Food Resource For Fishes Research Articles

Composition and Productivity of Zooplankton as a Food Resource for Fish from Lake Dood Tsagaan (Darkhad Depression, Mongolia)

Composition and Productivity of Zooplankton as a Food Resource for Fish from Lake Dood Tsagaan (Darkhad Depression, Mongolia)

Water-level fluctuations lead to changes in the diet of an omnivorous fish in a floodplain

Abstract The hydrological regime leads to fluctuations in the availability of food resources for fish, which may reflect in their diet variation. Our main goal was to analyze the relationship between water-level fluctuations and the diet and the body condition of Trachelyopterus galeatus in the Upper Paraná River floodplain. The fish used in the study were sampled quarterly along nine years, at nine sampling stations. Our results showed that diet of T. galeatus varied in response to oscillations in the hydrometric level, with the consumption of terrestrial invertebrates being positively related to hydrometric level, while the consumption of aquatic invertebrates was negatively related. The trophic niche breadth and feeding activity were not affected by hydrometric level, but the fish body condition was positively affected. The high food plasticity allows T. galeatus to consume the most available resources (e.g., terrestrial invertebrates in high water levels), which probably contributed to the increase in its body condition in higher hydrometric levels. In summary, the hydrological dynamic is fundamental for the diet variation of omnivorous fish, which can take advantage of the resource availability according to the hydrometric level, increasing its body condition when allochthonous resources as terrestrial invertebrates are supposed to be more available.

I’m not that Shallow – Different Zooplankton Abundance but Similar Community Composition Between Habitats in the San Francisco Estuary

Wetland restoration is a key management tool for increasing food availability for at-risk fishes in the San Francisco Estuary. To characterize the benefits of restoration sites, it is critical to quantify the abundance and composition of fish food resources in and near the wetlands. Characterization of zooplankton communities is considered particularly important, but accurate analysis of zooplankton samples is time-consuming and expensive. The recently established Fish Restoration Program (FRP) Monitoring Team assessed whether data from existing long-term monitoring surveys could be used to characterize shallow-water zooplankton communities before restoration. During the springs of 2017 to 2019, the FRP collected zooplankton samples near the mouth of tidal wetland sites, or immediately outside future restoration sites, and compared them to concurrent samples collected in deep water by existing long-term monitoring surveys. We found very few differences in community composition between shallow and deep samples, though a few taxa were more abundant in shallow water. Seasonal and interannual differences in composition and abundance showed that restoration sites provide varying food resources over time. There was significantly higher total abundance of zooplankton in deep versus shallow water, which may be a result of differences in zooplankton production, migration, or fish predation. Inconsistencies in towing speed and gear type may also be driving this result, rather than true habitat differences. This study indicates that monitoring of wetland restoration sites must rely on multiple years of data collected on the site—rather than relying on adjacent open-water sampling—and should include monitoring of epiphytic and epibenthic invertebrates as well as zooplankton.

What we know and don't know about the invasive zebra (Dreissena polymorpha) and quagga (Dreissena rostriformis bugensis) mussels.

We summarized existing knowledge on Dreissena polymorpha (the zebra mussel) and D. r. bugensis (the quagga mussel), including data on their taxonomy, systematics, evolution, life cycle, reproduction, feeding, growth and longevity, population dynamics, interspecific competition, habitat requirements, and distribution within and among waterbodies. We analyzed the history of spread of both species and the major pathways and vectors of their spread in Europe and North America. Special consideration was given to their ecological and economic impacts and their natural enemies, like waterfowl, fishes, and parasites, as well as the prevention of their introduction, early detection, control, and containment. We also outlined the most salient ecosystem services provided by zebra and quagga mussels, including water purification, nutrient recycling, culling the effects of eutrophication, biomonitoring, and their role as a food resource for fish and waterfowl. Finally, we identified major knowledge gaps and key studies needed to better understand the biology, ecology, and impacts of these aggressive freshwater invaders. Our review indicates that much crucial information on the quagga mussel is still missing, including key life history parameters, like spawning cues, fecundity, and longevity, particularly for the profundal zone of deep lakes.

