, é o principal fator controlador do funcionamento e da manutenção da biodiversidade do Pantanal. Estas condições hidrobiológicas, aliadas à beleza cênica, são grandes atrativos à atividade turística na região. O objetivo deste trabalho foi analisar como os diferentes atores sociais do turismo (pousadeiros, turistas estrangeiros, turistas brasileiros, pescadores profissionais, agentes SEMA, guias de turismo, moradores locais) percebem o pulso de inundação e como este pode influenciar esta atividade no Pantanal de Poconé, um dos polos turísticos do Pantanal, considerando o expressivo crescimento da atividade nos últimos anos e a escassez de estudos na região. Foram previamente identificados sete principais grupos sociais, que posteriormente foram entrevistados em entrevista do tipo estruturada (37 entrevistas gravadas). Estas foram transcritas para a análise dos resultados e aplicado uma ferramenta de análise de texto para contagem das palavras mais mencionadas por cada grupo social. A grande maioria dos pousadeiros é de fazendeiros tradicionais que passaram a desenvolver serviços de hotelaria, atendendo basicamente turistas estrangeiros. Foram identificados conflitos entre pecuaristas e pousadeiros, relativo a onça pintada, que representa prejuízos ao rebanho e aos pousadeiros uma fonte de renda quanto ao turismo de “observação de onça”; e conflito entre a população nativa, tanto moradores locais quanto pescadores profissionais, que almejam por participarem mais diretamente no turismo e das instâncias de poder, concentrada nos pousadeiros e/ou pecuaristas. O pulso de inundação exerce forte influência sobre o aproveitamento turístico do Pantanal de Poconé, mas não foi nitidamente compreendido pelos diferentes grupos sociais do turismo, tanto quanto a percepção da importância do pulso na sua atividade quanto ao entendimento do conceito em si. Os grupos com melhor capacitação técnica (guias de turismo e agentes ambientais) e os moradores locais e pescadores profissionais, nativos da região, apresentaram melhor compreensão destes dois aspectos do pulso de inundação. O estudo apontou ainda a importância de se desenvolver um turismo com maior identidade local, que incluam outros atrativos, como as festas tradicionais da rica cultura de Poconé e a diversidade de ecossistemas aquáticos e terrestres na época de cheia.
 
 Perception of the tourism social actors regarding the flood pulse of the Pantanal (MT, Brazil)
 
 ABSTRACT
 The Pantanal is the largest continuous floodplain on the planet. The periodic cycle of drought and flood, the so-called the flood pulse, is the controlling factor of the operation and maintenance of the Pantanal's biodiversity. These hydrobiological conditions, together with the scenic beauty, are great touristic attractions to the region. The objective of this work was to analyze how the different social actors of tourism perceive the pulse of flood and how it can influence the activity in the Pantanal of Poconé, one of the tourist centres of the Pantanal. The departing point of this research was the significant growth of activity in the last years and the scarcity of specific studies in the region. Seven main social groups were initially identified, which were later interviewed in a structured interview (37 recorded interviews in total). These were transcribed for the analysis of the results; the analytical tool Voyant tools was applied to count the main words mentioned by each social group. Results showed that the vast majority of the hostel owners are from traditional farmers who started to develop hotel services, catering mainly to foreign tourists. Conflicts between cattle ranchers and hostel owners were identified regarding the hunt of jaguars, in the form of losses to the herd against losses to the touristic activities based on "jaguar observation"; likewise, there are conflicts between the native population (professional fishermen and riverine), who seek to participate more directly in the tourism, and the business community in control of hostels and/or ranchers. The flood pulse exerts a strong influence on the tourist enjoyment of the Poconé Pantanal, but it was not clearly understood by the different social groups involved; the perception of the importance of the pulse is affected by the difficulty to understand the concept itself. The groups with better technical qualification (tourism guides and environmental agents) and the riverine and professional fishermen, natives of the region, showed a better understanding of these two aspects of the flood pulse. The study also revealed the importance of developing tourism with greater local identity, including other attractions, such as the traditional festivals of the rich culture of Poconé and the diversity of aquatic and terrestrial ecosystems during the flood season.
 
 KEYWORDS: Fishing; Socioenvironmental; Wetland.

Migration patterns and home range of pike-perch (Sander lucioperca, Linnaeus, 1758) in Dutch river systems

Pike-perch (Sander lucioperca L. 1758) is one of the freshwater species caught by professional fishermen in the Netherlands. The species is also popular with sport fishermen. Little is known about its migration and rehabilitation in large river systems. The aim of the present study was to obtain data on the movements of pike-perch in the Dutch large river systems and investigate when and how far individual fish swim up- or downstream. Seasonal migration was expected. The second objective was to gain information on how many fish pass the Haringvlietdam when migrating downstream during high discharge, and ending up in the North Sea. The third objective was to gain data on how many fish were caught by the fishermen. NEDAP TRAIL System® transponders were surgically implanted in 286 pike-perch between June 2007 and October 2008. Marked fish could be detected via several detection stations in the river systems throughout the Netherlands and one in the River Rhine station in Germany. Sport fishermen were asked to inform the organization when a marked fish was caught. Data collected between June 2007 and April 2010 indicate a pike-perch home range of 30–40 km, with some individuals migrating up to more than 200 km. A regional approach regarding fisheries management is necessary. No seasonal patterns were found. Swimming activity was highest during darkness. Results showed pike-perch around the Haringvlietdam swimming in the saltwater area on the sea side of the dam, and returning to the freshwater Lake Haringvliet, indicating that the structure of the dam is used for feeding, but also that the fish will die if the dam is closed when fish are still outside.

Metazoan parasites of Plagioscion squamosissimus, an invasive species in the Tietê River, São Paulo, Brazil.

This study focused on the characterization and analysis of communities and infra-communities of metazoan parasites of Plagioscion squamosissimus caught in Promissão Reservoir in the Tietê River in Borborema (21°39'58"S, 49°8'49"W), state of São Paulo, Brazil. Fifty adult specimens caught by professional fishermen in March 2015 were necropsied. The fish presented an average standard length of 25.2 ± 2.2 cm and average weight of 328.82 ± 89.03 g. A total of 5,227 specimens of metazoan parasites were collected: 2,880 (55.1%) adult Diplectanum piscinarius (Monogenoidea: Diplectanidae) and 2,347 (44.9%) Austrodiplostomum compactum metacercariae (Digenea, Diplostomidae), both with 100% prevalence and mean abundance of 57.6 and 46.9, respectively. Parasite diversity was low (species richness = 2), with a Simpson index (D) equal to 0.505, and low values of Brillouin (HB = 0.687) and Margalef diversity (I = 0.117) indices. Berger-Parker's index of dominance (p = 0.551) indicated a slight dominance of the monogenean parasite D. piscinarius. There was a positive correlation, assessed by Pearson coefficient between parasite abundance of D. piscinarius and standard length (r = 0.43) and weight (r = 0.51) of hosts.