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.

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.

Food deprivation does not affect growth performance of juvenile tambacu / Privação alimentar não afeta o crescimento de juvenis de tambacu

The objective of this study was to evaluate the efficiency of food deprivation on the growth performance of the commercially important hybrid fish tambacu (Piaractus mesopotamicus male × Colossoma macropomum female). For this, 171 juveniles of average length 8 cm and 11.4 g body mass were distributed in nine tanks, and allocated to three treatments: the fish were fed every day (control), fed for six days followed by one day of food deprivation (6F/1D) and fed for five days followed by two days of food deprivation (5F/2D). After 77 days, all animals achieved similar growth rates. Only animals submitted to two days of food deprivation presented hyperphagia. There was a reduction in total feed consumption of 3.8% and 10.8% for the 6F/1D and 5F/2D treatments, respectively. Our results suggest that juvenile tambacu exhibit total compensatory growth when submitted to food deprivation, and that a two-day deprivation could significantly reduce production costs for tambacu farmers.

O objetivo do estudo foi avaliar a eficiência da privação alimentar sobre o desempenho zootécnico de tambacu (Piaractus mesopotamicus x Colossoma macropomum). Para isso, 171 animais (massa: 11,4 ± 1.5 g; comprimento total: 8.0 ± 0.4 cm) foram alocados em nove tanques (19 peixes/tanque; n=3). Os peixes foram alimentados todos os dias (controle), alimentados durante seis dias seguidos de um dia de privação alimentar (6F/1D) e durante cinco dias seguidos de dois dias de privação alimentar (5F/2D). Após 77 dias, todos os animais alcançaram índices de crescimento similares. Somente os animais submetidos a dois dias de privação apresentaram hiperfagia. Houve redução do consumo total de ração em 3,8 e 10,8% para os tratamentos 6F/1D e 5F/2D, respectivamente. Os nossos resultados demonstram que os juvenis de tambacu exibiram crescimento compensatório total quando submetidos a privação alimentar, e a estratégia de 2 dias de privação alimentar pode reduzir significativamente os custos de produção de tambacu.

Fortifying pork liver mixture: Evaluation of protein quality and iron bioavailability - Part 2 / Mistura fortificadora a base de fígado suíno: avaliação da qualidade protéica e da biodisponibilidade de ferro - Parte 2

ABSTRACT Objective To evaluate the protein quality and iron bioavailability of a fortifying mixture based on pork liver. Methods Determinations of protein efficiency ratio, net protein utilization, true digestibility and hemoglobin regeneration efficiency by depletion and repletion were performed. In the depletion phase, the animals (male Wistar rats) received an iron-free AIN-93G diet and in the repletion phase they received the following diets: standard AIN-93G diet, fortifying mixture and standard diet containing heptahydrated ferrous sulfate for comparison. Results For standard AIN-93G diet and fortifying mixture the results were 3.75 and 4.04 for protein efficiency ratio and 3.53 and 3.63 for net protein retention, showing that the presence of pork liver in the diet promoted an increase in protein efficiency ratio and net protein retention (not statistically significant). True digestibility results obtained with the fortifying mixture (97.16%) were higher than those obtained with the standard AIN-93G diet (casein), but without significant difference. The hemoglobin regeneration efficiency values obtained for standard AIN-93G diet, fortifying mixture and standard diet containing heptahydrated ferrous sulfate were 50.69, 31.96 and 29.96%, respectively, showing a statistically significant difference between the control (standard AIN-93G diet) and test (fortifying mixture and standard diet containing heptahydrated ferrous sulfate) samples, but not between the test samples. Conclusion The fortifying mixture showed a high protein efficiency ratio value of 4.04 and a high relative biological value (108%) and it can be added to soups, creams and meats in day-care centers for the prevention of iron-deficiency in children of school age.

