Fish Trophic Guilds Research Articles

Trace elements in the water and fish of tropical watercourses in central Brazil

The aim was to compare the trace element concentrations found in samples of water (cadmium, copper, manganese, lead and zinc) from ten water catchments and muscle tissues (aluminum, iron, manganese, lead and zinc) from six fish trophic guilds, both samples collected in watercourses of the Upper Tocantins River, Goiás, Central Brazil. Trace element concentrations did not differ among the water catchments, except for Cu and Mn that exceeded the concentrations allowed by the environmental Brazilian legislation. The highest concentrations (Al, Fe, Mn, Pb e Zn) were found in fish of the guild detritivores, omnivores and terrestrial insectivores, while the aquatic invertivores showed the lowest ones; no correlation was observed between the concentrations of Mn, Pb and Zn of the water samples and fish muscle tissues. It suggests that the hydrological and chemical characteristics of watercourses sampled influence on a similar way the availability of trace elements in the water column. The differences of trace element concentrations observed among the trophic guilds do not display a trend based on fish feed strategy, but on the availability of the trace element in the environment, finding reinforced by the absence of relationship between trace elements concentrations of water and fish muscle tissue.

Difference in the trophic structure of fish communities between artificial and natural habitats in a tropical estuary

The present study tested the hypothesis that artificial habitats (pier and bridge) harbour different fish trophic guilds compared with natural habitats (mangrove roots) and that the trophic structure of fish communities on estuarine artificial habitats resembles adjacent coral reefs. High-definition cameras were used to survey the fish community associated with the different structures over a 6-month period. Benthos was also analysed following the point intercept method on the different habitats. In the estuary, fish abundance was up to threefold higher and species richness twofold higher on artificial structures compared with the natural habitat. Mangrove roots were mainly inhabited by juvenile carnivores, whereas the pier and bridge were mostly inhabited by sessile invertebrate feeders and roving herbivores. A less diverse benthic community was found on mangrove roots, mostly composed of mud and algae. In contrast, benthos at the bridge and pier was more diverse and dominated by sponges, octocorals and oysters. In addition, fish trophic structure from an adjacent coral reef area showed more than 60% similarity with the fish community on the artificial structures surveyed. The results of the present study indicate that artificial hard structures support unique fish communities compared with natural estuarine mangrove habitats.

Efeito da seca e da variação espacial na abundí­¢ncia de indiví­­duos nas guildas tróficas da ictiofauna em um reservatório no Semiárido Brasileiro

A abundí­¢ncia de indiví­­duos que compõem as guildas tróficas de peixes pode ser regida por modificações temporais e espaciais, considerando que perí­­odos e locais distintos dispõem de diferentes condições bióticas e abióticas. Assim, verificou-se o efeito da seca e das diferenças espaciais na abundí­¢ncia de indiví­­duos nas guildas tróficas da ictiofauna do reservatório de Pau dos Ferros, Rio Grande do Norte. Foram coletados peixes em quatro pontos, nos meses de fevereiro, maio, agosto e novembro de 2012. Após a captura, identificação e biometria, os itens alimentares dos estômagos e intestinos foram identificados e os seus volumes, estimados. Foi calculado o Índice Alimentar (IAi), sendo seus valores utilizados para determinar as guildas tróficas. Depois, verificou-se a similaridade entre as espécies das guildas tróficas. O número de indiví­­duos que compõem as guildas foi utilizado em uma matriz de similaridade, e os resultados desse procedimento foram ordenados em análises de escalonamento multidimensional não métrico (NMDS), para avaliar a distribuição temporal e espacial das guildas. As espécies foram classificadas em quatro guildas tróficas: insetí­­vora, detrití­­vora/iliófaga, herbí­­vora e piscí­­vora. Com base nessa classificação foi constatado que o perí­­odo de seca e a estrutura dos pontos de coleta favoreceram o estabelecimento das guildas insetí­­vora e detrití­­vora/iliófaga ao longo dos meses e pontos estudados, uma vez que o reservatório de Pau dos Ferros é um ambiente eutrofizado e de baixa profundidade, com alta produtividade primária e grande disponibilidade de insetos, detritos e sedimentos.

