Pikeperch Sander Lucioperca Research Articles

Tracking the invasive and euryhaline pikeperch Sander lucioperca in the lower River Thames using acoustic telemetry indicates no movements into areas of relatively high salinity.

Native to Central and Eastern Europe, the euryhaline pikeperch Sander lucioperca can acclimatize to elevated salinity levels (e.g., up to 30‰), but it remains unknown whether their invasive populations use this ability to inhabit and/or disperse through brackish waters, such as estuaries and inshore areas. To test whether invasive pikeperch show a propensity to move into areas of relatively high salinity, their spatial use and movement patterns (e.g., home range, distances moved, and movement rates) were assessed using acoustic telemetry in the upper River Thames estuary, southeast England. Analyses revealed that individual pikeperch were capable of moving relatively long distances in a short time (e.g., speeds up to 70 m min-1), with movement patterns associated more with tidal state and elevation at the water surface (both assumed to relate to changes in salinity) than diurnal changes. There were no recorded movements of any pikeperch into the more saline, downstream waters of the estuary where salinity levels were recorded to over 40‰, with the mean salinity in the most downstream area where pikeperch were detected being 1.39‰ (range of logger: 1.22-1.71). The results suggest that these pikeperch did not use high salinity waters when less saline waters were available, and thus the risk that they will use to move through high salinity areas to expand their invasive range appears low. Accordingly, efforts to minimize risks of the further dispersal of invasive pikeperch populations can focus on control and containment programmes within fresh waters.

Movements and habitat use of native and invasive piscivorous fishes in a temperate and channelized lowland river

AbstractLowland temperate rivers provide important habitats for piscivorous fishes, but with their year-round spatial and temporal habitat use is often poorly understood, including their use of off-channel habitats. Here, the movements and habitat use of the piscivorous native Northern pike Esox lucius and invasive pikeperch Sander lucioperca were investigated using acoustic telemetry in the highly regulated (through impoundment) lower River Severn, Western England over a 12-month period, where off-channel habitat availability was limited to a single boat marina. The movements of both species varied with season and temperature, with both species moving greater distances in spring. Increasing water temperatures up to 15 °C resulted in a higher frequency of movements of both species, but movements then decreased at temperatures higher than this. Northern pike detections in the river increased in periods of lower river discharge and warmer temperatures, with the off-channel refuge providing an important habitat all year round (78% of detections occurred there). While 63% of pikeperch detections also occurred in the marina, 89% of these detections occurred between December and April. These results thus emphasise the importance of this limited off-channel habitat as potential spawning locations for invasive pikeperch and foraging areas for native Northern pike.

Возраст и рост обыкновенного судака Sander lucioperca в разнотипных водоемах юга Западной Сибири

The age and growth of fish are the most important characteristics underlying the assessment of the state of fish stocks and the forecasting of future catches. The pike-perch Sander lucioperca (Linnaeus, 1758) is an alien fish species in Western Siberia. It was first introduced into the Ob basin in 1956. The introduction of this species into the Novosibirsk reservoir was carried out in 1959-1964, and into Lake Chany in 1964-1966. Currently, pike-perch is spread throughout the Ob basin and is an important fishery target. This study summarizes long-term data from the Novosibirsk branch of Russian Federal Research Institute of Fisheries and Oceanography ("VNIRO") about the growth of different-aged individuals of the pike-perch, collected during monitoring of aquatic biological resources in the Novosibirsk reservoir (54°20' N, 81°57'E) and Lake Chany (54°55'N, 77°31'E) over the last 10 years (2013-2022). These water bodies are of different types: the Novosibirsk reservoir was formed on the Ob River, the maximum depth reaches 25 m, the average depth is 8 m. The area of the reservoir is 1.07 thousand km^. Lake Chany is located in the Ob-Irtysh interfluve, drainless, filled due to the runoff of the Kargat and Chulym rivers, atmospheric precipitation and groundwater. The maximum depth is up to 8 m, average depth is 2 m. The area of the lake fluctuates greatly from year to year depending on the water level, in the long-term aspect it has tends to decrease, currently amounting to about 2 thousand km. The lake water has increased mineralization in most of the reaches. Fish collection for analysis of size characteristics is carried out annually from commercial catches. The total volume of material for this study was 2953 individuals from Lake Chany and 1102 individuals from the Novosibirsk reservoir. As a result of this work, it was found that in commercial catches in different types of water bodies in the south of Western Siberia, pike-perch has been known at the age of up to 14+ years over the last 10 years. In Lake Chany, there were mostly individuals of age groups 2+-4+, and in the Novosibirsk Reservoir - 3+-6+ (See Fig. 1). The pike-perch size of the same age from commercial catches varies greatly from one year to the next in Lake Chany, and in the Novosibirsk reservoir (See Fig. 2). It confirms the data on significant variability in growth rates of this species and indicating the need for a cautious approach to comparing the length and weight of pike perch in different observation periods. On average, over the last decade, pike-perch in Lake Chany is characterized by a slightly shorter standard length and greater weight than in the Novosibirsk Reservoir, however, the differences reach statistical significance (p < 0.001) only when comparing fish aged 2+ by standard length (See Fig. 3). The analysis of the relationship between the growth rate of pike-perch and environmental temperature showed that the absolute increase per year of standard length and weight of younger age groups fish in the Novosibirsk Reservoir has a statistically significant positive correlation with the temperature in April (r = 0.6110.775), and in Lake Chany - in May (r = 0.633-0.737) (See Tables 1, 2). Considering that the average April temperature in the area of the Novosibirsk reservoir is 1.9°C higher than in the area of Lake Chany, probably, in the latter, juvenile pike-perch begins to actively feeding a little later. It may explain the smaller sizes of pike-perch of younger age groups in Lake Chany compared to the Novosibirsk reservoir. The article contains 4 Figures, 2 Tables and 28 References. The authors express their gratitude to all colleagues - employees of the Novosibirsk Branch of "VNIRO", who over in different years took part in collecting the material. The Authors declare no conflict of interest.

Development of standards for artificial reproduction of pike perch Sander lucioperca in the West Siberian Fishery Basin (Novosibirsk region)

The results of fish-breeding works on artificial reproduction of sander — Stizostedion lucioperca in the West Siberian fishery basin, carried out at the fish-breeding and production base of LLC “Rybkhoz”, are presented. In the course of the research, standards for artificial reproduction of sander were worked out, taking into account the indicators approved for other regions of the country by the Order of the Ministry of Agriculture of the Russian Federation dated 30.01.2015 № 25, “On approval of the Methodology for calculating the volume of extraction (catch) of aquatic biological resources necessary to ensure the conservation of aquatic biological resources and ensure the activities of fish farms, when fishing for aquaculture (fish farming)”, as well as according to literary sources. Such biotechnical indicators have not been developed for the West Siberian Fishery basin before. The process is briefly described, including trapping, transportation and bonitization of producers, their injection, obtaining eggs, fertilization, de-gluing and incubation, rearing of sander juveniles up to 0.5 g. The producers selected for artificial reproduction were divided into three experimental groups by weight categories, which were subsequently kept in the same conditions to obtain reliable results fertilization and incubation of eggs. Recommendations are given on the selection of the most suitable producers of sander with an average weight of 1.7 kg, superior to other weight groups in terms of relative fertility, the percentage of maturation of producers and the percentage of fertilization of eggs obtained from them. Recommendations are also given on the conditions for the rearing of juvenile and its release into the reservoirs of the Novosibirsk region.