RESUMO Objetivo Avaliar a qualidade protéica e a biodisponibilidade de ferro de uma mistura fortificadora a base de fígado suíno. Métodos Foram determinados coeficiente de eficácia protéica, retenção protéica líquida, digestibilidade verdadeira e de eficiência da regeneração de hemoglobina (depleção e repleção). Na fase de depleção os animais (ratos da linhagem Wistar) receberam dieta (AIN-93G) isenta de ferro e na fase de repleção receberam as dietas: padrão AIN-93G (dietas padrão AIN-93G), mistura fortificadora e dieta-padrão com sulfato ferroso heptahidratado para comparação. Resultados Para dietas padrão AIN-93G e mistura fortificadora os resultados foram respectivamente 3,75 e 4,04 para coeficiente de eficácia protéica e 3,53 e 3,63 para retenção protéica líquida mostrando que a presença de fígado suíno promoveu aumento dos valores de coeficiente de eficácia protéica e retenção protéica líquida (sem diferença estatística). Resultados de digestibilidade verdadeira obtidos com a dieta mistura fortificadora (97,16%) foram maiores do que os obtidos com a dietas padrão AIN-93G (caseína), também sem diferença estatística. Os resultados de eficiência da regeneração de hemoglobina para dietas padrão AIN-93G, mistura fortificadora e sulfato ferroso heptahidratado foram respectivamente 50,69; 31,96 e 29,96% apresentando diferença estatística significativa entre a amostra controle (dietas padrão AIN-93G) e as amostras testes (mistura fortificadora e sulfato ferroso heptahidratado), porém não entre as amostras testes. Conclusão A mistura fortificadora se mostrou com alto coeficiente de eficácia protéica (4,04) e alto valor biológico relativo (108%) podendo ser adicionada às sopas, cremes, carnes em creches na prevenção e controle da anemia ferropriva em crianças em idade escolar.

The partitioning of food resources between two rodents in the subtropical region of southern Brazil

ABSTRACT The capybara (Hydrochoerus hydrochaeris) and nutria (Myocastor coypus) are herbivorous semi-aquatic rodents. Although these rodents occur in sympatry in southern South America, little is known about how the two species interact in relationship to food resources. In this context, the aim of this study was to analyze the food resource overlap, the feeding strategy and the diversity of the diet of capybaras and nutria. A micro-histological analysis of feces was used to study the diets. A total of 48 plant species belonging to 10 families were identified in the diet of H. hydrochaeris, and a total of 49 species belonging to 14 families were identified in the diet of M. coypus. According to the Amundsen graphical method, both rodents adopted a specialized strategy for feeding on Poaceae and a generalized strategy for other families. The results of a multivariate analysis of the dietary data showed significant differences between the two rodent species and among the seasons. These differences between diets may be related to the different proportions of each food item eaten. However, the dietary overlap between the two rodents in the Taim wetland was high, suggesting that partitioning of other resources ensured the coexistence of the species.

Feeding habits of billfishes (Carangaria: Istiophoriformes) in the Ecuadorian Pacific Ocean

The feeding habits of Makaira nigricans, Kajikia audax, Istiophorus platypterus (Istiophoridae), and Xiphias gladius (Xiphiidae) in the southeast Pacific Ocean were examined in Manta and Santa Rosa, Ecuador. This study describes the diets of these billfish species, evaluates dietary differences between species, and assesses seasonal differences in diet. A total of 274 M. nigricans, 321 K. audax, 267 I. platypterus, and 252 X. gladius were collected between February 2014 and April 2015. The scombrid Auxis spp. was the most important prey for M. nigricans, K. audax and I. platypterus, while the squid Dosidicus gigas was the most important prey for X. gladius. The results of the ANOSIM confirmed significant differences in feeding habits between the members of the family Istiophoridae and X. gladius. Seasonal differences for I. platypterus also were observed. Billfishes are specialist consumers with a narrow niche breadth (B a: M. nigricans and K. audax=0.1, I. platypterus=0.05, and X. gladius=0.04).(AU)