Nutrient regime, N:P ratios and suspended solids as key factors influencing fish tolerance, trophic compositions, and stream ecosystem health

The objectives of this study were to determine the effects of stream nutrient regime, N:P ratios and suspended solids on fish tolerance/trophic compositions and stream ecosystem health, based on multi-metric model, during 2008–2013. Also, stream ecosystem health was evaluated in relation to chlorophyll-a (CHL) as a measure of algal productivity or indicators of trophic state to water chemical parameters. Total number of sampled fish species were 50 and showed a decreasing trend from 2008 to 2013. The minnow of Zacco platypus, based on the catch per unit effort (CPUE), was the most dominant species (25.9%) among the all species. Spatial heterogeneity was evident in the fish tolerance guilds that showed the dominance of sensitive species (89%) in the headwaters (S1) and the dominance of tolerant species (57%) in the urban. These conditions were directly influenced by concentrations of nutrients and organic matter (COD). The N:P ratios, as a barometer of water pollution, had a negative linear function (R 2 = 0.40, P 0.05) to the two compositions, but phosphorus influenced directly the two guilds [slope (a) = -32.3, R 2 = 0.25, P < 0.01 in the In; a = 40.7, R 2 = 0.19, P < 0.01 in the Om]. Such water chemistry and fish trophic guilds determined the stream ecosystem health, based on the multi-metric fish model.

PREDICTING FACTORS THAT INFLUENCE FISH GUILD COMPOSITION IN FOUR COASTAL RIVERS (SOUTHEAST IVORY COAST) USING ARTIFICIAL NEURAL NETWORKS

The present study is focused on small coastal rivers in southeast Ivory Coast, aimed to predict species richness of fish guilds and to test contribution of environmental variables for explaining guild structure with Self-Organizing Map (SOM) and Backpropagation (BP) algorithms. The former method was applied to pattern the samples based on the richness of six major fish guilds observed (benthivores, invertivores, detritivores, piscivores, herbivores and omnivores). Four clusters were identified: cluster I was characterised by benthivores, cluster II was distinguished by invertivores, detritivores, piscivores and omnivores, cluster III had high richness of benthivores, invertivores and herbivores, and cluster IV had high numbers of omnivore, detritivore and piscivore species. The BP showed high predictability (0.89 for benthivores, 0.85 for omnivores and Odonata, 0.84 for herbivores). There was high correlation between observed and estimated values for piscivores (0.77) and detritivores (0.72); the poorest fit was for invertivores (0.63). The frequency histogram of residuals showed that most residuals lie around zero for all guilds. The most contributing variables in predicting the six fish trophic guilds were water temperature, conductivity, total dissolved solids, dissolved oxygen, depth, width, canopy and distance from source. This underlines the crucial influence of both instream characteristics and riparian environment.

계절적 몬순에 의한 댐 인공호 및 농업용 저수지에서의 영양상태지수(TSI), 경험적 수질 모델 및 어류 트로픽 구조

The key objective of this study was to evaluate trophic state and empirical water quality models along with analysis of fish trophic guilds in relation to water chemistry (N, P). Trophic state index (TSI), based on total phosphorus (TP) and chlorophyll-a (CHL), ranged between oligotrophic and hypereutrophic state, by the criteria of Nurnberg(1996), and was lower than the trophic state of total nitrogen (TN). Trophic relations of Secchi depth (SD), TN, TP, and CHL were compared using an empirical models of premonsoon (Pr), monsoon (Mo), and postmonsoon (Po). The model analysis indicated that the variation in water transparency of Secchi depth (SD) was largely accounted (p < 0.001, range of R2 : 0.76.0.80) by TP during the seasons of Mo and Po and that the variation of CHL was accounted (p < 0.001, R2 = 0.70) up to 70% by TP during the Po season. The eutrophication tendency, based on the TSITP vs. TSIN:P were predictable (R2 ranged 0.85.0.90, p < 0.001), slope and y intercept indicated low seasonal variability. In the mean time, TSIN:P vs. TSICHL had a monsoon seasonality in relation to values of TSIN:P during the monsoon season due to a dilution of reservoir waters by strong monsoon rainfall. Trophic compositions of reservoir fish reflected ambient contents of TN, TP, and CHL in the reservoir waters. Thus, the proportions of omnivore fish increased with greater trophic conditions of TP, TN and CHL and the proportions of insectivore fish decreased with greater trophic conditions.

Longitudinal use of feeding resources and distribution of fish trophic guilds in a coastal Atlantic stream, southern Brazil

This study described the use of food resources and the distribution of fish trophic guilds along the longitudinal gradient of a coastal Atlantic stream, southern Brazil. Allochthonous resources (terrestrial insects) predominated in the headwaters, whereas autochthonous food items (algae, fish) and detritus predominated in the mouth section. Detritivorous, aquaticinvertivorous, and terrestrial- and aquatic-insectivorous species occurred throughout the gradient, while omnivorous and piscivorous in the headwaters and middle stretches, respectively, and herbivorous in the middle and mouth. Detritivores and aquatic-insectivores were significantly more specialized than the other guilds, however, there was no evidence of a longitudinal increase in trophic specialization. Density and biomass of aquatic-invertivores and aquatic-insectivores decreased, whereas that of detritivores increased longitudinally. The distribution of trophic guilds was significantly associated with the stream section, where aquatic and terrestrial insectivorous were more frequent in rocky and flowed stretches from the headwater and detritivores in deeper environments with finer particles of substrate from the mouth. This suggests that fish assemblages in coastal streams with a steep longitudinal gradient may follow patterns in the use of food resources according with the food availability along the river, as predicted by the River Continuum Concept.

