Although many upstream effects of a dam on the trophic ecology of fish have been reported, little is known about their downstream effects on the isotopic niche of Amazonian predator fish. The authors ...used stable isotope analysis of δ13C and δ15N to determine the downstream effects of damming of the Uatumã River on the niche width, carbon energy sources and trophic position of peacock bass Cichla temensis comparing with a free‐flowing river in the Amazon basin, Brazil, during the peak flood and early falling water period of 2020. They found that the C. temensis population of the undammed river had a smaller niche width than the C. temensis population of the dammed river, despite the greater number of prey trophic levels utilized and the higher trophic position of C. temensis individuals. The results demonstrate that in both rivers there is a gradual shift in the contribution of prey fish sources to the diet of C. temensis throughout its growth, even among adult individuals. They conclude that the isotopic niche of C. temensis was altered by damming during the period of late high water to early low water in the Uatumã River.
Length‐weight relationship parameters were calculated for six fish species from São Marcos Bay, in Northeast Brazil (the segment between 02°35′55″S and 44°20′58″W; 02°34′53″S and 44°21′48″W; ...02º42′25″S and 44º26′46″W). The specimens were caught quarterly from April 2010 to February 2013, using monofilament gillnets (2, 4 and 6 cm between knots) from 100 m to 3,000 m long and 4 m to 6 m high. The present study covers a much wider size range for four species and adds new information for the maximum length of Notarius bonillai.
The aim of this study was to analyse the trophic ecology of speckled peacock bass Cichla temensis inhabiting two tributaries of the middle Negro River, the Aracá River and the Demeni River. Using an ...analysis of stomach contents and stable isotope composition (δ15N, δ13C) of scales, we describe the diet and evaluate the trophic position of subadult and adult individuals. We then test whether diet shifts and trophic positions occurred among successive size classes and among sample locations. The stomach content analysis confirmed the piscivorous feeding habit of the species and showed that the speckled peacock bass preyed on a variety species belonging to different trophic guilds. The length of the ingested prey increased with the size of the speckled peacock bass. Diet composition and trophic position were not different among size classes. δ13C values yielded significant shifts among the size classes: larger individuals displayed higher δ13C values than smaller individuals. Trophic position varied between locations, with lowest values observed in fish from the Aracá River. This study demonstrated that diet of C. temensis may vary according to the size of the fish, even at the subadult or adult stages, and according to the river/locality, even within a same basin. We then suggest that further studies take into account local availability of food resources to better explore C. temensis diet and tropic ecology.
Parameters of the length‐weight relationship (LWR) were calculated for five fish species from Amazon Basin. Samplings were carried out in ten lakes of the Solimões River floodplains during the four ...seasons of the hydrological cycle: rising water, high water, receding water, and low water, during two periods. The first period of eight years included samplings performed from 2001 to 2008 and the second sampling period of two years was from 2012 to 2013. Specimens were captured using gillnets (mesh sizes ranging from 30 to 120 mm between opposite knots) and standardized dimension of 20 m in length × 2 m in height. This study provides the LWR parameters for Acarichthys heckelii, Leporinus trifasciatus, Brycon amazonicus, Curimatella meyeri and Osteoglossum bicirrhosum.
Parameters of the length‐weight relationship (LWR) were estimated for seven fish species from Amazonian Equatorial coast of Maranhão, Brazil. Samplings were carried out in three sample points of the ...lower stretch of the Itapecuru River (2°57'6.2"S and 44°14'26.5"W; 3°0'33.0"S and 44°15'54.7"W; 3°3'42.9"S and 44°15'1"W). The specimens were caught quarterly from June 2012 to August 2014 using monofilament gillnets (10, 20, 30, 40, 50, 60, 70 and 80 mm between knots) from 10 m to 30 m long and 4 m to 6 m high. This study provides the LWR parameters for Schizodon dissimilis, Curimata macrops, Prochilodus lacustris, Geophagus surinamensis, Hassar affinis, Platydoras brachylecis and Hypostomus plecostomus.