Species diversity and dynamics fishery catch in Omsk region

There are 19 species of fish were noted, however, only 11 species included in the fishing statistics. The main commercial value are fishes of the genus Carassius (Carassius carassius and C. gibelio) — 47.6% of fish catches in the region and perch Perca fluviatilis — 22.4%. Roach Rutilus rutilus, pike Esox lucius, pike-perch Sander lucioperca, bream Abramis brama, peled Coregonus peled and carp Cyprinus carpio are relatively few in catches and account for 7.4, 6.2, 4.7, 4.6, 4.6, 1.2%, respectively. The composition of the fish community, as well as their ratio in catches, is not the same for different water bodies of the Omsk region. First of all, this is due to the peculiarities of fish ecology, the diversity of water bodies and the fishing strategy for them. The main volume of fish production in the region is provided by small and medium-sized lakes, in which more than 55% of the region’s fish are caught (average over last 7 years). About 39% of all fish in the region are caught on the large lakes Ik and Saltaim-Tenis. The total volume of fish caught in the region over the past 7 years is 9.2 thousand tons, which is significantly less than the potential volume of fish production — 20.9 thousand tons. The main reasons for the underutilization of stocks are: insufficient volumes of introduction and catch of peled and carp — objects of pasture aquaculture; overfishing in some years, leading to depletion of stocks and a decrease in catches in the following periods.

Otolith Biometry of Pikeperch Sander lucioperca from the Lakes Region of Turkey

Otolith Biometry of Pikeperch Sander lucioperca from the Lakes Region of Turkey

Interannual variability in the trophic niche of young‐of‐year fish belonging to four piscivorous species coexisting in a natural lake

Abstract Predatory fish species play a key role in aquatic ecosystems by exerting top‐down control on the food web. Also, their intra‐guild trophic interactions (i.e. competition) are crucial for the stability of the community. However, most studies focus on adult stages, while juveniles remain poorly studied, although their recruitment is the basis for the maintenance of predator populations. We analysed carbon and nitrogen stable isotopes ratios of the young‐of‐year of four coexisting widespread predatory fish species (northern pike Esox lucius, European perch Perca fluviatilis, pikeperch Sander lucioperca, and European catfish Silurus glanis), sampled over 3 years in a shallow natural lake. We found that the hierarchy in trophic position between species was consistent across years and similar to that known for adults, but with large variations around a general pattern: pike and pikeperch tended to occupy the highest trophic positions while perch occupied the lowest, and catfish had very varying positions. Species partitioned their niches to decrease interspecific competition, but with some occasional overlaps, contributing to preserving their body condition. Depending on density, which was particularly impacted by harsh environmental conditions, niche overlap fluctuated across years, leading to niche enlargement of densely populated species, except for catfish. These mechanisms enabled species coexistence, allowing the co‐occurrence of alien and native predators within the same ecosystem. This work advocates for time‐integrated studies of trophic webs because they capture the variability of their dynamics better than a static picture. This is particularly true for juveniles whose survival strongly depends on their capacity to cope with competition. Information from trophic mid‐term studies of juveniles provides valuable guidance for optimised management of species.

Fishes in the economy of Ancient Greek colonies (600 BC – 300 AD) on the Northern Black Sea Coast – new touches to an old portrait

