Hydrobiologia

Dias, Rosa Maria; Kashiwaqui, Elaine Antoniassi Luiz; Silva, João Carlos Barbosa da; Ortêncio Filho, Henrique; Gomes, Luiz Carlos; Souza, Geza Thaís Rangel e; Tófoli, Raffael Marcos; Machado, Marion Haruko; Agostinho, Angelo Antonio

doi: 10.1007/s10750-024-05674-4pmid: N/A

Understanding the trophic interactions and coexistence processes among waterbirds in floodplain ecosystems is of fundamental ecological importance. In the upper Paraná River floodplain, we assessed the diet of five sympatric waterbird species (Ardea alba, Ardea cocoi, Egretta thula, Nannopterum brasilianum, and Nycticorax nycticorax) and tested their differences in the diet, in addition to food overlap, differences in trophic niche breadths and stratum in the water column where they forage. The waterbirds’ stomachs were collected quarterly on the upper Paraná River floodplain, analyzed under a stereomicroscope, and the food items were identified. Only Egretta thula was classified as omnivorous, consuming various food resources, including insects, decapods, and fish. The other species were piscivorous, but differed in the types of prey. Food overlap was higher in the piscivorous species, but they exhibited high trophic niche breadth. The piscivorous waterbirds employ different strategies for exploiting food resources that allow species coexistence in the floodplain, avoiding direct competition. Our results highlight the importance of waterbirds as connectors across diverse environments, especially aquatic-terrestrial ecosystems. Since these waterbirds’ diet relies on fish, effective conservation and management strategies targeting fish communities are fundamental to maintaining biodiversity and functionality within the upper Paraná River floodplain.

Yamauchi, Kohei; Tanaka, Gengo

doi: 10.1007/s10750-024-05722-zpmid: N/A

A total of 107 species belonging to 45 genera were identified from 26 sites in the Ariake Sea, Kyushu, Japan. Two biofacies were identified by both Q-mode cluster analysis. Redundancy analyses (RDAs) were computed on the standardized 71 species × 23 sites matrix data and 23 sites × 28 environmental data. The water temperature of February (WT2) is a valuable ecological factor to determine the distribution of 24 species from the Ariake Sea. Based on the results of RDA, WT2 correlated with 11 sites selected for MAT using 24 species and site 11 was applied by a recent site as a reference. The predicted WT2 was well matched (10.4°C) compared with actual WT2 (10.5°C). The morphological variation in the aperture ratio of a sieve-type normal pore canal at a homological location of Cytheromorpha acupunctata showed a good correlation with chlorophyll of September, sediment type, and the dissolved oxygen of February and helps reconstruct these three environments. The APR is especially a good index for reconstructing dissolved oxygen.

Ballini, Lorenzo; Staffoni, Giorgia; Nespoli, Davide; Ottonello, Dario; Candiotto, Alessandro; Forte, Simone; Vezza, Paolo; Iannucci, Alessio; Fratini, Sara

doi: 10.1007/s10750-024-05723-ypmid: N/A

Freshwater ecosystems are experiencing one of the highest rates of biodiversity decline among extant ecosystems. To inform effective conservation actions, it is imperative to develop reliable monitoring techniques to assess the species richness of freshwater communities. In this study, we applied for the first time an eDNA metabarcoding assay on six watercourses in Liguria, northwestern Italy. Our first aim was to validate this method as a reliable monitoring tool for Ligurian fish communities. To reach this goal, we compared the results of the eDNA-based sampling with those obtained from two electrofishing campaigns carried out during the same season. The eDNA-based approach yielded congruent results with electrofishing data and showed a slightly higher resolution since it was able to detect two threatened species that were not detected by traditional monitoring. Just one species that eluded eDNA detection was electrofished instead. Thanks to a multi-marker metabarcoding approach, we were also able to detect other vertebrate species living in, or associated with, the sampled watercourses, such as aquatic birds and amphibians. Overall, our results confirmed that aquatic eDNA assay proves to be a valuable tool to monitor freshwater-related systems and to inform efficient management and protection schemes for such habitats.

