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Geometric morphometrics is a powerful tool for studying fish body shape; however, body posture can be a hindrance to these analyses. Here I introduce new R language tools for correcting multiple types of bending of 3D data based on the TPS suite (geometric morphometric software) “unbend specimens” methodology. In a sample dataset of darters, these R tools adequately accounted for posture artifacts otherwise evident across multiple principal component axes. I hope these new tools will facilitate the incorporation of 3D landmark data into the comparative analysis of fish body shape. [ABSTRACT FROM AUTHOR]

Pikeperch (Sander lucioperca) is a freshwater species and an internationally highly demanded fish in aquaculture. Despite intensive research efforts on this species, fundamental knowledge of skeletal muscle biology and structural characteristics is missing. Therefore, we conducted a comprehensive analysis of skeletal muscle parameters in adult pikeperch from two different origins, wild-caught specimens from a lake and those reared in a recirculating aquaculture system. The analyses comprised the biochemical characteristics (nucleic acid, protein content), enzyme activities (creatine kinase, lactate dehydrogenase, NADP-dependent isocitrate dehydrogenase), muscle-specific gene and protein expression (related to myofibre formation, regeneration and permanent growth, muscle structure), and muscle fibre structure. The findings reveal distinct differences between the skeletal muscle of wild and farmed pikeperch. Specifically, nucleic acid content, enzyme activity, and protein expression varied significantly. The higher enzyme activity observed in wild pikeperch suggests greater metabolically activity in their muscles. Conversely, farmed pikeperch indicated a potential for pronounced muscle growth. As the data on pikeperch skeletal muscle characteristics is sparse, the purpose of our study is to gain fundamental insights into the characteristics of adult pikeperch muscle. The presented data serve as a foundation for further research on percids' muscle biology and have the potential to contribute to advancements and adaptations in aquaculture practices. [ABSTRACT FROM AUTHOR]

The present study was performed to determine the effect of hCG, Ovaprim, and Ovarim on the efficiency of artificial reproduction in European perch (Perca fluviatilis), as well as the examination of the spermatological parameters of this fish. In the first treatment, hCG was used at 500 IU per kg body weight (BW) of broodstock. In second and third treatments, Ovaprim and Ovarim were used at 0.5mL per kg BW, respectively. The control group was injected with physiological saline at 0.5mL per kg BW. Eighteen female broodstocks with an average weight of approximately 78g were used in each treatment. Male broodstock was induced by injection of hCG at a dose of 250 IU per kg BW. According to the results, the fastest latency time (415.6 degree-hour) was observed in the hCG treatment and showed a significant difference with other treatments (P<0.05). The highest ovulation rate (100%) was observed in hCG and Ovaprim treatments and showed significant differences with Ovarim and control groups (P<0.05). The experimental treatments did not show any significant differences in other parameters (P>0.05). Based on the results, the mean volume of semen, spermatozoa activity, motility time and spermatocrit value of European perch were 2.9±1.7mL, 91.1±13.4%, 84.4±18.6s and 68.3±9.4%, respectively. Results of this study showed that hCG is more suitable than Ovaprim and Ovarim for the induction of spawning and artificial reproduction of European perch. Due to the more favorable effects of hCG, it is recommended to use this hormone in spawning induction and artificial reproduction of European perch broodstock. [ABSTRACT FROM AUTHOR]

In the Laurentian Great Lakes, the issue of barrier removal is complicated by the presence of non‐native species below barriers. A fish tracking study was conducted to guide efforts for barrier remediation decisions for the restoration of fish populations with a focus on Walleye (Scander vitreus) and Lake Sturgeon (Acipenser fulvescens) in the Black Sturgeon River, a river system fragmented by a dam which blocks access of fishes to the majority of a large, otherwise barrier‐free watershed. Data from 3 years of spawning migrations (2018–2020) indicated that the Walleye population in Black Bay likely consists of both river (65%) and lake spawners (27%), with the remaining individuals spawning in the bay or river in different years. Walleye and Lake Sturgeon showed consistent differences in the extent to which individuals migrated upstream in the river during the spawning season, despite expectations that both species would spawn at the base of the dam when prevented from further migration. The dam was presumably a barrier to migration for Lake Sturgeon, as nearly all Lake Sturgeon that entered the river migrated to the base of the dam. In contrast, few Walleye entering the river during the spawning season migrated to the dam annually. These findings suggest that Walleye and Lake Sturgeon may not benefit equally, at least in the short term, from barrier remediation or dam removal. [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]

Silver nanoparticles (AgNPs) are added as antibacterial and anti‐odor agents to a wide range of textiles, with high potential for release into aquatic environments via domestic wastewater. Previous work demonstrating the negative impacts of AgNP exposure on periphyton production suggests benthic primary production could be reduced in aquatic ecosystems impacted by AgNP discharge. To evaluate the potential for AgNPs to alter benthic–pelagic coupling in aquatic ecosystems, tissue‐stable isotope ratios of carbon and nitrogen from northern pike (Esox lucius) and yellow perch (Perca flavescens) were measured before, during, and after the addition of AgNPs to a whole‐lake ecosystem, and compared to those collected from a nearby reference lake. A shift in carbon isotope ratios toward more negative values was observed in both P. flavescens and E. lucius collected from the lake where AgNPs were added, with no shift in similar magnitude observed in E. lucius from the reference lake. Consequently, Bayesian estimates of benthic energy consumed decreased by 32% for P. flavescens and by 40% for E. lucius collected after AgNP additions relative to pre‐addition estimates, greater in magnitude or opposite in direction of trends observed in our reference lake. Analyses suggest no changes in fish nitrogen isotope ratios related to AgNP additions. We hypothesize that the observed reduction in littoral energy use of fish reported here is a response to AgNP settling in littoral benthic habitats—the main habitat in lakes supporting periphyton—as AgNP has been shown elsewhere to significantly reduce the rates of periphyton production. Further, our study highlights the need to broaden the scope of risk assessments for AgNPs and other emerging contaminants prone to settling to consider habitat‐specific impacts on resource utilization by organisms after their release into aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Invasive species are a major threat to ecosystem structure and function. For example, Bythotrephes cederströmii (Bythotrephes hereafter) invasions have significantly reduced native zooplankton density and biomass, resulting in competitive interactions with zooplanktivorous fishes. Young of year (YOY) walleye (Sander vitreus) are initially zooplanktivorous and have recently been shown to display reduced growth in Bythotrephes-invaded lakes. Here, we combined a bioenergetics model for larval walleye with changes in the zooplankton community following Bythotrephes invasion and predicted reduced larval walleye growth in the presence of Bythotrephes, supporting field observations. The model predicted greater negative impacts on larval walleye growth in oligotrophic compared with mesotrophic lakes, though reduced growth was only significant under oligotrophic conditions. Under Bythotrephes invasion, net energy available to growth over the simulated period was often observed to be negative (indicating mass loss). These combined results from the model suggest that Bythotrephes invasion could potentially lead to walleye recruitment failure, especially in low nutrient environments. This result was insensitive to differences in annual mean water temperatures ranging from 18.5 to 23.5 °C. As YOY growth, survival, and recruitment are ultimately linked to adult abundance and sustainability of managed stocks, our results highlight the potential impacts of Bythotrephes on the sustainability of walleye populations in boreal lakes. [ABSTRACT FROM AUTHOR]

Documenting the evolution and transformation of natural history collection catalogues into digital online databases provides insight into the relevance and importance of processes, tools and decisions taken. This paper describes some important steps of the computerisation of the MNHN Fish Collection catalogue into the GICIM database and the onset of the collaboration with FishBase. The first specimens in the collection were catalogued in the second half of the 19th century. The initial estimate, in 1983, was 80,000 lots (a lot is a set of specimens caught in a same place in a same time and preserved in a same container) containing 1 million specimens. In 1994, about 82,000 lots were registered while most of the collection was computerised to become the GICIM database (Gestion Informatisée des Collections d'Ichtyologie du Muséum national d'Histoire naturelle / Computerised Management of the MNHN Ichthyological Collections). As of January 1st, 2022, 137,021 lots were registered containing 442,712 specimens. This early computerisation and database publication on the Web triggered a collaboration with FishBase. At the end of a first project in 1996-1997, georeferenced occurrence data for 78,000 lots were sent from GICIM to FishBase after standardisation and matching of the fields, in particular the taxon and country names. The subsequent development of the data entry interface and the structure improvement of GICIM made possible the management of additional information, and facilitated an analysis of the collection's growth, and how the collection has been used over the past thirty years. This article highlights that specimens and their associated data are more valuable when they are placed in their historical perspective of acquisition facilitating quality control and interpretation. It also demonstrates that collections must keep the pace of the development of new technologies. Based on lessons learned during the 25 past years, the collaboration GICIM-FishBase will continue to push towards the exploration and application of new and more efficient methodologies. [ABSTRACT FROM AUTHOR]

Based on previous molecular phylogenetic analyses, Bothriocestus n. gen. is erected to accommodate bothriocephalid tapeworms that have an elongate scolex, a well-developed apical disc, and a narrow neck region, parasitize freshwater fishes in the Holarctic, and were previously placed in the polyphyletic genus Bothriocephalus Rudolphi, 1808 (Cestoda: Bothriocephalidea). Bothriocestus claviceps (Goeze, 1782) n. comb., a parasite of eels (Anguilla spp.) in the Holarctic region, is designated as the type species. Another species of the new genus, Bothriocestus cuspidatus (Cooper, 1917) (syn. Bothriocephalus cuspidatus Cooper, 1917) is redescribed from type and voucher specimens, and new material from the type host, the walleye, Sander vitreus (Mitchill, 1818) (Perciformes: Percidae), in Manitoba and Ontario (where the type locality is located) (Canada) and in New York state and Wisconsin. Bothriocestus cuspidatus of S. vitreus is characterized primarily by the possession of a narrow, long strobila (total length up to 18 cm) composed of distinctly craspedote, trapezoidal proglottids, with primary, secondary, and tertiary proglottids differing in size, and by an arrow-shaped (¼cuspidatus) scolex that is distinctly broader than the first proglottids, widest near the base in lateral view and gradually becoming broader toward the anterior end in dorsoventral view. A ‘‘dwarf’’ form of B. cuspidatus (total length of 9–27 mm) from Johnny darter, Etheostoma nigrum Rafinesque, 1820, and tessellated darter, Etheostoma olmstedi Storer, 1842 (both Percidae: Etheostominae), is also characterized morphologically in the present paper. [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.

