Search Results (11)

The increasing consumption of fish has raised public health concerns regarding fish-borne zoonotic helminths (FBZHs), which are recognized as significant food-borne parasites worldwide. In freshwater environments, Clinostomum complanatum, Opisthorchis felineus, Pseudamphistomum truncatum, Dibothriocephalus latus and Eustrongylides excisus are of particular concern in Italy and neighbouring countries. This study aimed to assess the prevalence of these FBZHs in five commercially and ecologically relevant freshwater fish species from Lake Varese, a heavily anthropized and understudied basin in northern Italy. A total of 59 fish were examined via necropsy and stereomicroscopic inspection of skeletal muscles. Only Eustrongylides spp. larvae were detected, with a prevalence of 16.9%. Molecular analysis (ITS region) identified them as E. excisus. This study reports, for the first time in Western Europe, E. excisus in Sander lucioperca (p = 12.5%) and Esox lucius (p = 8.3%). The highest prevalence occurred in Silurus glanis (p = 37.5%), followed by Perca fluviatilis (p = 25.0%), while Tinca tinca showed no infection. These findings confirm that among the FBZHs considered, E. excisus is currently present and expanding both in host range and geography in Italian lakes, underscoring the need for updated epidemiological data to support risk assessment, food safety and zoonotic parasite control in freshwater fisheries. Full article

Freshwater fish species play an important role in global aquaculture. Currently, sturgeon, carp, and tilapia are at the forefront of this industry. However, as human populations continue to grow, the demand for new sources of animal protein increases, making the use of other freshwater species in aquaculture essential. The pikeperch (Sander lucioperca) is one of the most promising fish species for European aquaculture, but its usage has been hindered by a lack of effective larval-rearing protocols. Most studies focus on using cultured or nutrient-rich zooplankton for larval cultivation, while natural zooplankton from the local environment are rarely used. In this study, we aim to investigate the nutritional requirements of pikeperch larvae by describing the taxonomic diversity and biochemical composition of zooplankton collected from a natural oligotrophic lake in Northwest Russia. The chemical composition of zooplankton is characterized by a high protein content (up to 70% of dry matter), a moderate lipid content (up to 25%), and a deficiency of certain fatty acids and amino acids. Specifically, there is a low concentration of docosahexaenoic acid and methionine. The dry matter content in the zooplankton averages 10%, with nitrogen-free extracts accounting for 4% and ash making up 4%. These biochemical parameters meet the nutritional requirements of freshwater pikeperch larvae, with the notable exception of the lower levels of DHA and methionine, which are typically characteristic of freshwater zooplankton. This information sheds light on the nutritional requirements of pikeperch larvae and the development of more efficient rearing methods. Full article

Food webs in estuarine ecosystems serve as important biological indicators. The feeding ecology of four keystone fish species, pikeperch (Sander lucioperca L.), smelt (Osmerus eperlanus L.), ruffe (Gymnocephalus cernua L.) and flounder (Platichthys flesus L.), in the Elbe and Odra estuaries was analyzed using stomach content analyses. Important prey of pikeperch were fishes and mysids in both estuaries. Amphipods were especially important as prey for smelt in the Elbe estuary, whereas smelt caught in the Odra estuary mainly consumed mysids. Ruffe fed mainly on amphipods in the Elbe estuary, while annelids (lower section) and insect larvae (upper section) were the most important prey in the Odra estuary. Flounder favored copepods as prey in the Elbe estuary, while bivalves were preferred in the Odra estuary. Higher dietary overlaps were found in the Elbe estuary between smelt vs. ruffe, pikeperch vs. ruffe, and pikeperch vs. smelt. In the Elbe estuary, a shift in the diet composition of pikeperch, smelt, and ruffe was observed from 2021 to 2022 compared to food analyses from the 1990s. These shifts included an increased consumption of amphipods, while mysids and copepods had recently decreased in their diets. These changes indicate a restructuring of the food web, potentially linked to environmental changes, which highlights the sensitivity of estuarine ecosystems. Full article