The importance of small-scale environment factors to community structure patterns of tropical rocky reef fish

Understanding the spatial distribution of fish species and fish trophic guilds in reef environments may help improve our knowledge about ecological relationships and therefore favour sound strategies for sampling, coastal management and conservation policy. To verify if small-scale changes are important in forming the fish community structure at a tropical rocky coastal island, we assessed the depth, structural complexity and wave exposure gradients. The community structure changed along all gradients analysed. The trophic guilds found on the sheltered, low and intermediate exposure zones, in the deepest areas and in areas of highest structural complexity showed significant differences when compared with the general assemblage. Rocky reefs, even of narrow (transversal) extension, can show great changes in fish community structure at so small a scale that these changes are generally overlooked. The relationships evidenced between community and environment provide strong support for the importance of considering a wide array of such distinct environmental conditions when determining the structure patterns of the community.

Predicting trophic guild and diet overlap from functional traits: statistics, opportunities and limitations for marine ecology

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 436:17-28 (2011) - DOI: https://doi.org/10.3354/meps09240 Predicting trophic guild and diet overlap from functional traits: statistics, opportunities and limitations for marine ecology C. Albouy1,2,*, F. Guilhaumon1,3,5, S. Villéger1, M. Mouchet1, L. Mercier1, J. M. Culioli4, J. A. Tomasini1, F. Le Loc’h2, D. Mouillot1,6 1Univ Montpellier 2 CC 093, UMR 5119, CNRS-UM2-IRD-IFREMER-UM1 ECOSYM, 34095 Montpellier, France 2IRD, UMR 212 EME, IRD IFREMER UMII, avenue Jean Monnet 34203 Sète cedex, BP 171, France 3’CITA-A (Azorean Biodiversity Group), Terra-Cha, Angra do Heroıismo, 9700-851, Terceira, Azores, Portugal 4Office de l’Environement de Corse, Reserve Naturelle des Bouches de Bonifacio, 20250 Corte, France 5’Rui Nabeiro’ Biodiversity Chair, CIBIO - Universidade de Évora. Casa Cordovil, Rua Dr. Joaquim Henrique da Fonseca, 7000-890 Évora, Portugal 6ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland 4811, Australia *Email: albouycamille@gmail.com ABSTRACT: Fish diets provide information that can be used to explore and model complex ecosystems, and infer resource partitioning among species. The exhaustive sampling of prey items captured by each species remains, however, a demanding task. Therefore, predicting diets from other variables, such as functional traits, may be a valuable method. Here, we attempted to predict trophic guild and diet overlap for 35 fish species using 13 ecomorphological traits related to feeding ecology. We compared linear discriminant analysis and random forest (RF) classifiers in their ability to predict trophic guild. We used generalized dissimilarity modelling to predict diet overlap from functional distances between species pairs. All models were evaluated using the same cross-validation procedure. We found that fish trophic guilds were accurately predicted by an RF classifier, even with a limited number of traits, when no more than 7 guilds were defined. Prediction was no longer accurate when finer trophic guilds were created (8 or more guilds), whatever the combination of traits. Furthermore, predicting the degree of diet dissimilarity between species pairs, based on their ecomorphological traits dissimilarities, was profoundly unreliable (at least 76% of unexplained variation). These results suggest that we can predict fish trophic guilds accurately from ecomorphological traits, but not diet overlap and resource partitioning because of inherent versatility in fish diets. More generally, our statistical framework may be applied to any kind of marine organism for which feeding strategies need to be determined from traits. KEY WORDS: Generalized dissimilarity modeling · Mediterranean · Fish · Non-linear model · Random forest · Versatility Full text in pdf format Supplementary material PreviousNextCite this article as: Albouy C, Guilhaumon F, Villéger S, Mouchet M and others (2011) Predicting trophic guild and diet overlap from functional traits: statistics, opportunities and limitations for marine ecology. Mar Ecol Prog Ser 436:17-28. https://doi.org/10.3354/meps09240 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 436. Online publication date: August 31, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

Fish communities on the world's warmest reefs: what can they tell us about the effects of climate change in the future?