Pikeperch (Sander lucioperca) has become a species of interest in aquaculture. It is a popular and economically valuable food fish and can produce high numbers of offspring. However, during early development, there are transition phases when high mortality rates concur with growth changes, vital organ transformations and a limited energy budget. Up to now, no study focused on the developmental adaption of muscle tissue in pikeperch, regardless of muscle tissue influencing essential traits such as locomotion and thus the competence to hunt prey and avoid predators. In the present study, therefore, the developmental myogenesis of pikeperch was analysed using specimens from early embryonic to larval development. Myogenic and developmental genes were utilized to gain insights into transcriptomic regulation during these stages by applying a nanofluidic qPCR approach. Result, three phases of myogenic gene expression, during somitogenesis, during the late embryonic development and during the larval development were detected. Increased myostatin expression showed an interim arrest of muscle formation between embryonic and larval myogenesis. Expression patterns of satellite cell gene markers indicated an accumulation of stem cells before myogenesis interruption. The here gained data will help to broaden the knowledge on percid myogenesis and can support pikeperch rearing in aquaculture. [ABSTRACT FROM AUTHOR]

Status of several large-river darter species is uncertain because of difficulties sampling deep-water habitats. We characterized the darter (Family: Percidae) community in main and side channel macrohabitats of the upper Mississippi River using a small-mesh benthic trawl at sites in five navigation pools and a portion of the lower St. Croix River encompassing nearly 200 river kilometers in 2016 and 2017. We captured six darter species in conjunction with a survey to assess crystal darter (Crystallaria asprella) (state endangered) status and estimated density (n/700 m2) and population size for selected species in navigation pools. No crystal darter were collected in 83 trawl tows, including tows made at historical crystal darter locations. However, a total of 154 western sand darter (Ammocrypta clara) (globally vulnerable) were captured with density estimates ranging among pools from 1.0 to 9.6 in main channel and 1.0 to 5.0 in side channel macrohabitats. The largest population estimate was 33,286 (95% confidence limit: 17,974–52,725) for western sand darter in all side channels in Pool 7. A total of 71 river darter (Percina shumardi) were captured with zero caught in some pools to a maximum mean density of 17.5/700 m2 in Pool 3. Highest population size was 14,829 (8260–25,127) for river darter in the lower St. Croix River. A total of 43 logperch (Percina caprodes) and 143 johnny darter (Etheostoma nigrum) were captured but exhibited clumped spatial distributions that hindered population estimates. Only three mud darter (Etheostoma asprigene) and one slenderhead darter (Percina phoxocephala) were captured in deep-water habitats. Crystal darter absence supports continued state endangered classification. However, our density and population estimates for western sand darter and river darter represent the first such estimates for the upper Mississippi River and perhaps the world and should be used as baselines for future comparisons. [ABSTRACT FROM AUTHOR]

Hatchery propagation techniques, such as pellet- rearing, can result in altered feeding behaviour. Walleye Sander vitreus (Mitchill) is a commonly propagated sportfish, yet little is known regarding its ability to switch to live prey post- stocking. The objectives were to evaluate temporal changes in diet composition and condition as well as evaluate the relationship between total length and presence of different prey consumed by stocked walleye fry and fingerlings. Fingerling walleye had higher average proportions of empty stomachs and benthic invertebrates but less fish that stocked walleye fry. The presence of zooplankton, benthic invertebrates or fish was not related to walleye length. Walleye condition was similar between cohorts and did not change over days post- stocking. Percent similarity index values between cohorts were variable (0.0 to 67.9%). It was concluded that stocked walleye fingerlings consume lower quality prey items than stocked fry counterparts at least up to 49- day post- stocking, which may have implications for post- stocking survival. [ABSTRACT FROM AUTHOR]

Background. European perch, Perca fluviatilis Linnaeus, 1758, is a predatory freshwater fish present also in the coastal waters of the Baltic Sea. The available catch data indicate that the population profile of this species is disrupted, and the condition of the population is not stable. The aim of this study was to determine the diversity and genetic structure of and assess phylogenetic links and gene flow between selected perch populations originating from various types of reservoirs in northern Poland. Materials and methods. A total of 392 perch were collected from selected bodies of water in north-western Poland and the fin samples were preserved in 96% ethanol or stored for short periods at –20°C. Genomic DNA was isolated, while for further mitochondrial DNA analysis, a 1081-bp fragment of the control region was amplified. Amplification products were sequenced and subjected to restriction analysis (PCR-RFLP) in order to determine the genetic diversity of the control region of mtDNA. The obtained sequences were analyzed using bioinformatics tools, and phylogenetic trees were generated to determine the degree of diversity between individuals in selected perch stocks. Results. Seven haplotypes were identified. Ten polymorphic sites were defined, and the degree of genetic diversity between selected haplotypes was determined. Based on the distribution of perch haplotypes, stocks from Pomeranian Bay (haplotypes F, D), the Szczecin Lagoon (haplotypes D, F, H), and the more homogeneous stocks from Pomeranian Bay (haplotypes F, D) and the Kamieński Lagoon (D, F) can be distinguished. Analysis of phylogenetic relations allowed identifying stocks with the most conserved genome, similar to the standard perch genome, and stocks that have become more genetically distant, probably due to the diversity of the inhabited ecosystems or natural hybridization observed in this species. Conclusion. European perch inhabiting waters of north-western Poland is a species with high plasticity, without isolated stocks or populations that can be clearly distinguished on a genetic basis. It does, however, have a tendency for mitochondrial genomic modifications, which is likely due to the broad spectrum of ecosystems inhabited by the species. Due to the homogeneity of the perch populations from the Szczecin Lagoon, the Kamieński Lagoon, and Lake Myśliborskie, they should be used for the restoration of populations in water bodies in which their genetic structure is severely disrupted. For the same reason, the policy of perch catches should be modified. The authors suggest increasing the protected size to 20 cm and limiting the catches of the species as by-catch by modifying fishing tools, including the introduction of a seasonal prohibition of tools that might eliminate individuals of 15–16 cm in length from natural waters in their spawning period.

