Mercury distribution in organisms, litter, and soils of the Middle Araguaia floodplain in Brazil.

Mercury (Hg) is a chemical element that, depending on its concentration, may become toxic to living organisms due to the ability of Hg to bioaccumulate in food chains. In this study, we collected samples of soil, litter, and organisms in the Middle Araguaia floodplain, Brazil. Total mercury (THg) concentrations in litter were significantly higher (p < 0.0001) than that in soil, ranging from 10.68 ± 0.55 to 48.94 ± 0.13 and 20.80 ± 1.07 to 55 .19 ± 1.59 ng g-1, respectively. Total mercury concentration levels in soil showed a linear, inversely proportional relationship with soil organic matter (SOM) contents and soil pH, consistent with the geochemical behavior of chemical elements in flooded environments. Ten orders of organisms were identified, and the average THg concentrations determined in their bodies were up to 20 times higher than those in soil and litter. We found a significant linear relationship between the levels of THg in litter and those found in soil organisms, thereby allowing the prediction of THg concentration levels in soil organisms through the analysis of litter at the sample units. The different dynamics and feeding habits of soil organisms and the concentration of THg in these organisms may be influenced by the river's course. This study provides evidence of the bioaccumulation of THg in soil organisms in the floodplain of the Middle Araguaia River, an important river basin in the Brazilian savanna.

Enameloid-bound δ15 N reveals large trophic separation among Late Cretaceous sharks in the northern Gulf of Mexico.

The nitrogen isotopic composition (15 N/14 N ratio, or δ15 N) of enameloid-bound organic matter (δ15 NEB ) in shark teeth was recently developed to investigate the biogeochemistry and trophic structures (i.e., food webs) of the ancient ocean. Using δ15 NEB , we present the first nitrogen isotopic evidence for trophic differences between shark taxa from a single fossil locality. We analyze the teeth of four taxa (Meristodonoides, Ptychodus, Scapanorhynchus, and Squalicorax) from the Late Cretaceous (83-84 Ma) Trussells Creek site in Alabama, USA, and compare the N isotopic findings with predictions from tooth morphology, the traditional method for inferring shark paleo-diets. Our δ15 NEB data indicate two distinct trophic groups, with averages separated by 6.1 ± 2.1‰. The lower group consists of Meristodonoides and Ptychodus, and the higher group consists of Scapanorhynchus and Squalicorax (i.e., lamniforms). This δ15 NEB difference indicates a 1.5 ± 0.5 trophic-level separation between the two groups, a finding that is in line with paleontological predictions of a higher trophic level for these lamniforms over Meristodonoides and Ptychodus. However, the δ15 NEB of Meristodonoides is lower than suggested by tooth morphology, although consistent with mechanical tests suggesting that higher trophic-level bony fishes were not a major component of their diet. Further, δ15 NEB indicates that the two sampled lamniform taxa fed at similar trophic levels despite their different inferred tooth functions. These two findings suggest that tooth morphology alone may not always be a sufficient indicator of dietary niche. The large trophic separation revealed by the δ15 NEB offset leaves open the possibility that higher trophic-level lamniforms, such as those measured here, preyed upon smaller, lower trophic-level sharks like Meristodonoides.

Trophic ecology of Acestrorhynchus falcirostris Cuvier, 1819 in island lakes on the lower stretch of the Solimões River, Amazon Basin / Ecologia trófica de Acestrorhynchus falcirostris Cuvier, 1819 em lagos de ilha no trecho inferior do Rio Solimões, Bacia Amazônica

Abstract The aim objective of this study was to determine the trophic ecology of juvenile and adult Acestrorhynchus falcirostris during the rising and flood (high-water) period in six island lakes adjacent to the Solimões River. As such, we investigated: i) the trophic position, through the fractional trophic niche; ii) the niche breadth; iii) niche overlap and iv) the food strategy of the species. The specimens were collected during the years 2014 to 2017, using gillnets with mesh sizes ranging from 30 to 120mm between opposite knots. Through the analysis of stomach contents, the preference in the consumption of items of animal origin was observed. Juveniles consumed insects in greater proportions (IAi% = 50%), while adults consumed fish (IAi%=99,98%). Despite the large supply of food items available in the high-water period, juveniles were the only ones to consume items of allochthonous origin, such as insects. Juveniles presented a different dietary strategy and dietary composition to adults. Juveniles were omnivores with a generalist strategy, while adults were piscivores with a specialist strategy. Thus, the food composition, niche breadth, trophic position and feeding strategy of Acestrorhynchus falcirostris change due to the stage of development.

Resumo O objetivo deste estudo foi determinar a ecologia trófica de juvenis e adultos de Acestrorhynchus falcirostris durante o período de enchente e cheia em seis lagos de ilha adjacentes ao rio Solimões. Assim, investigamos: i) a posição trófica, através do nicho trófico fracional; ii) a largura de nicho; iii) sobreposição de nicho; iv) a estratégia alimentar. Os espécimes foram coletados durante os anos de 2014 a 2017, utilizando redes de emalhar com malha variando de 30 a 120mm entre nós opostos. Por meio da análise do conteúdo estomacal, observamos a preferência no consumo de itens de origem animal. Os juvenis consumiram insetos em maiores proporções (IAi% = 50%), enquanto os adultos consumiram preferencialmente peixes (IAi% = 99,98%). Apesar da grande oferta de alimentos disponíveis no período da cheia, os juvenis eram os únicos a consumir itens de origem alóctone, como por exemplo, os insetos. Os juvenis apresentaram uma estratégia alimentar e composição alimentar diferente para os adultos. Os juvenis foram considerados onívoros com uma estratégia generalista, enquanto os adultos foram considerados piscívoros com uma estratégia alimentar mais especialista. Assim, a composição alimentar, amplitude do nicho, posição trófica e a estratégia alimentar de Acestrorhynchus falcirostris muda em função do estágio de desenvolvimento.