Los hábitos alimentarios de Makaira nigricans, Kajikia audax, Istiophorus platypterus (Istiophoridae) y Xiphias gladius (Xiphiidae) en el Océano Pacífico sudeste se examinaron en Manta y Santa Rosa, Ecuador. Este estudio describe las dietas de estas especies de peces de pico, evalúa las diferencias de la dieta entre especies y las diferencias estacionales en la dieta. Se obtuvo un total de 274 M. nigricans, 321 K. audax, 267 I. platypterus y 252 X. gladius entre febrero 2014 y abril 2015. El escómbrido Auxis spp. fue la presa más importante para M. nigricans, K. audax y I. platypterus, mientras que el calamar Dosidicus gigas fue la presa más importante para X. gladius. Los resultados de ANOSIM confirmaron diferencias significativas en los hábitos alimentarios entre los miembros de la familia Istiophoridae y X. gladius. También se observaron diferencias estacionales para I. platypterus. Los peces de pico son consumidores especialistas con una amplitud de nicho estrecha (B a: M. nigricans y K. audax=0.1, I. platypterus=0.05 y X.gladius=0.04).(AU)

Seasonal diet composition of Fundulus lima (Cyprinodontiformes: Fundulidae) in two oasis systems of Baja California Sur, Mexico

Fundulus lima inhabits river drainage systems and is threatened after the introduction of cichlids in the area. To support conservation programs, the spatial and temporal variation of the diet composition of this endangered killifish, was determined in two oasis systems of Baja California Sur, Mexico (San Ignacio and La Purisima river drainages), during rainy and dry seasons. F. lima was captured by using passive and active capture techniques. A total of 192 stomach contents of F. lima was analyzed. The contribution of each prey item in the diet composition was quantified by means of the indices of occurrence frequency (% OF), numerical (%N) and volume (%V) percentages. The relative importance of each prey item was determined according to the percentage of the Relative Importance Index (%RII). The similarity of the diet was calculated between hydrological basins (populations combined by basin), seasons (rainy versus dry months), sexes and size classes, by using Schoener’s resource overlap index. We used two ecological indices to determine the type of feeding strategy exhibited by the fish: (1) niche breadth of Levins and (2) proportional similarity of Feisinger. Sand was the most abundant item in the stomach content of killifishes from both drainages (39% and 47%, respectively). Diet composition was similar for both drainages (74%) as well as among their respective size classes; however, it was different between sexes. In both drainages, F. lima predated mainly on diatom algae, dipterous and trichopteran larvae, and fish scales during the dry season; while it preferred dipterous larvae, filamentous algae and ostracods in the rainy season. A feeding strategy of opportunist type was exhibited by F. lima during the rainy season, changing to specialist type during the dry season. This information will be the basis for future investigations related to the conservation of this endangered species and its habitat. Rev. Biol. Trop. 59 (4): 1669-1678. ...

Fundulus lima habita sistemas de aguas continentales, y se encuentra amenazado tras la introducción de cíclidos en el área de estudio. Para poder llevar a cabo programas de conservación, fue determinada la dieta de la sardinilla peninsular en peligro de extinción, en dos sistemas de oasis de Baja California Sur, México (cuencas de los rios San Ignacio y La Purísima), durante las épocas secas y de lluvias. Una gran proporción de arena fue encontrada en el contenido estomacal de este pez para ambas cuencas (39% y 47%, respectivamente). La composición de la dieta fue similar entre ambas cuencas (74%), como también dentro de sus respectivas clases de tallas; sin embargo, fue diferente entre sexos. Durante la época de secas, F. lima consumió principalmente diatomeas, larvas de dípteros y tricópteros, además de escamas de peces; mientras que en la época de lluvias tuvo preferencia por las larvas de dípteros, algas filamentosas y ostrácodos. Este pez exhibe una estrategia alimentaria de tipo oportunista durante la época de lluvias, la cual cambia a tipo especialista en la época de secas. Esta información será la base para futuras investigaciones relacionadas con la conservación de esta especie, en peligro de extinción, y su hábitat.