Sander lucioperca is an organism of growing importance for the aquaculture industry. Nonetheless, the rearing of S. lucioperca larvae is proving to be a difficult task as it is facing a high mortality rate during hatching and the change to exogenous feeding. To gain insight into growth patterns during this period, the authors analysed pikeperch embryos and larvae from 9 days before hatching to 17 days after hatch. Hereby they were able to describe a natural development by using close to natural conditions based on using a direct flow‐through supply of lake fresh water on specimens from a local wild population. The results show that between the early embryonic stages a steady growth was visible. Nonetheless, in between hatching and the start of exogenous feeding, a phase of growth stagnation took place. In the following larval stages, an increased growth with large size variations between individual specimens appeared. Both factors are conspicuous as they can indicate a starting point for cannibalism. With this analysis, the authors can provide a fundament to support the upcoming research on S. lucioperca and aid to optimize size‐sorting procedures for a higher survival of pikeperch stock in aquaculture. [ABSTRACT FROM AUTHOR]

The introduction of exotic species has the potential to cause resource competition with native species and may lead to competitive exclusion when resources are limiting. On the other hand, information is lacking to predict under what alternate trophic conditions coexistence may occur. Comparing diets of native yellow perch Perca flavescens and nonindigenous white perch Morone americana, we examined variation in resource partitioning and body condition across a prominent longitudinal nutrient gradient in Lake Erie (north‐eastern United States, Canada). As measured with Analysis of Similarity and Schoener's index, diet similarity declined monotonically from west to east tracking declines in nutrients, productivity and relative abundance of both species. Additionally, diet similarity increased from spring through fall, following seasonal development of stratification and hypolimnetic hypoxia—phenomena which tend to increase spatial overlap between these species. Finally, relative weights of both species peaked in the Central Basin (relative weights > 0.85), which, on average, had intermediate values of prey diversity, ecosystem trophic status and water clarity. Our results highlight that native yellow perch coexist with invasive white perch under a wide range of trophic conditions. Of importance to fishery managers, mesotrophy in the Central Basin correlated with the highest body conditions and intermediate prey resource partitioning, although the effect size was small and variable. While competitive exclusion appears unlikely, the goal of reducing nutrient inputs in Lake Erie could affect not only the distributions of both species but also stakeholder decisions about where to fish. [ABSTRACT FROM AUTHOR]

Understanding patterns of fish movement in large lake ecosystems is essential for determining appropriate management actions as differences in movement behaviour can influence life history traits such as growth and survival. Lake Winnipeg in Manitoba, Canada supports the 2nd largest walleye (Sander vitreus) commercial fishery in North America. We used mark-recapture models to determine movement and estimate survival of walleye between basins of Lake Winnipeg in historical and contemporary contexts, comparing a tag-recovery study completed historically during 1974–1977 with a contemporary (2017–2019) acoustic telemetry study. Mark-recapture models revealed comparably low but detectable annual transitions between basins from historical (0.3–1.2%) and contemporary datasets (7–8.5%). Historically, fish > 300 mm more frequently moved in a south to north direction. Contemporary estimates suggest similar length-based directionality in that fish > 350 mm were always more likely to move in a south-north direction. Contemporary annual survival derived from mark-recapture models ranged between 27 and 45% and 64.3% when derived from catch curve analysis, while independently derived annual historical survival estimates ranged between 50 and 69% and 45.5% from catch curve analysis. Using the contemporary dataset, we also observed seasonal variation in movement and survival between basins, with the greatest movement across the lake occurring during the fall. Our results demonstrate a persisting pattern of low but measurable movement, suggesting between basin movement is not unusual for Lake Winnipeg. Further, low walleye survival rates reported here for the two time periods studied, support recent management actions to reduce fishing pressure across the lake. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine the impact of different feed rations (0.5, 0.8, 1.1% fish biomass) on the rearing parameters of pikeperch, Sander lucioperca (L.), reared in a recirculating aquaculture system. The study comprised two experiments. In the first, the material used had been sorted by a mean body weight of 35.5 g, while in the second the pikeperch were divided into three size classes: smallest individuals (class S) with a mean body weight of 59.5 g, medium-sized individuals (class M) with a mean weight of 69.3 g, and largest individuals (class L) with a mean body weight of 84.8 g. The experiments ran for 42 days. At the conclusion of the experiments, the highest body weight and length, daily growth rate, and specific growth rate were attained by the group of fish fed the ration of 1.1% of the fish biomass in both experiments I and II. The feed conversion ratio was also the lowest in this feed ration group, and it differed significantly statistically among the experimental groups (P < 0.05). The feed ration of 0.5% of the fish biomass was only sufficient to maintain vital functions, but it contributed only slightly to growth. The different feed rations did not have a significant impact on the final value of the body weight coefficient of variation of the pikeperch reared in the two experiments. The results of the experiment also indicated that pikeperch is a species with weak stock hierarchy and domination structure.

This study aimed to determine the impact of immersing pikeperch (body weight approximately 94 g) in an aqueous solution of sodium chloride on gasometric, hematological, and biochemical indicators. The impact of the sodium chloride concentration (NaCl 10, 15, and 20 g L−1), immersion time (30 or 60 min) and time of blood sampling (0 h – blood drawn immediately following fish immersion; 24 h – blood drawn one full day after manipulation) was analyzed. The immersion protocol did not bring significant stress for tested fish as none of the tested parameters was different when compared to results obtained in a blank control group. The immersion times tested impacted the gasometric indicators and blood acid-base balance (0 h). The levels of most of the whole blood and plasma biochemical indicators analyzed (Na+, Cl-, glucose, lactate, total protein, globulin) differed significantly in fish exposed to 15 g L−1 and 20 g L−1 of NaCl from those in the blank control group. These changes were short-term and after 24 h the values of these indicators did not differ from those confirmed in the control group. Significant increases in the levels of hemoglobin, hematocrit, and red blood cells were confirmed in groups 10 g NaCl L−1/30 min/0 h and 20 g NaCl L−1/30 min/0 h and these changes persisted 24 h following immersion. Significant increases in the number of white blood cells (0 h) were confirmed in all groups, and this persisted for 24 h following immersion. The current study revealed transient, dose- and time-dependent stress reactions in pikeperch subjected to abrupt changes in water salinity and indicated that this species has significant recovery abilities in response to salinity shifts of short duration.