Drift macroalgae positively influence seagrass-associated nekton communities of the northern Gulf of Mexico

Drift macroalgae, often found in clumps or mats adjacent to or within seagrass beds, can provide additional food resources and habitat complexity, leading to increased animal abundance, but large concentrations can also inhibit faunal movements, smother benthic communities, and contribute to hypoxia, reducing nekton abundance. Despite its ubiquity, few studies have quantified drift macroalgal prevalence over large spatial scales or its effects on seagrass-associated nekton, hindering our understanding of the functional role of drift macroalgae in ecosystems. We quantified the relationship between drift macroalgal biomass and the seagrass-associated nekton community within five estuaries spanning 2000 km across the northern Gulf of Mexico. Overall, increases in macroalgal biomass within seagrass meadows significantly influenced community structure, increasing shrimp, crab, and fish abundances, but the effect varied by region. Relationships between species richness, diversity, organism size, and macroalgal biomass were not observed, suggesting that drift macroalgae provide additional habitat but not necessarily new niche space. Small nekton play a vital role in many local fisheries, providing valuable food resources for fish and invertebrates. Increased recruitment into macroalgae can benefit local fisheries by providing shelter and increased food resources, which may increase the survival, growth, and population size of recreationally and economically important species. While excess levels of drift macroalgae can negatively impact benthic plant and animal communities, particularly in eutrophic areas, the moderate levels observed during this survey were associated with positive effects on organismal abundance, suggesting that drift algal dynamics should be considered in habitat-based management strategies for coastal estuaries.

Long-term dynamics of forage base and food supply for nekton in the upper epipelagic layer of the western Bering Sea. Part 1. Composition and abundance of zooplankton and small-sized nekton

An updated concept for the state, dynamics, and production of plankton communities in the upper epipelagic layer of the western Bering Sea is presented based on the timeseries for 1986–2020. The zooplankton biomass in summer exceeded the biomass in fall season in 1.3–2.1 times for the layer of 0–50 m and in 1.1–1.8 times for the layer of 0–200 m, mostly because of decreasing abundance of copepods and chaetognaths that was not compensated by slight increase of the euphausiids and amphipods biomass. Interannual variations were higher and reached 2–3 times and 4–5 times, respectively. Abnormal blooming of certain ecological groups of zooplankton (either warm-water or cold-water) occurred in the anomalous years. Species structure of zooplankton community varied in dependence on oceanographic conditions, generally toward higher abundance in warmer environments. In spite of considerable impact of thermal regime, this dependence was not close and even was absent in some cases that indicated a complex organization of zooplankton communities subjected to influence of many environmental factors. Mean total biomass of large-sized zooplankton and micronekton (prey for large-sized nekton) in the upper epipelagic layer of the western Bering Sea is estimated as 41 . 106 t in summer and 24 . 106 t in fall season, its total production as 101 . 106 t and 67 . 106 t, respectively. In summer, production of non-predatory zooplankton (phyto- and euryphages) prevailed over the predatory zooplankton production, with exception of 2009 and 2013. On the contrary, production of zoophages prevailed in autumn due to successive seasonal changes in the epipelagic plankton communities. These modern data on biomass and production of the zooplankton communities indicate significant reserves of food resources for fish and squids in the deep-water Commander Basin, western part of the Aleutian Basin, and in the area at Cape Navarin.