To examine the role of climatic extremes in structuring reef fish communities in the Arabian region, reef fish communities were visually surveyed at four sites within the southern Persian Gulf (also known as the Arabian Gulf and The Gulf), where sea-surface temperatures are extreme (range: 12-35° C annually), and these were compared with communities at four latitudinally similar sites in the biogeographically connected Gulf of Oman, where conditions are more moderate (range: 22-31° C annually). Although sites were relatively similar in the cover and composition of coral communities, substantial differences in the structure and composition of associated fish assemblages were apparent. Fish assemblages in the southern Persian Gulf held significantly lower estimates of abundance, richness and biomass, with significantly higher abundances of smaller sized individuals than Gulf of Oman assemblages. Functionally, southern Persian Gulf sites held significantly lower abundances of nearly all the common fish trophic guilds found on Gulf of Oman sites, although higher abundances of herbivorous grazers were apparent. These results suggest the potential for substantial changes in the structure of reef-associated fish communities, independent of changes in habitat within an environment of increasing fluctuations in oceanic climate.

Seasonal and spatial variations of fish trophic guilds in a shallow, semi-enclosed tropical estuarine bay

A study on seasonal and spatial variations of feeding habits and trophic guilds of dominant fish species in Pattani Bay during March 2003 to February 2004 was aimed at classifying diet composition, identifying dominant food components of each species, categorizing trophic guilds of the community and evaluating effects of habitat characteristics and seasonality on guild organization. Most fishes showed high food intake, fed on a diverse range of food items but relied heavily on calanoid copepods and shrimps. All species, with the exception of Epinephelus coioides, were classified as specialist feeders. Four main dietary guilds were classified. Three of these were classified as the guilds dominated by at least two major food items. Significant variations in trophic guilds of 28 fish species based on habitat types and seasons were also identified. They could be divided into three seasonal groups and three site-groups and a single site. Trophic organization for each season and habitat ranged from two to four groups. This information identifies groups of fishes that seasonally and spatially utilize different food resources within a semi-enclosed estuarine bay ecosystem.

Influence of Non-point Source Pollution on Riverine Fish Assemblages in South West France

The relationship between non-point source pollution (NSP) and fish assemblages in the Garonne basin, SW France was studied. Two independent data sets were coupled, one containing 20 physico-chemical variables and another containing 40 fish species in 84 study sites. Species were classified in guilds according to their feeding habitat and their diet composition. The physico-chemical variables were log-transformed and standardized for a factor analysis in which they were grouped into four factors which accounted for 80% of the total variability. These were named according to factor loadings (i.e. a measure of the variance of a given variable) whose absolute values were larger than 0.5. Hence, the first factor (F1) was formed by variables linked to NSP, most notably by sodium, chloride, potassium, orthophosphates, nitrites and chemical oxygen demand. The second factor (F2) was related to alkalinity (i.e. bicarbonates, calcium, conductivity and pH). The third factor (F3) included oxygen saturation rate and dissolved oxygen, and F4 combined both temperature and flow. Factor scores (i.e. weighted sums of the original variables) were then introduced in stepwise multiple regression models as explanatory variables of log-transformed fish species richness of trophic guilds. The NSP factor was significant (p < 0.05) for the following models: benthic omnivores (r2 = 0.66), all species (r2 = 0.65), total benthic species (r2 = 0.63), total water-column species (r2 = 0.57), benthic invertivores (r2 = 0.32) and water-column invertivores (r2 = 0.16). The guilds for which NSP was not significant were water-column omnivores, water-column piscivores and benthic detritivores. Thus, there was evidence of an inversely proportional association, though not causation, of NSP with species richness of riverine fish trophic guilds on a large spatio-temporal scale. Fish assemblages may respond in different ways to NSP depending on their species composition, on the region and on the scale, and not only to physico-chemical properties of water.

