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Abstrakty XVII European Congress of Ichthyology 2023

European whitefish (Coregonus lavaretus)

Parasite fauna and condition of Coregonus lavaretus (L.) and Vimba vimba (L.) from the Odra River Estuary (north-western Poland)

Więcaszek Beata1, Linowska Angelika1, Tański Adam1, Czerniejewski Przemysław2, Korzelecka-Orkisz Agata1, Sawicki Wojciech3, Formicki Krzysztof1, Dąbrowski Jarosław4

Both common whitefish Coregonus lavaretus (sensu lato) and vimba bream Vimba vimba are very valuable economically fish species, however they are rare and endangered in the area of study. The main threats for these species are both difficult access and disappearance of the spawning grounds. The parasitological studies on these fish species are scarce, especially in the region of the Szczecin Lagoon and Lake Dąbie (Odra River Estuary). As so far, the examinations in this area are dedicated mainly to the commercially important fish. Parasitological examinations (performed in 2021-2022) focused on the skin, vitreous humor, eye lens, mouth and nasal cavities, gills, heart, gonads, spleen, gastrointestinal tract, kidneys, gallbladder, urinary bladder, and the peritoneum.

Parasites found were determined on the basis of their morphological characteristics. In the case of Coregonus lavaretus, they belonged to Protozoa, Cestoda, Nematoda, Molusca and Crustacea in the area of Szczecin Lagoon. The same taxa were reported from the Lake Dąbie, with one more, representing the phylum Acanthocephala. Condition factor for Coregonus lavaretus was higher in autumn than in spring (in both areas studied). Common whitefish were in better condition in Lake Dąbie when compared to population from the Szczecin Lagoon. In the case of vimba bream in the area of Szczecin Lagoon, parasites belonged to Microsporidia, Monogenea, Digenea, Nematoda, Molusca and Crustacea. The same taxa were reported from the Lake Dąbie, with one more species, represented the phylum Cestoda. Vimba bream were in better condition in the Szczecin Lagoon than the population in the Lake Dąbie.

Any new parasite species were found in the species studied, however their prevalence and infection intensity provide important information on habitat and trophic status of the studied fish species within the estuarine and freshwater ecosystem in the area studied. No one parasite species was dangerous for human’s health.

Diet analysis of Vimba vimba (L.) and Coregonus lavaretus (L.) populations from the Szczecin Lagoon and Lake Dąbie (Odra River Estuary)

Więcaszek Beata1, Rybczyk Agnieszka2, Czerniejewski Przemysław3, Tański Adam1, Korzelecka-Orkisz Agata1, Formicki Krzysztof1, Dąbrowski Jarosław4

The diet studies on vimba bream Vimba vimba and common whitefish Coregonus lavaretus (sensu lato) are scarce, especially in the region of the Szczecin Lagoon and Lake Dąbie (Odra River Estuary). To date, the examinations of fish diet in these areas were dedicated mainly to the commercially important fish. The analyses of fish diet in this study were performed in 2021 and 2022.

In the Dąbie Lake, the representatives of following taxa were noted in the common whitefish stomachs: Ostracoda, larvae of Chironomidae, Gammarus spp., fish remains, Cyclopidae, Oligochaeta, Bosmina spp., Copepoda, Dreissena polymorpha, and Gastropoda. In fish stomachs from the Szczecin Lagoon, the same components were noted in spring season, while in autumn the Trichoptera and Chironomidae larvae appeared. Index of relative importance (IRI) for common whitefish was the highest for Gastropoda, followed by Gammaridae (both in spring and autumn season) and amounted to 32.4% and 23.5% in spring, while 23.4% and 16.9% in autumn, respectively.

In the vimba bream stomachs from Dąbie Lake the following components of diet were found: fish eggs, Bivalvia, Copepoda, Gastropoda, Dreissena polymorpha, larvae of Chironomidae, Oligochaeta, Bacillariophyta, Cyanophyta, Cladocera and detritus. In stomachs of fish from the Szczecin Lagoon, additionally the Ephemeroptera, Homoptera and Diptera larvae, as well as Amphipoda were recorded. Index of relative importance (IRI) for vimba bream from Dąbie Lake was the highest for Chironomidae (51.4% in the spring season) and for Copepoda (34.7% in autumn), while in fish collected from the Szczecin Lagoon IRI was the highest for Dreissena polymorpha (17.7%), followed by the larvae of Diptera (14.6%).