Background. European perch, Perca fluviatilis Linnaeus, 1758, is a predatory freshwater fish present also in the coastal waters of the Baltic Sea. The available catch data indicate that the population profile of this species is disrupted, and the condition of the population is not stable. The aim of this study was to determine the diversity and genetic structure of and assess phylogenetic links and gene flow between selected perch populations originating from various types of reservoirs in northern Poland. Materials and methods. A total of 392 perch were collected from selected bodies of water in north-western Poland and the fin samples were preserved in 96% ethanol or stored for short periods at -20°C. Genomic DNA was isolated, while for further mitochondrial DNA analysis, a 1081-bp fragment of the control region was amplified. Amplification products were sequenced and subjected to restriction analysis (PCR-RFLP) in order to determine the genetic diversity of the control region of mtDNA. The obtained sequences were analyzed using bioinformatics tools, and phylogenetic trees were generated to determine the degree of diversity between individuals in selected perch stocks. Results. Seven haplotypes were identified. Ten polymorphic sites were defined, and the degree of genetic diversity between selected haplotypes was determined. Based on the distribution of perch haplotypes, stocks from Pomeranian Bay (haplotypes F, D), the Szczecin Lagoon (haplotypes D, F, H), and the more homogeneous stocks from Pomeranian Bay (haplotypes F, D) and the Kamienski Lagoon (D, F) can be distinguished. Analysis of phylogenetic relations allowed identifying stocks with the most conserved genome, similar to the standard perch genome, and stocks that have become more genetically distant, probably due to the diversity of the inhabited ecosystems or natural hybridization observed in this species. Conclusions. European perch inhabiting waters of north-western Poland is a species with high plasticity, without isolated stocks or populations that can be clearly distinguished on a genetic basis. It does, however, have a tendency for mitochondrial genomic modifications, which is likely due to the broad spectrum of ecosystems inhabited by the species. Due to the homogeneity of the perch populations from the Szczecin Lagoon, the Kamienski Lagoon, and Lake Mysliborskie, they should be used for the restoration of populations in water bodies in which their genetic structure is severely disrupted. For the same reason, the policy of perch catches should be modified. The authors suggest increasing the protected size to 20 cm and limiting the catches of the species as by-catch by modifying fishing tools, including the introduction of a seasonal prohibition of tools that might eliminate individuals of 15-16 cm in length from natural waters in their spawning period. [ABSTRACT FROM AUTHOR]

The European perch Perca fluviatilis L. serves as a host of different endohelminths of Trematoda, Cestoda, Nematoda, and Acanthocephala. Its natural range covers freshwater basins throughout much of Europe, including the Danube. Since information about endohelminths of European perch from this international river basin has been rather sporadic, the parasitological examinations of 700 perch from the central region of the Danube river basin in Slovakia were performed in October 2017 and April 2018. The larval stages of Triaenophorus nodulosus (Cestoda) were found in cysts located in the perch liver and adults of Proteocephalus percae (Cestoda) were isolated from the intestine. The larval stages of Eustrongylides sp. (Nematoda) and metacercariae of Clinostomum complanatum (Trematoda), both potential causative agents of fish-borne zoonoses, were found in the musculature. Spatial and seasonal differences in the occurrence of currently detected helminths were discussed with data on biological and environmental conditions of particular sampling site. [ABSTRACT FROM AUTHOR]

Increases in the population abundance of the piscivorous great cormorant (Phalacrocorax carbo) has led to conflicts with fisheries. Cormorants are blamed for decreased fish catches in many lakes in Poland. The aim of this paper is to describe to role of pikeperch (Sander lucioperca) in the diet of cormorants nesting in a colony on the island in Lake Warnołty. Since the breeding colony is located in the vicinity of Lake OEniardwy, the largest lake in Poland, the cormorants use the resources in this lake. In 2009-2016, 18,432 regurgitated fish were collected, of which 593 were pikeperch. The share of pikeperch among fish collected in 2009-2012 did not exceed 2%, but from 2013 this increased substantially to maximum of 38.2% in 2015. The smallest pikeperch had a standard length of 8.4 cm, and the largest 42.5 cm. Pikeperch mean length differed by year, and the length distribution was close to normal. The sizes of the regurgitated pikeperch indicate that cormorants prey almost exclusively on juvenile specimens. The results of the present study indicate that cormorant predation has a significant impact on pikeperch populations in lakes in the vicinity of the colony, and the great cormorants are possibly a significant factor in the effectiveness of pikeperch management. When planning for the management of fish populations in lakes subjected to cormorant predation pressure, it should be borne in mind that predation by this piscivorous bird species impacts the abundance and size-age structure of fish populations.