The article presents the results of a thorough study of fish remains recovered during the excavations of three ancient Greek cities (Olbia, Berezan and Chornomorka) in the northern part of the Black Sea coast. These materials are dated in the range of 600 BC – 300 AC (in the case of Olbia and Berezan), and 500–400 BC for Chornomorka. Fish bones were processed for the identification of species used by the inhabitants of these ancient cities for food. The remains of about ten fish species are present in the studied sample. Of them, sturgeons (Acipenser spp.) were the most numerous in the region at that time. The other species which were usually caught in these ancient Greek cities are mostly represented by carp fishes (roach, common bream, white bream, blue bream, common carp, and crucian carp), but also European catfish Silurus glanis, pike Esox lucius, and pikeperch Sander lucioperca. The weight and size of some fish individuals were reconstructed based on complete bones. Comparison of the specimens from individual samples (series) showed no significant differences in their total length and weight. The economic activity of ancient settlements of the Northern Black Sea region is of interest to archaeologists for a long time. Many of the aspects of this activity, such as agriculture, crafts, and architecture, have been explored quite well (e.g., Christodoulou 2016 and references therein). At the same time, fishery, an important direction of the economy of coastal cities providing a valuable animal protein, often falls out of the scope of research interests. A significant amount of materials collected by archaeologists in the north of the Black Sea coast during the 20th century is still not processed and remains unpublished. Therefore, it is difficult to create a holistic picture of the economy of ancient Greek cities. A valuable information about fishing and fish consumption in ancient cities of the Northern Black Sea region according to archaeological data and osteological collections is presented in Lebedev (1960), Zhiteneva (1964), Hojte (2005), Morales et al. (2007) and Odrin (2010). A few recent publications are focused on the fish osteological material from ancient Greek cities discovered on the Northern Black Sea coast. Archaeozoological studies can show how important fish was in the diet of people, which species were preferred, and how intensive was fishing in this region in different periods. In addition, it is possible to find out whether there was a fish trade between these cities using the ratio of cranial and postcranial elements of the skeleton. Such studies can prove or disprove the statements of Strabo or Herodotus, who wrote about the culinary preferences of ancient Greeks. Therefore, the aim of this article is to present in detail the results of the study of fish bone samples from Olbia, Berezan and Chornomorka in the range from their formation (600 BC) until the end of the Roman period (300 AD). By comparing data from different periods, it is possible to track the role of fishery in the economy of these settlements and its dynamics over time. Key words: Olbia, antiquity, Berezan, archaeozoology, fishing, ancient Greeks, Black Sea

Carotenoids and retinoids in the gonad of brood-stock pikeperch: accumulation during vitellogenesis and influence on egg quality in farmed pikeperch Sander lucioperca.

Carotenoids are determinants of reproductive fitness and egg quality. Here we studied the accumulation of astaxanthin (AX), canthaxanthin (CA) zeaxanthin (ZX), lutein (LU), retinol (RX) and dehydroretinol (DR) during vitellogenesis comparing previtellogenic and vitellogenic pikeperch (Sander lucioperca) eggs (n = 5 each), as well as selected tissues (liver, fat and muscles) in first süawning females (1176-1450 g). Futhermore, we compared egg batches with high (88-99% hatching rate, n = 5) or low (40-67% hatching rate, n= 5) egg quality. Vitellogenic follicles revealed higher concentrations of DR, RX, ZX and LU compared to previtellogenic follicles. Neither CA nor AX was detectable. In parallel, DR and RX were mobilized in the liver. In adipose and muscle tissue, comparing previtellogenic and vitellogenic females, no significant differences in carotenoid/retinoid content were observed. In high quality egg batches, both DR and RX were increased. LU was lower in high quality than in low quality eggs. In a conclusion, the amount of retinoids seems suboptimal in low quality egg batches and increased DR and RX are desirable in pikeperch. Since hypervitaminosis of retinoids can be problematic though, supplementation of the food with carotenoids, which can serve as precursors for retinoids, has to be carried out carefully.

Содержание тяжелых металлов в мышечной ткани судака Sander lucioperca в разных плесах Рыбинского водохранилища

The Rybinsk Reservoir is one of the largest artificial reservoirs in Russia. The Sheksna reach of the Reservoir is worst anthropogenically affected due to the waste waters of the Cherepovets industrial plants. Heavy metals en-tering the Reservoir can accumulate in the body of fish including the predators ‒ the last link in the trophic chains of the Reservoir. Purpose of the study is to register the concentration of heavy metals in the muscles of the pikeperch Sander lucioperca in the Rybinsk Reservoir and to define its compliance with the Russian and international standards. The fish were caught in the feeding period with a trawl in the Sheksna and Volzhsky reaches, measured, and fatness coefficients were calculated according to Fulton and Clark. The content of Cd, Cr, Pb, Cu, Mn, Fe, Al, Co, Ni, V was determined in the fish muscle tissues. Fatness of pikeperch from the Rybinsk Reservoir, regardless of the level of the local anthropogenic pollution, corresponded to the mean values typical to this species. In the pikeperch muscles the content of nickel and vanadium was below the detection limit. On average, the tissues contained Cd 0.004, Cr 0.095, Pb 0.028, Cu 0.734, Mn 0.205, Fe 4.986, Al 12.538, Co 0.002 in mg/kg wet weight. Concentration of Fe, Al, Mn in the muscle tissues of pikeperch from the Sheksna reach significantly exceeded the values of Fe, Al, Mn in the muscle tissue of pikeperch in the Volga reach. Consumption of pikeperch meat from the Rybinsk Reservoir is not potentially hazardous to human health, since concentrations of heavy metals in the muscle tissues of the studied species do not exceed the permissible levels of elements, according to the Russian and international standards.