Domínguez-Petit, Rosario; Cousido-Rocha, Marta; Pennino, Maria Grazia; Abad, Esther; Riveiro, Isabel; Costas, Gersom; Cerviño, Santiago

doi: 10.1007/s10750-024-05726-9pmid: N/A

The mean weight-at-age of fish species is an indicator of fish growth and physiological condition, as well as a basic parameter for assessing and managing fish stocks. Here, we investigate the temporal trends of the mean weight-at-age of four different commercial species with different life strategies: (i) the short-lived pelagic European sardine (Sardina pilchardus), (ii) the horse mackerel (Trachurus trachurus) and two medium-lived benthic, (iii) the megrim (Lepidorhombus whiffiagonis) and iv) the four-spotted megrim (Lepidorhombus boscii), in North Atlantic Iberian waters from 2000 to 2018. Generalised additive models were implemented to identify the main (density-dependent and density-independent) drivers of fish weight-at-age variability: abundance, sex, maturity, sea surface temperature, sea bottom temperature, North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation indices. In all four species, abundance had a negative effect on mean weight-at-age. Temperature affected mean weight-at-age in sardine and megrim, while NAO influenced it in horse mackerel and four-spotted megrim. In the case of the sardine, we observed a progressive decrease in the mean weight-at-age of adults in the series in contrast to the four-spotted megrim; however, there was no effect of year on either horse mackerel or megrim. We discuss the influence of life strategy on fish response to drivers.

Qian, Tian; Diao, Fei; Jeppesen, Erik; Han, Yanqing; Li, Kuanyi; He, Hu

doi: 10.1007/s10750-024-05727-8pmid: N/A

Biomanipulation by piscivore stocking has been widely used for restoration of temperate shallow lakes, but long-term results have been mixed. In warm (i.e., subtropical/tropical) lakes where omni-benthivorous fish prevail, the effects of piscivore stocking on small fish, plankton communities, and water quality have not been well elucidated yet. Here, we conducted a mesocosm experiment in the subtropics to examine the top-down and bottom-up effects of stocking of a native piscivorous fish, mandarin fish (Siniperca scherzeri). The experiment consisted of two treatments (piscivore present/absent) in triplicate, lasting for 90 days and including two periods. Crucian carp (Carassius carassius) were stocked twice to simulate the recruitment of small fishes. Our results showed that stocking of mandarin fish significantly reduced the abundance of crucian carp but did not increase zooplankton biomass nor reduced the phytoplankton biomass, the concentrations of nutrients or suspended solids, suggesting that both top-down and bottom-up control of phytoplankton were unaffected by stocking mandarin fish. Moreover, the presence of mandarin fish did not help maintain a clear water state in the period of crucian carp recruitment. Our results indicate that piscivore stocking may not help control phytoplankton biomass in subtropical shallow mesocosms, at least on the short term.

Bakker, Theo C. M.; Hiermes, Meike; Müller, Björn; Martin, Sebastian; Rennison, Diana J.; Rick, Ingolf P.

doi: 10.1007/s10750-024-05728-7pmid: N/A

We studied phenotypic and genetic adaptation of the visual system of three-spined sticklebacks, Gasterosteus aculeatus, from North Uist, Scotland. We quantified differences in opsin gene expression of the four cone opsin genes among wild-caught fish from three lakes with clear and from three with tea-stained water and their offspring that were raised in clear water. In addition, visual sensitivity of wild-caught fish was modelled from opsin expression levels. Wild-caught fish from tea-stained waters had a lower SWS1 proportional expression than fish from clear waters, a difference that tended to be maintained in lab-bred fish. Compared to lab-bred fish, wild-caught fish had a higher SWS1 but lower SWS2 proportional expression independent of water clarity. For RH2 and LWS there were significant interactions between generation and water clarity. Reproductively mature fish had a higher LWS but lower proportional expression of RH2 than non-reproductive fish. Sex did not have a significant effect on expression. There was a significant positive association and, depending on chromophore ratio, a distinct match between the centre wavelengths, used as a proxy for spectral distribution, of ambient habitat light and spectral sensitivity indicating that the visual system of sticklebacks is tuned to their local light environment, suggesting adaptation.

Geletu, Temesgen Tola; Tang, Shoujie; Zhao, Jinliang

doi: 10.1007/s10750-024-05729-6pmid: N/A

As native genetic resources of Nile tilapia populations face numerous anthropogenic and natural disturbances, we aimed to identify populations worthy of conservation management to facilitate the natural evolutionary trajectory of this species. Here, we used the ddRAD-seq approach for population genomic analysis and delineation of conservation units (CUs). In total, 209 fin-clip samples from nine wild populations in Ethiopia were subjected to ddRAD-seq, producing 121,149 high-quality SNPs that were used for downstream analyses. Genetic diversity metrics revealed low-to-moderate levels of within-population genetic variation, with population pairwise FST analysis indicating significant genetic differentiation between populations from the Nile River Basin and those from the Ethiopian Rift Valley lakes. Genetic clustering analyses suggested the presence of 3–4 genetic groups. A combined outlier loci detection approach identified thousands of putative SNPs under selection, with enrichment analysis revealing genes and pathways associated with environmental response, metabolism, growth, and reproduction. Moreover, recently outlined workflows for CU delineation have identified three CUs that are of interest for conservation and aquaculture applications.