Trophic ecology of Acestrorhynchus falcirostris Cuvier, 1819 in island lakes on the lower stretch of the Solimões River, Amazon Basin

Abstract The aim objective of this study was to determine the trophic ecology of juvenile and adult Acestrorhynchus falcirostris during the rising and flood (high-water) period in six island lakes adjacent to the Solimões River. As such, we investigated: i) the trophic position, through the fractional trophic niche; ii) the niche breadth; iii) niche overlap and iv) the food strategy of the species. The specimens were collected during the years 2014 to 2017, using gillnets with mesh sizes ranging from 30 to 120mm between opposite knots. Through the analysis of stomach contents, the preference in the consumption of items of animal origin was observed. Juveniles consumed insects in greater proportions (IAi% = 50%), while adults consumed fish (IAi%=99,98%). Despite the large supply of food items available in the high-water period, juveniles were the only ones to consume items of allochthonous origin, such as insects. Juveniles presented a different dietary strategy and dietary composition to adults. Juveniles were omnivores with a generalist strategy, while adults were piscivores with a specialist strategy. Thus, the food composition, niche breadth, trophic position and feeding strategy of Acestrorhynchus falcirostris change due to the stage of development.

Resumo O objetivo deste estudo foi determinar a ecologia trófica de juvenis e adultos de Acestrorhynchus falcirostris durante o período de enchente e cheia em seis lagos de ilha adjacentes ao rio Solimões. Assim, investigamos: i) a posição trófica, através do nicho trófico fracional; ii) a largura de nicho; iii) sobreposição de nicho; iv) a estratégia alimentar. Os espécimes foram coletados durante os anos de 2014 a 2017, utilizando redes de emalhar com malha variando de 30 a 120mm entre nós opostos. Por meio da análise do conteúdo estomacal, observamos a preferência no consumo de itens de origem animal. Os juvenis consumiram insetos em maiores proporções (IAi% = 50%), enquanto os adultos consumiram preferencialmente peixes (IAi% = 99,98%). Apesar da grande oferta de alimentos disponíveis no período da cheia, os juvenis eram os únicos a consumir itens de origem alóctone, como por exemplo, os insetos. Os juvenis apresentaram uma estratégia alimentar e composição alimentar diferente para os adultos. Os juvenis foram considerados onívoros com uma estratégia generalista, enquanto os adultos foram considerados piscívoros com uma estratégia alimentar mais especialista. Assim, a composição alimentar, amplitude do nicho, posição trófica e a estratégia alimentar de Acestrorhynchus falcirostris muda em função do estágio de desenvolvimento.

Community-scale relationships between body shape and trophic ecology in tropical demersal marine fish of northeast Brazil.

Functional morphology investigates the relationships between morphological characters and external factors, such as environmental, physical and ecological features. Here, we evaluate the functional relationships between body shape and trophic ecology of a tropical demersal marine fish community using geometric morphometrics techniques and modelling, hypothesizing that shape variables could partially explain fish trophic level. Fish were collected over the continental shelf of northeast Brazil (4-9°S). Analysed fish were distributed into 14 orders, 34 families and 72 species. Each individual was photographed in lateral view, and 18 landmarks were distributed along the body. A principal component analysis (PCA) applied on morphometric indices revealed that fish body elongation and fin base shape were the main axes of variation explaining the morphology. Low trophic levels (herbivore and omnivore) are characterized by deep bodies and longer dorsal and anal fin bases, while predators present elongated bodies and narrow fin bases. Fin position (dorsal and anal fins) on the fish body is another important factor contributing to (i) body stability at high velocity (top predators) or (ii) manoeuvrability (low trophic levels). Using multiple linear regression, we verified that 46% of trophic level variability could be explained by morphometric variables, with trophic level increasing with body elongation and size. Interestingly, intermediate trophic categories (e.g., low predators) presented morphological divergence for a given trophic level. Our results, which can likely be expanded to other tropical and nontropical systems, show that morphometric approaches can provide important insights into fish functional characteristics, especially in trophic ecology.

Effect of trophic position on mercury concentrations in bottlenose dolphins (Tursiops truncatus) from the northern Gulf of Mexico.