Structure of tropical river food webs revealed by stable isotope ratios

Fish assemblages in tropical river food webs are characterized by high taxonomic diversity, diverse foraging modes, omnivory, and an abundance of detritivores. Feeding links are complex and modified by hydrologic seasonality and system productivity. These properties make it difficult to generalize about feeding relationships and to identify dominant linkages of energy flow. We analyzed the stable carbon and nitrogen isotope ratios of 276 fishes and other food web components living in four Venezuelan rivers that differed in basal food resources to determine 1) whether fish trophic guilds integrated food resources in a predictable fashion, thereby providing similar trophic resolution as individual species, 2) whether food chain length differed with system productivity, and 3) how omnivory and detritivory influenced trophic structure within these food webs. Fishes were grouped into four trophic guilds (herbivores, detritivores/algivores, omnivores, piscivores) based on literature reports and external morphological characteristics. Results of discriminant function analyses showed that isotope data were effective at reclassifying individual fish into their pre‐identified trophic category. Nutrient‐poor, black‐water rivers showed greater compartmentalization in isotope values than more productive rivers, leading to greater reclassification success. In three out of four food webs, omnivores were more often misclassified than other trophic groups, reflecting the diverse food sources they assimilated. When fish δ15N values were used to estimate species position in the trophic hierarchy, top piscivores in nutrient‐poor rivers had higher trophic positions than those in more productive rivers. This was in contrast to our expectation that productive systems would promote longer food chains. Although isotope ratios could not resolve species‐level feeding pathways, they did reveal how top consumers integrate isotopic variability occurring lower in the food web. Top piscivores, regardless of species, had carbon and nitrogen profiles less variable than other trophic groups.

A comunidade de macroinvertebrados aquáticos e características limnológicas das lagoas Carioca e da Barra, Parque Estadual do Rio Doce, MG

A comunidade de macroinvertebrados aquáticos, freqüentemente utilizada na avaliação da qualidade de água, foi investigada em dois sistemas lênticos do Médio Rio Doce, que se apresentam sob diferentes status de conservação. As lagoas da Barra e Carioca foram amostradas em suas margens e na região limnética, retirando-se água para caracterização física e química e sedimento para coleta de organismos bentônicos. A lagoa da Barra, que vem sofrendo sucessivos impactos pela ação antrópica, mostrou teores mais baixos de oxigênio dissolvido, elevada condutividade elétrica e sua comunidade bentônica, menor riqueza (14 taxa, contra 33 presentes na lagoa Carioca). A análise das guildas tróficas da ictiofauna sugere que a pressão de predação sobre a comunidade de macroinvertebrados é também maior na lagoa da Barra. A lagoa Carioca, além de apresentar maior riqueza de taxa, mostrou uma comunidade melhor estruturada em termos de grupos funcionais de alimentação, refletindo seu melhor estado de conservação, por estar dentro dos limites do Parque Estadual do Rio Doce.

Fish Trophic Guilds and the Stucture of a Tropical Stream: Weak Direct vs. Strong Indirect Effects

Freshwater fishes exhibit spectacular biodiversity in the tropics. In contrast to temperate streams, where insectivorous fishes generally predominate, detrital— and algalfeeding fishes are widespread components of tropical ichthyofaunas. I compared the direct and indirect effects of a variety of fishes in structuring a neotropical stream insect assemblage. An exclosure/enclosure experiment was preformed to examine the role of different fish trophic guilds and densities on patterns of patch colonization by invertebrates. Insectivorous characid fishes had relatively weak impacts on overall invertebrate abundance, although significant reductions were observed for selected taxa (the mayflies Baetis sp. 2 and Leptohyphes, and the caddisflies Smicridea and Alisotrichia). This contrasted sharply with the strong effects of the grazing armored catfish Chaetostoma milesi and the detritivore Prochilodus mariae, which caused significant reductions in abundance of common taxa throughout the invertebrate assemblage. In addition, grazers and detritivores substantially reduced the amount of sediments and associated detritus accumulated on stream bottom substrata. A second experiment was preformed to evaluate the mechanism by which grazing and detritivorous fishes influence insect abundance. Insect abundance was compared between a treatment where resource depression and bioturbation was simulated by removing sediments manually to fish exclosure/enclosure treatments. As in the previous experiment, grazers and detritivores significantly reduced the abundance of many common invertebrate taxa, as well as detrital and algal resources. However, taxon—specific differences in colonization of the sediment—removal treatment suggest that several factors are important in explaining responses to fishes by insects. Many common taxa displayed decreases in abundance both in sediment—removal and fish treatments, indicating that sediment—processing activities by epibenthic fishes are important in explaining patch colonization for many members of the invertebrate assemblage. However, sediment depletion is not sufficient to explain the response of the abundant invertebrate, Baetis sp. 1, which showed substantial reductions in cages containing fishes (open and grazer enclosures), but high densities in both the fish—exclusion and the sediment—removal treatments. These data suggest that intimidation by fish, as measured by the presence of grazers, results in low rates of patch use by this numerically dominant mayfly. These findings contrast with studies reporting relatively weak effects of fishes in temperate zone streams. Fishes may be strong interactors in some neotropical steams, not through direct lethal consumption of prey, but rather by modifying the distribution and abundance of resources important to stream insects. In some instances the simple intimidation associate with the presence of a diverse and abundant fauna of bottom—feeding fishes also may influence insect abundance and distribution.