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Novel introductions of largemouth bass, Micropterus salmoides, often cause negative impacts on endemic populations of prey fishes and interspecific competitors. Although many studies have investigated trophic interactions between M. salmoides and smallmouth bass, Micropterus dolomieu, few have included chain pickerel, Esox niger, as a competitor despite similarities in their habitat use. We used stable isotope analysis to investigate the trophic ecology of a recently introduced population of M. salmoides in the Wolastoq|Saint John River. Specifically, we measured carbon (δ13C) and nitrogen (δ15N) isotopes to describe isotopic niches and infer resource use of introduced M. salmoides, M. dolomieu, E. niger, and native yellow perch, Perca flavescens, at various life stages. Our results showed that isotopic niche overlap occurred between M. salmoides and other study species, indicative of resource competition. However, resource use plasticity, as demonstrated by a wide variety of resources (marine, terrestrial, littoral, and pelagic) used by all study species, could potentially reduce interspecific competition. Our findings indicate that competition is highest between adult M. salmoides and E. niger, but the presence of a seasonal marine resource can provide important contributions to diets and potentially reduce competition. Further research should focus on monitoring of long‐term trends to identify the dynamics of all study species as M. salmoides populations become further established and dispersed. [ABSTRACT FROM AUTHOR]

ABSTRACT Artificial propagation and wild release may influence the genetic integrity of wild populations. This practice has been prevalent in fisheries for centuries and is often termed ‘stocking’. In the Laurentian Great Lakes (Great Lakes here‐on), walleye populations faced declines from the 1950s to the 1970s, prompting extensive stocking efforts for restoration. By the mid‐2010s, walleye populations showed signs of recovery, but the genetic legacy of stocking on population structure at the genomic level remains unclear. Using a dataset of 45,600 genome‐aligned SNP loci genotyped in 1075 walleye individuals, we investigated the genetic impacts of over 50 years of stocking across the Great Lakes. Population structure was associated with both natural geographic barriers and stocking from non‐native sources. Admixture between Lake Erie walleye and walleye from the re‐populated Tittabawassee River indicate that stocking may have re‐distributed putatively adaptive alleles around the Great Lakes. Genome scans identified FST outliers and evidence of selective sweeps, indicating local adaptation of spawning populations is likely. Notably, one genomic region showed strong differentiation between Muskegon River and walleye from the Tittabawassee River, which was re‐populated by Muskegon strain walleye, suggesting admixture and selection both impact the observed genetic diversity. Overall, our study underscores how artificial propagation and translocations can significantly alter the evolutionary trajectory of populations. The findings highlight the complex interplay between stocking practices and population genetic diversity, emphasising the need for careful management strategies to preserve the genetic integrity of wild populations amidst conservation efforts. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The pikeperch (Sander lucioperca, Linnaeus, 1758), with its unique characteristics, has gained increasing attention in the aquaculture sector. These include its highly valued and delicious meat, soft white tissue with few intermuscular bones, commendable growth performance, and favorable market acceptance. It is farmed in North, Central, Western, and East Europe through recirculation aquaculture systems (RAS), net pens, and pond aquaculture. Nevertheless, the sensitivity of pikeperch to environmental changes and other aquaculture activities has made the need to provide optimal rearing conditions for the growth and survival of this valuable species a priority in its propagation and rearing industry, whereas the aquaculture stressors (e.g., handling, transporting, stocking density) and environmental conditions (e.g., photoperiod, temperature, oxygen status, water quality, oxidative stress) are inevitable factors in pikeperch aquaculture industries that affect the entire life cycle. Meanwhile, examining the adaptive or maladaptive responses of pikeperch to these stressors, in addition to being able to determine the tolerance limit of the fish, sheds light on the type of tissue, involved organs, and adaptive or maladaptive drivers of the fish. Certainly, identifying this tolerance limit and the organs involved is crucial to optimize the breeding conditions and provide the welfare of these valuable species. Hence, the effects of environmental stressors on pikeperch physiological changes deserve further investigation. Therefore, to help ameliorate management methods in pikeperch culture, this review discussed the pikeperch adaptive or maladaptive reactions to various environmental stressors. Accordingly, this paper identified the leading and complementary indicators (effective causes) inducing stress in pikeperch during aquaculture operations and identified management errors to conserve its safety, welfare, and survival. It will prevent destructive stress consequences that lead to disease, retardation, or lack of growth and reproduction in this species. [ABSTRACT FROM AUTHOR]

The effect of different feed rations on RAS-based pikeperch juveniles' growth parameters was studied. Juvenile pikeperch were reared in three separate experiments (I, II, and III) at a temperature of 24 °C with initial body weights of the fish at 1.3, 9.4, and 25.6 g, respectively. Four applied feed rations increased by 0.5% in each experiment: 3.0, 3.5, 4.0, and 4.5% of body weight per day (BW day−1) in experiment I; 2.0, 2.5, 3.0, and 3.5% BW day−1 in experiment II; 1.0, 1.5, 2.0, and 2.5% BW day−1 in experiment III. Each experiment in triplicates lasted 28 days. The fish were reared in tanks with working volumes of 1.0 m3 each. All experiments were performed in the same recirculating aquaculture system. The stocking density in experiments I, II, and III was 800, 400, and 200 individuals per tank, respectively. The results of experiment I showed the highest specific growth rate (SGR), weight gain (WG), and biomass gain at the feed ration of 4.5% BW day−1 (P < 0.05). In experiment II, feed ration from 2.5 to 3.5% BW day−1 showed the highest final weight (P < 0.05). In experimental III, feed ration of 2.0 and 2.5% BW day−1 showed the highest final weight, SGR, and WG (P < 0.05). Only in experiment III, based on SGR and WG, second-order polynomial regression showed that the optimal feed ration for pikeperch was 2.35–2.39% BW day−1. [ABSTRACT FROM AUTHOR]

The results of our preliminary studies indicated that the diets of predatory fishes can be bioindicators of faunistic changes in ecosystems and indirectly of changes taking place in aquatic environments in the Pomeranian Bay. We examined the diet composition of top predators Gadus morhua, Sander lucioperca, Perca fluviatilis, and the mesopredator Neogobius melanostomus. The diet composition of the perch, pikeperch, and round goby in the Pomeranian Bay was analyzed for the first time. Our findings indicated that perch, an euryphagous species, is the best potential bioindicator because it is present in the area studied most of the year and has a low to moderate feeding index (FI). Baltic cod, also an euryphagous species, could be a good bioindicator in the areas where it is abundant and occurs frequently, but not in the Pomeranian Bay, where it is caught mainly in the fall. Round goby, which is present in the area studied and had a low FI, is a stenophagous species that preys mainly on benthic species, while pikeperch had a very high FI and the least number of prey species in its diet. The results of trophic interaction analysis among the predators analyzed and their non-native/invasive prey are also provided. [ABSTRACT FROM AUTHOR]