dos Reis, Renan B.; Stabile, Bruno H. Mioto; Frota, Augusto; Ferrer, Juliano; de Oliveira, Alessandra V.; da Graça, Weferson J.

doi: 10.1007/s10750-024-05731-ypmid: N/A

Cambeva perkos was described using the morphology of specimens from tributaries of the Rio Uruguay (Upper Uruguay ecoregion) and one paratype from the Rio Tibagi (Upper Paraná ecoregion). Recent sampling near the Ponta Grossa Arch, a key uplift that changed the fluvial dynamics in southern Brazil, revealed the presence of additional specimens in the Upper Parana ecoregion and also in the Ribeira de Iguape ecoregion. Through these samples (including sample tissues), we tested if the populations of the Upper Uruguay, Upper Paraná, and Ribeira de Iguape ecoregions constituted different species and if the phylogeographic pattern was impacted by recent geomorphological events that allowed headwater captures. Using COI, we delimited C. perkos “sensu stricto” from a putative new species of Cambeva, estimating their divergence around 14.5 Mya, likely due to ancient erosion events in Serra do Repartimento and Serra Geral. Furthermore, the two species are not closely related according to the COI arrangement. In addition, we recognized three morphotypes belonging to the putative new species, which did not show a unique signature of differentiation through COI. Lastly, we hypothesized that recent erosions (2.2 Mya) in the Ponta Grossa Arch influenced the geographic distribution of the new species.

Guan, Minsha; Zhang, Yunlin; Li, Wei; Li, Na; Qi, Lin; Shi, Kun; Zhang, Yibo; Qin, Boqiang; Huang, Changchun

doi: 10.1007/s10750-024-05735-8pmid: N/A

Wind deeply impacts the short-term temporal-spatial dynamics of cyanobacterial blooms in large, shallow and eutrophic lakes, but the quantitative contributions of wind wave to cyanobacterial blooms remain unclear. In this study, we assessed the frequency of surface cyanobacterial blooms, in response to wind wave in Lake Taihu, China, based on high-frequency hourly GOCI images and long-term meteorological, hydrological and ecological environment records from 2011 to 2020. Results showed marked monthly and seasonal variabilities of cyanobacterial blooms frequency with two peaks in summer and autumn. Spatially, the prevailing wind directions from summer to winter, shifting from southeast to northwest winds, promoted the downwind horizontal drift and accumulation of surface cyanobacterial blooms from northwest to southwest in Lake Taihu. Moreover, we found significantly negative correlations between wind wave and cyanobacterial bloom frequency, particularly during the cyanobacterial bloom growth season from April to November. Further analysis revealed the determining role of wind wave in controlling cyanobacterial bloom dynamics in Lake Taihu, with contributions of 62.12% and 57.63% in spring and summer, respectively. Our findings offer an important scientific insight for the effective collection of harmful blooms in inland freshwater lakes under both nutrient management and climate change scenarios.

Seabra, Lidia Brasil; Huckembeck, Sônia; Freitas, Tiago Magalhães da Silva; Lobato, Cleonice Maria Cardoso; Penha, Izabella Cristina da Silva; Prata, Erival Gonçalves; Montag, Luciano Fogaça de Assis

doi: 10.1007/s10750-024-05736-7pmid: N/A

This study examined the diet and assimilation of basal resources by the redeye piranha, Serrasalmus rhombeus, in a low-flow section of the Xingu River, Brazil. Samples of both individuals and basal resources were collected monthly from December 2020 to November 2021, encompassing a complete hydrological cycle. The stomach contents of the individuals and tissue samples of the species were submitted to stable isotope analysis for δ13C and δ15N. The species exhibited a predominantly piscivorous diet, with no observed variation in diet composition or feeding intensity across different hydrological periods. However, δ15N levels in the species varied between periods, indicating potential shifts in the availability and assimilation of basal resources during controlled flood pulses. The trophic position of the species was higher during flood periods and lower during low-water periods. Mixing models revealed the assimilation of different basal sources in each period, with the significance of terrestrial producers evident in almost all periods except during ascending. These findings are crucial for understanding the trophic dynamics of predators in flooded forests with reduced flow, highlighting the reliance of S. rhombeus on piscivory while being supported by terrestrial basal sources in its trophic chain.