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The Ichthyological Collection of the Faculty of Food Sciences and Fisheries, West Pomeranian University of Technology in Szczecin was founded by Professor Eugeniusz Grabda at the Faculty of Fisheries, Agricultural University of Olsztyn in 1955. In 1968, the collection, with the entire faculty moved to Szczecin and immediately started to develop in the wake of the global expansion of the Polish fisheries fleet in the late 1960s and early 1970s. The main focus were the finfish, but other items represented also aquatic invertebrates, reptilians, and mammals. In the early 1980s, the exhibition halls of the museum were closed and converted to an experimental aquarium unit. The collection was gradually moved either to glass display cabinets in the hallways of the building or to the storage. After a major renovation of the building, the museum officially re-opened on 13 February 2020. The collection consists of 759 specimens with 329 dry ones, 430 formalin preserved, three specimens of tunicates, and one of cephalochordate. This paper provides the inventory list of the collection in the taxonomic arrangement of Nelson with updates from recent ichthyological publications. The most unique exhibit is a female of Acipenser oxyrinchus Mitchill, 1815 caught in 1965 in the Vistula River (next-to-last specimen captured in Poland in the wild), at present the extinct species in the Baltic Sea basin. Important items of our collection are also Salmo salar Linnaeus, 1758 breeders caught in the Drawa River in 1970, currently extinct in Poland in the wild since the 1980s.

Round goby Neogobius melanostomus (Pallas 1814) has become a significant component in the diet of piscivorous fish from the Pomeranian Bay (Bornholm Basin, Baltic Sea). Proper identification of fish species in the diet of predators is significant in biological studies of fish and other aquatic animal species, and, with regard to N. melanostomus, it is important to the knowledge of trophic web structures in areas this species has invaded. A total of 142 individuals of N. melanostomus, measuring 16-174 mm standard length, were examined. Seventy-two fishes were caught during monitoring surveys in fishing grounds, whereas 70 were found in the stomachs of European perch Perca fluviatilis, pike-perch Sander lucioperca and Baltic cod Gadus morhua. The objective of the present study was to analyse the sagittal otoliths to identify variations in outer shape with increases in fish length; expand and correct descriptions of the sagitta, lapillus and asteriscus otoliths; and evaluate the relationships among otolith dimensions and fish standard length. The otoliths were described morphologically. The analysis of the outer shape of sagittal otoliths using Fourier analysis and multivariate statistics exhibited great phenotypic variability that was associated with fish length, including within pairs in individuals and/or among individuals in length classes. In addition, the asterisci and lapilli of N. melanostomus from selected specimens, which were described for the first time with regard to fish length, were found to be less variable compared to sagittal otoliths. This study presents the first analysis of intrapopulation phenotypic plasticity of N. melanostomus sagittal otolith morphology as it is linked to fish size.

This paper reports the occurrence of three new fish species, extremely rare in the Baltic Sea, and provides new data on their parasite fauna. The fish collected were Barbus barbus (Linnaeus, 1758), Salvelinus fontinalis (Mitchill, 1814), and Scophthalmus rhombus (Linnaeus, 1758). Their taxonomic identity was confirmed through genetic analyses using DNA extracted from fin clips. The stomach contents were examined, and age was determined by otolith or scale readings. Parasitological examinations focused on the skin, vitreous humour, eye lenses, mouth and nasal cavities, gills, gonads, viscera, and muscles. Furthermore, the changes of fish species composition over 20 years in Pomeranian Bay were analysed. The sequence comparisons against GenBank records revealed that sequences obtained for B. barbus and S. rhombus from Pomeranian Bay represent new rhodopsin barcodes. Record of the juvenile B. barbus in this study is the first in the Baltic Sea. Scophthalmus rhombus is a new host for the ciliate Trichodina jadranica, while Neogobius melanostomus (Pallas, 1814) is a new food item in the diet of S. rhombus in the Baltic Sea. Acanthocephalan Pomphorhynchus laevis found in the adult specimen of B. barbus and myxozoan Myxobolus musculi, noted in the juvenile specimen, have not been recorded previously in this fish species in Polish waters. Species collected as bycatch can potentially be used for monitoring potential changes in the overall fish community structure and biodiversity.