The pikeperch (Sander lucioperca) is an economically important freshwater fish and a valuable food with high market acceptance. It is undergoing important changes in growth and regulatory metabolism during the ontogeny. Hence, the current study aims to investigate the mRNA expression of the growth hormone (gh)/insulin-like growth factor (igf) axis (ghr, igfI, igfbp, igfr), muscle regulatory factors (pax7, myf5, myod, myogenin, mrf, mymk, mstn), and osteogenesis-related genes (colla1a, fib1a, on, op, ostn) from hatching through day 40th post-hatching (DPH). The average total length (TL) of larvae measured at hatching was 3.6 ± 0.4 mm (67 degree days), and at the end of the experiment (40 DPH, 777 degree days), it was 27.1 ± 1.1 mm. The results showed three phases of gene expression in day 0 (egg), larval, and juvenile stages of pikeperch, which can be a progression or transition from the initial state toward the juvenile state. The expression pattern of myf5, mymk, and fib1a genes showed the highest value at day 0. The growth hormone receptor gene (ghr) and igfbp5 were raised to 1 DPH, whereas increased expression of igfI, igfII, igf1bp4, igf1rb, myod2, and mrf4 was detected at 14 DPH. The myod1, pax7, op, ostc, on, igf1ra, and col1a1a genes were highly expressed at 21 DPH and juvenile stages. According to the PLS-DA model, the most relevant VIPs are myf5 and mymk as best markers of earlier stages and igf1ra, ostc, pax7, and ghr as markers of later stages of ontogeny. Results from this study suggest that basal metabolism, growth of body cells and muscles, and bone proliferation and development can be regulated by the dynamic changes in gene expression patterns in this species. The identified genes will help to understand the basic biological process of pikeperch larvae and development, which is very important in pikeperch farming Full article

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. Full article

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. Full article

First feeding of many fish larvae depends on live feed. A comparative investigation on the effectiveness of different types of live feed is not available to our knowledge. Hence, we conducted a study to examine the effect of different types and combinations of live feed on the performance (survival rate, total length, body width, body mass, malformation rate) of pikeperch, Sander lucioperca, larvae. From day 0 (onset of exogenous feeding) to day 10, the saltwater rotifer Brachionus plicatilis, the freshwater rotifer Brachionus calyciflorus, the ciliate Paramecium bursaria, copepods (nauplii and copepodites) from a lake population, and Artemia nauplii were tested. Feeding with B. plicatilis, B. calyciflorus, and P. bursaria resulted in high survival rates of 80% and a homogenous and significant growth (increase in total length of 50% and in body width of 20%). As follow-up feed, copepod nauplii and Artemia nauplii were tested from day 11 to day 20. Copepod nauplii were superior to Artemia nauplii, as larvae fed with copepods showed higher survival rates (67–70% versus 38–47%) and a more homogeneous growth. A switch from seawater live feed to freshwater live feed or vice versa resulted in decreased survival rates. Therefore, a feeding regime consisting of B. calyciflorus or P. bursaria followed by copepods is considered optimal as first feed of pikeperch. The malformation rate was not affected by the tested feeding regimes. To investigate the wider applicability and transferability of these findings, complementary investigations were performed on burbot, Lota lota, and the freshwater whitefish Coregonus atterensis. The feeding regimes used for S. lucioperca larvae were also suitable for Lota lota. Moreover, L. lota could be fed with lake copepods from the onset of exogenous feeding. For C. atterensis, initial feeding with B. plicatilis, B. calyciflorus, or P. bursaria had no positive effects. Feeding with copepods from the onset of exogenous feeding was optimal considering survival rate and growth. Therefore, optimal first feeding regimes are very species specific and should be established for each new species. Full article

A new cultivation system with the chlorophyte Monoraphidium contortum combined with a self-sustaining culture of the freshwater rotifer Brachionus calyciflorus was applied for Sander lucioperca (L.) larviculture. Survival, morphometrics, as well as fatty acid composition of pikeperch larvae were analyzed after a ten-day feeding period. By using the pseudo-green water technique with improved aeration and water movement at the surface, survival rates reached up to 94%, with a total larval length of 8.1 ± 0.3 mm and a specific length growth rate of up to 4.1% day⁻¹ for S. lucioperca. The biochemical composition of B. calyciflorus and especially its contents in C18 PUFAs and suitable n-3/n-6 ratios met the nutritional requirements of pikeperch larvae. The high abundance of highly unsaturated fatty acids (HUFAs) in the diet appeared to be less important in the first feeding due to a possible retention of essential fatty acids, which originate from the yolk sac reserves, at adequate levels. Exponential growth of microalgae and zooplankton under the applied conditions was most effective when stocking M. contortum five days and B. calyciflorus three days before adding the fish larvae. Appropriate timing and sufficient live feed density allowed a successful integration of B. calyciflorus into pikeperch larviculture. We hypothesize that feeding pikeperch larvae with a self-sustaining Brachionus-culture under pseudo-green water conditions with minor disruptions during larviculture will improve survival and growth. This system is a first step towards pikeperch larviculture inside recirculated aquaculture systems (RAS) under continuous feed supply with live feed within the same aquaculture unit. Full article