In this study, we conducted association analysis between microsatellite markers and growth traits such as body weight, total length, body length, body height, body thickness, head length, snout length, caudal stalk height and caudal length in the F3 population of pikeperch (Sander lucioperca), the fast-growing strain, to identify markers for genetic breeding. The average allele number for each marker was 4.5. The average observed heterozygosity at 0.746 (ranging from 0.520 to 0.954), with expected heterozygosity recorded at 0.691 (with a range of 0.441 to 0.851). The average polymorphism information content was 0.641. The results showed that 38 microsatellite markers had significant association with at least one trait (P<0.05), among which 21 markers, such as HLJSL018, HLJSL021 and HLJSL022, had extremely significant association with the corresponding trait (P<0.01). Specifically, we detected several 2-21 significant microsatellite markers for 9 traits, ranging from 2 to 21, of which only two markers (HLJSL039 and HLJSL042) were identified for body length (P<0.05)； but there are 21 markers significantly associated with the height of the tail stalk, among which 11 markers such as HLJSL018, HLJSL021, and HLJSL022 are highly significant (P<0.01). There are 8 markers significantly associated with body mass, of which HLJSL018 and HLJSL067 are highly significant (P<0.01). A total of 195 dominant genotypes, with a proportion of over 5% higher than the overall mean, were obtained in 38 markers. Each marker obtained 1-10 dominant genotypes, among which HLJSL073 obtained the least dominant genotypes and HLJSL079 obtained the most dominant genotypes. In summary, we assessed the genetic structure of the pikeperch breeding population and identified markers closely associated with growth traits, which can inform the genetic selection of pikeperch. [ABSTRACT FROM AUTHOR]

Understanding inter-annual variation in the density of young-of-the-year fish is an important tool for assessing stock status and guiding management decisions. We analyzed data spanning from 2003 to 2022 collected at Lipno Reservoir in Czechia. The study aimed to identify factors influencing the density of pikeperch (Sander lucioperca), a valuable predatory fish species in European waters. A bimodality test for the size class distribution has revealed the existence of two distinct YOY cohorts: extremely small (ES) and ordinary fingerlings. Using the Bayesian horseshoe prior method with 37 potential predictors, followed by linear regression, we observed that certain environmental factors similarly influenced both cohorts. Higher temperatures during spring and summer, coupled with increased densities of large and medium-sized cladocerans, positively affected the density of both cohorts. However, distinct influences were observed: for ordinary fingerlings, increased summer precipitation and a lower abundance of predators were beneficial, whereas, for ES fingerlings, summer copepod density emerged as an additional positive factor. This study emphasizes the importance of a detailed investigation of factors influencing pikeperch recruitment. Examining these drivers provides a clearer insight into the causes of variations in the early life stage, which is crucial for monitoring and managing populations in temperate reservoirs. [ABSTRACT FROM AUTHOR]

The first evidence for a population establishment of the pikeperch Sander lucioperca in a Balkan reservoir is presented. During a fish monitoring campaign, both adult and juvenile specimens of the species were captured. We employed the Aquatic Species Invasiveness Screening Kit (AS-ISK) to evaluate the invasiveness potential of the species within the reservoir. The estimated AS-ISK score indicated a high risk of invasiveness, with expectations of increased risk in the future. [ABSTRACT FROM AUTHOR]

One of the most persistent challenges in walleye larviculture is the high rate of unobserved mortality occurring within the first 30 days post-hatch. Walleye larviculture is characterized by high mortality rates, but oftentimes, only a fraction of the total mortality in walleye larviculture is observed. Unobserved mortality is frequently attributed to a high rate of cannibalism, but decomposition of larvae and other factors may also be important contributors. Unobserved mortality can make walleye larviculture especially challenging as accurately estimating daily feed rations and forecasting larval production rely on accurate counts of surviving fish. Despite the importance of unobserved mortality, there is little empirical evidence available that assesses the temporal occurrence and causes of unobserved mortality in walleye larviculture. This study assessed when unobserved mortality occurs during walleye larviculture by examining survival at three timepoints (8, 15, and 30 days post-stocking). Tanks were cleaned daily and dead fry were enumerated to account for observed mortality. At the end of each treatment period, the tanks were drained, all remaining fry were enumerated, and the unobserved mortality rate was calculated. While observed mortality trended higher as trial duration increased, unobserved mortality did not increase significantly from the 8-day treatment suggesting that the bulk of unobserved mortality occurs during the first 8 days of walleye larviculture. [ABSTRACT FROM AUTHOR]

Objective: Coldwater releases from reservoirs support economically valuable sport fisheries for salmonids in the southern United States. The tailwater of Lewis Smith Dam in northwestern Alabama supports the only coldwater fishery in the state, with monthly stockings of about 1500 catchable‐size (200–406 mm total length) Rainbow Trout Oncorhynchus mykiss. Historically, the return to angler creel has been low in this fishery, and few large Rainbow Trout are caught. Numerous potential predators of stocked trout exist in this tailwater, including Gulf‐strain Striped Bass Morone saxatilis, which are stocked annually in a downstream reservoir. Thus, the objective of this study was to quantify the amount of predation, which occurs on Rainbow Trout in the Smith Lake tailwater. Methods: Potential predators of Rainbow Trout were collected six times over a 3‐week period after stocking in March, May, June, and October 2018. Result: Rainbow Trout were found in the stomachs of Striped Bass, hybrid striped bass (White Bass Morone chrysops × Striped Bass), Largemouth Bass Micropterus nigricans, and Chain Pickerel Esox niger. Only Striped Bass exhibited substantial predation on stocked Rainbow Trout, with 75% of these fish having at least one trout in their stomach. Of all identifiable prey items, Rainbow Trout composed 82% of the Striped Bass diet by number across all four sample months and constituted more than 65% of the Striped Bass diet by number in each sample month. Bioenergetics models predicted that a population of 500 Striped Bass living continuously in the tailwater from March through October could consume all Rainbow Trout stocked during each month. If Striped Bass vacated the area or switched from trout to other diet items for one‐third of each month, they could still consume almost 60% of stocked trout. Conclusion: Results of this study demonstrate that Striped Bass are significant predators of Rainbow Trout in the Smith Lake tailwater and are likely one of the main factors mediating Rainbow Trout survival and persistence in this fishery. Impact statementLow return rates to anglers of stocked Rainbow Trout in an Alabama tailwater fishery are likely due to high rates of predation by native Gulf‐strain Striped Bass. This research demonstrates that Striped Bass in the tailwater could consume 60% or more of the stocked trout during each month. [ABSTRACT FROM AUTHOR]

The effect of photoperiod on the growth performance, survival rate, swim bladder inflation (SBI) and presence of vertebral anomalies was evaluated in pikeperch larvae reared under intensive production in a recirculating system (RAS). Three different photoperiods were tested from 1 to 30 days post hatch, 12:12 LD, 16:8 LD and 24:0 LD. Larvae were stocked with an initial density of 100 larvae per liter, light intensity of 100 lx and 16.0°C water temperature. The SGR among treatments ranged between 11.17 and 12.04% day−1. The highest survival rate (56.7 ± 2.4%) was found in 24:0 LD with a negative effect on the number of larvae with SBI. The highest presence of vertebral anomalies at 30 dph was found in 24:0 LD (40.8 ± 8.2%) compared to 12:12 LD (2.5 ± 1.4%) and 16:8 LD (1.7 ± 1.6%). These results suggest that constant light compromises culture of pikeperch larvae in RAS. A 16:8 LD photoperiod seems suitable for the growth performance, SBI and low vertebral anomalies at this life stage. [ABSTRACT FROM AUTHOR]