Azov Anchovy Engraulis encrasicolus maeoticus (Engraulidae) under the Sea of Azov Salinization in 2014–2018

The paper considers the effect of the Sea of Azov salinization on the food supply to anchovy Engraulis encrasicolus maeoticus as the level of salinity was rising from 12.7 to 14.0‰ during 2014–2018. In 2014 food supply to the anchovy dramatically deteriorated compared with the initial period of the salinization (2006–2013). Small individuals dominant in the population exhibited extremely low lipid content, which appear to have led to a decrease in reproduction and, therefore, the stock decline in the subsequent years. As the population size decreased, the food supply improved; the lipid content in the anchovy body increased by 40–50% in 2015–2018. Fish of the older age groups became dominant in the population, which indirectly suggests a drop in recruitment and the population aging. The work discusses the impact of the change in the fish food resources on the anchovy food supply over the current period of the Sea of Azov salinization (2006–2018)

Aquaculture waste as food for amphipods: the case of Gammarus insensibilis in marsh ponds from southern Spain

Amphipods are emerging as an alternative food resource for fishes and cephalopods in aquaculture. Gammarus insensibilis (Stock, 1996), one of the dominant amphipods inhabiting marsh ponds in southern Spain, has been recently proposed as a promising candidate for being intensively cultured due to its adequate nutritional profile, large body size, and high natural densities. The main aim of this study was to determine whether waste products of aquaculture (such as detritus in the form of fish feces or Ulva sp.) provided an adequate diet for the amphipod in comparison to other traditional diets, such as Artemia nauplii or phytoplankton. G. insensibilis was cultured twice in tanks with 5 treatments: 4 experimental diets (detritus, Ulva sp., Artemia nauplii, and phytoplankton) were used, and one no-feed treatment. Amphipods fed with the two alternative diets, detritus and Ulva, showed promising survival higher than 40% and high concentrations of palmitic acid (16:0), oleic acid (18:1n9), arachidonic acid (20:4n6) (ARA), eicosapentaenoic acid (20:5n3) (EPA), and docosahexaenoic acid (22:6n3) (DHA). Therefore, large-scale culture of this amphipod using inexpensive diets in indoor facilities could provide a nutritious product for aquaculture. The potential development of a sustainable culture using this species in marsh ponds is also discussed in the context of Integrated Multi-Trophic Aquaculture (IMTA).

Characterisation of constructed ponds and factors influencing their macroinvertebrate communities on the lower Waikato River floodplain, New Zealand

ABSTRACT Ponds are increasingly being constructed to enhance amenity values in human-dominated lowland landscapes, but little is known of design features that influence macroinvertebrates which can provide important food resources for fish and waterbirds. We quantified pond characteristics, sampled benthic and water-column macroinvertebrates in winter, and related abundance, biomass and community composition to characteristics of 34 ponds on the lower Waikato River floodplain, northern New Zealand. Compositionally different macroinvertebrate communities occupied water-column and benthic habitats. Landscape setting had a significant effect on benthic composition in terms of biomass, while the independent effects of frequency of pond drying or flooding, respectively, influenced benthic (abundance, biomass) or water-column (abundance) communities. Distance-based linear models highlighted physicochemical conditions, water depth regimes and riparian vegetation composition as key variables accounting for dissimilarity in total macroinvertebrate biomass between ponds. Our results indicate that managing hydrological stability of ponds in terms of permanence and flooding influences the composition and biomass of invertebrate communities. Within this hydrological template, design of appropriate depth regimes and riparian conditions can enhance accrual of macroinvertebrate biomass, thereby increasing food resources for fish and waterbirds.