Summary: Etmopterus spinax is a deep-sea shark species that inhabits the northeast Atlantic and the western Mediterranean Sea. Skagerrak and Kattegat are reported to be part of the distribution of the species, but it has never been noted in the southern Baltic. Lacking any commercial value and commonly discarded in trawl and longline fisheries, E. spinax has been poorly studied. We reported on the first record of one specimen of E. spinax caught in the Pomeranian Bay on October 13, 2016 at a depth of 10 m. It was a female measuring 42.7 cm in total length. The morphological examination of the specimen was supported with COI barcode analysis, whereas species assignment to the population of origin was conducted based on a control region (CR) sequence of mtDNA. COI and CR sequence searches against GeneBank confirmed its identity as E. spinax and revealed that the specimen shared identical haplotypes with fish from populations in the Azores, Rockall Trough, and west of Ireland in the northeast Atlantic. The stomach contents, parasitic fauna, and hepatosomatic index of the individual were also examined. Only one L3 larval Anisakis simplex nematode specimen was collected from the stomach lumen of the shark. The specimen could have arrived in the Pomeranian Bay along with an inflow from the North Sea. In December 2014, a strong Major Baltic Inflow brought large amounts of water into the Baltic Sea, followed by some inflows of moderate intensity. Keywords: Etmopterus spinax, Anisakis simplex, Pomeranian Bay, Southern Baltic Sea, Inflow from the North Sea

Atlantic cod ( Gadus morhua L.) is one of the most important fish species in the fisheries industries of many countries; however, these fish are often infected with parasites. The detection of pathogenic larval nematodes is usually performed in fish processing facilities by visual examination using candling or by digesting muscles in artificial digestive juices, but these methods are both time and labor intensive. This article presents an innovative approach to the analysis of cod parasites from both the Atlantic and Baltic Sea areas through the application of rough set theory, one of the methods of artificial intelligence, for the prediction of food safety in a food production chain. The parasitological examinations were performed focusing on nematode larvae pathogenic to humans, e.g., Anisakis simplex, Contracaecum osculatum, and Pseudoterranova decipiens. The analysis allowed identification of protocols with which it is possible to make preliminary estimates of the quantity and quality of parasites found in cod catches before detailed analyses are performed. The results indicate that the method used can be an effective analytical tool for these types of data. To achieve this goal, a database is needed that contains the patterns intensity of parasite infections and the conditions of commercial fish species in different localities in their distributions.

The snakeblenny, Lumpenus lampretaeformis, is a post glacial relict from the last ice age in the Baltic Sea. Reliable data on its diet, parasite fauna, distribution, population size, and population trends in the Baltic Sea are lacking. In the Polish zone it has been observed only in ICES subdivisions 25 (Slupsk Furrow) and 26 (Puck Bay, Krynica Morska, Wladyslawowo and Vistula mouth fishing grounds) at depths of 30-70 m; however, in recent decades only one finding of snakeblenny in Polish waters has been reported. This paper reports the record of one female specimen from the Gulf of Gdansk. The individual’s morphological characters, stomach contents, parasitic fauna, age and gonadosomatic index were examined. The parasitological examination, which was undertaken for the first time on a specimen from the Baltic Sea since the 1930s, revealed that L. lampretaeformis was the host of one parasite species, namely a juvenile acanthocephalan Echinorhynchus gadi. Additionally, Pontoporeia fermorata and Halicryptus spinulosus were recorded in the stomach of snakeblenny for the first time in the Baltic Sea. CORRESPONDING AUTHOR: B. Wiecaszek [+], E. Sobecka, K. Gorecka Department of Hydrobiology, Ichthyology and Biotechnology of Breeding, Faculty of Food Sciences and Fisheries West Pomeranian University of Technology in Szczecin 71-550 Szczecin, 4, K. Krolewicza st., Poland e-mail: beata.wiecaszek@zut.edu.pl M. Szulc Department of Sea Fisheries, Maritime University Waly Chrobrego 1/2, 70-500 Szczecin, Poland

This paper presents the results of studies on endangered and rare non-commercial fish species (Spinachia spinachia, Nerophis ophidion, Syngnathus typhle, Agonus cataphractus, Pholis gunnellus, Enchelyopus cimbrius, Cyclopterus lumpus) and one lamprey species (Lampetra fluviatilis), recorded as bycatch during monitoring surveys in 2010–2013 in the Pomeranian Bay. Two species were observed for the first time in the Pomeranian Bay: A. cataphractus and E. cimbrius. Descriptions of parasite fauna are provided for C. lumpus and E. cimbrius, which were infected with four pathogenic species from Neomonada, Digenea, Nematoda, and Acanthocephala. Almost all parasite species were new in the hosts examined.