The present study was conducted in the Hammam Debagh reservoir northeastern Algeria from November 2019 to April 2020. To study the age and growth of the Pikeperch (Sander lucioperca) population in this reservoir, 126 specimens were sampled, including 77 males and 49 females. The ages, total lengths, and total weights of the samples ranged from 0- 7 years, 15.7- 57.1cm and 92.1 to 1883g, respectively. The age of the fish was determined by the direct method (scalimetry). The lenght-weight relationship was described by the equation TW = 0.003TL3.28 for total weight and EW = 0.002TL3.43 for eviscerated weight. The ANCOVA test showed no significant difference between the sexes’ slopes of the length-weight relations (F = 3.445, P> 0.05). The von Bertalanffy growth parameters deduced by introducing the average age/length couples were L∞ = 61.86cm; K= 0.30 year-1, and t0 = -0.52. The equation of the linear growth curve according to the von Bertalanffy model was written as Lt = 61.86 (1-e - 0.3(t+0.52) ), and the equation of the weight growth curve was written as Wt = 2253.96 (1-e -0.3(t+0.52)) 3.28 . The studied species showed a higher rate of masculinity (61.11%) than of femininity (38.89%). The overall sex ratio was in favor of males (SR = 1.57, χ² = 6.22; P< 0.05), except in March when males dominated (SR = 3: 1 ; χ² = 6.00 ; P< 0.05). The monthly variation of the sex ratio was constant throughout the study. The evolution of the sex ration according to the size of the fish showed no significant difference between males and females (0.806 ≤ χ² ≤ 2.123 ; P˃ 0.05). [ABSTRACT FROM AUTHOR]

Purpose. To create a general bibliographic list of English-language scientific publications devoted to the peculiarities of pikeperch (Sander lucioperca Linnaeus, 1758) reproduction in natural and artificial conditions using various technologies as well as to briefly highlight Englishlanguage professional sources, in which the main attention is paid to the specifics of pikeperch development in the first stages of ontogenesis -- starting from embryonic development and ending with the age-0+. Methodology. An interdisciplinary approach was used to create this thematic Englishlanguage bibliography. Its was based on the practical application of the principles of analytics and systematics. In turn, the limits of applicability of the latter were outlined by holistic and selective methods. The actual bibliographic core consists of sources that are found in the vast majority on the Internet, mostly with free access to the full texts. Findings. A thematic bibliography of 149 English-language sources is included. All of them are placed in alphabetical order by author or title and are drawn in accordance with the requirements of the State Standard of Ukraine (DSTU 8302:2015 "Information and documentation. Bibliographic reference. General provisions and rules of compilation" with amendments -- UKND code 01.140.40) and the most common international standard (APA style). The absolute majority of the mentioned sources were published in the last 25 years in wellknown international journals («Aquaculture International», "Aquaculture Report", "Aquatic Research", "Biologia", "Czech Journal of Animal Science", "Ecology of Freshwater Fish", "Fish Physiology and Biochemistry", "Journal of Applied Ichthyology", "Knowledge and Management of Aquatic Ecosystems", "North American Journal of Aquaculture", "Turkish Journal of Fisheries and Aquatic Sciences", etc.). Practical Value. The presented thematic English-language bibliography can be used in educational, research, organizational and other types of activities related to the reproduction and preservation of aquatic living biological resources in Ukraine and in other countries of the world. The sources given in it will deepen and supplement the knowledge of scientists and producers regarding the peculiarities of reproduction and ontogenesis of pikeperch at the stages from gastrula to the age-0+. [ABSTRACT FROM AUTHOR]

The effect of stocking density on the rearing performance of pikeperch juveniles was studied. Three separate experiments (I, II and III) were conducted with fish of an initial average body weight of 1.3, 6.7 and 19.2 g, respectively. Each experimental design consisted of three treatments (three replicates) with different initial stocking densities (low, medium and high). Experiments lasted 28 days in a recirculating aquaculture system (21°C, 24L:0D) with an initial stocking density of 0.78, 1.04 and 1.30 kg m−3 in experiment I, 2.68, 4.02 and 5.36 kg m−3 in experiment II, and 3.84, 7.68 and 11.52 kg m−3 in experiment III. The results of our study showed that in experiment I, the use of a stocking density of 1.04 kg m−3 resulted in the highest body weight and survival, as well as the lowest feed conversion ratio and cannibalism. In experiments II and III, the pikeperch growth rate decreased, and their feed conversion ratio increased gradually with increasing stocking density. Our study demonstrated that based on growth parameters, densities of 1.04, 2.68 and 3.84 kg m−3 can be used for pikeperch with an initial body weight of 1.3, 6.7 and 19.2 g, respectively. [ABSTRACT FROM AUTHOR]

Objective: Walleye Sander vitreus are important sport fish that are commonly stocked to supplement populations. Increases in Smallmouth Bass Micropterus dolomieu abundance have prompted concerns regarding potential predation by these and other piscivores on stocked Walleye. Our objectives were to assess the timing and duration of predation on stocked Walleye, the frequency of occurrence and percent composition of Walleye in predator diets, and the percentage of stocked Walleye consumed. Methods: We collected Smallmouth Bass, adult Walleye, Largemouth Bass M. nigricans, and Northern Pike Esox lucius diets in May (prestocking) and June–September (poststocking) 2019 and 2021 from three bays in Lake Oahe, South Dakota. We stocked two bays with Walleye (30–32 mm; 255–1649 Walleye/ha), whereas one bay was unstocked and served as a reference. We estimated Smallmouth Bass population abundance using Schnabel capture–recapture models, and we used bioenergetics to estimate the percentage of stocked age‐0 Walleye consumed. Result: We found age‐0 Walleye in up to 11.4% of Smallmouth Bass diets and 14.6% of adult Walleye diets during the poststocking period. A single Largemouth Bass consumed one Walleye at 3 days poststocking (DPS), whereas we did not identify Walleye in Northern Pike diets. Daily mean percent composition by weight (±95% confidence interval) of age‐0 Walleye in diets peaked at 43.2 ± 35.1% at 3 DPS for Smallmouth Bass and 49.8 ± 97.7% at 14 DPS for adult Walleye. Following the peaks, age‐0 Walleye percent composition by weight rapidly declined and was generally 0% after 25 DPS. Smallmouth Bass abundance was 0.4–5.6 fish/ha, whereas recaptures of other predator species were insufficient for reliable population estimates. We estimated that Smallmouth Bass consumed 29,930 age‐0 Walleye in 2019 and 12,535 age‐0 Walleye in 2021 (up to 14.7 ± 4.7% of stocked fish), potentially representing an important source of stocking mortality. Conclusion: Our research provides insights into the effects of poststocking predation on age‐0 Walleye by Smallmouth Bass and, to a lesser extent, Walleye, Largemouth Bass, and Northern Pike. Managers should consider predation on stocked fingerling Walleye from resident predators and should contemplate alternative stocking locations or timing to reduce potential predation. Impact statementPredation may influence poststocking survival. We found that Smallmouth Bass were the most common predators of stocked age‐0 Walleye, predation generally occurred within 14 days poststocking, and up to 14.7% of stocked fish were consumed. Our results can guide management decisions for improving Walleye stocking success. [ABSTRACT FROM AUTHOR]