Case study on the aptness of in-pond raceways for pikeperch, Sander lucioperca, grow-out

Pikeperch Sander lucioperca is a species of increasing presence in recirculation aquaculture system and the vast majority of thus far research was dedicated to its indoor farming. Concerning the present pond infrastructure in Central and East Europe, it is of interest to evaluate the intensive pond-connected system for pikeperch rearing. Therefore, the present study evaluated the grow-out performance in recirculation aquaculture system (RAS) and in-pond-raceway (IPR) in triplicated tanks. A 16-week trial with 1-year-old pikeperch (mean weight 215.7 ± 8.1 g RAS and 217.7 ± 2.6 g IPR) was conducted from June to October evaluating both culture and welfare parameters. Significantly higher final mean weight (443.1 ± 17.5 vs 400.6 ± 13.2) and lower feed conversion (2.1 ± 0.1 vs 3.0 ± 0.1) was obtained in fish reared in IPR. Cortisol levels were overall higher in the RAS group throughout the trial being significantly higher at the first and last sampling. Elevated lysozyme levels were found in IPR in the first half of the trial, while further on they were higher in RAS being significantly higher compared to IPR in middle sampling. Thus, both in terms of culture performance and fish welfare, IPR proves aptness for pikeperch rearing. This study presents the first insight into the suitability of pond-connected intensive rearing of pikeperch describing IPR as a promising system for final grow-out during the growing season. More comprehensive studies in terms of stocking densities and growing period are required to explore the full potential of pikeperch outdoor farming.

Risk of invasiveness of non-native fishes in the South Caucasus biodiversity and geopolitical hotspot

Aquatic invasions are one of the major threats for freshwater ecosystems. However, in developing countries, knowledge of biological invasions, essential for the implementation of appropriate legislation, is often limited if not entirely lacking. In this regard, the identification of potentially invasive non-native species by risk screening, followed by a full risk assessment of the species ranked as higher risk, enables decision-makers to be informed about the extent of the threats posed to the recipient (risk assessment) area. In this study, 32 non-native extant and horizon fish species were screened for their risk of invasiveness under current and predicted climate conditions for the South Caucasus – a biodiversity and geopolitical hotspot that includes the countries of Armenia, Azerbaijan and Georgia. Overall, the number of very high-risk species increased from four (12.5%) under current climate conditions to 12 (37.5%) under predicted climate conditions. The highest-risk species under both conditions included the already established gibel carp Carassius gibelio and topmouth gudgeon Pseudorasbora parva, the locally translocated pikeperch Sander lucioperca and the horizon North African catfish Clarias gariepinus. Under predicted climate conditions, a very high risk of invasiveness was predicted also for the translocated three-spined stickleback Gasterosteus aculeatus and Eurasian perch Perca fluviatilis, for the already established eastern mosquitofish Gambusia holbrooki, ruffe Gymnocephalus cernua, sharpbelly Hemiculter leucisculus and Nile tilapia Orechromis niloticus, and for the horizon pumpkinseed Lepomis gibbosus and largemouth bass Micropterus salmoides. Future research on the non-native species in the South Caucasus should be conducted both country- and region-wide and should account not only for the high biodiversity, but also for the critical geopolitical situation affecting the study area.