The research was conducted on the parasite fauna and food composition of Eutrigla gurnardus caught as by-catch in commercial catches of the Atlantic cod Gadus morhua near the Shetland Islands. Thirteen species and two genera of pathogens were identified, including six species and one genus recorded for the first time in this host. Copepoda — Euphausiacea dominated in the stomach contents (they are also the intermediate hosts for most of the parasites found), while Gadidae dominated among the fish. A checklist of E. gurnardus parasites is included.

Summary An Atlantic cod, Gadus morhua L., with unique golden pigmentation was caught during a commercial trawl on the Svalbard Bank. Stomach content analysis excluded the possibility of golden pigmentation resulting from diet. Skin morphology, mitochondrial and molecular species markers and also the concentration of melatonin (MEL) were examined. Skin samples from five areas below and above the lateral line contained correctly developed melanophores, but their distribution was different from those observed in the skin samples of standard coloured cod. Only the difference between the numbers of melanophores below the lateral line was statistically significant (8 vs 19.8 in standard coloured cod). DNA analyses allowed exclusion of the possibility of interspecies hybridisation with haddock Melanogrammus aeglefinus. MEL concentrations in the skin sample of the golden cod compared to the control sample of standard coloured cod were similar and with no statistically significant differences. Some abnormalities observed in the detailed morphology and melanophore distribution suggest a genetic or hormonal nature in the golden pigmentation of the cod. Some of these, e.g. mutations of TYR (tyrosinase) genes or of the MSH (melanophore-stimulating hormone) level can be tested in further analyses.

Background. Chiasmodon harteli Melo, 2009 is a rarely captured deepwater fish. Even though the taxonomy of this genus is fairly well resolved, very little is known about the biology of individual Chiasmodon species. The objective of the presently reported study was to supplement new knowledge on C. harteli. Materials and methods. A single female specimen of C. harteli was captured on 1 July 2008 off the south-eastern coast of Greenland during bottom trawling at the depth of 1000 m. Morphometric and meristic data were collected and absolute values of the measurements [to the nearest 0.1 mm] were also related to the fish standard length and head length. To determine the gonad maturity stage, ovaries were fixed in Bouin’s solution and buffered formalin (4%), dehydrated, embedded in paraffin wax, cut into 5-μm histological sections and finally stained with haematoxylin and eosin. Parasitological examinations covered the skin, eyes, mouth, nasal cavities, gills, gonads, spleen, gastrointestinal tract, liver, kidneys, peritoneum, and muscles. Parasites recovered were preserved in 70% ethanol. Results. Detailed morphometrics, including metric and meristic characters, as well as dentition formula, are provided. The individual studied was a mature female. The ovaries were in stage I  (Merson scale) (mature, featuring oocytes in early vitellogenesis and oogonies). The mean oocyte cell diameter was 84.62 ± 4.67 µm, while the range: 45.05–114.08 µm. The fish hosted only one parasite species—Anisakis simplex (Nematoda; encysted L3 larvae). The stomach of the specimen studied was enlarged, although completely empty. Conclusion. This is the first substantiated record of this species since its original description in 2009. The structure of female gonads of C. harteli was described here for the first time. The acquired data on the gonadal development may shed new light on the species’ reproduction and may help to approximate the spawning time. The nematode A. simplex were reported herein for the first time in a Chiasmodon.

The first occurrence of striped red mullet Mullus surmuletus in the Pomeranian Bay (in 2007) and the occurrence of three very rarely noted species (tub gurnard Chelidonichthys lucerna , Atlantic horse mackerel Trachurus trachurus , thicklip grey mullet Chelon labrosus ) collected in 2007–2008 in the Pomeranian Bay, Szczecin Lagoon and Lake Dąbie are reported. Their expansion is probably due to increased sea temperatures resulting from climate change, as well as the inflow of saline water. The ‘visitors’ hosted eight pathogens from four taxonomic groups: Protozoa, Nematoda, Acanthocephala and Mollusca. Nematodes, the most numerous ones, were found in three host species. All the parasite species were new for the hosts examined; only the larvae of the acanthocephalan Corynosoma strumosum had already been recorded in one of the hosts ( Chelidonichthys lucerna ). The stomachs of almost all the fish examined were empty, but the species composition of the parasite fauna found showed that the fish must have ingested some food in the Pomeranian Bay.