This study is focused on the comparison of production efficiency (growth, survival, and development) and economic evaluation of large-scale larvae culture in pikeperch (Sander lucioperca) using Artemia (Group A) compared to using rotifers and the subsequent combination of rotifers and Artemia (Group R) as a first exogenous feed following weaning and intensive culture of juveniles. Both experimental groups were stocked with the same initial density (100 pcs per litre) of larvae at 4 days post hatching (DPH). Each group was cultured in triplicate until 65 DPH. Assessed parameters included FBW (final body weight), FTL (final total length), SGR (specific growth rate), SR (survival rate), CR (cannibalism rate), SBI (swim bladder inflation rate), and TDR (total deformity rate). Production costs were confronted with total number of all produced and high-quality juveniles to determine the cost per one juvenile. Juveniles in Group A displayed more rapid growth (significantly higher FBW, FTL and SGR). On the other hand, parameters concerning quality of the fish (SBI, SR, Share of high quality juveniles and TDR) were significantly higher in Group R. Statistical difference in CR also benefits Group R. Production of bigger share of high-quality juveniles in Group R decreased overall production cost per one high-quality juvenile by 59.7%, from 0.72 EUR in Group A to 0.29 EUR in Group R. Use of established feeding protocols confirmed significant production and economic improvements in pikeperch larvae culture and production of high-quality juveniles. Even though the price of rotifer cultivation significantly exceeded the price of Artemia purchase and cultivation, the production cost of high-quality pikeperch juveniles significantly decreased. [ABSTRACT FROM AUTHOR]

The study tested the effect of daily feed ration (DFR: 0.5%, 0.75%, 1.0%, 1.25%, and 1.5% of fish biomass) on juvenile pikeperch (Sander lucioperca) with an initial body weight of 21.5 ± 5.1 g and total length of 144.5 ± 8.5 mm. The pikeperch were fed floating feed at 8-hour intervals for a duration of 84 days. By the end of the experiment, the group fed DFR of 1.5% exhibited the highest body weight (51.5 ± 16.1 g) and total length (188.2 ± 17.8 mm). The weight heterogeneity, measured as the coefficient of variation (CV), ranged between 30.29 and 33.24%. The specific heterogeneity rate (SHR) ranged from 304.44 to 334.94‰/day. The group with DFR of 1.0% exhibited the highest degree of heterogeneity. Minor fin erosion was observed in the caudal fin by the end of the experiment. No significant differences were revealed in selected biochemical parameters indicating the liver, spleen, and intestinal function. All the fish tested were adequately fed, being provided sufficient nutrients for the proper growth of pikeperch. The DFR of 1.5% was evaluated as the most favourable. This amount of feed supported a higher number of values for Fulton's coefficient (FC), specific growth rate (SGR), thermal growth rate (TGR), fish weight heterogeneity, growth of total fish biomass (BG), and optimum level of biochemical parameters in blood plasma. [ABSTRACT FROM AUTHOR]

Lactic acid bacteria (LAB) probiotics were evaluated for their impact on the microbiota and development of pikeperch (Sander lucioperca) larvae during their initial feeding stage (first 21 days). Pikeperch larvae were exposed to LAB probiotics in two ways: (1) via the live-feed only (Treatment 1, live-feed) or (2) via the live-feed and the larval culture water (Treatment 2, probiotic) in comparison to a control group without LAB supplementation. Total length (TL), myomere height (MH), and survival rate were significantly increased in the probiotic compared the Control group. The administration of probiotics significantly positively influenced the microbiome's diversity. Specifically, the relative abundance of Cytophagales decreased and that of several other taxa increased in both probiotic treatments although differences between treatments became statistically insignificant by day 21. Furthermore, the different treatments had distinct and significant impacts on digestive enzyme development such as protease and lipase, with the most prominent differences occurring at seven days post-hatching (dph). Taken together, these results indicate that the use of LAB in both the live-feed and rearing water has a positive impact on the larvae microbiota and digestive enzyme development in turn positively impacting their development and viability under intensive rearing conditions. [ABSTRACT FROM AUTHOR]

Movements of common fish species in large lakes that are inadequately known is challenging for fisheries management. Pikeperch (Sander lucioperca) (n = 478; mean length = 42.1 cm; SD = 7.0), bream (Abramis brama) (n = 775; mean length = 31.1 cm; SD = 5.3) and roach (Rutilus rutilus) (n = 939; mean length = 21.4 cm; SD = 2.0) were marked with individual T‐anchor tags to investigate movements in Lake Vesijärvi, a large lake situated in southern Finland consisting of several basins and managing by multiple entities. All species moved between basins, but only rarely moved outside tagging areas. The recapture rate of pikeperch was higher than roach and bream. Tagged fish consistently crossed municipality borders and water ownership units, thereby forming shared stocks, which underlined the importance of cooperation in lake restoration and a need to unite fragmented water ownership. Management of fisheries for cyprinid fishes could be more efficient if fishing targeted the most suitable areas without considering restrictions due to fragmented water ownership. Tagging data provided information on which parts of a large lake should be subjected to uniform pikeperch fisheries management. The importance of other species catch varied between different parts of the lake, thereby requiring different fishing regulations. Tagging data on common fish species provided valuable information on fish movements to support spatially explicit fisheries management. [ABSTRACT FROM AUTHOR]

This trial aimed to customize pikeperch (Sander lucioperca) larval nutrition using live feed enrichments based on Chlorella vulgaris and Trachydiscus minutus. Pikeperch larvae were fed with rotifers and Artemia enriched with C. vulgaris and T. minutus during the first 17 days after exogenous feeding (started 4 days post‐hatching [dph]) and only Artemia until 20 dph. Larvae were exposed to seven different enrichments: (a) Nannochloropsis occulata (Nanno 3600 reed Mariculture) (Control), (b) C. vulgaris cultured at 20°C in BG‐117 medium (BG20), (c) C. vulgaris cultured at 30°C in BG‐117 medium (BG30), (d) T. minutus cultured at 15°C (T15), (e) T. minutus cultured at 25°C (T25), (f) C. vulgaris cultured at 20°C in urea medium (U20), and (g) C. vulgaris cultured at 30°C in urea medium (U30). After 20 days, no significant differences were found between treatments on total length, standard length, myomere height, and eye diameter. On the contrary, significant differences were found in larval fatty acid composition after the trial period. Larvae from the BG30 treatment showed a significantly higher concentration of docosahexaenoic acid (5.61%), and larvae from the T25 treatment had a higher concentration of eicosapentaenoic acid 12.95%. Furthermore, larvae from the U20 treatment had a significantly higher arachidonic acid concentration of 0.116%. Overall, regarding essential fatty acid concentration, a significant difference was observed between the control treatment (Nannochloropsis) and the other treatments. No adverse effects were found on growth or survival when Nannochloropsis‐enriched live feed was replaced with the other enrichments. This trial's results will help optimize the pikeperch larvae's nutritional requirements and diversify the live feed enrichments used during the first feeding. [ABSTRACT FROM AUTHOR]