Impacts of Recreational Angling on Fish Population Recovery after a Commercial Fishing Ban

It is often assumed that recreational fishing has negligible influences on fish stocks compared to commercial fishing. However, for inland water bodies in densely populated areas, this assumption may not be supported. In this study, we demonstrate variable stock recovery rates among different fish species with similar life histories in a large productive inland freshwater ecosystem (Kaunas Reservoir, Lithuania), where previously intensive commercial fishing has been banned since 2013. We conducted over 900 surveys of recreational anglers from 2016 to 2021 to document recreational fishing catches and combined these catch estimates with drone and fishfinder device-based assessments of recreational fishing effort. Fish population recovery rates were assessed using a standardized catch-per-unit-effort time series in independent scientific surveys. We show that recreational fishing is slowing the recovery of predatory species, such as pikeperch Sander lucioperca (Linnaeus, 1758) and Eurasian perch Perca fluviatilis Linnaeus, 1758. The estimated annual recreational catches for these species were 19 tons (min-max of 7–55 tons) and 9 tons (4–28), respectively, which was considerably higher than the average commercial catch before the fishery closure (10 and 1 tons, respectively). In contrast, the recovery of roach Rutilus rutilus (Linnaeus, 1758), rarely caught by anglers (annual recreational catch of ca 3 tons compared to ca 100 tons of commercial catch), has been rapid, and the species is now dominating the ecosystem. Our study demonstrates that recreational fishing can have strong and selective impacts on fish species, reduce predator abundance, alter relative species composition and potentially change ecosystem state and dynamics.

The Effect of Some Natural Antioxidants on Quality Properties of Pikeperch (Sander lucioperca) Meat Balls

Bu çalışmada bazı doğal antioksidanların sudak balığı (Sander lucioperca) köftelerinin kalitesine etkileri araştırılmıştır. Bu amaçla balık kıymasına portakal ve limon özütü hem birlikte hem de ayrı ayrı ilave edilerek çeşitli baharat ve katkı maddeleri ile balık köfteleri elde edilmiştir. Çalışmada portakal özütü ilaveli grup (P), limon özütü ilaveli grup (L), portakal ve limonun birlikte ilave edildiği grup (PL) ve hiçbir meyve özütünün ilave edilmediği klasik balık köftesi grubu (K) olmak üzere 4 farklı grup oluşturulmuştur. Balık köfteleri raf ömrü tespiti amacıyla duyusal ve mikrobiyolojik analizleri yapılmış ve 4±1oC’de muhafaza edilmiştir. Mikrobiyolojik analizlerde Toplam Mesofilik Aerobik Bakteri (TMAB), Toplam Psikrofilik Aerobik Bakteri (TPAB) ve Laktik Asit Bakteri (LAB) sayıları depolama süresince gruplara göre farklı değerler sergilemiştir. Çalışma sonuçlarına göre, kullanılan bitki özütleri sudak köftelerini daha iyi korumuştur. Kontrol grubu 15 günde tüketilemeyecek duruma gelirken L ve PL grupları 19. günde, P grubu 21. günde raf ömrünü tamamlamıştır. Duyusal olarak en çok beğenilen grup P grubu olmuştur. En uzun ömürlü ürün de yine P grubu sudak köfteleri olmuştur.

The effectiveness of human chorionic gonadotropin in stimulation of second spermiation in pikeperch Sander lucioperca during the spawning season