An industrial multigear fishing fleet from Venezuela emerged in 2009 as a governmental strategy to reduce the impact of industrial trawling on the Venezuelan coast of the North Brazil Shelf Large ...Marine Ecosystem. The current study aimed to examine the spatial–temporal distribution of fishing effort and the catch levels obtained by the Venezuelan industrial multigear fishing fleet during the period 2015–2018. Fishing gear types employed by this fleet in order of preference were as follows: bottom longline (target sea catfishes family Ariidae), trap (target snappers family Lutjanidae), pelagic longline (target tunas family Scombridae), hand line (target mackerels family Scombridae), and shark longline (target sea catfishes and sharks families Carcharhinidae, Squalidae, Sphyrnidae, Ginglymostomatidae, Alopiidae, and Triakidae). The kernel intensity estimator determined that the main fishing area was the North Brazil Shelf (comprising 95% of the total fishing sets). Fishing effort (fishing sets per trip) distribution may be associated with oceanic fronts present in the region. A change in the dynamics of the fleet were recorded, with an increase in the use of bottom longlines, along with a decrease in the use of traps, possibly due to overfishing of resources caught by traps. The analyses of covariance showed a linear and positive relationship between the catch and fishing effort but with significant changes over the study period for traps and bottom longlines, since in the years where the fishing effort of traps was lower there were greater catches by unit of effort, and vice versa for bottom longlines, where lower catches by unit effort were obtained in years with greater effort.
Individual dietary specialization is one of the factors that promotes variation in resource use at the individual level. Here we used stable isotope analysis of multiple tissues with different ...turnover rates to examine the degree of individual specialization in two sub-populations of the predator
inhabiting both fragmented and undammed rivers within the Uatumã River basin of the Amazon. Our results showed that the undammed river provides better conditions to promote individual dietary specialization than the fragmented river. This study contributes to the understanding of how specific life history characteristics of populations of generalist predators are impacted by fragmentation within megadiverse environments such as the Amazon basin.
This research reports the LWR of ornamental fish from floodplain lakes of the Solimões River basin. The fish were caught in the Paciência island (a fluvial island) in two lakes Sacambú and Cacau ...using purse seine 7 m × 4 m and mesh size = 3 mm, once during the flood in June 2017 and dry in January 2018. The specimens captured were anesthetized using eugenol 15 mg · L–1, fixed formalin 10% and stored ethanol 70% after 10 days. This study provides the LWR parameters for the species Anablepsoides micropus, Anchoviella jamesi, Cichlasoma amazonarum, Heros efasciatus, Ctenobrycon hauxwellianus, Copella nattereri and Hemigrammus levis. The parameter a ranged from 0.0092 to 0.0229, b ranged from 2.78 to 3.50 and the R2 ranged from 0.985 to 0.998. The results represent new information about ornamental fish from floodplain lakes, with new LWR for five species that are not present in FishBase data set and probably are new for science. This study is preliminary and much work needs to be done especially in the Solimões River floodplain areas and with our research we hope to encourage new studies in the region.
This research reports the LWR of ornamental fish from floodplain lakes of the Solimões River basin. The fish were caught in the Paciência island (a fluvial island) in two lakes Sacambú and Cacau ...using purse seine 7 m × 4 m and mesh size = 3 mm, once during the flood in June 2017 and dry in January 2018. The specimens captured were anesthetized using eugenol 15 mg · L–1, fixed formalin 10% and stored ethanol 70% after 10 days. This study provides the LWR parameters for the species Anablepsoides micropus, Anchoviella jamesi, Cichlasoma amazonarum, Heros efasciatus, Ctenobrycon hauxwellianus, Copella nattereri and Hemigrammus levis. The parameter a ranged from 0.0092 to 0.0229, b ranged from 2.78 to 3.50 and the R2 ranged from 0.985 to 0.998. The results represent new information about ornamental fish from floodplain lakes, with new LWR for five species that are not present in FishBase data set and probably are new for science. This study is preliminary and much work needs to be done especially in the Solimões River floodplain areas and with our research we hope to encourage new studies in the region.
Esta investigación informa el LWR de peces ornamentales de lagos de llanuras aluviales de la cuenca del río Solimões. Los peces fueron capturados en la isla de Paciência (una isla fluvial) en dos lagos Sacambú y Cacau utilizando cerco 7 m × 4 m y tamaño de malla = 3 mm, una vez durante la inundación en junio de 2017 y seco en enero 2018. Las muestras capturadas se anestesiaron con eugenol 15 mg · L–1, se fijaron formalina al 10% y se almacenaron etanol al 70% después de 10 días. Este estudio proporciona los parámetros LWR para las especies Anablepsoides micropus, Anchoviella jamesi, Cichlasoma amazonarum, Heros efasciatus, Ctenobrycon hauxwellianus, Copella nattereri y Hemigrammus levis. El parámetro a varió de 0.0092 a 0.0229, b varió de 2.78 a 3.50 y el R2 varió de 0.985 a 0.998. Los resultados representan nueva información sobre peces ornamentales de lagos de llanuras aluviales, con nuevos LWR para cinco especies que no están presentes en el conjunto de datos FishBase y probablemente son nuevos para la ciencia. Este estudio es preliminar y queda mucho trabajo por hacer, especialmente en las áreas de la llanura aluvial del río Solimões y con nuestra investigación esperamos alentar nuevos estudios en la región.
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