Far from urban areas: plastic uptake in fish populations of subtropical headwater streams.

This study investigated the occurrence of plastic particles in the digestive tracts of fish from headwater streams in a human-thinly populated region of the subtropical Sinos River basin in southern Brazil. In total, 258 individuals from 17 species were collected using electric fishing. Thirty-eight percent (38%) of the specimens contained plastic particles. All of them were fibers, with a maximum count of 43 per individual. Plastic fibers were the fourth most abundant food category. Results showed that the uptake of these plastic particles was proportional to the number of ingested food items. Fiber counts in the guts correlated with the uptake of Trichoptera, which are invertebrates using plastic particles to construct their protective cases. No significant difference in plastic uptake was detected between benthic and water column fish. No evidence of bioaccumulation of plastic particles was found in the intestines. The distance from urban areas was not related to the number of ingested plastic particles, concluding that plastics are ubiquitous and available to biota, even in remote locations. The most probable source of these particles is residences close to the streams which discharge the sewage of washing machines without any treatment.

Aspects of fish conservation in the upper Patos Lagoon basin.

The Patos Lagoon basin is a large (201 626 km(2) ) and complex drainage system in southern Brazil. The lagoon is 250 km long and 60 km wide, covering an area of 10 360 km(2) . The exchange of water with the Atlantic Ocean occurs through a 0·8 km wide and 15 m deep inlet, fixed by 4 km long jetties, at the southernmost part of the Patos Lagoon. The estuarine area is restricted to its southern portion (10%), although the upper limit of saline waters migrates seasonally and year to year, influenced by the wind regime and river discharge. The known number of recorded limnetic fish species is 200, but this number is expected to increase. A higher endemism is observed in fish species occurring in upper tributaries. The basin suffers from the direct impact of almost 7 million inhabitants, concentrated in small to large cities, most with untreated domestic effluents. There are at least 16 non-native species recorded in natural habitats of the Patos Lagoon basin, about half of these being from other South American river basins. Concerning the fishery, although sport and commercial fisheries are widespread throughout the Patos Lagoon basin, the lagoon itself and the estuarine area are the main fishing areas. Landing statistics are not available on a regular basis or for the whole basin. The fishery in the northern Patos Lagoon captures 31 different species, nine of which are responsible for most of the commercial catches, but only three species are actually sustaining the artisanal fishery: the viola Loricariichthys anus: 455 kg per 10 000 m(2) gillnet per day, the mullet Mugil liza: 123 kg per 10 000 m(2) gillnet per day and the marine catfish Genidens barbus: 50 kg per 10 000 m(2) gillnet per day. A decline of the fish stocks can be attributed to inadequate fishery surveillance, which leads to overfishing and mortality of juveniles, or to decreasing water quality because of urban and industrial activities and power production. Global climatic changes also represent a major threat to the Patos system by changing the frequency of El Niño-La Niña-Southern Oscillation (ENSO).

The effects of press and pulse disturbance by long and short-term pollution on the fish community in the Sinos River, RS, Brazil.

The fish fauna of the Sinos River has been subjected to severe pollution since the 1970´s. Continuous discharges of industrial and municipal sewage cause hypoxia and often even fish kills. The objectives of the present study are to assess long-term effects of pollution on the fish community over a time scale of approximately ten years and to investigate recuperation of the fish fauna after a massive fish kill in 2006. To assess the long-term impacts, seasonal sampling was conducted from September 2007 to March 2009 in four sites which were investigated in 1998/99 with the same methodology. The effects of the fish kill were investigated by comparing the present fauna in the affected river stretch with the fauna of an unaffected adjacent river stretch. The collective community properties richness and Shannon diversity changed during the ten year interval in a consistent pattern. Richness and Shannon diversity increased significantly in all sites, abundance values, however, did not. Analysis of species constancy and cluster analysis showed that the differences between the 1998/99 and 2007/09 studies were relatively small. The comparison of the reaches affected by the 2006 fish kills showed a rapid recovery within one year. Probably the Sinos fish fauna suffered the most severe impacts in the 70s of the last century, which could not be documented by this study. After an initial decline, the community displays relatively stable patterns with a tendency of recovery. After a severe fish kill, faunal recovery was rapid, probably favoured by the proximity of unpolluted source areas and physical habitat integrity of the Sinos River.

Otolith atlas of fish of the Sinos River.

Otoliths are calcium carbonate structures located in the inner ear of fish; they are responsible for hearing and balance. The inner ear has three pairs of otoliths: the lapilli, the sagittae and the asterisci. The sagittae otoliths are the largest and their format is species-specific. Because of their composition, otoliths can resist to the digestive tract of ichthyophagous species, and they can be used as an important tool for identifying species of fish found in stomach contents. The purpose of this work is to provide a photographic guide of the sagittae otoliths of the main fish species from the Sinos River. This atlas consists of photographs of the sagittae otoliths of 36 species belonging to 15 families distributed in five orders.

Diel and seasonal movements of grumatã Prochilodus lineatus (Valenciennes 1836) (Characiformes: Prochilodontidae) in the Sinos River, Southern Brazil.