Long term changes in commercial fish catches and fish composition in Szczecin Lagoon

Przemysław CZERNIEJEWSKI1, Krzysztof FORMICKI2, Adam TAŃSKI2, Agata KORZELECKA-ORKISZ2, Jan KRZYSTOLIK2, Radosław PIESIEWICZ2

1 Faculty Research Station in Ińsko, Faculty of Food Science and Fisheries, West-Pomeranian University of Technology in Szczecin, Poland

2 Department of Hydrobiology, Ichthyology and Biotechnology of Reproduction, Faculty of Food Science and Fisheries , West-Pomeranian University of Technology in Szczecin, Poland

Keywords: Fisheries, fishing yields, species composition, Szczecin Lagoon,

Szczecin Lagoon is a reservoir that forms part of the Oder Estuary and is separated from the sea by two islands, Uznam and Wolin. The first information on fish occurring in this area was provided by archaeological excavations. Analyses of fish remains from these sites have shown that the local population fished at least 20 ichthyofauna species (Chełkowski et al. 1998, Filipiak and Chełkowski 2000). The first detailed ichthyofaunal studies of this basin were carried out in the early 20th century by Henking (1923) and Neuhaus (1923).

Zimdars (1941) reported that in the interwar period Szczecin Lagoon was inhabited by 22 fish species, while 14 species appeared only sporadically. He also indicated that the species structure of ichthyofauna was dominated by roach (31.54%), eel (15.71%), and bream (12.57%), and the annual fishing yield ranged from 2200 to 4900 tons of fish. After World War II, fishing yields fluctuated between 1800 and 3700 tons of fish, and the catch per unit effort ranged from 31.4 kg/ha to 75.7 kg/ha (Wiktor 1960, Wysokiński et al. 1997).

The long-term exploitation of fish resources in Szczecin Lagoon, as well as the variability of environmental conditions, were the causes of changes in the fishing yields and the structure of ichthyofauna. Currently, perch (36.96%), roach (25.59%), and bream (25.28%) dominate the structure of harvested fish, although pikeperch, accounting for 4.30% of the catch (data from 2004-2017), is also of great economic importance. The catches of whitefish and vimba are of little importance in the structure of ichthyofauna; therefore, irregular stocking of these species has been carried out since the 1970s to compensate for environmental impact resulting from dredging the waterway through Szczecin Lagoon and building a gas port.

According to catch data from 1931-2021, the fishing history of Szczecin Lagoon can be divided into seven periods. The first period, from 1931 to 1939, is characterized by an increase in catches and experimental stocking. The second period, from 1939 to 1945, saw no fishing due to the World War II. The third period, from 1947 to 1949, saw an increase in catches (from 1200 to 3700 tonnes) due to an increase in fishing effort resulting from the influx of workers from the eastern borderlands of Poland. The fourth period, from 1950 to 1957, was characterized by a significant decline in fishing yields (from 3700 t to 1300 t). The fifth period, from 1957 to 1975, saw a growth in fishing yields up to 3900 t. The sixth period, from 1975 to 1990, saw fishing yields fluctuate between 2500 t and 4000 t. The seventh period, from 1991 to the present, has seen a decrease in fishing yields.

Currently, research is being conducted with the aim of developing a plan for the conservation of the natural resources of two bi-environmental species of fish, the common whitefish Coregonus maraena (formerly lavaretus) and the vimba Vimba vimba, which are both threatened and economically valuable, residing in Szczecin Lagoon and the estuary zone of the Rega River. This plan involves the development and application of innovative and pro-ecological methods to support the reproduction of these species in their early ontogeny.

The project was co-financed under the EU Operational Programme „Fisheries and the Sea 2014-2020”, Specific objective 1.3. Contract number 00001-6520.3-OR1600003/19/20.

Heavy metal distribution in various tissues of Sea trout (Salmo trutta m. trutta) from the Rega river in northern Poland

Kamila Pokorska-Niewiada1, Agata Witczak1, Przemysław Czerniejewski2, Adam Tański3, Agata Korzelecka-Orkisz3, Krzysztof Formicki3

  1. Department of Toxicology, Dairy Technology and Food Storage, Faculty of Food Science and Fisheries, West-Pomeranian University of Technology in Szczecin, Poland
  2. Faculty Research Station in Ińsko, Faculty of Food Science and Fisheries, West-Pomeranian University of Technology in Szczecin, Poland
  3. Department of Hydrobiology, Ichthyology and Biotechnology of Reproduction, Faculty of Food Science and Fisheries, West-Pomeranian University of Technology in Szczecin, Poland