• Movement rules coded a priori often lack tradeoffs between environmental factors. • An eco-genetic modeling framework allows movement rules to emerge from the model. • Simulated yellow perch reacted to five simultaneous dynamic environmental gradients. • Survival and growth increased throughout simulations with movement rule evolution. • Eco-genetic modeling is flexible and applicable to many animal behavior scenarios. Agent-based, spatially-explicit models that incorporate movement rules are used across ecological disciplines for a variety of applications. However, appropriate movement rules may be difficult to implement due to the complexity of an individual's response to both proximate and ultimate cues, as well as the difficulty in directly assessing how organisms choose to move across their environment. Environmental cues may be complex and dynamic, and therefore, movement responses may require tradeoffs between preferred levels of different environmental variables (e.g., temperature, light level, and prey availability). Here, we present an approach to determine appropriate movement rules by setting them as heritable traits in an eco-genetic modeling framework and allowing movement rules to evolve during the model rather than setting them a priori. We modeled yellow perch, Perca flavescens , movement in a simulated environment and allowed perch to move in response to high-resolution vertical gradients in temperature, dissolved oxygen, light, predators, and prey. Evolving movement rules ultimately increased fish growth and survival over generations in our model, indicating that evolving movement rules led to improved individual performance. We found that emergent movement rules were consistent across trials, with evolved movement rules incorporating different weights of these environmental factors and the most rapid selection on temperature preference. This case study presents a flexible method using eco-genetic modeling to determine appropriate movement rules that can be applied to diverse scenarios in spatially-explicit ecological modeling. [ABSTRACT FROM AUTHOR]

How spawning stock size, environmental conditions and recruitment relate to each other is an essential question in understanding population dynamics of exploited fish stocks. We estimated the recruitment of Eurasian perch (Perca fluviatilis), one of the most important species in coastal fisheries in northern Baltic Sea, and examined the factors that determine perch recruitment success. We hypothesized that perch spawning population biomass and summer water temperature would increase perch recruitment, with potential density dependence, while the effect of the population size of pikeperch (Sander lucioperca) would be negative. Different forms of general stock–recruitment functions, with and without density dependence, and with and without water temperature and pikeperch population size as environmental factors were fitted to long-term (1981–2014) stock assessment data of perch and pikeperch in the Archipelago Sea, southwestern coast of Finland. Perch spawning stock biomass (ages 5–14), water temperature in June–July and pikeperch stock size (ages ≥ 1) at spawning year best explained variation in perch recruitment. The results supported the predictions: perch recruitment increased with spawning stock in density-dependent manner, pikeperch effect on perch recruitment was negative and summer temperature effect was positive suggesting environmentally affected competitive interaction between these two percids. [ABSTRACT FROM AUTHOR]

In the present paper, species of the Proteocephalus-aggregate de Chambrier, Zehnder, Vaucher, and Mariaux, 2004 (Cestoda: Proteocephalidae) reported from centrarchid and percid fishes in North America are reviewed, and their taxonomic status is critically assessed based on a study of type specimens and new material from Canada and the United States. The following 3 species, supposedly strictly specific to their fish definitive hosts, are recognized as valid: (1) Proteocephalus fluviatilisBangham, 1925 (new synonyms Proteocephalus osburniBangham, 1925 and Proteocephalus microcephalusHaderlie, 1953; Proteocephalus ‘robustus’ nomen nudum) from the smallmouth and largemouth bass, Micropterus dolomieu (Lacépède) (type host) and Micropterus salmoides (Lacépède) (both Centrarchidae); (2) Proteocephalus luciopercaeWardle, 1932 (new synonym Proteocephalus stizostethiHunter and Bangham, 1933) from the walleye, Sander vitreus (Mitchill) (type host), and sauger, Sander canadensis (Griffith et Smith) (Percidae); and (3) Proteocephalus pearseiLa Rue, 1919, a parasite of the yellow perch, Perca flavescens Mitchill (Percidae). All species are illustrated based on new, properly heat-fixed material. Scanning electron micrographs of the scoleces of percid tapeworms P. luciopercae and P. pearsei, as well as the bass tapeworms P. fluviatilis and Proteocephalus ambloplitis (Leidy, 1887), the latter of which does not belong to this Proteocephalusaggregate, are provided for the first time together with a simple key to species identification of proteocephalids from centrarchiform and perciform teleost fishes. [ABSTRACT FROM AUTHOR]

Eurasian perch (Perca fluviatilis) were sampled in April, from May to June and at the end of August to test whether the current season (i.e. feeding conditions) affects the fishes' stomach size (i.e. volume and weight). A wide range of size data were analysed to reveal the relationship between fish size (length and weight) and stomach size. No significant differences in length-specific stomach volume or stomach weight were found in fish sampled at different times of the year. However, there were differences between seasons in the size of the stomach in relation to body weight, as length-specific body weight changes during the year because of the development of gametes and changes in nutritional status. Both stomach volume and weight grew obeying the power function up to about 20 cm in total length of perch. Yet, the growth was faster than that predicted by the cube law in relation to fish length, i.e. allometric. In larger fish, stomach growth decreased in relation to growth in length, and the relative weight of the stomach even decreased in the largest size class. These dynamics match well with the typical pattern of growth and ontogenic shift in diet from small invertebrates to fish. A non-proportional power function relationship was found between stomach weight and stomach volume. [ABSTRACT FROM AUTHOR]