Marine species from the Gulf of Mexico often have higher mercury (Hg) concentrations than conspecifics in the Atlantic Ocean. Spatial differences in Hg sources, environmental conditions, and microbial communities influence both Hg methylation rates and the bioavailability of Hg to organisms at the base of the food web. Mercury bioaccumulates within organisms and biomagnifies in marine food webs, and therefore reaches the greatest concentrations in long-lived marine carnivores, such as dolphins. In this study, we explored whether differences in trophic position and foraging habitat among bottlenose dolphins (Tursiops truncatus) from the northern Gulf of Mexico (nGoM) contributed to the observed variation in skin total Hg (THg) concentrations. Using the δ13C and δ34S values in dolphin skin, we assigned deceased stranded dolphins from Florida (FL; n = 29) and Louisiana (LA; n = 72) to habitats (estuarine, barrier island, and coastal) east and west of the Mississippi River Delta (MRD). We estimated the mean trophic position of dolphins from each habitat using δ15N values from stranded dolphin skin and tissues of primary consumers taken from the literature following a Bayesian framework. Finally, we compared trophic positions and THg concentrations among dolphins from each habitat, accounting for sex and body length. Estimated marginal mean THg concentrations (µg/g dry weight) were greatest in dolphins assigned to the coastal habitat and estuarine habitats east of the MRD (range: 2.59-4.81), and lowest in dolphins assigned to estuarine and barrier island habitats west of the MRD (range: 0.675-0.993). On average, dolphins from habitats with greater THg concentrations also had higher estimated trophic positions, except for coastal dolphins. Our results suggest that differences in trophic positions and foraging habitats contribute to spatial variability in skin THg concentrations among nGoM bottlenose dolphins, however, the relative influence of these factors on THg concentrations are not easily partitioned.

Ontogenetic diet shifts of rough scad Trachurus lathami in the North Patagonian shelf (south-west Atlantic Ocean).

Rough scad Trachurus lathami is a key pelagic fish in the Argentinean continental shelf (ACS, south-west Atlantic Ocean), with recent increases in abundance. It is a main prey of fishes and marine mammals, and shares the environment with commercially relevant pelagic species (Engraulis anchoita and Scomber colias), playing an important role linking lower and upper trophic levels in the ecosystem. This study aims to determine the ontogenetic changes in the diet composition, feeding strategy, trophic niche breadth and trophic level of T. lathami in the North Patagonian Shelf (43°-45°30'S). The stomach contents of adult fish (n = 238) were analysed. The results suggest a clear ontogenetic shift in the diet at a size of ~190 mm. Smaller individuals (160-190 mm) were specialized on misidaceans, and showed the highest trophic level, while larger T. lathami (221-230 mm) consumed decapods (Peisos petrunkevitchi) and teleosts (eggs and larvae). Trophic niche breadth was higher at the medium-sized class (191-220 mm), which mainly preyed on copepods (Calanoides carinatus) and chaetognaths (Sagitta spp.), evidencing a more diverse diet and a rather generalist strategy. Updated information on the trophic ecology of T. lathami evidences its extremely plastic feeding behaviour, being able to adapt its trophic niche to the most readily available food items from the mesopelagic community.

What fisher diets reveal about fish stocks.

Tracking fish consumption could provide additional information on changes to fish stocks, one of the planet's main protein sources. We used data on seafood consumption in fishing villages in Brazil over time to test for changes in: species richness, diversity, and composition, fish size and trophic levels, consumption of endangered species, and functional diversity (namely, species with different behavioral and habitat preferences). Our results demonstrate the potential to include this additional data source to complement fisheries data, especially in data-poor countries. With respect to Brazil specifically, we identified a decrease in both the average trophic level and size of the species consumed. While the consumption of endangered species had always been low, most of these species changed over time, thereby suggesting that many, especially elasmobranchs, may have become rare on the plates. Although it may be hard to fully isolate cultural changes from biodiversity changes when it comes to analyzing consumption data, by examining diets it is possible to identify aspects worth investigating further, such as, whether the decrease in dietary trophic levels mirrors a decrease in environmental trophic levels. In places where fisheries data are either inexistent or limited, diet track surveys, such as household expenditure programs, can help trace the changes caused by fisheries in stocks and habitats.

Feeding habits of Urotrygon microphthalmum (Myliobatiformes: Urotrygonidae) caught off northeastern Brazil

The feeding habits of Urotrygon microphthalmum, a Critically Endangered (CR) species, were investigated through stomach contents analysis from specimens caught on bottom double rigged otter trawls in Pernambuco state, Brazil, between March of 2010 and March of 2012. A total of 338 stomachs were analyzed, and 31 food items were identified in the diet of U. microphthalmum. The species ingests mainly shrimps. The diets between males and females were not different, and an ontogenetic diet shift was not observed. The estimated species' trophic level is 3.5, classifying it as a secondary order consumer.(AU)

Os hábitos alimentares de Urotrygon microphthalmum, uma espécie Criticamente Em Perigo (CR), foram investigados através de análise de conteúdo estomacal de espécimes capturados no arrasto duplo com portas no estado de Pernambuco, Brasil, entre março de 2010 e março de 2012. Um total de 338 estômagos foram analisados e 31 item alimentares foram identificados na dieta de U. microphthalmum. A espécie ingere principalmente camarões. A dieta entre machos e fêmeas não foi diferente e não foi observada mudança ontogenética na dieta. O nível trófico estimado da espécie é 3,5, classificando-a como consumidora de segunda ordem.(AU)

Feeding habits of Urotrygon microphthalmum (Myliobatiformes: Urotrygonidae) caught off northeastern Brazil

The feeding habits of Urotrygon microphthalmum, a Critically Endangered (CR) species, were investigated through stomach contents analysis from specimens caught on bottom double rigged otter trawls in Pernambuco state, Brazil, between March of 2010 and March of 2012. A total of 338 stomachs were analyzed, and 31 food items were identified in the diet of U. microphthalmum. The species ingests mainly shrimps. The diets between males and females were not different, and an ontogenetic diet shift was not observed. The estimated species' trophic level is 3.5, classifying it as a secondary order consumer.(AU)

Os hábitos alimentares de Urotrygon microphthalmum, uma espécie Criticamente Em Perigo (CR), foram investigados através de análise de conteúdo estomacal de espécimes capturados no arrasto duplo com portas no estado de Pernambuco, Brasil, entre março de 2010 e março de 2012. Um total de 338 estômagos foram analisados e 31 item alimentares foram identificados na dieta de U. microphthalmum. A espécie ingere principalmente camarões. A dieta entre machos e fêmeas não foi diferente e não foi observada mudança ontogenética na dieta. O nível trófico estimado da espécie é 3,5, classificando-a como consumidora de segunda ordem.(AU)

Biología alimentaria de Prochilodus mariae durante la primera fase de crecimiento / The Prochilodus mariae feeding habits during their first growth phase / Biología alimentar de Prochilodus mariae durante a primeira fase de crescimento

Resumen Entre los más importantes peces del río Meta se encuentra Prochilodus mariae (bocachico llanero o coporo), tanto por su mayor tamaño dentro de los bocachicos de la cuenca, como por su aporte a la biomasa trófica y de las pesquerías de la región. En el presente trabajo se evaluó el régimen alimenticio de poslarvas (inicio de la alimentación exógena) del coporo Prochilodus mariae, hasta el inicio de la fase de alevino (aletas completas y cuerpo con escamas), en condiciones simuladas durante los primeros 30 días de alimentación exógena. Los estanques en tierra del IALL, asignados para el desarrollo de este trabajo, fueron abonados orgánicamente con (bovinaza y heno) teniendo en cuenta las condiciones que suceden cada año, a las entradas de aguas en las áreas de inundación de los afluentes, los que fueron sembrados con larvas obtenidas por reproducción inducida a densidad de veinte larvas / m2 y con el 80% de su saco vitelino absorbido. Cada dos días, durante 30 días, a las 8:00 h, fueron colectadas poslarvas junto con las muestras de zooplantcton y fitoplancton y fijados en formol bufferado al 4%. Los índices de frecuencia (IF) de los contenidos estomacales de siete poslarvas/estanque y los ítems alimenticios como oferta hallados en aguas y perifiton fueron evaluados. Los análisis se realizaron con un total de 156 ejemplares que oscilan entre intervalos de 6-8.99; 9-17.99; 18-26.99; 27-35.99; 36-44.99; 45-47.99 mm de longitud total. Las poslarvas del primer intervalo exploran organismos relacionados con el perifiton principalmente bacterias, protozoos y algas en este primer muestreo se caracterizó porque el 66.7% de las poslarvas presentaron estómagos vacíos. En las poslarvas del segundo intervalo el IF de los contenidos mostró una tendencia por el consumo de organismos pelágicos con preferencia por los cladóceros. En el último intervalo los alevinos inician el consumo de detritos (materia orgánica particulada, bacterias, hongos) y otras formas del fitoplancton cercano a las paredes y fondo del estanque.

Abstract Prochilodus mariae (bocachico llanero or coporo) is amongst the most important fish in the Meta River (a major left tributary of the Orinoco River); along with being the largest of the Prochilodus species in the river basin, flannel-mouth characiforms contribute greatly to the dynamics of the region's food chain and fisheries. This work was aimed at assessing Prochilodus mariae post-larvae feeding habits during their first thirty days of exogenous feeding until the beginning of the alevin stage. Simulations were made in the Instituto de Acuicultura de los Llanos (IALL) facilities' earthen fish ponds to closely resemble the fishes' natural annual water and feeding conditions. The ponds had been organically fertilised with cattle manure and hay and were then periodically inundated and drained to simulate the Meta River's tributaries natural/annual floodplains or areas that are periodically inundated by high water levels. The ponds were stocked with larvae obtained by artificial spawning at twenty larvae/m2 density when around 80% of their yolk sacs had been absorbed. Post-larvae and pond water samples containing zooplankton and phytoplankton were collected at 8 am every other day for 30 days and fixed in 4% buffered formalin. Seven post-larvae/pond stomach/gut contents (frequency of fullness index - FI) were analysed from 156 specimens divided into size intervals ranging from 6-8.99, 9-17.99, 18-26.99, 27-35.99, 36-44.99 and 45-47.99 mm in length. Food items' frequency of abundance (i.e. supply) in the pond water and periphyton were estimated. First-size interval post-larvae explore periphyton-related organisms for their food source (mainly bacteria, protozoans and algae). This first sampling was characterised by 66.7% of the post-larvae having empty stomachs. Second-size interval post-larvae FI tended reflect the consumption of pelagic organisms, having a preference for microcrustaceans (cladocerans and copepods). The longest alevins (45-47.99 mm long) started consuming detritus (particulate organic matter, bacteria and fungi) and other forms of phytoplankton close to the sides and bottom of the fishponds.