Estratégia alimentar com ciclos de restrição e realimentação no desempenho produtivo de juvenis de tilápia do Nilo da linhagem GIFT / Feeding strategies with cycles of restriction and refeeding on growth performance of Nile tilapia juveniles, GIFT line

O objetivo deste estudo foi avaliar a ocorrência de resposta compensatória no desempenho produtivo de juvenis de tilápia do Nilo Oreochromis niloticus, linhagem GIFT, submetidos a diferentes estratégias alimentares. Foram utilizados 135 juvenis de tilápia, distribuídos em nove tanques de polietileno de 100L cada. As estratégias testadas foram: grupo controle (alimentado todo dia), grupo alimentado por cinco dias seguidos de dois dias de restrição de alimento (5A/2R) e grupo alimentado por quatro dias seguidos de três dias de restrição de alimento (4A/3R). Foram avaliados parâmetros físico-químicos da água e de desempenho produtivo. Os resultados foram submetidos à análise de variância, e as médias foram comparadas pelo teste Tukey, a 5 por cento de probabilidade. A qualidade de água, o fator de condição e a conversão alimentar não foram influenciados pela estratégia alimentar. O grupo alimentado com a estratégia 5A/2R apresentou peso final, ganho de peso e taxa de crescimento específico semelhantes ao grupo continuamente alimentado (7,8 e 9,2g; 6,4 e 7,8g e 2,7 e 3,0 por cento dia-1, para peso final, ganho de peso e taxa de crescimento especifico, respectivamente). A estratégia 4A/3R apresentou os piores resultados de desempenho produtivo, e a estratégia 5A/2R pode ser usada na alimentação de juvenis de tilápia do Nilo sem prejuízo ao desempenho produtivo, possibilitando inclusive redução de até 22,5 por cento na quantidade de alimento ofertada.

The objective of this study was to evaluate the occurrence of compensatory answer on productive performance of Nile tilapia Oreochromis niloticus juveniles, GIFT line, submitted to different feeding strategies. It was used 135 juveniles tilapias distributed in nine 100L polyethylene tanks each. The tested strategies were the control group (fed everyday), group fed for 5 days followed by 2 days of food restriction (5A/2R) and group fed for 4 days followed by 3 days of food restriction (4A/3R). Were evaluated physical chemical water parameters e growth performance. Results were submitted to an analysis of variance and averages compared by Tukey test 5 percent. Water quality, condition factor and feed conversion were not influenced by feeding strategy. Group fed 5A/2R strategy showed final weight, weight gain and specific growth rate similar to group continually fed (7.8 e 9.2g; 6.4 e 7.8g e 2.7 e 3.0 percent day-1, for final weight, weight gain and specific growth rate, respectively). The strategy 4A/3R showed the poorest productive performance. Strategy 5A/2R can be used in Nile tilapia juveniles feeding without damage to the fish productive performance, allowing a reduction of up to 22.5 percent on the feed quantity offered.

Feeding ecology of juvenile dog snapper Lutjanus jocu (Bloch and Shneider, 1801) (Lutjanidae) in intertidal mangrove creeks in Curuçá estuary (Northern Brazil)

The diet and feeding ecology of juvenile dog snapper (Lutjanus jocu) were investigated in 92 specimens collected in four intertidal mangrove creeks of Curuçá estuary, Northern Brazil, between September 2003 and July 2004. No significant differences in total length were found between the sampling months. Feeding intensity was high as indicated by high stomach fullness index and low vacuity index. The most important prey was Penaeidae, followed by Grapsidae and Porcellanidae. The diet of juvenile dog snapper showed clear seasonal differences. Specimens from dry season (September and November) and dry / wet season transition (January), were specialists feeding exclusively on Penaeidae. However, the specimens from wet season (March and May) and wet /dry season transition (July) that consumed mainly Grapsidae, Penaeidae and Porcellanidae were generalist. These seasonal changes in diet could be related to variations in food availability.