Parasite community structure of cod from Bear Island (Barents Sea) and Pomeranian Bay (Baltic Sea) A total of 142 cods: 60 from the South-East Ground of Bear Island and 82 from the Pomeranian Bay (Baltic Sea) were examined for their ecto- and endoparasites. Twenty different parasite species, comprising one Myxosporea, three Cestoda, four Digenea, seven Nematoda, three Acanthocephala and two Crustacea were found. The parasite component communities comprised 1446 individuals (17 species, six higher taxa) from the Bear Island and 6588 individuals (nine species, three higher taxa) from Pomeranian Bay. The observed parasite host specificity was low, and the intensity in a single fish ranged from one to 279 specimens. The eudominant parasite species were Echinorhynchus gadi, Hemiurus levinseni and Contracaecum osculatum. The dominant parasite communities from the Bear Island were nematodes, but acanthocephalans dominated in cod from the Baltic Sea. It appears that one group of parasites, better adapted for the specific conditions of the macrohabitat, has replaced another. The most prevalent parasites were E. gadi, Anisakis simplex, C. osculatum and Hysterothylacium aduncum, and the mean values of crowding were the highest for E. gadi and Pomphorhynchus laevis. The nematode Camallanus lacustris was noted in this host species for the first time. Only six species of parasites were common to cod from both fishing grounds.

Analysis of stomach contents of 52 cod (Gadus morhua callarias) individuals (TL 37.0–58.0 cm) caught in November 2003 in the coastal waters of the Gulf of Gdansk showed the presence of the prawn Palaemon elegans, a malacostracan species that has been recently reported as abundant in various parts of the Baltic Sea. This is the first observation of P. elegans as a cod food item in the Baltic Sea. The prawns were found in 88.5% of the stomachs analysed, accounting for 17% and almost 7% of food weight of cod

This is a checklist of 51 pathogens of lamprey species found in Poland, including European river lamprey Lampetra fluviatilis (Linnaeus, 1758), European brook lamprey Lampetra planeri (Bloch, 1784), Ukrainian brook lamprey Eudontomyzon mariae (Berg, 1931), Danubian brook lamprey Eudontomyzon vladykovi Oliva and Zanandrea, 1959 and sea lamprey Petromyzon marinus Linnaeus, 1758.

Effect of Specific Host Body Pigmentation on the Number and Species Composition of the Parasites of Golden Specimen of CodGadus MorhuaL. From the Svålbard AreaParasitological examination was carried out on a single specimen of the northeast Atlantic codGadus morhua morhuaL., of the unusual golden pigmentation, described for the first time in literature. It was collected together with commercially caught cod of typical colouration in the Svålbard Bank area. Only few endoparasites were found. The golden cod individual hosted five species of parasites: four species of nematodes (Anisakidae) and one of acanthocephalan (Echinorhynchidae). The species composition of parasites was probably affected by the specific golden skin pigmentation of the host.

The Baltic is a semi-enclosed sea characterised by decreasing salinity in the eastern and northern direction with only the deeper parts of the southern Baltic suitable as spawning grounds for marine species like cod. Baltic cod exhibits various adaptations to brackish water conditions, yet the inflow of salty North Sea water near the bottom remains an influence on the spawning success of the Baltic cod. The eastern Baltic population has been very weakly studied in comparison with the western population. The aim of this study is to demonstrate for the first time genetic differentiation by the use of a large number of SNPs between eastern and western Baltic populations existing in differentiated salinity conditions. Two cod samples were collected from the Bay of Gdansk, Poland and one from the Kiel Bight, Germany. Samples were genotyped using a cod derived SNP-array (Illumina) with 10 913 SNPs. A selection of diagnostic SNPs was performed. A set of 7944 validated SNPs were analysed to assess the differentiation of three samples of cod. Results indicated a clear distinctness of the Kiel Bight from the populations of the eastern Baltic. FST comparison between both eastern samples was non-significant. Clustering analysis, principal coordinates analysis and assignment test clearly indicated that the eastern samples should be considered as one subpopulation, well differentiated from the western subpopulation. With the SNP approach, no differentiation between groups containing ‘healthy’ and ‘non-healthy’ cod individuals was observed.