Resumo Entre os peixes mais importantes do rio Meta encontra-se Prochilodus mariae (bocachico llanero ou coporo), devido a ser dos maiores bocachicos da bacia, assim como a sua contribuição para a biomassa trófica e pesca da região. O presente trabalho pretende avaliar a dieta das pós-larvas do coporo Prochilodus mariae, até ao início da fase de alevinos em condições simuladas durante os primeiros trinta dias de alimentação exógena. Os estanques do IALL destinados ao desenvolvimento deste trabalho, foram fertilizados organicamente com (esterco bovino e feno) atendendo às condições que ocorrem a cada ano, na entrada de água nas áreas de alagamento dos afluentes, que foram semeados com larvas obtidas por reprodução induzida na densidade de vinte larvas / m2 e com 80% do saco vitelino absorvido. A cada dois dias, durante 30 dias, às 8:00 da manhã, as pós-larvas eram recolhidas juntamente com a água, e fixadas em formalina tamponada a 4%. Foram avaliados os índices de frequência (IF) do conteúdo estomacal de sete pós-larvas/tanque e itens alimentares encontrados nas águas e perifiton. As análises foram realizadas com um total de 156 espécimes entre 6-8,99; 9-17,99; 18-26,99; 27-35:99; 36-44,99; 45-47,99mm de comprimento total. As pós-larvas do primeiro intervalo exploram organismos relacionados com o perifiton principalmente bactérias, protozoários e algas, esta primeira amostragem foi caracterizada porque 66,7% das pós-larvas apresentavam estômagos vazios. Nas pós-larvas do segundo intervalo o IF do conteúdo estomacal mostrou uma tendência para o consumo de organismos pelágicos com preferência pelos cladóceros. No último intervalo, os alevinos começam a consumir detritos (partículas orgânicas, bactérias, fungos) e formas de fitoplâncton ligadas às superfícies do substrato (feno) e ao fundo do tanque.

Hábitos alimenticios de Caranx vinctus (Perciformes: Carangidae), especie de importancia comercial en la bahía de Acapulco, Guerrero, México / Feeding habits of Caranx vinctus (Perciformes: Carangidae), a commercially important species in Acapulco Bay, Guerrero

Introducción: Caranx vinctus es una especie importante en las pesquerías locales, utilizada como fuente de proteína para el consumo humano, sin embargo, su ecología trófica es poco conocida en las costas de Pacífico mexicano. Objetivo: Conocer los hábitos alimenticios de C. vinctus. Metodología: Se analizaron los contenidos estomacales de 268 ejemplares, capturados mediante el arte de pesca, chinchorro playero, en la sociedad cooperativa Playa las Hamacas, en la Bahía de Acapulco, Guerrero, México. Se aplicó el índice de importancia relativa específica de la presa (% PSIRI) para determinar las principales categorías alimenticias (ítems). La amplitud de la dieta se calculó utilizando el índice de Levin. Las posibles diferencias en la dieta por sexo, madurez sexual o temporada se identificaron a través del índice Morisita Horn y un análisis multivariado ANOSIM. Resultados: Los principales ítems fueron crustáceos representados principalmente por larvas megalopa de Portunoidae (16.51 %), Teleostei (12.7 %), materia orgánica no identificada (11.2 %), y Anchoa ischana (10.6 %) El índice de Levin indica baja amplitud del nicho trófico (Bi = 0.29) por lo que se le puede considerar como un depredador especialista con marcadas preferencias hacia algunos tipos alimentarios. El índice de Morisita Horn indicó que, se presentó un traslape entre las dietas por sexo (hembras y machos Cλ = 0.84), pero no entre madurez sexual (Juveniles y adultos Cλ = 0.56) y temporadas (Lluvias y secas Cλ = 0.03). Un análisis ANOSIM indicó que había diferencias significativas en la dieta de C. vinctus por sexo, madurez sexual y temporada. Conclusión: Se estableció que de manera general C. vinctus es una especie zooplantófaga e ictiófaga (Nivel Trófico = 3.39).

Abtract Introduction: Caranx vinctus is an important species in local fisheries, used as a source of protein for human consumption, however, its trophic ecology is little known on the Mexican Pacific coast. Objective: Know the feeding habits of C. vinctus. Methods: The stomach contents of 268 specimens, captured beach nets, in the Playa Las Hamacas cooperative society, in Acapulco Bay, Guerrero, Mexico, their food items were analyzed. The prey-specific index of relative importance (% PSIRI) was applied to determine the main food categories (breadth was calculated using Levin's index. Possible differences in the diet by sex, sexual maturity, or season were identified through Morisita Horn index and a multivariate ANOSIM analysis. Results: Crustaceans mainly represented by megalopa larvae of Portunoidae (16.51 %), Teleostei (12.7 %), unidentified organic matter (11.2 %), and Anchoa ischana (10.6 %) were the most important food items. The Levin index indicates low amplitude of the trophic niche (Bi = 0.29) so C. vinctus can be considered as a specialist predator with marked preferences towards some food items. The Morisita Horn index indicated that there was an overlap between sexes (females and males Cλ = 0.84), but not between sexual maturity (Juveniles and adults Cλ = 0.56) and seasons (Rainy and dry Cλ = 0.03). ANOSIM analysis indicated that there were significant differences in the diet of C. vinctus by sex, sexual maturity, and season. Conclusion: It was established that in general C. vinctus is a zoplantophage and ichthophagus species (Trophic Level = 3.39).

Feeding habits of the cockfish, Callorhinchus callorynchus (Holocephali: Callorhinchidae) from off northern Argentina

The feeding habits of Callorhinchus callorynchus were investigated in coastal waters off northern Argentina. The effect of body size, seasons and regions was evaluated on female diet composition using a multiple-hypothesis modelling approach. Callorhinchus callorynchus fed mainly on bivalves (55.61% PSIRI), followed by brachyuran crabs (10.62% PSIRI) and isopods (10.13% PSIRI). Callorhinchus callorynchus females showed changes in the diet composition with increasing body size and also between seasons and regions. Further, this species is able to consume larger bivalves as it grows. Trophic level was 3.15, characterizing it as a secondary consumer. We conclude that C. callorynchus showed a behavior of crushing hard prey, mainly on bivalves, brachyuran, gastropods and anomuran crabs. Females of this species shift their diet with increasing body size and in response to seasonal and regional changes in prey abundance or distribution.(AU)

Los hábitos alimentarios de Callorhinchus callorynchus fueron investigados en las aguas costeras del norte de Argentina. Se evaluó el efecto del tamaño del cuerpo, la temporada y la región sobre la composición de la dieta de las hembras mediante un enfoque de modelado de múltiples hipótesis. Callorhinchus callorynchus se alimentó principalmente de bivalvos (55,61% PSIRI), seguido de cangrejos brachyuras (10,62% PSIRI) y de isópodos (10,13% PSIRI). Las hembras de C. callorynchus presentaron cambios en la dieta con incremento del tamaño del cuerpo, la temporada y la región. Además, esta especie es capaz de consumir bivalvos de mayor tamaño a medida que incrementa el tamaño del cuerpo. El nivel trófico fue calculado en 3,15, caracterizando a esta especie como un consumidor secundario. Concluimos que C. callorynchus presentó un comportamiento de triturador de presas duras, principalmente bivalvos, cangrejos y gasterópodos. Las hembras de esta especie cambian su dieta con el incremento del tamaño del cuerpo y en respuesta a cambios temporales y regionales en la abundancia y distribución de sus presas.(AU)

Feeding habits of the cockfish, Callorhinchus callorynchus (Holocephali: Callorhinchidae) from off northern Argentina

The feeding habits of Callorhinchus callorynchus were investigated in coastal waters off northern Argentina. The effect of body size, seasons and regions was evaluated on female diet composition using a multiple-hypothesis modelling approach. Callorhinchus callorynchus fed mainly on bivalves (55.61% PSIRI), followed by brachyuran crabs (10.62% PSIRI) and isopods (10.13% PSIRI). Callorhinchus callorynchus females showed changes in the diet composition with increasing body size and also between seasons and regions. Further, this species is able to consume larger bivalves as it grows. Trophic level was 3.15, characterizing it as a secondary consumer. We conclude that C. callorynchus showed a behavior of crushing hard prey, mainly on bivalves, brachyuran, gastropods and anomuran crabs. Females of this species shift their diet with increasing body size and in response to seasonal and regional changes in prey abundance or distribution.(AU)

RESUMEN Los hábitos alimentarios de Callorhinchus callorynchus fueron investigados en las aguas costeras del norte de Argentina. Se evaluó el efecto del tamaño del cuerpo, la temporada y la región sobre la composición de la dieta de las hembras mediante un enfoque de modelado de múltiples hipótesis. Callorhinchus callorynchus se alimentó principalmente de bivalvos (55,61% PSIRI), seguido de cangrejos brachyuras (10,62% PSIRI) y de isópodos (10,13% PSIRI). Las hembras de C. callorynchus presentaron cambios en la dieta con incremento del tamaño del cuerpo, la temporada y la región. Además, esta especie es capaz de consumir bivalvos de mayor tamaño a medida que incrementa el tamaño del cuerpo. El nivel trófico fue calculado en 3,15, caracterizando a esta especie como un consumidor secundario. Concluimos que C. callorynchus presentó un comportamiento de triturador de presas duras, principalmente bivalvos, cangrejos y gasterópodos. Las hembras de esta especie cambian su dieta con el incremento del tamaño del cuerpo y en respuesta a cambios temporales y regionales en la abundancia y distribución de sus presas.(AU)

Feeding habits of the fishes Euthynnus lineatus and Scomberomorus sierra (Perciformes: Scombridae) in the Eastern Tropical Pacific / Hábitos alimentarios de los peces Euthynnus lineatus y Scomberomorus sierra (Perciformes: Scombridae) en el Pacífico Tropical Oriental

Introduction: Black skipjack, Euthynnus lineatus, and Pacific sierra, Scomberomorus sierra, are of great economic importance in the small-scale fishery of the Tropical Eastern Pacific and in particular in the study area. Objectives: The objectives of the present study were to assess the diet components of E. lineatus and S. sierra, as well as to evaluate the niche width, trophic level, and trophic overlap between the two species, by size and season. Methods: Biological samples were obtained weekly from small-scale fishery catches in Bahía de Acapulco, Mexico. The E. lineatus sampling period occurred from October 2016 to October 2017, whereas S. sierra was sampled from October 2016 to June 2018. The Prey-specific Index of Relative Importance (% PSIRI) was used to evaluate the importance of each prey item in the diet of the predator. Levin´s index (Bi) was used as a measure of niche width. The Morisita-Horn index was used to evaluate diet overlap by size (juveniles or adults), by season (dry or wet), and between the two species. The trophic level (TL) of predators was calculated using the Cortés´ method. Results: A total of 262 E. lineatus stomachs were analyzed (42 % were empty and 58 % contained food) and a total of 209 S. sierra stomachs were analyzed (74.6 % were empty and 25.3 % contained food). Of the total E. lineatus specimens sampled, 107 were juveniles and 155 were adults. Black skipjack juveniles fed on five food items and adults fed on 13 food items. Of the total S. sierra specimens sampled, 75 were juveniles and 134 were adults. Pacific sierra juveniles and adults fed on five food items. The diet of the two species comprised fish, mollusks, and crustaceans. The two species showed narrow niche width. The diet of juvenile and adult E. lineatus presented differences with growth, contrary to what was observed for juveniles and adults of S. sierra. There were no significant differences in diet by season for both species. The trophic overlap obtained between the two species was low. The trophic level calculated for both species indicated that are tertiary consumers. Conclusions: Black skipjack and Pacific sierra are tertiary predators and present a specialist behavior, feeding mainly on fish from the families Engraulidae and Clupeidae. Although a degree of similarity in the dietary food components of these species was observed, there was not a high degree of interspecific competition for food.

