Intraspecific competition is a fundamental selective force in animals, leading to various specializations that influence ecological interactions. Diet composition and trophic position at the early life stages substantially influence fish growth, survival, and recruitment success. Yet, most studies focus disproportionately on adult stages, leaving critical knowledge gaps in our understanding of early life history. To address this, we used young of the year (YOY) pikeperch (Sander lucioperca) as a model species and investigated the intraspecific interaction and degree of trophic partitioning between three intra-annual cohorts (extremely small (ES), ordinary and piscivorous YOYs) using stable isotope (SI) and gut content analysis (GCA). Analysis of SI metrics unveiled that an ontogenetic diet shift was linked to increasing body size, leading to significant trophic niche variation among intra-annual cohorts. The piscivorous cohort occupied the highest trophic position, followed by the ordinary and ES cohorts. There was no overlap in the isotopic niche between the intra-annual cohorts, considering the 40% standard ellipse area. The GCA showed two distinct feeding patterns: the ES cohort exclusively consumed zooplankton, while the ordinary cohort had a more diverse diet, feeding on zooplankton and benthic macroinvertebrates. The piscivorous cohort (≥ 80 mm) predominantly fed on their conspecifics and YOY perch (Perca fluviatilis). Our study demonstrates that YOY pikeperch intra-annual cohorts exhibit a broad size range and unique ontogenetic feeding patterns, with vital implications for population dynamics and ecological interactions. These differences are likely due to different hatching dates, environmental factors, and individual ability to become predatory. Furthermore, this work emphasizes the need for comparative studies to better understand trophic dynamics and uncover the ecological factors shaping the early life stages of fish.

• Klíčová slova
• gut content analysis, intraspecific competition, ontogeny, piscivory, stable isotopes,
• Publikační typ
• časopisecké články MeSH

Pikeperch (Sander Lucioperca) belongs to main predatory fish species in freshwater bodies throughout Europe playing the key role by reducing planktivorous fish abundance. Two size classes of the young-of-the-year (YOY) pikeperch are known in Europe and North America. Our long-term fish survey elucidates late-summer size distribution of YOY pikeperch in the Lipno Reservoir (Czechia) and recognizes two distinct subcohorts: smaller pelagic planktivores heavily outnumber larger demersal piscivores. To explore molecular mechanisms accompanying the switch from planktivory to piscivory, we compared brain transcriptomes of both subcohorts and identified 148 differentially transcribed genes. The pathway enrichment analyses identified the piscivorous phase to be associated with genes involved in collagen and extracellular matrix generation with numerous Gene Ontology (GO), while the planktivorous phase was associated with genes for non-muscle-myosins (NMM) with less GO terms. Transcripts further upregulated in planktivores from the periphery of the NMM network were Pmchl, Pomcl, and Pyyb, all involved also in appetite control and producing (an)orexigenic neuropeptides. Noncoding RNAs were upregulated in transcriptomes of planktivores including three transcripts of snoRNA U85. Thirty genes mostly functionally unrelated to those differentially transcribed were alternatively spliced between the subcohorts. Our results indicate planktivores as potentially driven by voracity to initiate the switch to piscivory, while piscivores undergo a dynamic brain development. We propose a spatiotemporal spreading of juvenile development over a longer period and larger spatial scales through developmental plasticity as an adaptation to exploiting all types of resources and decreasing the intraspecific competition.

• Klíčová slova
• (Sander (Stizostedion) lucioperca), brain transcriptome, cannibalism, developmental plasticity, heterochrony, snoRNA,
• MeSH
• alternativní sestřih * MeSH
• genetická transkripce MeSH
• mozek * metabolismus   MeSH
• nekódující RNA * genetika   metabolismus   MeSH
• okounovití * genetika   fyziologie   MeSH
• regulace genové exprese fyziologie   MeSH
• transkriptom * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• nekódující RNA * MeSH

European catfish is a large-bodied apex predator, a key species in native areas, but invasive in others where it negatively impacts local aquatic fauna necessitates catfish regulation. However, traditional ichthyological methods face challenges in capturing it. The study presents a detailed description of the efficient long-line method, refined through 48 sampling campaigns across twelve European water bodies. This method proves cost-effective and technically undemanding, requiring an average of 5.6 bait fish to catch one European catfish per day. The long-lines outperform other techniques, with the highest Biomass per unit effort (BPUE) of 6.205 kg of catfish per man-hour and minimal by-catch (0.276 kg per man-hour). In contrast, fyke nets, the second most efficient method, achieve a BPUE of 0.621 kg of catfish per man-hour with 3.953 kg of by-catch per man-hour. To optimize long-line catches, a 15 m distance between branch lines and regular relocation is recommended. Live fish is the most effective bait with no significant differences observed among species. However, earthworms, a less controversial alternative, are also efficient, especially for smaller catfish. Our recapture approach using various ichthyological methods revealed no hook avoidance behavior by catfish after a previous catch or avoidance by a certain part of the population. The long-line method is suitable for population regulation, scientific research, and conservation efforts and is the most effective means of capturing live European catfish.

• Klíčová slova
• Bait, Ichthyological method, Large-bodied predator, Non-native area, Predation pressure,
• Publikační typ
• časopisecké články MeSH

Piscivory in cyprinids (Cyprinidae) is extremely rare. Specifically, common bream (Abramis brama) and common carp (Cyprinus carpio) are zooplanktivorous fish in deep lentic waters. Nevertheless, we observed predation by these two cyprinids under natural conditions in the Vír Reservoir, Czech Republic. We conducted diet analysis for cyprinids caught by trawling and gillnets and the large amount of young-of-the-year (YOY) perch (Perca fluviatilis), with sizes of 37-52 mm standard length, were found in their digestive tracts. In 2010, a large amount of YOY perch caused a significant decrease in Daphnia spp. size and abundance in the reservoir. Hence, a food deficit was induced for the cyprinids, apparent also from the poor nutritional condition of common bream which was much worse than the condition of those in similar reservoirs. Common carp and common bream shifted to forced piscivory, and they utilized the YOY perch as an alternative food source. In contrast, smaller species, such as roach (Rutilus rutilus) and bleak (Alburnus alburnus), widely utilized planktonic cyanobacteria. In the following year, YOY perch occurred in significantly lower numbers and conversely, Daphnia spp. size and abundance were significantly higher. The forced piscivory was not observed. Our results indicate a switch to forced piscivory by cyprinids, which was caused by a shortage of their natural food source. Moreover, this phenomenon presents an effective mechanism for reduction in the numbers of YOY perch, ensuring the stability of the ecosystem.

• MeSH
• kapři fyziologie   MeSH
• okounovití fyziologie   MeSH
• potravní řetězec * MeSH
• predátorské chování fyziologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH