Feeding patterns in a fish community of Baia da Onça,a floodplain lake of the Aquidauana River,Pantanal, Brazil

Abstract The stomach contents of 24 species of fish and unidentified species from four genera in a floodplain lake of the Pantanal were studied. Fish were collected during the dry season when the lake was isolated from the main river. A community food ingestion index (feeding index weighted by consumer biomass, FIWCB, where 0 < FIWCB < 1) was calculated to quantify feeding patterns. Detritus and algae ingested by Curimatidae were responsible for 46.5% of the FIWCB, while that for algae ingested by Loricariidae (armoured catfish) accounted for 13.2%. The importance of detritus in fish diets is discussed as a strategy for shortening food chains, thereby increasing community efficiency, and as a consequence, fish biomass. It was learnt that the main route of energy flow in this perennial lake was through the detritus chain. The floodplain lakes function as a dry season feeding ground for small-sized species of fish, which are potential prey for the more highly valued larger species of fish.     

Seasonality of energy sources of Colossoma macropomum in a floodplain lake in the Amazon – lake Camaleão, Amazonas, Brazil

Abstract  Stomach content and stable isotopes of tambaqui, Colossoma macropomum (Cuvier), were use to determine seasonality of energy sources in a floodplain lake in the central Amazon. The turnover time of carbon in young tambaqui was fast enough to detect a broad seasonal variation both in stomach content and tissue isotopic signal of carbon and nitrogen. The relative importance of food items varied with water level. C₃ plants (seeds and fruits) contributed between 55% and 95% of the biomass fraction of tambaqui. Zooplankton contributed a minimum of 26% of the nitrogen fraction during periods of flooding, and a maximum of 67% in the dry season. C₄ plants (macrophyte leaves and roots) contributed a maximum of 26% of the biomass fraction and 13% of the N fraction mainly during the flooding period. The feeding habits and behaviour of tambaqui are complex and linked to the flood pulse.     

应用稳定同位素技术研究崂山湾夏季鱼类群落的摄食生态

崂山湾是黄海沿岸众多海湾之一,也是当前增殖放流的重要水域,研究该区域鱼类群落结构及其食物网结构,有着非常重要的生态意义和实用价值。本研究根据2014年6月和8月在崂山湾海域进行的底拖网调查,分析该海域夏季鱼类群落的优势种组成,并通过测定稳定同位素对其摄食生态进行研究。结果表明,崂山湾夏季鱼类群落的优势鱼种共有10种,包括六丝矛尾鳅虎鱼、中华栉孔鳅虎鱼、红狼牙鳅虎鱼、皮氏叫姑鱼、白姑鱼、小黄鱼、绿鳍鱼、短吻红舌鳎、斑鲨和赤鼻棱鳀;夏季崂山湾不同月份鱼类群落的优势种组成差异较大。各优势鱼种间δ13C值存在显著差异,结合胃含物分析结果表明6月鱼类群落食物的主要来源均为底层饵料,而8月鱼类群落的食物来源则更广泛。崂山湾夏季2个月鱼类群落的优势鱼种间的δ15N值均存在显著差异,最大分别相差4.61‰和3.70‰。崂山湾6月鱼类群落的优势种包括了中营养级鱼类和高营养级鱼类,鱼类群落的平均营养级为3.90,主要是底栖动物食性鱼类;而8月鱼类群落的优势种包括了低营养级鱼类和中营养级鱼类,鱼类群落的平均营养级为3.37,包括浮游动物食性和底栖动物食性2种食性类型,以底栖动物食性鱼类为主。线性回归分析表明崂山湾夏季10种优势鱼种除皮氏叫姑鱼、斑鲨、短吻红舌鳎和绿鳍鱼的营养级与体长无线性相关外,其余优势鱼种的营养级均与体长呈显著的正相关。这主要由于它们随着体长的增加,摄食高营养级的饵料增加,低营养级的饵料减少,自身的营养级也随之升高。     

Trophic ecology of speckled peacock bass Cichla temensis Humboldt 1821 in the middle Negro River,Amazon, Brazil

The aim of this study was to analyse the trophic ecology of speckled peacock bass Cichla temensis inhabiting two tributaries of the middle Negro River, the Aracá River and the Demeni River. Using an analysis of stomach contents and stable isotope composition (δ¹⁵N, δ¹³C) of scales, we describe the diet and evaluate the trophic position of subadult and adult individuals. We then test whether diet shifts and trophic positions occurred among successive size classes and among sample locations. The stomach content analysis confirmed the piscivorous feeding habit of the species and showed that the speckled peacock bass preyed on a variety species belonging to different trophic guilds. The length of the ingested prey increased with the size of the speckled peacock bass. Diet composition and trophic position were not different among size classes. δ¹³C values yielded significant shifts among the size classes: larger individuals displayed higher δ¹³C values than smaller individuals. Trophic position varied between locations, with lowest values observed in fish from the Aracá River. This study demonstrated that diet of C. temensis may vary according to the size of the fish, even at the subadult or adult stages, and according to the river/locality, even within a same basin. We then suggest that further studies take into account local availability of food resources to better explore C. temensis diet and tropic ecology.     

Protein‐sparing effect by dietary lipid increase in juveniles of the hybrid fish tambatinga (♀Colossoma macropomum × ♂Piaractus brachypomus)

This research assessed four levels of crude protein—200, 250, 300 and 350 g/kg—associated with two crude lipid concentrations—110 and 140 g/kg—in diets for juveniles of tambatinga (♀Colossoma macropomum × ♂Piaractus brachypomus) over 63 days. The fish (15.2 ± 0.2 g) were distributed in 24–160 L tanks (11 fish/tank) in a 4 × 2 completely randomized factorial design (n = 3). Increasing the lipid content in the diets reduced (p < 0.05) the protein requirements for weight gain from 326 g/kg (diets with 110 g/kg LIP) to 255 g/kg (diets with 140 g/kg). Protein retention in the fish increased (p < 0.05) when they were fed up to 293 g/kg CP and 140 g/kg LIP; in the diets with 110 g/kg LIP, protein retention decreased linearly (p < 0.05) as the protein content in the diets increased. Feed efficiency increased (p < 0.05) when the fish received up to 308 g/kg CP regardless of lipid concentration (p > 0.05). In conclusion, tambatinga juveniles at 15–120 g have a minimum requirement of 255 g/kg CP and 140 g/kg CL and a protein:energy ratio of 17.4 g CP kJ/digestible energy (DE).     

Stable isotope analysis of energy sources for larvae of eight fish species from the Amazon floodplain

Abstract – Aquatic macrophytes form the most productive habitat of the Amazon floodplain and account for more than 60% of the net primary production of the ecosystem. Aquatic grasses are the dominant macrophytes and the main feeding ground of Amazonian larval fish. The present study used stable isotopes of nitrogen and carbon to measure the contribution of aquatic grasses to the production of eight larval fish, and describes the structure of the trophic chain. The carnivore larvae were at the third trophic level, and the detritivores were at the second and third trophic levels. The contribution of aquatic grasses to larval fish production was variable. It could reach a mean value of 25% for three species, but its contribution probably did not exceed 12% in the other five species.     

三峡库区干流鱼类食物网动态及季节性变化

为了解三峡大坝蓄水后库区干流鱼类食物网结构及营养关系的构成,应用碳(δ¹³C)、氮(δ¹⁵N)稳定性同位素技术,分别于2010年夏季(7月份)和冬季(12月份)对三峡库区巫山至万州段干流鱼类食物网结构及营养关系的季节变化进行了探讨,并与2005年夏季该区域鱼类食物网结构和营养关系组成情况进行了比较。结果显示:本次(2010年)调查颗粒有机物(POM)和固着藻类样品δ¹³C值分别为-25.62‰～-23.72‰、-19.81‰～-19.47‰,且无显著性季节(夏季和冬季)差异。POM 和固着藻类(内源性营养物质)是三峡库区巫山至万州段干流鱼类食物网基础能量的主要来源,但外源性营养物质输入也是其基础能量来源的重要补充途径。与2005年相比,2010年该区域鱼类食物网中消费者δ¹³C值富集度和食物网营养级长度均有所增加。该研究结果对三峡库区鱼类资源增殖放流和生态修复有重要指导意义。     

Ontogeny and dietary specialization in brown trout (Salmo trutta L.) from Loch Ness, Scotland, examined using stable isotopes of carbon and nitrogen

Abstract – The trophic ecology of many fish species in cold temperate lakes is often characterized by a generalist or opportunist strategy. In this study, the diets of polytrophic brown trout in Loch Ness, Scotland, have been examined using stable isotopes of carbon and nitrogen to complement gut content analyses and aging by otolith annuli counts. Using the stable isotope ratios, it was possible to trace trout ontogeny from parr development in a natal river to piscivory in the pelagic. Potential dilution of maternal isotope signatures from eggs to parr was also demonstrated. Despite the low productivity of the loch, intraspecific variability in isotope ratios suggested dietary specialization, rather than opportunism, in some individuals.     

Feeding level-scaled retention efficiency, growth and energy partitioning of a marine detritivorous fish, redlip mullet (Liza haematocheila T. & S.)

The effects of feeding level on growth, retention efficiency, faeces production and energy partitioning of redlip mullet were studied. A practical diet was used and fed at six levels from starvation, 1%, 2%, 3%, 4% of body weight (BW) to satiation for 3 weeks. The temperature was kept at 24±1°C. Reducing the feeding amount resulted in significantly lower weight gain, and retention efficiency was significantly affected by feeding levels and attained the maximum at maximum feeding intake. Feeding 2% BW was the minimum required for fish to maintain growth. Fish carcass composition under different feeding levels could be divided into three groups: (1) starvation and FL1; (2) FL2 and FL3 and (3) FL4 and satiation, with significant differences among the groups but no differences in the groups except that ash content remained at constant value. Body composition of fish of group 2 was close to initial fish. The thermal‐unit coefficient was 0.0381 at satiation, and significantly increased with increasing feeding levels. In order to accurately estimate basal metabolism (HeE), another trial on the relationship between HeE (kJ) and BW (g) was carried out. An exponential curve as HeE=0.1255BW^0.8386 explained this relationship. Intake energy (IE) increased from 11.30 to 63.08 kJ per fish, matching with different feeding levels. Energy allocated to growth of IE decreased with reducing feeding amount. There was a linear relationship between metabolism energy and retention energy in percentage.     

Patterns of stable carbon and nitrogen isotopes in the baleen of common minke whale Balaenoptera acutorostrata from the western North Pacific

ABSTRACT:   Stable carbon and nitrogen isotope ratios were determined in the baleen plates of 17 common minke whales Balaenoptera acutorostrata from the north-western Pacific Ocean off Japan, as well as prey species (krill Euphausia pacifica , Japanese anchovy Engraulis japonicus and Pacific saury Cololabis saira ) collected in the stomach contents, to investigate the trophic relationship between the minke whales and their prey. A few δ¹⁵N-depleted peaks occurred along the length of baleen plates for 10 males irrespective of stomach content (anchovies and sauries). Similar δ¹⁵N-depleted peaks were also found for one female and two immature individuals. It was likely that these δ¹⁵N-depleted peaks formed in early summer. The stable nitrogen isotope ratio (δ¹⁵N) values in Pacific saury (9.3 ± 1.4‰) did not differ significantly from that in Japanese anchovy (8.8 ± 0.9‰). In contrast, δ¹⁵N in krill (7.2 ± 0.5‰ in July and 8.0 ± 0.2‰ in September) were significantly lower than in the Pacific saury. Thus, these peaks may reflect the dietary change from krill to fishes in the feeding migration of the whales. Growth rate of the baleen plate was estimated to be 129 mm/y, and it appeared that a dietary record of about 1.4 years remained in the baleen plate. For two immature whales, the maximum value of δ¹⁵N occurred at the tip of baleen. This δ¹⁵N enrichment may possibly be useful for discriminating weanlings and older whales.     

Feeding patterns in five predatory fishes of the high Paranà River floodplain (PR, Brazil)

Abstract— Between March 1992 and February 1993 five piscivorous fish species, Acestrorhynchus lacustris (Reinhardt, 1874), Hoplias malabaricus (Bloch, 1794), Rhaphiodon vulpinus Agassiz, 1829, Salminus maxillosus , Valenciennes, 1840 and Plagioscion squamosissimus (Heckel, 1840), of the high Paranà River floodplain showed a wide total prey spectrum though only three to four taxa were dominant in their diet. Shrimp, Macrobrachium amazonicum , were also common to the majority of species. Seasonal and spatial variations occurred throughout the study period probably due the availability of prey species. The main resources shared by the predators were also the most abundant in the area, with consumption markedly focused on prey about 5.0 cm long. Detrended correspondence analysis was effective in discriminating two groups of predators species that exploited distinct microhabitats. The predators with the least scores consumed small characids that inhabit mid-water or the littoral region, whereas those with the largest scores consumed prey associated to the bottom.     

荣成俚岛斑头鱼摄食生态研究

2010年3月至2011年2月逐月采集荣成俚岛近海的743尾斑头鱼(Hexagrammos agrammus),探讨其摄食生态特征。结果表明,斑头鱼为底栖生物食性鱼类,摄食的饵料生物包括11个类群,主要摄食多毛类(Polychaeta),其次是鱼卵、海藻类、海草类、口足类(Stomatopoda)、端足类(Amphipoda)和鱼类等。食物组成随季节和体长而变化:除四季均大量摄食多毛类以外,春季还摄食口足类和虾类,夏季还摄食鱼类和蟹类,秋季还摄食鱼卵和鱼类,冬季摄食鱼卵比例最高;体长80 mm的斑头鱼喜食海草和海藻等植物性饵料,体长80~199 mm的个体喜食多毛类、鱼类和虾蟹类等,体长199 mm的个体主要摄食鱼类、多毛类和鱼卵等。摄食强度也随季节和体长而变化:夏季摄食强度最高,春季和秋季次之,冬季最低(不停食);体长100 mm的个体摄食强度最高,随着体长增加而逐渐下降,体长180 mm以上的个体又随体长和年龄的增大而逐渐升高。对斑头鱼5个饵料生物样品进行了DNA条形码鉴定,其中4个饵料生物样品鉴定到种,1个饵料生物样品鉴定到属。结论认为,斑头鱼的摄食习性会随季节、个体生长和栖息海域饵料生物的种类和丰度的不同而发生变化。     

Resource use of crucian carp along a lake productivity gradient is related to body size,predation risk,and resource competition

Generalist fish species can feed on a wide resource spectrum and across trophic levels depending on resource availability and trophic interactions. Crucian carp (Carassius carassius) represents a good candidate species to investigate variation in the trophic ecology of generalist fish as it can be found in highly variable fish communities and its resource use is well documented. In this study, we explored the trophic ecology of crucian carp at the individual and population levels using stable isotope and gut content analysis. We tested if trophic resource use varied according to lake productivity, predation risk, intra- and interspecific competition, or individual fish size. We found that crucian carp resource preference was highly variable among and within lakes. In predator-free lakes, small crucian carp occurred in high densities, showed increased interindividual specialisation, and relied mainly on pelagic zooplankton. In presence of predators, large crucian carp occurred in low densities and included greater proportions of benthic macroinvertebrates in their diet. This shift in resource use was further favoured in productive, shallow lakes where littoral prey were probably abundant. Resource partitioning was an important factor determining crucian carp niche use, as fish had higher trophic position in absence of other cyprinids. Crucian carp showed highly dynamic resource use and food preferences in response to variable environmental conditions. Overlooking complex diet preferences of generalist fish may lead to an oversimplification of freshwater community dynamics.     

Assessment of the relative contribution of dietary nitrogen from fish meal and biofloc meal to the growth of Pacific white shrimp (Litopenaeus vannamei)

The relative contribution of the dietary nitrogen supplied by fish meal and a biofloc meal to the growth of Pacific white shrimp was evaluated using stable isotope analysis. Biofloculated material was obtained from an experimental tilapia culture system. Five formulated diets were supplied. Two of them consisted in isotopic controls having only fish meal or biofloc meal as protein source. Three mixed diets were formulated with varying proportions of these ingredients on a dietary nitrogen basis (75:25, 50:50 and 25:75). At the end of the trial, survival rates were similar (92–100%) but significant differences in mean final weight were observed and a negative correlation between the inclusion of biofloc meal and weight gain was evidenced. Mean final weight in shrimp fed on diet containing only fish meal was 2.8 g, while mean final weight of animals fed on diet containing 50% biofloc was 1.9 g. Isotopic mixing models indicated that all diets contributed higher proportions of dietary nitrogen from fish meal than from biofloc meal. Dietary nitrogen available in diets containing 25%, 50% and 75% of biofloc meal was incorporated in muscle tissue as 5%, 41% and 64% respectively. Diet supplying 25% of nitrogen from biofloc was the only mixed diet eliciting growth comparable to diet containing only fish meal. Lower growth and nitrogen deposition in shrimp fed on diets containing high proportions of biofloc meal were possibly associated to the use of only two protein sources and a restriction of essential amino acids.     

Reproductive migration of fish and movement in a series of reservoirs in the Upper Parana River basin,Brazil

This study evaluates the effectiveness of two fish passes at two hydropower dams (Canoas I and II) in the Upper Parana basin, which form part of a cascade of three reservoirs. Fish from 12 migratory species (3089 specimens) were captured during their ascending, reproductive migration and were tagged with hydrostatic tags. The recapture data (294 specimens over two consecutive years) showed that there is a strong tendency for the maintenance of ascending migration through reservoirs with fish passes but with differences in migratory activity within the same species. No eggs, larvae or juveniles of these species were found in samples collected over 5 years in the reservoirs above the fish passes. These data suggest that fish passes have contributed to the restoration of the migratory routes of adult fish but that in the absence of suitable spawning or nursery habitats for these species; they probably act as ecological traps and do not contribute to the recruitment of the species.     

Diversity of fish and fisheries from the Lake Encantada Environmental Protection Area,Ilhéus,Brazil

• 1. Lake Encantada, in the basin of the Almada River (Bahia State), has an area of 650.5 ha and a perimeter of 13.3 km. In 1993, an area of 11 800 ha around the lake was designated an Environmental Protection Area (Class V category). The main goal of this study was to identify fish species in the lake and to determine possible threats to their conservation.
• 2. Fish samples were obtained with gillnets between May 2002 and February 2004, and used to calculate indices of species diversity Shannon (H′), richness (d) and evenness (J′).
• 3. Eleven fish species comprising nine families were collected during the sampling period. Three introduced species occurred in the lake: Prochilodus argenteus, endemic to the São Francisco river basin, and two African species, Oreochromis niloticus and Clarias gariepinus. In overall ranking, Prochilodus argenteus was first in number of individuals (46%) and weight (59%), followed by Genidens genidens in numbers (31%), and Clarias gariepinus in weight (15%).
• 4. The occurrence and dominance of introduced species is discussed as well as their possible impacts on the trophic structure of this ecosystem.

Copyright © 2007 John Wiley & Sons, Ltd.     

崂山湾春季鱼类群落的摄食生态及其主要种类

崂山湾位于黄海的胶州湾和丁字湾之间,海湾开阔,是当前增殖放流的重点海域。根据2014年5月在崂山湾海域进行的底拖网调查,分析了该海域春季鱼类群落的种类组成和摄食生态。结果表明,崂山湾春季鱼类群落共32种鱼类,隶属8目,21科,30属;以鲈形目(Perciformes)的虾虎鱼科(Gobiidae)和石首鱼科(Sciaenidae)种类最多;优势种有皮氏叫姑鱼(Johnius belengerii)、短吻红舌鳎(Cynoglossus joyneri)和矛尾虾虎鱼(Chaeturichthys stigmatias),主要种有大泷六线鱼(Hexagrammos otakii)、斑鰶(Clupanodon punctatus)、赤鼻棱鳀(Thrissa kammalensis)、丝虾虎鱼(Cryptocentrus filifer)、方氏云鳚(Enedrias fangi)和银鲳(Pampus argenteus)。崂山湾春季鱼类群落的种类丰富度指数R为3.19,多样性指数H′为2.34;均匀度指数J′为0.68。胃含物分析结果表明,春季崂山湾生态系统鱼类群落的平均营养级为3.52;主要包括了浮游动物食性、杂食性和底栖动物食性3种食性类型,以底栖动物食性鱼类为主。在当前捕捞、气候变化和人类活动等多重压力下,海湾生态系统承受了巨大的压力,针对不同的海湾生态系统进行基础调研,可为制订相应的增殖放流、渔业保护和管理策略提供重要科学依据。     