Studies of the physiological state of 3-year-old pikeperch from a lake (natural habitat), ponds, and fish farm cages show significant differences in the size, mass, biochemical, hematological, and histophysiological parameters of fish. Farmed fish are larger (length 26.2 cm; weight 242.1 g) than lake individuals (27.6 cm and 278.2 g, vs. 23.7 cm and 162.6 g in pond pikeperch) and have higher index values of liver (3.68 vs. 1.42 and 1.03% in lake and pond fish, respectively), gonads (0.73 vs. 0.15 and 0.08%), and abdominal fat (8.61 vs. 1.87 and 2.30%). The chemical composition of the body of farmed fish is characterized by a large quantity of lipids (9.4 vs. 2.5 and 3.6%, respectively) and nitrogen-free extracts (NFEs) (3.4 vs. 2.5 and 2.4%), muscle—protein (21.0 vs. 19.0 and 19.2%), and liver—lipids (26.6 vs. 11.1 and 7.5%, respectively) and NFEs (9.6 vs. 1.9 and 2.5%), as well as low moisture (51.7 vs. 69.3 and 71.5%), protein (11.2 vs. 16.6 and 17.2%), ash (0.9 vs. 1.1 and 1.3%), and vitamin C (67.5 vs. 87.9 and 97.6%) contents. The fatty acid (FA) composition of the muscle lipids of farmed fish is generally comparable to that of lake and pond fish—the main groups of FAs are at a similar level: polyunsaturated FAs in the range of 37.0–40.6% of the total FAs, saturated FAs 25.5–29.6%, and monounsaturated FAs 28.0 and 23.2% in farmed and lake fish and 17.5% in pond fish. The content of arachidonic acid 20:4n-6 in farmed fish is extremely low (1.0 vs. 8.0 and 11.5% of the total FAs). Liver lipids of farmed fish contain a large amount of oleic acid 18:1n-9 (30.3 vs. 16.2 and 15.0% of the total FAs in lake and pond fish) and n-6 polyunsaturated FAs (17.5 vs. 8.4 and 7.1%), in particular, linoleic acid 18:2n-6 (7.0 vs. 1.9 and 0.2%). The blood of farmed fish, compared to pond fish, differs in a lower content of hemoglobin (64.8 vs. 74.8 g/L) and an increased content of immature lymphocytes (11.6 vs. 6.1%) and immature erythrocytes (2.2 vs. 1.1%). The gonads of farmed fish are at stage III of maturity with an average oocyte diameter of 478.9 µm; lake fish has two stages of oocyte maturity—the previtellogenic oocytes of protoplasmic growth, 62.7 µm in size, and significantly larger vitellogenic oocytes of trophoplasmic growth, 227.6 µm. In pond pikeperch, gonads correspond to stage II of maturity and oocytes are 58.3 µm in size. Certain differences in pikeperch from lakes, ponds, and farm conditions are associated with the different conditions in which they are kept and fed. [ABSTRACT FROM AUTHOR]

Pikeperch (Sander lucioperca Linnaeus, 1758) is a wide-ranged percid predator fish characterised by a great ecological value in the Eurasian freshwater and brackish ecosystems. It is also one of the most famous fish species of Lake Balaton (Hungary), where a unique (genetically separated) pikeperch stock lives. However, until now, no detailed information was available about the pikeperch population genetic structure in Lake Balaton. In the present study, the population genetic structure of the pikeperch assemblages in the lake was revealed by using microsatellite markers. Commercial fishery and angler catch data going back more than 100 years verified that the pikeperch has always been a key element of Lake Balaton's fish stock utilization. Results of genetic data analyses showed that the pikeperch in the Lake Balaton forms a metapopulation system, in which only the westward stocks show certain separation. Moreover, it seems that the exploitation and mass fish kills that happened in the 1960s and 1970s may have had only a slight impact on the population genetic structure of Balaton pikeperch stocks. The information about genetic features and utilization changes of pikeperch stocks can help to develop area-specific management plans and ensure the long-term survival of this carnivore fish species characteristic of Lake Balaton. [ABSTRACT FROM AUTHOR]

The early-life history stages of fish are sensitive to environmental change and therefore can indicate habitat quality as well as help predict recruitment of resident and transient fishes. In 2019, as part of the Lake Erie Cooperative Science and Monitoring Initiative, we conducted a lake-wide assessment of the ichthyoplankton community in U.S. nearshore waters and international offshore waters. The goal of this work was to characterize the larval fish community across the lake and assess species composition, phenology, and distribution of larvae. Ichthyoplankton were sampled weekly using bongo nets at ports beginning at the Detroit River and along the southern shore of Lake Erie to Dunkirk, NY, and less frequently in the Niagara River and offshore areas. Larval fish were present from March 26 through August 29, 2019. The first taxon to emerge was Lake Whitefish in all basins, followed by Walleye, Yellow Perch, and catostomids, depending on port. Mean total density peaked in mid-June due to high catches of Gizzard Shad, Morone spp., and Freshwater Drum in the western basin. Few fish were collected in the offshore sites. Taxa richness, diversity, and larval density were higher in the western basin and lower in the central and eastern basins, generally following the productivity gradient. This was the first study to provide a comprehensive community assessment of the ichthyoplankton community of Lake Erie and can provide a baseline to assess future change, especially in community composition or phenology, of larvae which are likely to respond to climate and habitat change. [ABSTRACT FROM AUTHOR]

Size differences are common in the aquaculture of fishes. In the larviculture of cannibalistic species such as pikeperch, they majorly influence mortality rates and consequently provoke losses in the aquaculture industry. With this study, we aim to reveal molecular differences between small and large pikeperch of the same age using a set of 20 genes associated with essential developmental processes. Hereby, we applied a general study design to early and late larval pikeperch before the onset of piscivory to explore the causes of growth differences in these developmental groups. The analysis of the expression levels showed developmental but not size-related differences in PGC1A, TGFB1, MYOD1, MRF4, and the collagens COL1A1 and COL1A2. Furthermore, increased head lengths were found in larger late larvae compared to their smaller conspecifics. While no uniquely size-related expression differences were found, the expression patterns of PGC1A in combination with TGFB1 as regulators of the citric acid cycle indicate a possible influence of mitochondrial energy metabolism. Furthermore, expression differences of MYOD1 and MRF4 point out possible temporal advantages of myogenetic processes in the larger late larval group and hypothesise growth advantages of the larger late larvae resulting from various influences, which provide a promising target for future research. [ABSTRACT FROM AUTHOR]

Micro RNAs (miRNAs) are short non-coding RNAs that act as post-transcriptional gene expression regulators. Genes regulated in vertebrates include those affecting growth and development or stress and immune response. Pikeperch (Sander lucioperca) is a species that is increasingly being considered for farming in recirculation aquaculture systems. We characterized the pikeperch miRNA repertoire to increase the knowledge of the genomic mechanisms affecting performance and health traits by applying small RNA sequencing to different developmental stages and organs. There were 234 conserved and 8 novel miRNA genes belonging to 104 families. A total of 375 unique mature miRNAs were processed from these genes. Many mature miRNAs showed high relative abundances or were significantly more expressed at early developmental stages, like the miR-10 and miR-430 family, let-7, the miRNA clusters 106-25-93, and 17-19-92. Several miRNAs associated with immune responses (e.g., slu-mir-731-5p, slu-mir-2188-5p, and slu-mir-8159-5p) were enriched in the spleen. The mature miRNAs slu-mir-203a-3p and slu-mir-205-5p were enriched in gills. These miRNAs are similarly abundant in many vertebrates, indicating that they have shared regulatory functions. There was also a significantly increased expression of the disease-associated miR-462/miR-731 cluster in response to hypoxia stress. This first pikeperch miRNAome reference resource paves the way for future functional studies to identify miRNA-associated variations that can be utilized in marker-assisted breeding programs. [ABSTRACT FROM AUTHOR]