This study focused on supplementing pikeperch (Sander lucioperca) larvae with rotifers fed with Chlorella vulgaris during the first 15 days post hatching (dph). Larvae were fed a combination of rotifers and artemia under three different enrichments: A) Nannochloropsis occulata, B) Chlorella vulgaris, and C) a commercial enrichment—Selco, Spresso from INVE. After 17 days from the trial initiation differences were found between treatments on survival rate, myomere height (MH), fatty acid composition, and stress tolerance. In terms of survival, larvae from treatment b (74.5%) and c (66%) excelled over the control (a) treatment (59%). Furthermore, larvae from both the Chlorella (b) and the Selco (c) treatments showed more resilience to stress conditions (10% and 37% reduction in mortality) when exposed to high salinity conditions (18ppt) for 3 h (stress response). Overall, larvae from treatments b and c performed better than those receiving a non-enriched diet (a), likely due to the higher levels of Essential Fatty Acids (EFA) and the ability of pikeperch to desaturate and elongate fatty acids (FA) with 18 carbons to LC PUFAs (Polyunsaturated Fatty Acids). The present study provides valuable input for designing improved feeding protocols, which will increase the efficiency of pikeperch larval culture. Full article

This trial tested the use of lactic acid bacteria (LAB) on pikeperch (Sander lucioperca) larvae during their first feeding. The trial included the use of two probiotic treatments and one control (no probiotics). Pikeperch larvae were exposed to LAB as follows: (1) the live feed (Treatment 1, live feed) or (2) via the live feed and the larval rearing water (Treatment 2, probiotic). Significant differences were found between the treatments in terms of total length (TL), myomere height (MH), overall survival, and the tolerance to a high salinity challenge. Larvae exposed to LAB via both the live feed and the rearing water had a significantly higher overall survival rate (85%) than the other two treatments at 21 dph. When both treatments were subjected to high salinity rates (18 parts per thousand (ppt)), both treatments exposed to LAB demonstrated higher survival rates than the control treatment (28% and 40% survival rate at 180 min for the live feed and probiotic treatments, respectively, as compared with a 100% mortality rate at 150 min for the control). At the same time, larvae exposed to the probiotic treatment had a significantly higher TL as compared to the control after 12 and 21 days post hatch (dph) (probiotic 7.13 ± 0.21 and 11.71 ± 1.1 mm, control 5.86 and 10.79 mm at 12 and 21 dph, respectively). The results suggest that the use of LAB in both the live feed and the rearing water has a positive effect on pikeperch larval quality by strengthening their resilience to stress conditions, as well as improving the growth and survival rates. Full article

Cannibalism occurs in many cultured fish species, especially at the larval and juvenile stages of piscivorous taxa. In farmed percid species, such as pikeperch (Sander lucioperca), intra-cohort cannibalism is a major issue inducing significant losses of the initial stocking density during the first weeks of rearing. Therefore, the present study was designed to investigate the effects of perch larvae (Perca fluviatilis) as live prey on growth, survival and cannibalism in pikeperch larvae under experimental conditions. Additionally, zootechnical and behavioural variables linked to aggressiveness (S postures, attacks, bites and ingestion), and group structures were considered. The survival rate was not different between the two groups (72% with prey vs. 69% without prey), but the cannibalism rate was higher in the group with the prey (28% vs. 10%). The means of final weight and length of pikeperch larvae were higher in the group fed with perch larvae, but size heterogeneity measured by the coefficients of variation for these two parameters did not differ. The specific growth rate was higher in the group fed with perch larvae, but there was no difference between the two groups concerning Fulton’s condition factor. Among all the behavioural variables (aggressiveness, group structure), none differed between the two groups. Full article