Keywords: distribution of metals, Sea trout, Rega river

Fishes that inhabit surface waters are exposed to various types of harmful substances that originate mainly from human activities. Heavy metals are among the most important pollutants because they occur throughout ecosystems, can be determined in critical amounts, and are known to bioaccumulate and biomagnify. Heavy metals can affect vital functions and reproduction in fishes, weaken the immune system, and cause pathological changes. Thus, fishes are bioindicators of environmental contamination, and they play an important role in monitoring heavy metals in aquatic ecosystems. The aim of the study was to assess the distribution of selected metals (Zn, Ni, Fe, Mn, Cr, Cu, Li, Pb, Cd) in the muscles and organs (liver, kidneys, gonads, gills) of sea trout (Salmo trutta m. trutta) from the Rega River in northern Poland. The content of metals was determined using inductively coupled plasma–atomic emission spectrometry (ICP-AES) and graphite furnace–atomic absorption spectrometry (GF-AAS).  

Because of its essential reproductive functions, zinc was accumulated primarily in the gonads (59.1 mg/kg). The gills accumulated the largest amounts of manganese (2.05 mg/kg), chromium (0.26 mg/kg), and nickel (0.12 mg/kg). The highest amounts of iron (80.5 mg/kg), copper (5.43 mg/kg), and lithium (0.148 mg/kg) were determined in the kidneys and livers. The relationship of the level of accumulation among the organs for the most toxic elements of lead and cadmium was as follows: gills>kidney>liver>gonads>muscles. Muscles contained the smallest amounts of all the heavy metals analyzed, which is important in terms of human fish consumption.  

The level of these elements in the fish from the river analyzed indicated that the fish inhabit a high quality environment. 

The project was co-financed under the EU Operational Programme „Fisheries and the Sea 2014-2020”, Priority 2. Contract number 00001-6521.1-OR1600002/17/18.

Diet analysis of Vimba vimba (L.) and Coregonus lavaretus (L.) populations from the Szczecin Lagoon and Lake Dąbie (Odra River Estuary)

WIĘCASZEK Beata1, RYBCZYK Agnieszka2, CZERNIEJEWSKI Przemysław3, TAŃSKI Adam1, KORZELECKA-ORKISZ Agata1, FORMICKI Krzysztof1, DĄBROWSKI Jarosław4

  1. Department of Hydrobiology, Ichthyology and Biotechnology of Reproduction, Faculty of Food Science and Fisheries, West-Pomeranian University of Technology in Szczecin, Poland
  2. Department of Aquatic Bioengineering and Aquaculture. Faculty of Food Science and Fisheries, West-Pomeranian University of Technology in Szczecin, Poland
  3. Faculty Research Station in Ińsko, Faculty of Food Science and Fisheries, West-Pomeranian University of Technology in Szczecin, Poland
  4. Institute of Technology and Life Sciences in Falenty, Poland

Keywords: whitefish, vimba bream, diet, IRI, Szczecin Lagoon, Dabie Lake

Diet studies on the vimba bream Vimba vimba and common whitefish Coregonus lavaretus (sensu lato) are limited, particularly in the region of Szczecin Lagoon and Lake Dąbie (Odra River Estuary). Previously, examinations of fish diet in these areas focused mainly on commercially important fish. The analysis of fish diet in this study was conducted in 2021 and 2022.

In Lake Dąbie, the stomachs of common whitefish contained the following: Ostracoda, Chironomidae larvae, Gammarus spp., fish remains, Cyclopidae, Oligochaeta, Bosmina spp., Copepoda, Dreissena polymorpha, and Gastropoda. In Szczecin Lagoon, the same components were observed in the spring season, while Trichoptera and Chironomidae larvae appeared in the autumn. The index of relative importance (IRI) for common whitefish was highest for Gastropoda, followed by Gammaridae, in both the spring and autumn seasons. The IRI for Gastropoda and Gammaridae was 32.4% and 23.5%, respectively, in spring and 23.4% and 16.9% in autumn.

In the stomachs of vimba bream from Lake Dąbie, the following diet components were found: fish eggs, Bivalvia, Copepoda, Gastropoda, Dreissena polymorpha, Chironomidae larvae, Oligochaeta, Bacillariophyta, Cyanophyta, Cladocera, and detritus. In the stomachs of fish from Szczecin Lagoon, Ephemeroptera, Homoptera, and Diptera larvae, as well as Amphipoda were additionally recorded. The IRI for vimba bream from Lake Dąbie was highest for Chironomidae (51.4% in spring) and for Copepoda (34.7% in autumn), while in fish collected from Szczecin Lagoon, the IRI was highest for Dreissena polymorpha (17.7%), followed by Diptera larvae (14.6%).