Analysis of previously published characteristics of the downstream migration of juvenile cyprinids (Cyprinidae) and percids (Percidae) from the Volga and Ivankovskoe, Volgogradskoe, and Tsimlayanskoe reservoirs is presented. In case of river damming, migrations of river fish are modified first of all due to transformation of the hydrophysical and morphological structure of the water course creating a different biotopic pattern influencing life activities of fish, including migratory behavior. In contrast to the natural river, where the conditions controlling the characteristics of the downstream migration change gradually from the upper reaches to the lower reaches, ecological barriers are formed in the dammed river—the water reservoir and the dam—which essentially change these conditions. A leading role in formation of these barriers and in regulation of the downstream migration is performed by the morphological complexity of a water body and by the intensity of water exchange. These factors act both on the scale of the whole water reservoir and on the scale of local biotopes where the downstream migration takes place and behavioral mechanisms act efficiently. The synergistic effect of these factors (a high ramification index of the reservoir at a low water exchange) may decrease the intensity of emigration of fish juveniles from a reservoir by several orders of magnitude. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine the impact of different feed rations (0.5, 0.8, 1.1% fish biomass) on the rearing parameters of pikeperch, Sander lucioperca (L.), reared in a recirculating aquaculture system. The study comprised two experiments. In the first, the material used had been sorted by a mean body weight of 35.5 g, while in the second the pikeperch were divided into three size classes: smallest individuals (class S) with a mean body weight of 59.5 g, medium-sized individuals (class M) with a mean weight of 69.3 g, and largest individuals (class L) with a mean body weight of 84.8 g. The experiments ran for 42 days. At the conclusion of the experiments, the highest body weight and length, daily growth rate, and specific growth rate were attained by the group of fish fed the ration of 1.1% of the fish biomass in both experiments I and II. The feed conversion ratio was also the lowest in this feed ration group, and it differed significantly statistically among the experimental groups (P < 0.05). The feed ration of 0.5% of the fish biomass was only sufficient to maintain vital functions, but it contributed only slightly to growth. The different feed rations did not have a significant impact on the final value of the body weight coefficient of variation of the pikeperch reared in the two experiments. The results of the experiment also indicated that pikeperch is a species with weak stock hierarchy and domination structure. [ABSTRACT FROM AUTHOR]

Abstract Two types of gonadotropin-releasing hormones (GnRH) were identified as gnrh1 and gnrh2 in pikeperch Sander lucioperca. The administration of rodent leptin on hypothalamic organ cultures of immature pikeperch resulted in significantly elevated levels of gnrh2, but not in gnrh1 mRNA, whereas kisspeptin-10 administration did not affect gnrh1 or gnrh2 expression. These results represent preliminary insights into leptin-GnRH-signaling on a hypothalamic level in fish, potentially coupling fat metabolism and the activation of the reproductive axis during puberty. Mammalian leptin and kisspeptin-10, however, failed to initiate a consistent response in pikeperch and their use cannot be recommended.

In vertebrates, the carbohydrate polymer polysialic acid (polySia) is especially well known for its essential role during neuronal development, regulating the migration and proliferation of neural precursor cells, for instance. Nevertheless, sialic acid polymers seem to be regulatory elements in other physiological systems, such as the reproductive tract. Interestingly, trout fish eggs have polySia, but we know little of its cellular distribution and role during oogenesis. Therefore, we localized α2,8-linked N-acetylneuraminic acid polymers in the ovaries of Coregonus maraena by immunohistochemistry and found that prevalent clusters of oogonia showed polySia signals on their surfaces. Remarkably, the genome of this salmonid fish contains two st8sia2 genes and one st8sia4 gene, that is, three polysialyltransferases. The expression analysis revealed that for st8sia2-r2, 60 times more mRNA was present than st8sia2-r1 and st8sia4. To compare polysialylation status regarding various polySiaT configurations, we performed a comparable analysis in Sander lucioperca. The genome of this perciform fish contains only one st8sia2 and no st8sia4 gene. Here, too, clusters of oogonia showed polysialylated cell surfaces, and we detected high mRNA values for st8sia2. These results suggest that in teleosts, polySia is involved in the cellular processes of oogonia during oogenesis.

Among the morphological anomalies that have been reported in fish so far, abnormalities in scale shape and structure have been described from a limited number of species worldwide. The aim of the present study was to extend this knowledge by identifying and describing such scale abnormalities in freshwater fish from the Kaniv Reservoir, Ukraine. Scale deformities were common in most of the species investigated (Cyprinidae, 10 spp.; Percidae, 2 spp.; Esocidae, 1 sp.), with some differences in the number of cases among them. A wide variety of scale deformities was found, classified into two major categories, slight and severe. In all, 211 abnormal scales (172 slight and 39 severe deformities) were observed and described. The scale deformities described herein could help direct future work on the relationships between the condition of the environment and fish health. This study identifies and describes scale abnormalities in freshwater fish from the Kaniv Reservoir, Ukraine. Many scale deformities were found and were classified into two major categories: slight and severe. In all, 211 abnormal scales (172 slight and 39 severe deformities) were observed and described. The scale deformities described herein could help direct future work on relationships between environmental conditions and fish health. [ABSTRACT FROM AUTHOR]

Released hatchery-origin fish must survive and reproduce for supplementation to recover collapsed native populations, yet monitoring fitness is challenging, because physical tags are not passed from parent to offspring. Parentage-based tagging (PBT) is a method in which all captive-bred parents are genotyped (i.e., given a molecular tag), and their wild-caught hatchery offspring are identified via genetic pedigree analysis. The sauger (Sander canadensis) is a highly migratory, freshwater percid (perch species), native to central and eastern North America. In the Wind River basin, Wyoming the species' abundance has declined considerably since 2002, and in 2013 stakeholders initiated a hatchery program to recover the population. We estimated the statistical sensitivity and accuracy of PBT using 17 microsatellites to identify hatchery-origin saugers captured in the wild. We completed in vitro and in silico experiments that demonstrated 98% sensitivity and 99% accuracy of PBT in distinguishing hatchery- and natural-origin saugers. Moreover, our experiments showed that accuracy is robust to factors expected to decrease assignment accuracy, including highly related parents (i.e., full siblings) and differing proportions of true parents included in the analysis. This research highlights that our ability to assign parentage and estimate fitness is high, and that PBT is an effective way to monitor recovery of saugers in the Wind River, basin Wyoming. [ABSTRACT FROM AUTHOR]