The aim of the present study was to evaluate the effectiveness of human chorionic gonadotropin (hCG) in stimulation of second spermiation in already reproduced pikeperch males during the same spawning season. Fish (mean weight 919.9 ± 236.9 g) were divided into the control saline-injected group, and two groups injected with 200 and 400 IU hCG/kg body weight. Forty-eight hours following injection (at a temperature of 16.7 °C) the percentage of fish producing useable amounts of semen increased from 30% in the control group up to 80% in the treated fish and the highest volume of semen was recorded in fish treated with 400 IU/kg BW hCG. Spermatocrit (50.7 ± 9.1%) and sperm concentration (17.5 ± 5.0 × 109 spermatozoa/mL) were significantly higher in control fish than those recorded in hCG-treated fish (24.8 ± 7.7% and 8.1 ± 2.4 × 109 spermatozoa/mL in 200 IU/kg; 32.3 ± 17.6% and 10.9 ± 7.5 × 109 spermatozoa/mL in 400 IU/kg). No significant differences were observed between the groups with respect to sperm motility (as a spermatozoa activity time and percentage); however, a change in plasma alkaline phosphatase activity was found in the group injected with 400 IU/kg of hCG. The lack of significant differences in plasma metabolites and cortisol between control and hCG-treated fish indicated that the hCG had no effect on the stress response. Testosterone levels were significantly increased in the hCG-treated fish, whereas no significant differences in 17β-estradiol were recorded. No differences between the groups in plasma levels of thyroid hormones suggested lack of hCG-induced effect on hypothalamus-pituitary-thyroid axis. The results of this study demonstrated that the spermiation of already reproduced pikeperch males could be induced by hCG during the same spawning season. Based on the results on semen volume and concentration, injection with hCG could improve the efficiency of pikeperch reproduction to reduce the number of brooders and costs of juvenile pikeperch production.

Expanding East: Great Cormorants Phalacrocorax carbo Thriving in the Eastern Baltic and Gulf of Finland

Great Cormorants Phalacrocorax carbo in the eastern Baltic are expanding in numbers. Eight colonies in Estonia, Finland and the Russian Federation were investigated in 2007. Brood size and condition of large nestlings were determined and indicate that food provisioning was not a limiting factor. Food items consisted of both pelagic and benthic prey, with marked differences among the colonies. Eelpout Zoarces viviparus and Roach Rutilus rutilus were the most important prey according to fish mass. For pelagic prey this was Sprat Sprattus sprattus. Additional data in later years support the conclusion that the species experienced a rapid expansion at the time of investigation. Two factors are likely to have contributed to improved conditions for Cormorants in this part of the eastern Baltic. First, the low abundance of predatory fish such as Cod Gadus morhua and Pikeperch Sander lucioperca as a result of overfishing by commercial fisheries as well as climate change has, most likely, caused small benthic and pelagic prey fish to thrive. Second, increased eutrophication has probably fuelled the fish production. Based on fish species taken and the number of Cormorants present, the conclusion seems justified that any interaction between Cormorants and fisheries is unlikely at the scale of the Finnish Gulf, although locally measurable effects of Cormorant consumption on commercial yield may exist. As a visible, relatively new apex predator to the system, the Great Cormorant may well be an indicator of the ecological condition of the system. Monitoring of Cormorants (numbers, distribution, food, breeding success) may therefore provide useful data which can be used to assess the recovery of the benthic and pelagic parts of the food web.

Dietary contributions of the alien zebra mussel Dreissena polymorpha in British freshwater fish suggest low biological resistance to their invasion

AbstractNative communities can resist the establishment and invasion of alien species through consumptive and/or competitive interactions. The extent of consumptive resistance from freshwater fish to the invasion of zebra mussels Dreissena polymorpha, a globally invasive Ponto-Caspian species, was assessed in two areas in Britain using stable isotope analysis, where mixing models predicted the contribution of putative prey resources (including zebra mussel) to fish diet. Across the sites and species, only roach Rutilus rutilus were predicted to have a diet where zebra mussels contributed highly (predicted contribution: 44%), with literature suggesting that their functional morphology would have facilitated their consumption of this prey item. Predicted contributions of zebra mussels to common bream Abramis brama diet was comparatively low (29%), despite them being present to much larger sizes than roach, and with pike Esox lucius, perch Perca fluviatilis and pikeperch Sander lucioperca also predicted to have low dietary contributions of zebra mussels (0.08%, 24% and 24%, respectively). These results suggest the consumptive resistance to its invasion in Britain has been low and, correspondingly, if there is a management desire to further limit the invasion of zebra mussels then relying on biological resistance to limit their invasion appears to be insufficient.