Typology of historical sources and the reconstruction of long‐term historical changes of riverine fish: a case study of the Austrian Danube and northern Russian rivers

Historical data are widely used in river ecology to define reference conditions or to investigate the evolution of aquatic systems. Most studies rely on printed documents from the 19th century, thus missing pre‐industrial states and human impacts. This article discusses historical sources that can be used to reconstruct the development of riverine fish communities from the Late Middle Ages until the mid‐20th century. Based on the studies of the Austrian Danube and northern Russian rivers, we propose a classification scheme of printed and archival sources and describe their fish ecological contents. Five types of sources were identified using the origin of sources as the first criterion: (i) early scientific surveys, (ii) fishery sources, (iii) fish trading sources, (iv) fish consumption sources and (v) cultural representations of fish. Except for early scientific surveys, all these sources were produced within economic and administrative contexts. They did not aim to report about historical fish communities, but do contain information about commercial fish and their exploitation. All historical data need further analysis for a fish ecological interpretation. Three case studies from the investigated Austrian and Russian rivers demonstrate the use of different source types and underline the necessity for a combination of different sources and a methodology combining different disciplinary approaches. Using a large variety of historical sources to reconstruct the development of past fish ecological conditions can support future river management by going beyond the usual approach of static historical reference conditions.     

Carrying capacity and potential environmental impact of fish farming in the cascade reservoirs of the Paranapanema River,Brazil

The objective of this study was to simulate changes in water quality standards caused by the installation of aquaculture parks for caged fish farming in the eight large artificial reservoirs in the Paranapanema River according to the different scenarios of technical and legal limitations: (i) occupancy of 1% of the total surface of the reservoirs and (ii) occupancy according to the environmental carrying capacity. For water quality modelling, these two scenarios were simulated to determine the trophic state index (TSI) of each reservoir. Based on the total area of all reservoirs in the first scenario, the fish farm facilities would occupy 18.3 km² and have an annual fish production of an estimated 513 thousand MT. However, because of limitations in the carrying capacity, the annual production in the second scenario would be 98 thousand MT and the fish farm facilities would occupy 3.5 km². Simulating the TSI for the first scenario, approximately 75% of the total area of all reservoirs was estimated to change from oligo or mesotrophic conditions to eutrophic, supereutrophic and hypereutrophic conditions, and four reservoirs may become completely eutrophic (Canoas 2, Canoas 1, Taquaruçu and Rosana). For the second scenario, however, eutrophic areas accounted for less than 30% of the total, although the Taquaruçu and Rosana reservoirs were still at risk of total eutrophication. These results indicate as well‐intentioned legislation can have unintended environmental consequences in dynamic social–ecological aquaculture systems as in the case of large reservoirs in the Paranapanema River.     

Spatial organisation of fish assemblages in the Chishui River,the last free‐flowing tributary of the upper Yangtze River,China

The Chishui River is the last free‐flowing tributary of the upper Yangtze River, China, which has an important role in fish conservation. This study aimed to explore the spatial organisation of fish assemblages in this river. Field sampling was conducted biannually between 2015 and 2017 at 41 sites from its headwater and downstream. One hundred and twenty‐two fish species were captured, including 34 endemic, 15 threatened and six exotic species. Fish assemblages varied significantly along the longitudinal gradient. Based on cluster and ordination analyses, 41 sampling sites could be divided into five site‐groups, corresponding to the headwater, upstream, midstream, downstream and the Xishui‐branch, respectively. The splitting of fish assemblages was consistent with the geographical divisions. However, fish species changed gradually along the longitudinal gradient rather than abruptly, which was consistent with the River Continuum Concept (RCC). In the headwaters and upstream, fish assemblages were mainly dominated by cold‐water and rheophilic species, while in the lower stretches, fish assemblages were dominated by warm‐water and limnophilic species. According to null models, fish assemblages were significantly nonrandomly structured at the basin scale, but randomly structured at the regional scale. This study is an important step in understanding the assembly rules of fish assemblages in this free‐flowing river and provides useful information for future fish conservation and ecological restoration.