A new Henneguya species, H. jaczoi sp. n., is described from perch (Perca fluviatilis) from Lake Balaton, Hungary. This species infects the palatal region of the fish, forming large plasmodia in the thickened caudal part of the buccal cavity and at the dorsal ends of the cartilaginous gill arches. The species differs from the gill-dwelling Henneguya species of perch and pike (Esox lucius) both morphologically and in molecular aspects. The authors conclude that the type species H. psorospermica Thélohan is a specific parasite of pike, while the species forming plasmodia in the gills of perch corresponds to H. texta Cohn, which was hitherto regarded as a synonym of H. psorospermica. Besides the above-mentioned species, H. creplini was frequently found in pikeperch (Sander lucioperca) and Volga pikeperch (Sander volgensis), but no Henneguya infection has been recorded in ruffe (Gymnocephalus cernua), which is a common percid fish of the lake and is known to be the type host species for H. creplini. [ABSTRACT FROM AUTHOR]

Background: The importance of transposable elements (TEs) in the genomic remodeling and chromosomal rearrangements that accompany lineage diversification in vertebrates remains the subject of debate. The major impediment to understanding the roles of TEs in genome evolution is the lack of comparative and integrative analyses on complete taxonomic groups. To help overcome this problem, we have focused on the Antarctic teleost genus Trematomus (Notothenioidei: Nototheniidae), as they experienced rapid speciation accompanied by dramatic chromosomal diversity. Here we apply a multi-strategy approach to determine the role of large-scale TE mobilization in chromosomal diversification within Trematomus species. Results: Despite the extensive chromosomal rearrangements observed in Trematomus species, our measurements revealed strong interspecific genome size conservation. After identifying the DIRS1, Gypsy and Copia retrotransposon superfamilies in genomes of 13 nototheniid species, we evaluated their diversity, abundance (copy numbers) and chromosomal distribution. Four families of DIRS1, nine of Gypsy, and two of Copia were highly conserved in these genomes; DIRS1 being the most represented within Trematomus genomes. Fluorescence in situ hybridization mapping showed preferential accumulation of DIRS1 in centromeric and pericentromeric regions, both in Trematomus and other nototheniid species, but not in outgroups: species of the Sub-Antarctic notothenioid families Bovichtidae and Eleginopsidae, and the non-notothenioid family Percidae. Conclusions: In contrast to the outgroups, High-Antarctic notothenioid species, including the genus Trematomus, were subjected to strong environmental stresses involving repeated bouts of warming above the freezing point of seawater and cooling to sub-zero temperatures on the Antarctic continental shelf during the past 40 millions of years (My). As a consequence of these repetitive environmental changes, including thermal shocks; a breakdown of epigenetic regulation that normally represses TE activity may have led to sequential waves of TE activation within their genomes. The predominance of DIRS1 in Trematomus species, their transposition mechanism, and their strategic location in "hot spots" of insertion on chromosomes are likely to have facilitated nonhomologous recombination, thereby increasing genomic rearrangements. The resulting centric and tandem fusions and fissions would favor the rapid lineage diversification, characteristic of the nototheniid adaptive radiation. [ABSTRACT FROM AUTHOR]

Seasonal changes in several physiological endpoints of the perch Perca fluviatilis in the temperate climatic conditions were examined. Hepatic antioxidant enzyme activities (superoxide dismutase, catalase, and glutathione-S-transferase) varied dramatically throughout the annual cycle. Driven by internal and external factors, the greatest values of the studied characteristics were timed to the periods of spawning and elevated water temperature. The results of this study showed high plasticity of the fish’s antioxidant system, which allows the perch to bear naturally occurring oxidative stress. [ABSTRACT FROM AUTHOR]

Exploring species-environment relationships to identify essential habitat areas is recognized as an effective way for resource conservation and management. Because of ecological and economic importance of Yellow Perch (Perca flavescens) in Lake Erie, it is essential to develop appropriate habitat models to analyze habitat supply of this species. Empirical species-environment models for two age-groups (juveniles and adults) at two depth strata were developed based on a long-term (27 years) gillnet survey data. Models incorporated interactive terms indicate a high degree of prediction accuracy and satisfied the assumption of residual independence. As a benthivorous species, high-quality habitat is mainly distributed in the bottom waters. Suitable habitat for adults is also found in the mid-waters in the central and east basins. Weighted suitability index per unit area differs significantly among years, basins, and vertical strata. Currently, quota allocation among jurisdictions is determined by using GIS applications of jurisdictional surface area of waters within each management unit. The outputs from our study can be used to revise the current quota allocation schemes and habitat-based quota allocation protocol will provide more scientific and rational total allowable catch for each jurisdiction. [ABSTRACT FROM AUTHOR]

The process of speciation is often synonymous with the evolution of reproductive isolation, and the tempo at which reproductive barriers evolve can provide insight into the underlying mechanisms of divergence. Darters are a diverse group of North American freshwater fish in which behavioral isolation appears to evolve rapidly; however, little is known about hybrid sterility among darter species. Here, six allopatric pairs of darter species were hybridized via in vitro fertilization and offspring were reared to reproductive age. Hybrid sterility appears more pronounced in male hybrids. Additionally, levels of hybrid sterility increase with genetic distance across species pairs. Understanding sex determination and sex-specific gene expression in darters will provide further insight into the evolution of hybrid sterility. [ABSTRACT FROM AUTHOR]