The present study aimed to assess the effects of thermal manipulation on the vitellogenesis and final oocyte maturation (FOM) in pikeperch. Two groups of fish were stocked in two separate tanks of the climate chamber. One group was stocked at 10-month age (THERMAL), while the other was continually kept under stable photothermal conditions until 19-month-age (CONTROL) and then transferred to a climate chamber. The progress of vitellogenesis was assessed via evaluation of the oocyte diameter at the mid- and late-autumn phases, and the gonadosomatic index (GSI) at the late-autumn phase. Finally, females from the CONTROL group were hormonally stimulated before (WARMING) and after (STABLE) increase of the temperature from wintering to spawning, and the FOM progress, ovulation and plasma levels of 17 α, 20β dihydroxy progesterone (DHP) were assessed. Significantly larger oocytes at the mid-autumn phase (878.8 ± 40.1 µm vs 836.5 ± 46.5 µm) as well as the GSI at the end of the autumn phase (10.5 ± 1.7% vs 7.6 ± 1.1%) were noticed in THERMAL fish. Significantly faster FOM was seen in fish under the WARMING post-stimulation regime, and these fish had higher DHP levels at the moment of hormonal stimulation (5.4 ± 1.4 ng/ml vs 3.8 ± 1.2 ng/ml). According to the obtained results, it appears that photothermal induction of fish at a younger stage might have a positive impact on the first spawning, while the WARMING thermal regime seems to be more efficient in stimulating the FOM in fish upon first wintering. [ABSTRACT FROM AUTHOR]

Animal movement is increasingly affected by human alterations to habitat and climate change. In wetland systems, widespread hydrologic alterations from agriculture have changed the shape, function, and stability of shallow streams and wetland habitats. These changes in habitat quality and quantity may be especially consequential for freshwater fishes such as Grass Pickerel (Esox americanus vermiculatus), a small predatory fish found in disjunct populations across southern Ontario and listed as Special Concern under Canada's Species at Risk Act. To characterize Grass Pickerel movement response to stream-channel alterations, Fisheries and Oceans Canada implemented a tracking study to monitor the movements of a Grass Pickerel population in an agricultural drain on the Niagara Peninsula (Ontario, Canada). From 2009 to 2013, 2007 Grass Pickerel were tagged and tracked in the 37.3 km2 Beaver Creek watershed using a combination of mark-recapture surveys and eight fully automated passive integrated transponder tag antennas. Most individuals moved within 500 m (i.e., stationary fish) while 16% of the fish moved > 500 m (i.e., mobile fish), with a maximum median movement distance of 1.89 km and a maximum movement distance of 13.5 km (a long-tail distribution). Most movements occurred near the largest confluence where only a few were long-distance upstream or downstream movements. Mobile fish were larger than their stationary counterparts. Grass Pickerel in sites with higher abundance had more mobile fish, implying potential density dependence. Our results highlight that, while a long-distance dispersal ability exists in extant Grass Pickerel populations, the current conditions of riverscapes may prevent these dispersals from occurring. For declining Grass Pickerel populations, limitations to their movement ecology may substantially increase the likelihood of local extirpations. [ABSTRACT FROM AUTHOR]

The nutrient and fatty acid composition of the muscle tissues in the dorsal (D), ventral (V), and caudal (C) regions of the pike perch were determined in this study. Pike perch had 19.63% protein, 0.92% lipid, 78.36% moisture, and 1.04% ash. The whole muscle (WM) (0.92%) of pike perch had the highest lipid content, followed by C (0.82%), V (0.73%), and D regions (0.69%). The results of the study revealed that total polyunsaturated fatty acid (PUFA) (32.37%-37.05%) values were higher than those of total saturated fatty acids (SFA) (29.96%-31.76%) and monounsaturated fatty acid (MUFA) (17.26%-20.81%) in all whole muscle (WM) and different regions (D, V, and C) of the pike perch. The highest SFA, MUFA, and PUFA amounts were in D, WM, and D regions, respectively. In all groups, the amount of Docosahexaenoic acid (DHA) (12.97-15.43%) was higher than Eicosapentaenoic acid (EPA) (5.66-6.97%). While there was no difference between regions in terms of EPA value, the difference between regions in terms of DHA values was found to be important (p <0.05). The highest EPA and DHA values were detected in the D region. Atherogenicity index (AI) (0.47-0.48), thrombogenicity index (TI) (0.33-0.35), hypocholesterolemic/hypercholesterolemic ratio (H/H) (2.01-2.07) and n-6/n-3 (0.47-0.51) ratios were at recommended levels in all regions (WM, D, V, and C) and there was no regional difference (p > 0.05). The results showed that the fatty acid composition of the pike perch varies according to different body regions, it is rich in nutrient content and has the recommended level of AI, TI, H/H, and n-6/n-3 ratios. It can be concluded that pike perch has beneficial health effects on human nutrition. [ABSTRACT FROM AUTHOR]

The pikeperch (Sander lucioperca) is a species with a high potential for aquaculture and a valuable food with high market acceptance. The aim of the study was to evaluate the functional ontogeny of digestive enzyme of pikeperch from hatching to 45 days-post fertilization, 777 degree-day (DPF, dd) under culture condition. The average total length (TL) of larvae measured at hatching was 3.6 ± 0.4 mm (5 DPF; 67 dd) and at the end of experiment (45 DPF, 777 dd) was 27.1 ± 1.1 mm. The survival rate was 80–90% during the experiment period. Inhibition zimography reveals the presence of nine bands with proteolytic activity in the digestive tract of juvenile pikeperch. Zimography results during the ontogeny revealed that in larvae at 8 DPF (108 dd) and 13 DPF (189 dd), three bands were presented. The variations observed in the enzymatic activity reflected a high amount of total protease activity at 10 DPF (133.5 dd). Regarding pepsin, its activity was observed for the first time at 26 DPF (378.9 dd). Lipase activity remained constant from hatching to 26 DPF (378.9 dd). The highest amount of α-amylase activity was detected at 15 DPF (211.5 dd) and 45 DPF (777 dd). The low lipase enzyme activity suggested that live feeds with low lipid were more suitable than diets containing high lipid levels; larvae had also early capability to digest nutrient-dense diet that was high in protein. According to results the pikeperch larvae possess after the exogenous feeding, a functional digestive system with high activities that indicated the gradual development of the digestive system. [ABSTRACT FROM AUTHOR]

The article discusses how climate change is impacting species interactions in aquatic ecosystems, particularly with warm-adapted fish expanding their range northward into lakes previously dominated by cool-adapted fish like walleye. While it may seem intuitive that removing warm-adapted species would benefit cool-adapted species, research by Jarvis et al. suggests that under alternate thermal conditions, this may not always be the case. Understanding these shifts in species interactions is crucial for scientists and natural resource managers to prepare for unexpected outcomes in managing ecosystems under changing climatic conditions. [Extracted from the article]