The project was co-financed under the EU Operational Programme „Fisheries and the Sea 2014-2020”, Specific objective 1.3. Contract number 00001-6520.3-OR1600003/19/20.

Parasite fauna and the condition of Coregonus lavaretus (L.) and Vimba vimba (L.) from the Odra River Estuary (north-western Poland)

WIĘCASZEK Beata1, LINOWSKA Angelika1, TAŃSKI Adam1, CZERNIEJEWSKI Przemysław2, KORZELECKA-ORKISZ Agata1, SAWICKI Wojciech3, DĄBROWSKI Jarosław,4 FORMICKI Krzysztof1,1

  1. Department of Hydrobiology, Ichthyology and Biotechnology of Reproduction, Faculty of Food Science and Fisheries, West-Pomeranian University of Technology in Szczecin, Poland
  2. Faculty Research Station in Ińsko, Faculty of Food Science and Fisheries, West-Pomeranian University of Technology in Szczecin, Poland
  3. Department of Applied Microbiology and Physiology of Human Nutrition, Faculty of Food Sciences and Fisheries, West-Pomeranian University of Technology in Szczecin, Poland
  4. Institute of Technology and Life Sciences in Falenty, Poland

Keywords: Parasites, whitefish, vimba bream, Szczecin Lagoon, Dabie Lake

Both the common whitefish Coregonus lavaretus (sensu lato) and the vimba bream Vimba vimba are highly valued economically as fish species, yet they are rare and endangered in the Odra River Estuary due to difficult access and the disappearance of their spawning grounds. Despite their ecological significance, parasitological studies on these fish species are scarce, particularly in Szczecin Lagoon and Lake Dąbie region (Odra River Estuary). Previously, examinations in this area primarily focused on commercially important fish species. To address this knowledge gap, we conducted parasitological examinations on these fish species from 2021 to 2022, focusing on various organs and tissues, including the skin, vitreous humor, eye lens, mouth and nasal cavities, gills, heart, gonads, spleen, gastrointestinal tract, kidneys, gallbladder, urinary bladder, and peritoneum.

The parasites found were identified based on their morphological characteristics. For Coregonus lavaretus in Szczecin Lagoon, the identified parasites belonged to Protozoa, Cestoda, Nematoda, Molusca, and Crustacea. The same taxa were found in Lake Dąbie, along with an additional species from the phylum Acanthocephala. The condition factor of Coregonus lavaretus was higher in autumn than in spring in both areas studied. The common whitefish in Lake Dąbie were in better condition than the population in Szczecin Lagoon. For the vimba bream in Szczecin Lagoon, parasites belonged to Microsporidia, Monogenea, Digenea, Nematoda, Molusca, and Crustacea. The same taxa were found in Lake Dąbie, with an additional species from the phylum Cestoda. The vimba bream in Szczecin Lagoon were in better condition than the population in Lake Dąbie.

Although no new parasite species were found in the studied fish species, their prevalence and infection intensity provided important information on the habitat and trophic status of the studied fish species within the estuarine and freshwater ecosystem in the study area. None of the parasite species identified posed a threat to human health.

The project was co-financed under the EU Operational Programme „Fisheries and the Sea 2014-2020”, Specific objective 1.3. Contract number 00001-6520.3-OR1600003/19/20.

The population structure of sea trout (Salmo trutta L., 1758) spawning in the Rega River (southwest Baltic basin, Poland).

TAŃSKI Adam1, CZERNIEJEWSKI Przemysław2, BRYSIEWICZ Adam3, KORZELECKA-ORKISZ Agata1, WIĘCASZEK Beata1, Radosław PIESIEWICZ1, Jan KRZYSTOLIK1, FORMICKI Krzysztof1

  1. Department of Hydrobiology, Ichthyology and Biotechnology of Reproduction, Faculty of Food Science and Fisheries, West-Pomeranian University of Technology in Szczecin, Poland
  2. Faculty Research Station in Ińsko, Faculty of Food Science and Fisheries, West-Pomeranian University of Technology in Szczecin, Poland
  3. Institute of Technology and Life Sciences in Falenty, Poland

Keywords: Sea trout, Rega river, size structure

Salmonid fish of the family Salmonidae represent some of the most economically valuable fish species. Among those that migrate to the Baltic rivers for spawning, the sea trout (Salmo trutta L.) and Atlantic salmon (Salmo salar L.) are targeted for fishing, with the former accounting for roughly 90-95% of migratory salmonid fish. This high proportion of sea trout spawners has allowed for regular restocking of rivers in northern Poland for almost six decades. The restocking is carried out due to the sea trout’s commercial value and the pressures from both angling and commercial fishing.