Introducción: El barrilete negro, Euthynnus lineatus, y la sierra del Pacífico, Scomberomorus sierra, son peces que presentan gran importancia económica en la pesca artesanal del Pacífico Tropical Oriental y de manera particular en el área de estudio. Objetivos: Los objetivos del presente trabajo son determinar los componentes alimentarios de la dieta de E. lineatus y S. sierra, así como determinar la amplitud del nicho, el nivel trófico y el traslape trófico entre ambas especies, por tallas y por temporada climática. Métodos: Las muestras biológicas se obtuvieron semanalmente de las capturas realizadas por las pesquerías de pequeña escala llevadas a cabo en la Bahía de Acapulco. El periodo de muestreo de E. lineatus se realizó desde octubre 2016 hasta octubre 2017, mientras que el de S. sierra de octubre 2016 hasta junio 2018. El Índice de Importancia Relativa Específica de la Presa (% PSIRI) se usó para evaluar la importancia de cada ítem presa en la dieta del depredador; el índice de Levin (Bi) se usó como una medida de la amplitud del nicho; el índice de Morisita-Horn se usó para evaluar el traslape entre las dietas por talla (juveniles y adultos), por temporada climática (seca y lluviosa) y entre las dos especies. El nivel trófico (TL) de los depredadores fue calculado usando el método de Cortés. Resultados: Se analizaron en total 262 estómagos de E. lineatus (42 % vacíos y 58 % con alimento) y 209 estómagos de S. sierra (74.6 % vacíos y 25.3 % con alimento). Del total de organismos muestreados de E. lineatus, 107 se consideraron organismos jóvenes y 155 adultos. Los jóvenes de barrilete se alimentaron de 5 ítems alimentarios y los adultos se alimentaron de 13. En el caso de S. sierra, 75 organismos se consideraron jóvenes y 134 adultos. Los jóvenes y adultos de sierra se alimentaron de cinco ítems alimentarios. La dieta de ambas especies se compone por peces, moluscos y crustáceos. Las dos especies presentaron una amplitud del nicho trófico estrecho. La dieta de jóvenes y adultos de E. lineatus presentó diferencias alimentarias de acuerdo con su crecimiento, contrario a lo observado entre jóvenes y adultos de S. sierra. Entre temporadas climáticas, la dieta no presentó variaciones significativas en ambas especies. Asimismo, el valor de traslape trófico obtenido entre ambas especies fue bajo. El nivel trófico determinado para ambas especies indicó que son consumidores terciarios. Conclusiones: El barrilete negro Euthynnus lineatus y la sierra del Pacifico Scomberomorus sierra son depredadores terciarios y presentan un comportamiento especialista, principalmente sobre peces de las familias Engraulidae y Clupeidae. Aunque se observó una similitud en los componentes alimentarios de estas especies, no existe un alto grado de competencia interespecífica por el alimento.

Species richness and functional structure of fish assemblages in three freshwater habitats: effects of environmental factors and management.

In this study, the inverted trophic hypothesis was tested in the freshwater fish communities of a reservoir. The distribution of fish species in three freshwater habitats in the Jurumirim Reservoir, Brazil, was examined using both species richness and the relative proportions of different trophic groups. These groups were used as a proxy for functional structure in an attempt to test the ability of these measures to assess fish diversity. Assemblage structures were first described using non-metric multidimensional scaling (NMDS). The influence of environmental conditions for multiple fish assemblage response variables (richness, total abundance and abundance per trophic group) was tested using generalised linear mixed models (GLMM). The metric typically employed to describe diversity; that is, species richness, was not related to environmental conditions. However, absolute species abundance was relatively well explained with up to 54% of the variation in the observed data accounted for. Differences in the dominance of trophic groups were most apparent in response to the presence of introduced fish species: the iliophagous and piscivorous trophic groups were positively associated, while detritivores and herbivores were negatively associated, with the alien species. This suggests that monitoring functional diversity might be more valuable than species diversity for assessing effects of disturbances and managements policies on the fish community.

First evidence of microplastic ingestion by fishes from the Amazon River estuary.