Causes of Daphnia midsummer decline in two deep meromictic subalpine lakes

Abstract Daphnia are key organisms in pelagic food webs, acting as a food resource for fish and predatory zooplankton and regulating phytoplankton through grazing. Its population dynamic follows regular seasonal patterns, with spring peaks followed by summer population declines (midsummer declines, MSDs). Midsummer declines show high inter‐annual variation, which has been attributed to different causes. However, the mechanisms controlling the MSD remain poorly understood, especially in deep stratified lakes. We tried to disentangle the factors causing Daphnia MSDs in Lake Lugano and Lake Iseo (in Switzerland and Italy), two deep peri‐alpine lakes with similar trophic status and vertical mixing dynamics, characterised by phosphorus accumulation in the hypolimnion and variable mixing during late‐winter turnovers. Specifically, we assessed the effects of three different hypothetical pathways according to which: (1) winter air temperature controls MSDs by influencing mixing depth during turnovers and epilimnetic phosphorus replenishment; (2) vernal air temperature influences MSD by accelerating the timing of spring population peak; and (3) summer temperature influences MSDs by increasing fish predation. We assessed the relative strength of these pathways using structural equation modelling on long‐term datasets for the two lakes (29 years for Lake Lugano and 19 years for Lake Iseo). Between the hypothesised pathways, the one driven by winter air temperature (through P replenishment) influenced Daphnia abundance in spring in both lakes, but the effects propagated to summer Daphnia abundance only in Lake Lugano. Additionally, summer Daphnia abundance was influenced by the summer air temperature through a positive (although weak) effect. By comparison, vernal air temperature had no detectable effects on summer Daphnia abundance. The results revealed marked differences between the meromictic study lakes and the shallow hypertrophic water bodies that were the focus of previous research on Daphnia MSD, and also between the two study lakes. The influence of epilimnetic P replenishment on the summer Daphnia abundance in Lake Lugano, which was recovering from past eutrophication, may have reflected the greater susceptibility of deep, stratified lakes to P depletion after spring compared to shallow hypertrophic lakes or reservoirs. This effect might not have been detected in Lake Iseo because P was more consistently depleted during the study period (i.e. variance in the predictor was too low to detect an effect). This study highlighted the complexity of the effects of climate variability on Daphnia MSD in deep lakes, showing that the responses can differ even between two neighbouring lakes with similar vertical mixing dynamics and trophic status. At the same time, the results suggest that future increases in winter air temperature, caused by global warming, may cause critically low densities of Daphnia during spring and summer and compromise the ability of zooplankton to control phytoplankton biomass.

Beavers alter stream macroinvertebrate communities in north‐eastern Utah

Abstract Understanding changes in macroinvertebrate communities is important because they play a large role in stream ecosystem functioning, and they are an important food resource for fish. Beaver‐induced changes to stream morphology could alter macroinvertebrate communities, which in turn could affect food webs and ecosystem function. However, studies investigating the effects of North American beaver activities on macroinvertebrates are rare in the inter‐mountain west, an area with high potential for beaver‐assisted restoration. The aim of this study was to quantify differences in the macroinvertebrate community between unaltered segments of streams and within beaver ponds in north‐eastern Utah, U.S.A. We assessed macroinvertebrate species richness, biomass, density, functional feeding group composition, mobility group composition, and macroinvertebrate habitat characteristics to test the hypothesis that macroinvertebrate communities will differ among habitat types (undammed stream segments and beaver ponds) in beaver‐occupied streams. Beaver pond communities significantly differed from lotic reach communities in many ways. Beaver ponds were less diverse with 25% fewer species. Although there was variability among streams, in general, beaver ponds had 75% fewer individuals and 90% lower total macroinvertebrate biomass compared to lotic reaches. Regarding functional feeding groups, beaver ponds contained more engulfers, while lotic reaches contained more scrapers, filterers, and gatherers. For mobility groups, beaver ponds had more sprawlers, while lotic reaches had more clingers. Swimmers were also more prevalent in lotic reaches, although this is probably due to the abundance of Baetis within lotic reaches. More beaver pond taxa were classified as lentic‐dwelling insects, while more lotic reach taxa were categorised as preferring lotic habitats. The creation of ponds by beavers fundamentally altered the macroinvertebrate community in north‐eastern Utah streams. Such changes to stream macroinvertebrate communities suggest that recolonisation of beavers across North America may be altering stream functioning and food webs. Our study highlights the need to further investigate the effects of beaver recolonisation on stream communities.

Urbanisation affects the diet and feeding selectivity of the invasive guppy Poecilia reticulata

AbstractThe process of urbanisation is increasing the frequency and magnitude of fluctuations in the availability of food resources for fish. In this study, we investigated whether the diet and prey selected by the guppy Poecilia reticulata reflect the different levels of urbanisation using the total area of impervious surface soil as the metric. Rural streams (low percentage of urbanisation—LPU) and urban streams (high percentage of urbanisation—HPU) were sampled during both the rainy and dry seasons. The hypothesis tested was that the diet and selective behaviour differ spatially and seasonally between LPU and HPU streams. Among the analysed items, seasonal significant differences were only observed in HPU streams. In LPU streams, the trophic spectrum was wider, and a higher diversity of prey was selected. In HPU streams, the diet richness was lower with a dominance of Chironomidae, and there was also less variability in selected prey. Ephemeroptera and Trichoptera were always avoided, but Coleoptera were avoided only in LPU, while Oligochaeta were avoided in HPU streams. Thus, the diet and prey selected by P. reticulata were different between LPU and HPU streams, and this species has potential to compete for food with the native fauna in a wide variety of environmental conditions and available resources. Therefore, this dietary flexibility probably offers competitive advantages when colonising and establishing in a new habitat.

Eroding Traditional Knowledge Systems Plea Scientific Validation: Ecological Characterization of Traditionally Managed Semi-Deep Water Rice Field Agroecosystem in Barak Valley, Assam, Northeast India

Traditional ecological knowledge (TEK) systems illustrate various ways and means of natural resource utilization and management, which has come into being through keen observations as well as the age-old trial and error methods. However, such knowledge systems are gradually eroding due to various reasons. Proper documentation, characterization, scientific validation, and popularization of such knowledge systems would help in preserving them for posterity. The present study characterizes the ecological attributes of a traditional rice farming system called Asra in Karimganj district of Barak Valley, Assam. The objective was to investigate the water properties and community composition of plankton and rice stem epiphyton of the water logged Asra rice field agro-ecosystem. The substantial contribution of Asra rice field ecosystems in maintaining the overall biodiversity of the system has been highlighted in the present study. The study revealed the presence of 77 genera of phytoplankton and 55 genera of rice stem phyto-epiphyton, which belonged to six major classes viz., Bacillariophyceae, Chlorophyceae, Cyanophyceae, Euglenophyceae, Xanthophyceae and Zygnemophyceae. Besides, 29 genera of zooplankton and 14 genera of rice stem zoo-epiphyton belonging to five major groups viz., Protozoa, Cladocera, Copepoda, Ostracoda and Rotifera were also recorded. The study shows that the Asra rice fields are rich repository of plankton and rice stem epiphyton, the natural live food resources for fish. The study emphasizes on conservation of traditional farming system like Asra, and stresses on the need for sustainable utilization of the existing bioresources in such system by introducing the concurrent practice of rice-fish culture in the study area.

Abundance, Habitat Conditions, and Conservation of the Largha Seal (Phoca largha) During the Past Half Century in the Bohai Sea, China

The largha seal (Phoca largha) is critically endangered in China because of human harassment and habitat destruction. The Bohai Sea is their southernmost breeding site in the world and the only site in China. Long-term studies of the largha seal population in the Bohai Sea were reviewed. The seal population size significantly decreased by more than 80%, from approximately 8000 individuals in the 1940s to 1500 in the 2000s. In the past few decades, the ice formation conditions have been favorable for seals; however, seawater has been severely polluted, and available fish food resources have significantly decreased. In addition, heavy marine transportation has caused increasing levels of seawater and noise pollution. The deteriorating marine environmental conditions in the Bohai Sea most likely affected the largha seal population dynamics, and despite the seal hunting prohibition enacted in 1988, the population has been declining. No successful law has been executed so far by the Chinese government to reduce marine pollution in the Bohai Sea, which may negatively impact seal survival. More efficient protection measures for the species and control measures to improve the marine environment in the Bohai Sea are urgently needed.

Impacts of stream riparian buffer land use on water temperature and food availability for fish

ABSTRACTRestoration of degraded freshwater ecosystems has gained considerable attention in the USA over the past decades. However, most projects focus almost entirely on the restoration of physical habitat or specific water quality parameters, while ignoring critical ecological processes related to food web re-establishment. In this study, we investigate the impact of riparian habitat in different stages of restoration on food availability for fish in four streams in Pennsylvania, USA. The riparian buffer habitats ranged from open meadow to mature forest and included new to long-term restoration sites. We quantified abundance and community composition of aquatic macroinvertebrates and riparian arthropods with aerial and ground-dwelling life history strategies. We found that riparian habitat and water temperature exert a strong influence over potential food resources for fish, with the open meadow habitat having highest abundance of terrestrial and aquatic insects, lowest taxa richness, and possible multivoltine aquatic insect life-history. Our results provide insight into the importance of riparian buffer habitat and water temperature on the composition of food availability for fish species of concern such as brook trout. The significant differences emphasize the need to include food web dynamics into riparian habitat restoration design to guide future rehabilitation projects focusing on fish conservation.

Effects of long and short flooding years on the feeding ecology of piscivorous fish in floodplain river systems

Floodplain river systems are extremely dynamic environments, where alternating dry and flooded periods affect the availability of food resources for fish. For piscivores, during drought years, a decreased availability of prey is expected, resulting in diets dominated by fewer items, narrower trophic niches with high dietary overlap. During floods, habitats become more similar, and, combined with increased connectivity, provide a wider diversity of prey to piscivores, decreasing dietary overlap and presenting wider trophic niches. This study aimed to evaluate the potential impacts of long periods of flooding on the trophic ecology of nine piscivorous fish in the upper Parana River basin. In drought years, diets were dominated by small characids, presenting narrower niches with higher dietary overlap. The opposite situation was observed during wet years, with different species responses, likely due to species-specific feeding strategies. High niche overlap was observed between native and non-native species, suggesting competition. The inclusion of non-native species in the native piscivorous diet is a concerning fact, as its causes and possible impacts are still unknown. In conclusion, long flooding pulses affect the diets of piscivorous fish in different ways by either increasing or decreasing niche breadth and overlap according to species-specific characteristics.

鲢鳙鱼养殖小型水库底栖动物群落季节动态

PDF HTML阅读 XML下载 导出引用 引用提醒 鲢鳙鱼养殖小型水库底栖动物群落季节动态 DOI: 10.5846/stxb201607271533 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 湖北省科技计划研究与开发项目（2013BBA049）；江西省教育厅青年基金项目（GJJ13018）；南昌大学鄱阳湖环境与资源利用教育部重点实验室开放基金（13006457） Seasonal dynamics of zoobenthos communities in a small reservoir stocked with silver and bighead carp Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:底栖动物是鱼类重要的天然饵料，评估水体中底栖动物的现存量可以指导渔业生产中鱼类的放养数量。为了探究淡水生态养殖水库中底栖动物群落的季节动态，于2013年4月、7月、10月和2014年1月对三河水库的底栖动物群落进行了调查分析。研究共采集到7个属的底栖动物，隶属于颤蚓科、摇蚊科和蠓科，未采集到软体动物。相对重要性指数 （IRI） 计算结果表明，菱跗摇蚊属 Clinotanypus （IRI=7136）、颤蚓属 Tubifex （IRI=6734） 和尾鳃蚓属 Branchiura （IRI=1384） 是优势类群，分别占总捕获数量的34.26%、50.38%和10.96%。不同季节之间底栖动物的总密度和生物量差异显著 （P < 0.05），均为冬季 > 春季 > 夏季 > 秋季。冬季总密度 （4100个/m2） 和总生物量 （10.14 g/m2） 最高，春季 （1446个/m2； 1.07 g/m2） 次之，夏季 （579个/m2； 0.66 g/m2） 较低，秋季 （492个/m2； 0.64 g/m2） 最低。非度量多维尺度分析 （MDS） 和群落相似性分析表明底栖动物群落结构季节差异显著 （P =0.001），2013年三河水库的底栖动物群落可明显划分为3个：春季群落、夏秋季群落和冬季群落。皮尔森相关分析表明，底栖动物总密度与溶氧和营养盐呈正相关关系，与其他水理化因子呈显著负相关关系 （P < 0.05）。冗余分析表明，氨氮、盐度、pH和浊度是三河水库底栖动物群落季节差异的显著影响因子（P < 0.05），总氮对底栖动物群落的季节差异具有边缘显著影响 （P =0.08）。 Abstract:Zoobenthos is an important natural food resource for fishes. Assessing the standing crop of zoobenthos in water bodies can provide the guideline for stocking fishes in fishery production. To explore the seasonal dynamics of zoobenthic communities in freshwater aquaculture reservoirs, investigations were conducted in April, July, and October 2013, and January 2014, to determine the composition of zoobenthic communities in the Sanhe Reservoir. The relationships between zoobenthic communities and environmental factors (water temperature, pH, turbidity, salinity, dissolved oxygen, chlorophyll a, NH4+-N, NO3- -N, total nitrogen, and total phosphorus) were analyzed. In this study, seven genera of zoobenthos belonging to Tubificidae, Chironomidae, and Ceratopogouidae were detected. The results of the index of relative importance (IRI) showed that Clinotanypus (IRI=7136), Tubifex (IRI=6734), and Branchiura (IRI=1384) were dominant groups, which accounted for 34.26%, 50.38%, and 10.96% of total abundance, respectively. The total density and biomass of zoobenthos significantly varied among seasons (P < 0.05), and both were highest in winter (4100 ind./m2 , 10.14 g/m2), followed by spring (1446 ind./m2 , 1.07 g/m2), and summer (579 ind./m2 , 0.66 g/m2), and were lowest in autumn (492 ind./m2 , 0.64 g/m2 , respectively). The zoobenthic communities in the Sanhe Reservoir mostly consisted of oligochaetes and chironomid larvae, which exhibited characteristics of higher density and lower biomass. Tubifex was the most dominant group in spring. Tubifex and Branchiura were dominant groups in summer and autumn. Chironomidae and Tubifex were dominant groups in winter. Significant differences in zoobenthic communities among seasons were found by non-metric multi-dimensional scaling (MDS) and similarity analysis (P =0.001). Zoobenthic communities in the Sanhe Reservoir showed three temporal communities, i.e., spring community, summer-autumn community, and winter community. Pearson correlation analysis indicated that total density of zoobenthos was positively correlated with dissolved oxygen and nutrients. However, the total density of zoobenthos had significant negative correlations with water temperature, pH, salinity, turbidity, and chlorophyll-a content (P < 0.05). Redundancy analysis suggested that NH4+-N, salinity, pH, and turbidity were important factors, which had significant effects on seasonal variation of zoobenthic communities (P < 0.05). Total nitrogen concentration had marginally significant effects on seasonal differences of zoobenthic communities (P =0.08). In the pelagic zones of the small reservoir stocked with higher density of fishes, organism deposition resulted in a narrower habitat for the distribution of molluscs, such as shellfish and snails. Therefore, the composition of benthic fauna was dominated by oligochaetes and insect larvae. The differences in predator pressure on zoobenthos caused by fishes in different seasons had direct effects on the seasonal dynamics of zoobenthic communities in the fish stocked reservoir. In addition, the distribution of some benthic feeding fish, such as Pelteobagrus fulvidraco, might lead to the decrease in zoobenthos density in the reservoir. 参考文献 相似文献 引证文献

Changes in diet and niche breadth of a small fish species in response to the flood pulse in a Neotropical floodplain lake

This study tested the hypothesis that the flood pulse affects the diet composition and the niche breadth of Moenkhausia forestii, a small characid fish inhabiting the littoral zone of lakes. To this end, we compared the diet composition (at the population and individual levels) between hydrological periods (high and low water phases) in a floodplain lake of the Upper Paraná River. PERMANOVA revealed differences in the diet between periods (pseudo F 1,38 = 8.5; p < 0.001), with predominant consumption of chironomid larvae and Ephemeroptera (aquatic resources) in the low-water period and an increase in the contribution of terrestrial resources (Hymenoptera, Coleoptera, and Orthoptera) during the high-water period. Based on the PERMDISP results, inter-individual variability in M. forestii diet also differed between periods (F 1,38 = 5.80; p = 0.02), with higher values during the high-water period resulting in a dietary niche expansion. During the low-water period, we observed the dominance of chironomid larvae in the diets of most individuals, resulting in lower inter-individual variability and thus narrower niche breadth. The diet of M. forestii was affected by the flood pulse at both the population and individual levels. The most important difference was found in the origin of food items; during the low-water period, the diet consisted mainly of aquatic resources, and during the high-water period, there was a large contribution of terrestrial resources. This variation is related to the increased availability of allochthonous resources in the high period, when terrestrial areas are flooded by the overflow of the river, thereby increasing the input of resources into the aquatic environment. The increased availability of food resources during this period allowed the expansion of the trophic niche of M. forestii , accompanied by the highest richness (19 items) and the highest evenness of food items. Our findings demonstrated that the flood pulse affected the composition of the M. forestii diet at both the population and individual levels. These results support the importance of the flood pulse, which connects aquatic and terrestrial ecosystems, in providing food resources for fish.

Diel variation in metabolism and ammonia excretion of Marphysa sanguinea (Polychaeta: Eunicidae)

Polychaetes provide an excellent food resource for fish and represent the dominant zoobenthos in marine ecosystems. Diel variation in the rates of metabolism and ammonia-N excretion of Marphysa sanguinea were studied. The worms were grouped according to their wet body weight into small (S; 1.24±0.06 g), medium (M; 4.00±0.30 g), and large (L; 8.54±1.08 g) categories. Their weight-specific metabolic rates, based on aerobic respiration (R), were measured at 16°C (±0.2°C) and classed as either routine (R R) or standard (R S) rates. Both respiration types decreased with increasing body weight. Respiration was described by R = a W b, where b was -0.400 9 and -0.532 0 for R R and R S, respectively. Diurnal changes in R S for each group was relatively flat, with a slightly increasing trend with time, but was relatively stable as a whole. R R of the diurnal variation of worms was higher than R S, but both had similar overall trends. The peak values of specific dynamic action (SDA) (R SDA) in the S, M, and L groups were 2.704, 1.149, and 0.682 mg/(g∙h), respectively. The durations of SDA were 13, 6, and 6 h, respectively and the energy expenditures of SDA were 377.98, 117.34, and 74.94 J/g, respectively. These data indicate that the metabolic rates were higher in smaller individuals, which is advantageous for their rapid growth.

Alien macroinvertebrates and fish in the Dnieper River basin

The results of the study on spread, pathways, vectors, and ecological impact on the native fauna of alien invertebrate and fish species in the Dnieper River basin are presented. The relationship between invasive processes and basin hydrology is analyzed. It is shown that the main factor in spreading of alien species in the central part of the basin was related to the damming of the river, turning it into a cascade of reservoirs, and introduction of PontoCaspian species into the rese rvoirs. The differences in pathways and vectors for upstream, middle, and downstream parts of the river were revealed. In the midstream reservoirs, the main pathway was intentional introduction aimed at the improvement of valuable fish food resources, whereas that for the upstream part of the Dnieper and Pripyat rivers was shipping and natural spread. The "Black List" of invertebrates and fish for the studied basin is proposed.