Lake Erie walleye (Stizostedion vitreum) recruitment fluctuates annually and depends partially on their diet and growth during their first year of life. In recent decades, age‐0 walleye diet and growth may be responding to food web changes in western Lake Erie. To determine how age‐0 walleye have responded to changes in prey species and abundance, we compared diet between 2019, 2014 and 1994–1999. Larval walleye ate predominantly cyclopoids in 2019, compared to 1994–1999 when calanoids were the most consumed copepod. Juvenile walleye ate predominantly large cladocerans and benthic invertebrates in 2019, compared to 2014 and 1994 when fish was the most consumed prey. Additionally, in 2019 and 2014, age‐0 walleye ate two of the current aquatic invasive species (AIS), Bythotrephes longimanus and Neogobius melanostomus, and the historical AIS, Osmerus mordax. Age‐0 walleye were smaller in 2019 than in 2014 and switched to consuming more AIS and less fish suggesting that more energetically favourable prey were not available. While age‐0 walleye showed adaptation to new prey and conditions, they had a lower quality diet because they consumed less fish, but also because the invasive fish they now consume have a lower energy density than native species. However, lower quality diet and size may not result in reduced survival, if adequate alternative prey is available. Continued monitoring of age‐0 walleye diet could provide confirmation that lower diet quality during the first year decreased walleye growth and aid to identify any effects changes in age‐0 diets has on recruitment to the adult population. [ABSTRACT FROM AUTHOR]

The Baltic Sea has been under intense environmental changes in the recent decades, such as climate change, eutrophication and increasing abundance of top‐predators, which pose serious challenges to its aquatic life. For informed conservation measures and sustainable yields, we need to understand how the populations are being affected. Accordingly, we used long‐term data series (covering the period between 1980 and 2021) to assess how these changes have affected populations of an ecologically and economically important predatory fish, the pikeperch (Sander lucioperca), in the coastal waters of Finland in the northern Baltic Sea. We investigated the estimates of abundance and recruitment, commercial and recreational catch statistics and growth and mortality rates. We found a clear increase in the total catches in the northernmost part of the Finnish coast (Bothnian Bay) that were not explained by changes in fishing effort, indicating increased abundance, most likely due to higher water temperature. In the southern part of the study area (Archipelago Sea), density‐dependent factors prevented the development of particularly strong year classes, despite the beneficial conditions of warming seawater and consecutive warm summers. Individual growth has increased in younger age groups, contributing to an upward trend in the spawning population biomass. We also uncovered a declining trend in the total mortality in the southern area, despite increased abundances of cormorants and seals, explained by reduced total fishing mortality. These results show that the pikeperch is one of the species that has, thus far, benefited from the environmental change in the northern Baltic Sea, strengthening its role in the ecosystem. [ABSTRACT FROM AUTHOR]

Until 2006, the Lipno Reservoir had the largest catches of pikeperch in the Czech Republic, but since 2007 it has partially collapsed. This collapse was preceded by oligotrophication, when phosphorus concentrations declined by 25%. Conservation measures from 2009 to 2015 partially improved the population from 2015, but pikeperch biomass did not reach previous levels. Unsuccessful spawning and low survival of pikeperch fry were suspected as possible reasons. Pelagic trawling for pikeperch younger juveniles in June and older juveniles in August indicated that extreme mortality in the first year of life, rather than limited spawning, was the reason for low pikeperch recruitment. Large interannual differences in pikeperch density were observed in both spring and summer, and the growth was generally low. Pikeperch fry density changed over a trophic gradient with the highest densities in the eutrophic upper reservoir parts, while differences between depths were much less pronounced due to the lack of temperature and oxygen depth stratification in summer. Oligotrophication of the reservoir in recent years is probably partly responsible for the high mortality and slow growth of pikeperch fry that are still zooplanktivorous, resulting in a lower probability of surviving their first winter. Given the changing conditions in the reservoir, measures should be taken to strictly conserve populations to maintain self‐sustaining pikeperch populations in the Lipno Reservoir. [ABSTRACT FROM AUTHOR]

Abundance, size (standard length, LS) and growth rate of early pikeperch (Sander lucioperca) 0+ juveniles were monitored in the epipelagic and bathypelagic layers near the dam, and in the middle and upper sections at the canyon‐shaped Římov Reservoir (Czech Republic) during the day on 26 and 29 May, and during the night on 5 and 11 June in 2008. The greatest abundance of 0+ fish was observed in the middle section of the reservoir and their LS increased upstream from the dam towards the reservoir's tributary. Moreover, larger and older pikeperch 0+ juveniles migrated to the bathypelagic layer during the day. The epilimnetic temperature and productivity (expressed as chlorophyll‐a concentration) gradients were suggested as the main drivers affecting the distribution and growth of the fish. [ABSTRACT FROM AUTHOR]

The aquaculture production of pikeperch has reached commercial scale in a number of European countries, but the high mortality of early life cycle stages and minor understanding of nutritional requirements are still major bottlenecks. To investigate the fate of fatty acids during early development, weaning and rearing, pikeperch larvae and juveniles from a commercial recirculating aquaculture system (RAS) were sampled over 2 months for morphometric data, as well as fatty acid composition, with a total of 6 sampling days, with four to five replicates per sampling day and between 1 and 25 pikeperch larvae per individual sample, depending on larval biomass. The biomass of sampled pikeperch larvae varied from 0.1 to 420 mg (dry mass DM), depending on the age of the larvae, and the initial length of the pikeperch larvae was about 4.5 mm. Our data confirm that, accompanied by an exponential increase in dry mass, total fatty acids (TFAs) in larval tissues increased with the beginning of exogenous feed uptake and were depleted between days 13 and 25 post hatch, most likely associated with the weaning and metamorphosis of the larvae. We conclude that all fatty acid classes may serve as metabolic fuel during metamorphosis, but the ultimate fatty acid composition is strongly impacted by the available feed. The chosen diet probably caused a lack of alpha-linolenic (18:3n-3; ALA) and docosahexaenoic acid (22:6n-3; DHA) during larval development and a shortage of vaccenic (18:1n-7), alpha-linolenic (18:3n-3; ALA) and arachidonic acid (20:4n-6; ARA) in juvenile pikeperch. This led to low DHA/EPA ratios 13 days post hatch, a high EPA/ARA ratio at days 41 and 56 post hatch and a fluctuating ratio of alpha-linolenic acid to linoleic acid (18:2n-6; LA). A temporary lack of essential fatty acids can cause dysfunctions and eventually mortalities in pikeperch larvae and juveniles. Despite high larval growth rates, the biochemical composition of the first fed Artemia and microdiets was most likely not sufficient and in need of improvement. We suggest that deficiencies must be compensated, e.g., through the substitution of the offered Artemia with more suitable live feed organisms, such as freshwater rotifers, and the enrichment of current microdiets in order to prevent high mortalities during pikeperch rearing and weaning. [ABSTRACT FROM AUTHOR]