This study investigated occurrence of microplastic particles in digestive tracts of fishes from the Amazon River estuary. A total of 189 fish specimens representing 46 species from 22 families was sampled from bycatch of the shrimp fishery. Microplastic particles removed from fish gastrointestinal tracts were identified using Attenuated Total Reflectance - Fourier Transform Infrared (ATR-FTIR). In total, 228 microplastic particles were removed from gastrointestinal tracts of 26 specimens representing 14 species (30% of those examined). Microplastic particles were categorized as pellets (97.4%), sheets (1.3%), fragments (0.4%) and threads (0.9%), with size ranging from 0.38 to 4.16 mm. There was a positive correlation between fish standard length and number of particles found in gastrointestinal tracts. The main polymers identified by ATR-FTIR were polyamide, rayon and polyethylene. These findings provide the first evidence of microplastic contamination of biota from the Amazon estuary and northern coast of Brazil.

Patterns of the parasite communities in a fish assemblage of a river in the Brazilian Amazon region.

This paper characterizes the pattern of ectoparasite and endoparasite communities in an assemblage of 35 sympatric fish from different trophic levels in a tributary from the Amazon River system, northern Brazil. In detritivorous, carnivorous, omnivorous and piscivorous hosts, the species richness consisted of 82 ectoparasites and endoparasites, but protozoan ectoparasites such as Ichthyophthirius multifiliis, Piscinoodinium pillulare and Tripartiella sp. were dominant species predominated, such that they were present in 80% of the hosts. The taxon richness was in the following order: Monogenea > Nematoda > Digenea > Crustacea > Protozoa > Acanthocephala = Cestoda > Hirudinea. Among the hosts, the highest number of parasitic associations occurred in Satanoperca jurupari, Aequidens tetramerus, Hoplerythrinus unitaeniatus, Hoplosternum littorale, Cichlasoma amazonarum, Chaetobranchus flavescens, Squaliforma emarginata, Chaetobranchopsis orbicularis and Hoplias malabaricus. A weak positive correlation between ectoparasite abundance and length of the hosts was observed. Ectoparasite communities of detritivorous, carnivorous and omnivorous hosts were similar, but these differed from the communities of piscivorous hosts. Larval endoparasite species with low host specificity were the main determinants of the parasite infracommunity structure of the fish assemblage. Fish assemblage had few species of helminth that were specialist endoparasites, while many were parasites at the larval stage, infecting intermediate and paratenic hosts. Finally, carnivorous and omnivorous hosts harbored endoparasite communities that were more heterogeneous than those of detritivorous and piscivorous hosts. This result lends supports to the notion that the feeding habits of the host species are a significant factor in determining the endoparasites fauna.

Eating down the food chain: generalism is not an evolutionary dead end for herbivores.

The role of trophic specialisation in taxonomic diversification remains unclear. Plant specialists diversify faster than omnivores and animalivores, but at shorter macroevolutionary scales this pattern sometimes reverses. Here, we estimate the effect of diet diversification on speciation rates in noctilionoid bats, controlling for tree shape, rate heterogeneity and macroevolutionary regimes. We hypothesise that niche subdivision among herbivores positively relates to speciation rates, differing between macroevolutionary regimes. We found the rate at which new herbivorous lineages originate decreases as rates of diet evolution increase. Herbivores experience higher speciation rates, but generalist herbivores and predominantly herbivorous omnivores speciate faster than specialised herbivores, omnivores and animalivores. Generalised herbivory is not a dead end. We show that analysing ecological traits and diversification requires accounting for macroevolutionary regimes and within- and between-clade variation in evolutionary rates. Our approach overcomes the high false-positive rates of other methods and illuminates the roles of herbivory and specialisation in speciation.

Ecosystem indicators of a small-scale fisheries with limited data in Madeira River (Brazil) / Indicadores ecossistêmicos de uma pesca de pequena escala com dados limitados no rio Madeira (Brasil)

This work presents an indicators-based analysis of a small-scale fishery operating in the middle Madeira River (Brazil), a tributary of Amazon River. We used landing species (kg) recorded daily by the Porto Velho fishermen’s colony from 1990 to 2009, with total length recorded in five selected years. The species were classified by trophic level, and the Fishing-in-Balance, L index, and size class distributions were calculated. In addition, differences in yearly total landings (kg) were correlated with the Madeira river water level (cm). The average annual catch was 566.5 tonnes (± 193.6), with significant variation between the years not correlated to the river water level. The ecosystem indicators showed a stable tendency, with oscillations in the latter years reflecting an increased catch of higher trophic level and larger species. Fisheries managers in data-limited regions should consider these indicators for fish stock analyses to be low cost, practical, and easy to calculate.

Este trabalho apresenta uma análise baseada em indicadores para pesca de pequena escala que opera no médio rio Madeira (Brasil), afluente do rio Amazonas. Foram utilizados dados de desembarques diários da Colônia de Pescadores de Porto Velho que registrou a produção das espécies (kg) capturadas entre 1990 e 2009 e o comprimento total durante cinco anos. As espécies foram classificadas por nível trófico, e foram calculados o balanço na pesca, índice L e as classes de tamanho. Além disso, as diferenças nos desembarques totais anuais (kg) foram correlacionadas com o nível da água do rio Madeira (cm). A captura anual média foi de 566,5 toneladas (± 193,6), com variação significativa entre os anos e não correlacionadas com o nível da água do rio. Os indicadores do ecossistema mostraram uma tendência estável, com oscilações nos últimos anos, refletindo maior captura de espécies com maiores comprimentos e nível trófico. Os gestores de pesca em regiões com dados pesqueiros limitados podem considerar esses indicadores para análises de estoque de peixes como de baixo custo, práticos e fáceis de calcular.