A dieta e a ecologia alimentar de juvenis de Lutjanus jocu foram verificadas em 92 espécimes coletados em quatro canais de maré do estuário do rio Curuçá, Norte do Brasil, entre setembro de 2003 e julho de 2004. O comprimento total dos peixes coletados não apresentou diferenças significativas entre os meses amostrados. A intensidade alimentar foi elevada conforme indicado pelos altos valores do índice de repleção estomacal e os baixos valores do índice de vacuidade. A presa mais importante foi Penaeidae, seguida por Grapsidae e Porcellanidae. A dieta de juvenis de L. jocu apresentou diferenças sazonais evidentes. Os espécimes da estação seca (setembro e novembro) e transição seca/chuvosa (janeiro) foram considerados especialistas alimentando-se exclusivamente de Penaeidae. No entanto, os espécimes da estação chuvosa (março e maio) e da transição chuvosa/seca (julho), que alimentaram-se principalmente de Grapsidae, Penaeidae e Porcellanidae, foram considerados generalistas. Esta mudança sazonal na dieta poderia estar relacionada com a disponibilidade do alimento.

Ontogenetic and seasonal shifts in the diet of the pemecou sea catfish Sciades herzbergii (Siluriformes: Ariidae), from a macrotidal mangrove creek in the Curuçá estuary, Northern Brazil

The feeding ecology of pemecou sea catfish (Sciades herzbergii) was studied bimonthly from September 2003 to July 2004 in a macrotidal mangrove creek at Curuçá estuary, Brazil. Feeding activity and relative importance of prey groups were assessed in 528 and 226 specimens (6.2 to 36.0 cm total length), respectively, using stomach contents. A total of 1 820 specimens were caught. The fish left the creek with an average of 2.2 % of their body weight in prey. Feeding activity was lower in the dry season (September and November 2003) than in the rainy season (January to May 2004). The diet was dominated by Ocypodidae and Grapsidae. Feeding strategies of the pemecou sea catfish indicated a slight variation between the diets of adults and juveniles; however; the main factor leading to diversification in the diet were the seasons. Opportunistic feeding behavior was observed in the dry season, shifting to more specialized feeding in the wet season. This temporal diet shift may be explained by the environmental seasonal variations (e.g. transparency of the water, high water level) in the intertidal mangrove creek habitat. Rev. Biol. Trop. 56 (2): 861-873. Epub 2008 June 30.

Estudiamos la ecología trófica del bagre guatero Sciades herzbergii, con periodicidad bimestral, desde septiembre de 2003 a julio de 2004, en un canal de marea del estuario del río Curuçá, norte de Brasil. Del total de 1820 ejemplares capturados, analizamos la actividad alimentaría y la importancia de las diferentes fuentes de alimento por evaluación de los contenidos estomacales de 528 y 226 ejemplares (longitud corporal 6,2 a 36,0 cm), respectivamente. S. herzbergii sale del canal de marea con un valor promedio de 2,2 % de su peso corporal como alimento. El ritmo alimentario fue menor durante el período seco (septiembre a noviembre de 2003) que en el lluvioso (enero a mayo de 2004). Los análisis de los contenidos estomacales de 226 ejemplares indicaron una dieta con predominio de Ocypodidae y Grapsidae. Las estrategias alimentarías de S. herzbergii mostraron pequeñas diferencias entre las dietas de los adultos y de los jóvenes, pero la variación estacional fue el factor que mejor definió la diversificación de la dieta. En el período seco hubo un comportamiento oportunista en la alimentación, cambiando a una dieta mas especializada durante el período lluvioso. Esta variación temporal en la dieta corresponde con la variación estacional en los hábitats del canal de marea.