The effect of live feed diets containing Brachionus plicatilis (B) and Apocyclops panamensis (A) was investigated on pikeperch larval survival, growth, and fatty acid composition in two experiments (E1 and E2). Up to six different diets were provided to the larvae, in which the letters of the diet names represent the live feed organisms as mentioned above and the subsequent number of feed organisms per larva and day. In E1, start cultures with 35 larvae/L were supplied with two diets (B200 and B100 + A100) 7 days until 10 days post hatch (dph). In E2, 50 larvae/L were fed six diets, B280 + A120, B340 + A60, B400, B420 + A180, B510 + A90, and B600. The highest survival and specific growth rates (SGR) occurred in B200 (E1). In E2, B340 + A60 performed best. A trend of increasing survival rates was found in E1 from 68.9% (B100 + A100) to 71.6% B200 and in E2 from 64.0% (B280 + A120) to 93.7% (B340 + A60). Larval SGR tended to increase with higher shares of dietary B. plicatilis in both experiments. The polyunsaturated fatty acid, linoleic acid (LA), followed the same pattern as survival and SGR increasing until a plateau was reached, indirectly indicating a feeding threshold. B. plicatilis provided the LA to pikeperch larvae, which seemed to play an important role in this feeding period. Consequently, a live feed diet should contain at least 340 B. plicatilis ind. larva−1 day−1 and 6.3 B. plicatilis per milliliter until 10 dph to improve pikeperch larviculture. [ABSTRACT FROM AUTHOR]

High-frequency data from dissolved oxygen (DO) loggers were obtained during and before a massive summer fish kill event in the oxbow lake Doubka in the Elbe river basin, Czech Republic, and evaluated in the context of meteorological data. In the period from 3 June to 1 September 2020, extreme fluctuations of DO in the surface layer of water were recorded (values in the range of 0–25.48 mg l−1). The DO concentrations were affected by phytoplankton photosynthesis and fluctuated within 12 h from more than 100% saturation (in the afternoon) to zero (at dawn). DO values near the bottom were less variable (0–9.67 mg l−1) and after mid-July, zero values prevailed. A huge fish kill associated with windy weather occurred between 26 and 28 August 2020, resulting in more than 800 kg of dead fish. High percentages of dead fish were of the northern pike (Esox lucius), the pikeperch (Sander lucioperca) and the European catfish (Silurus glanis). Wind-induced water mixing (when oxygenated water containing phytoplankton moved from the surface to the anoxic bottom) and subsequent depletion of oxygen by decomposition processes in the organic substrate of the bottom, in combination with limited sunshine in the same period, resulted in a 2-day lack of oxygen both in the surface layer of water and near the bottom. Repeated fish kills probably contribute to the massive occurrence of the resistant and invasive topmouth gudgeon (Pseudorasbora parva) at the locality. [ABSTRACT FROM AUTHOR]

Walleye Stizostedion vitreum support recreational fisheries throughout their range but increasingly require annual stockings to maintain populations. In many areas of their distribution, Walleye broodfish are collected annually and manually spawned onsite before fertilized eggs are transported to fish culture facilities for rearing. As such, efficiency of these programs is reliant on effective capture of broodfish. Generalized additive models were used to explain the influence of eight environmental factors on catch per effort (CPE) of ripe female Walleye and male Walleye during brood collection events from Hillsdale Reservoir, Kansas, using data from 2009 to 2021 (excluding 2020). The ripe female model explained 63% of the deviance in CPE and identified the day of year, water temperature, moon illumination, previous autumn CPE of preferred‐length fish (CPEp), and previous autumn proportional size distribution of preferred‐length fish (PSDp) as influential variables. The male model explained 64% of the deviance in CPE and identified the day of year, change in barometric pressure from the previous day, water temperature, and previous autumn proportional size distribution of quality‐length fish PSDq as influential variables. These findings provide useful information regarding collection of Walleye broodfish and can be leveraged to increase efficiency of future operations range‐wide. [ABSTRACT FROM AUTHOR]

Within the predator–prey relationship, predator behavior is less studied. Even in natural populations, it shows great diversity, and the factors influencing this are even less known. Among these factors, the personality type of the individual, (including exploration, and neophilia) and the practice significantly influence the success of adapting to a changing environment and switching to new prey types. In the present study, we investigated the first five consecutive foraging trials on live fish prey in naïve pikeperch individuals, which previously consumed or refused pelleted food. We hypothesized that individuals which were willing to consume alternative (pelleted) food would also show higher foraging success on living prey and that the practice would influence the learning process. Our results show that the timing of prey detection is influenced by exploratory behavior, the latency of the first attack by the aptitude for consuming pellets, and both traits by the individual's practice. However, neither of the factor affects the latency and success rate of capturing the prey, suggesting that predation is an independent behavioral trait. [ABSTRACT FROM AUTHOR]

Disentangling the role of factors responsible for juvenile fish dispersal is essential to understand the ecology of individual species, setting the corresponding conservation status and evaluating the potential risk in case of invasion. Because of their small body size and high sensitivity to environmental conditions, juvenile fish movements have largely been explained by external factors such as wind-induced water currents. In this study, early hatched pikeperch (Sander lucioperca) of hatchery origin were marked with oxytetracycline hydrochloride, stocked into a bay near the dam of a deep reservoir, and then monitored at approximately 10-day intervals using fix-frame trawling for 43 and 51 days after stocking, in 2007 and 2008, respectively. In both years, marked pikeperch were captured throughout the study period in the bay and closed dam section of the reservoir. After one month, individuals were captured in the middle section of the reservoir, approximately 5 km upstream from the stocking site. Four individuals were recaptured in the tributary section of the reservoir, about 10 km upstream from the stocking site during the last sampling in 2007. The farthest distance detection followed periods of strong wind. During daytime sampling, marked pikeperch were captured in both the warm epipelagic layer above the thermocline and the cold bathypelagic layer below the thermocline. The later sampling represented a community of vertically migrating individuals originally thought to consist only of reservoir-born and reservoir-experienced fish. This study suggested the high mobility and flexibility of 0+ pikeperch, as well as their unexpected behavioral plasticity. [ABSTRACT FROM AUTHOR]

Muskellunge Esox masquinongy, Northern Pike E. lucius, Walleye Sander vitreus, and Largemouth Bass Micropterus salmoides are popular sport fish that often co‐occur in aquatic systems. Although numerous studies have investigated interactions among these species, the simultaneous evaluation of diet patterns and niche overlap among all four species has not been conducted. Our experimental design aimed to quantify diet overlap among Muskellunge and the other piscivores, while lakes without Muskellunge were also sampled to compare the diets of the other piscivores in their presence or absence. Diets of piscivores from 10 Minnesota lakes were collected via gastric lavage and quantified using an index of relative importance. Diets of individual species were compared among seasons and predator length categories, and among‐species comparisons were also conducted by season and relative to Muskellunge presence using permutational multivariate ANOVA (PERMANOVA). Muskellunge consumed a wide range of prey, whereas Northern Pike and Walleye diets consisted primarily of Yellow Perch Perca flavescens and centrarchids. Largemouth Bass consumed more invertebrates, especially crayfish Faxonius spp. No species exhibited seasonal diet shifts, but diets were different among length categories for all species except Walleye. Although nonmetric multidimensional scaling ordinations indicated shared prey use, PERMANOVA results indicated that the diets of Muskellunge and Largemouth Bass were most different from each other and the other piscivores' diets across all seasons. Conversely, Northern Pike and Walleye diets were similar regardless of season or Muskellunge presence. Finally, lake‐scale habitat variables were correlated with piscivore diets, and Yellow Perch abundance was correlated with Walleye diets. Our results indicate that while Muskellunge, Northern Pike, Walleye, and Largemouth Bass can coexist in a variety of lakes, populations of important prey and habitat variables should be examined before management actions (e.g., stocking) are implemented to ensure adequate prey availability and to ensure that competition among these piscivores is not increased to the detriment of existing fisheries. [ABSTRACT FROM AUTHOR]