Accumulation of 25 elements in gills, liver, gonads, and muscle of European chub (Squalius cephalus), Cactus roach (Rutilus virgo), and pikeperch (Sander lucioperca) from Zlatar reservoir (Serbia).

Accumulation of Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Se, Si, Sr, and Zn was analyzed in gills, liver, gonads, and muscle of European chub (Squalius cephalus), Cactus roach (Rutilus virgo), and pikeperch (Sander lucioperca) from Zlatar reservoir (Serbia) using inductively coupled plasma optical emission spectrometry (ICP-OES). The highest concentrations of Cu in liver as well as Ba, Ca, Fe, Mn, Na, P, and Sr in gills were detected in all fish species, while the lowest concentrations of Cu, Fe, Mn, Na, and Zn were detected in muscle. Pikeperch had significantly lower concentrations of Ba in all tissues compared to the other species, as well as Fe, P, and Sr in muscle, K, Mg, Mn, Sr, and Zn in gills, and Fe in gonads. European chub had significantly higher concentrations of Ca, Cu, and Zn in muscle, Cu in liver, and Cr and Cu in gonads compared to Cactus roach and pikeperch. Cd concentration in one individual of Cactus roach exceeded the maximum allowed concentration. The muscle was exposed to the lowest pressure of metal pollution in all species, and European chub accumulated more metals compared to the other species. There is no significant health risk due to consumption of investigated species. A major hazard index (HI) contributor in all species was Hg. According to the target carcinogenic risk factor (TR), target hazard quotient (THQ), and HI, men are under lower health risk compared to the women. The TR and THQ for As, Cr, Cu, Fe, Mn, Ni, and Zn as well as HI values were higher for European chub compared to the other species. On the other hand, THQ for Hg was highest for pikeperch.

Impact of spawning season on fillet quality of wild pikeperch (Sander lucioperca)

Pikeperch (Sander lucioperca) is a freshwater fish that has become increasingly popular as a food fish. Within this study, the influence of the spawning process on meat quality was investigated. For this purpose, adult pikeperch was examined directly before and after spawning, and compared regarding physical meat parameters and lipid composition. The results indicate that after spawning, the values of the pH, the electrical conductivity and the yellowness value of fillet were significantly higher than those of the animals sampled before spawning. Analysis of the sum of the total lipid content indicates no differences before and after closed season, but differences in the fatty acid profile were present. Despite significant lower MUFA concentrations, the EPA and DHA showed unaffected high contents. Therefore, the fish muscle indicated an equivalent meat quality. Nevertheless, the significant changes of some physical meat quality parameters after spawning season could have a particular impact on the shelf life and storage of the pikeperch fillet, highlighting the need for further research.

Analysis of Autozygosity Using Whole-Genome Sequence Data of Full-Sib Families in Pikeperch (Sander lucioperca).

Pikeperch (Sander lucioperca) has emerged as a high value species to the aquaculture industry. However, its farming techniques are at an early stage and its production is often performed without a selective breeding program, potentially leading to high levels of inbreeding. In this study, we identified and characterized autozygosity based on genome-wide runs of homozygosity (ROH) on a sample of parental and offspring individuals, determined effective population size (N e ), and assessed relatedness among parental individuals. A mean of 2,235 ± 526 and 1,841 ± 363 ROH segments per individual, resulting in a mean inbreeding coefficient of 0.33 ± 0.06 and 0.25 ± 0.06 were estimated for the progeny and parents, respectively. N e was about 12 until four generations ago and at most 106 for 63 generations in the past, with varying genetic relatedness amongst the parents. This study shows the importance of genomic information when family relationships are unknown and the need of selective breeding programs for reproductive management decisions in the aquaculture industry.