The Rega River, which hosts salmon and sea trout each year, is one of the most important salmon rivers in Poland. The catchment area of the river, covering an area of 2673 km2, is located in the frontal moraine zone, and its agricultural character makes it highly susceptible to anthropogenic pressure. In recent decades, the construction of water infrastructure, which has hindered migration, and the deterioration of water quality have contributed to the loss of natural spawning habitats, causing changes not only in the numbers of migratory fish entering spawning grounds but also in intrapopulation characteristics.

This research, which is part of an ongoing project, aimed to conduct a comparative analysis of the basic population and biological characteristics of sea trout entering the Rega River for spawning during the 2019-2021 seasons. The mean total length of the caught fish between 2019 and 2021 was 62.2 cm, with a range of 47.2-80.9 cm. The dominant individuals were those with lengths ranging between 55.0-60.0, 60.1-65.0, and 65.1-70.0 cm, which constituted over 85% of the examined fish. The mean unit weight of spawners was 2163.4 g, with a range of 990.0-3896.0 g. The mean value of the Fulton condition factor was 0.80. Compared to data from the second half of the 20th century, a decline in the number of sea trout population entering the Rega River was observed. The captured individuals of the same length presently possess a lower unit weight and condition.

The project was co-financed under the EU Operational Programme „Fisheries and the Sea 2014-2020”, Priority 2. Contract number 00001-6521.1-OR1600002/17/18.

The possibilities of reproduction of anadromous salmonid fish in the tributaries of the Baltic Sea – a case study of the Ina River.

Adam BRYSIEWICZ1, Adam TANSKI2, Przemyslaw CZERNIEJEWSKI3, Agata KORZELECKA-ORKISZ2, Jan KRZYSTOLIK2, Radosław PIESIEWICZ2, Krzysztof FORMICKI2

  1. Institute of Technology and Life Sciences in Falenty, Poland
  2. Department of Hydrobiology, Ichthyology and Biotechnology of Reproduction, Faculty of Food Science and Fisheries, West-Pomeranian University of Technology in Szczecin, Poland
  3. Faculty Research Station in Ińsko, Faculty of Food Science and Fisheries, West-Pomeranian University of Technology in Szczecin, Poland

Keywords: Sea trout, reproduction, spawning grounds

Sea trout (Salmo trutta m. trutta L.) belongs to the most valuable anadromous species that enter Polish rivers from the sea. However, this bi-environmental fish faces numerous obstacles when it migrates to the upper reaches of the rivers. The primary difficulties arise from hydro-technical development, which often creates impassable barriers for fish and aquatic organisms. Improperly conducted land reclamation activities also cause changes in the riverbed structure, leading to siltation and the loss of natural spawning grounds for this species.

Sea trout, like other salmonid fish, require specific gravelly-sandy spawning grounds in which to build their nests for reproduction. Despite years of restorative activities aimed at supporting and restoring populations of salmonid fish, including stocking, these efforts still appear to be insufficient.

In response, alternative methods of supporting natural reproduction of salmonid fish in rivers have been initiated in the United States and Scandinavia, and are now increasingly used worldwide, including in Poland. One such method involves the construction of artificial spawning grounds in selected locations in natural watercourses.

As part of an EU-funded project aimed at supporting the natural reproduction of salmonid fish in the catchment area of the Lower Oder River and Szczecin Lagoon, using the Ina River as a case study, the preliminary stage of the project identified a predominance of sandy substrates in most of the watercourses. The content of sand particles with a diameter ranging from 1.00 mm to 0.10 mm varied from 69.99% to as much as 98.84%. However, in some stretches of the Ina River and its tributaries, high levels of siltation were observed. Hydrochemical analyses of the water were carried out throughout the year. The results showed that most of the water quality indicators were suitable for salmonid fish.

A year prior to the construction of spawning grounds in the upper part of the Ina basin, the number of salmonid fish nests was low. Nine spawning grounds were subsequently constructed in selected locations that were specially adapted to meet the environmental requirements of salmonid fish. This led to a significant increase in the number of nests to 23 after one year and 21 after two years. The principal component analysis revealed that the number of nests was positively correlated with both the main components based on the characteristics of the riverbed and the main component based on the chemical parameters. Consequently, fish nests were mainly located in areas characterized by high water flow rates, conductivity, hardness, and alkalinity.

The project was co-financed under the EU Operational Programme „Fisheries and the Sea 2014-2020”, Priority 1. Contract number 00006-6520.13-OR1600008/19/20.