The myxosporean specimens were noted in grey gurnard Eutrigla gurnardus (L.) from the area near the Shetland Islands. The structure and dimensions of its vegetative stage differ from earlier descriptions. A sequence of small subunit ribosomal RNA gene obtained during the current study differs from other Ceratomyxa spp. available in GenBank. A phylogenetic position of parasite based on the 18S rDNA fragment was estimated. The proposed name for this myxosporean is Ceratomyxa gurnardi sp. n.

Background. Asian pangasiids (Actinopterygii: Siluriformes: Pangasiidae), commonly referred to as “panga”, have recently became an important item on the European fish markets. The fish are currently imported from south-east Asia but the growing consumers’ demand is likely to motivate European fish growers to culture the “panga” locally. This in turn could bring about unforeseeable consequences for the aquatic environment. The presently reported study provides the first record of a pangasiid fish (two specimens) from the European natural waters. We attempted to identify the fish through complex morphometric procedures and to study all their parasites, thus determining their potential threat for the environment. Materials and methods. Two specimens of pangasiid fish were captured in a pond, in the city of Szczecin, Poland. The fish were examined following procedures commonly accepted in morphological studies yielding detailed measurements. The key structures were described and illustrated (e.g., the shape of dentition on both the vomerine and palatine plates). The measurements were taken with an electronic calliper and a dissecting microscope (Nikon SMZ 1000), coupled with the Lucia Measurement System. Additionally, during necropsy, selected organs were checked for the presence of parasites. Results. One of the fish specimens hosted the monogenoid parasite, Thaparocleidus caecus, that has never been found in Europe. Metric and meristic characters of fish studied, as well as the presence of monogenoid T. caecus suggest that the fish found were representatives of Pangasianodon hypophthalmus, however, some features, especially those related to the ratio between fins and body or total length, differ markedly from the species description. Comparative analysis suggested that the two specimens collected in Szczecin are hybrids, most likely of P. hypophthalmus with other species, of unknown origin, presumably imported from Thailand. Conclusion. The specific identity of pangasiids imported alive to Europe should be monitored in the future. Additional genetic studies are needed. The monogenoid parasite found on the fish studied poses no threat to the native ichthyofauna (because of its very narrow host-specificity).

In the present paper authors demonstrate detailed biomorphometry of one specimen of the sabrefish (Cyprinidae, Cypriniformes) from the lake D±bie near Szczecin, one specimen of saithe (Gadidae, Gadiformes) caught in the Pomeranian Bay near town Kołobrzeg, and one specimen of sea bass (Moronidae, Perciformes) collected in the Pomeranian Bay, too, near village Trzęsacz.

In the present paper the detailed biometric characteristics of walleye pollock (involving 25 metric and 12 meristic features) is demonstrated, with regard to both sexes. In addition, the comparison is made between the population studied and population of walleye pollock from the Bering Sea (concerning data available in literature) in order to find out if any differences statistically significant exist.

Analysis involving 31 metric and 8 meristic characters was performed on 76 individuals of Atlantic argentine. Moreover, the material investigated was characterised in view of length (l.t.) and weight distribution. Results were presented with regard to both sexes.

The present paper describes biometric characters of eel-pout, Zoarces viviparus (L.) involving 28 metric and 12 meristic features. 208 specimens were examined with regard to both sexes. The materials studied was collected in May 1988, in the Pomeranian Bay. Furthermore, the problem of sex dimorphism in the species, as well as the degree of water salinity-vertebral count relationship were discussed.

Morphometric characteristic of southern blue whiting is presented. It embraces 31 measurable and 9 meristic features. Studies were made on 119 fishes (44 females and 75 males) caught near the Burdwood Bank in the period March-April, 1981. The results were taken advantage of in discussing the homogeneity of southern blue whiting stocks inhibiting various waters of the south hemisphere. Problems of sexual dimorphism in this species have also been discussed.