Prochilodus lineatus is a reophilic migratory species of economical importance for local fisheries which is widely distributed in Brazil. The present study investigated diel and seasonal movement patterns, spawning migration and habitat use of P. lineatus in the Sinos River, Southern Brazil. Between August 2002 and March 2004, 19 grumatãs were tagged internally with digitally coded radio transmitters. Tracking was conducted weekly by boat or aircraft, and six fixed data loggers recorded movements of tagged fish. Results showed that the mean distance covered per fish and day was positively related with fish weight (p = 0.03; n = 19). Grumatã showed preference for river streches surrounded by wetlands (p < 0.001; n = 286). Their diel activity pattern displayed one peak at 7 hours, and a second at 15 hours. During the night, activity was significantly reduced (p = 0.01). The seasonal movements pattern showed increased activity in October 2002 - March 2003 and from October 2003 to January 2004. Multiple regression analysis did not show a significant relationship between distance covered and temperature or water level (p = 0.116; n = 19). No synchronized long distance spawning migrations were observed. The mean distance covered by the individuals/day showed a negative significant relationship with number of tracking days (p = 0.022; n = 19), indicating a higher probability of being captured for more mobile individuals. The preservation of the still existing wetlands and reduction of the fishing pressure are essential for the future conservation of the grumatã population of the Sinos River.

The fish community as an indicator of biotic integrity of the streams in the Sinos River basin, Brazil.

The basin of the Sinos River, located in the northeastern part of Rio Grande do Sul state, Brazil, has been highly impacted by industrial and urban activities. Water quality is low because of domestic and industrial sewage discharges. Most of the tributaries have suffered drastic structural interventions like canalisations and the removal of riparian vegetation. The aims of this study were to: 1) assess the diversity of fish at 34 sampling sites in twenty-four tributaries of the Sinos River basin; 2) quantify impact level by the Shannon-Wiener diversity index and an adapted Index of Biotic Integrity (IBI); and 3) check the interference of environmental impacts, formerly quantified in a Stream Corridor Assessment Survey (SCAS), on the fish assembly and 4) compare the relationship between the IBI with stream order. Fish sampling was performed by electric fishing in the period from April 2004 to August 2006. A total of 4,869 individuals were sampled, representing 61 species, 14 families and six orders. Significant relationships of the Shannon-Wiener index and IBI with SCAS scores and stream orders were found. Of all impacts that make up the SCAS score, only channel modifications were significantly correlated with IBI. These results indicate that the adaptation of the IBI was effective and performed better than the Shannon-Wiener diversity index when related directly to specific impact categories. The application of the IBI with the SCAS and the other variables was efficient in the tributaries of the Sinos River basin because it showed the biotic degradation in accordance with changes in physical habitat.

Interactions between benthic macroinvertebrates and fishes in a low order stream in Campos de Cima da Serra, RS, Brazil / Interações entre macroinvertebrados bentônicos e peixes em um rio de baixa ordem nos Campos de Cima da Serra, RS, Brasil

Benthic macroinvertebrates constitute the link between organic matter input in streams and fishes. However, the possibility of influence of predators on the invertebrates is still a controversial issue. The possibility of alteration of the benthic community by the modification in predation in a stream in the South of Brazil was studied by means of an exclusion experiment under semi-natural conditions. The exclusion showed an increase in the abundance of Plecoptera in the river where the rainbow trout was introduced, the larvae of Trichoptera also increased in abundance in the units of fish exclusion. This difference does not confirm the pressure applied by the trout on the benthic macro fauna due to differences in ichthyofauna and in the habitat of both rivers. Nevertheless, it points to the need for the development of studies concerning the trophic relations and the possible effects of this introduction in the aquatic biota.

Os macroinvertebrados bentônicos exercem a ligação entre a entrada de matéria orgânica nos rios e os peixes. Porém, a possibilidade de influência dos predadores sobre os invertebrados é uma questão ainda controversa. A possibilidade de alteração da comunidade bentônica, pela modificação na predação em um rio no sul do Brasil, foi estudada através de um experimento de exclusão em condições seminaturais. A exclusão resultou no aumento na abundância de Plecoptera no rio onde é feita a introdução de truta arco-íris; as larvas de Trichoptera também aumentaram em abundância nas unidades onde se efetuou a exclusão. Essa diferença não pode ser atribuída à presença das trutas, devido às diferenças na ictiofauna e de habitat dos dois rios. Entretanto mostra a necessidade de desenvolvimento de estudos acerca das relações tróficas e possíveis efeitos desta introdução sobre a biota aquática

Interactions between benthic macroinvertebrates and fishes in a low order stream in Campos de Cima da Serra, RS, Brazil.

Benthic macroinvertebrates constitute the link between organic matter input in streams and fishes. However, the possibility of influence of predators on the invertebrates is still a controversial issue. The possibility of alteration of the benthic community by the modification in predation in a stream in the South of Brazil was studied by means of an exclusion experiment under semi-natural conditions. The exclusion showed an increase in the abundance of Plecoptera in the river where the rainbow trout was introduced, the larvae of Trichoptera also increased in abundance in the units of fish exclusion. This difference does not confirm the pressure applied by the trout on the benthic macro fauna due to differences in ichthyofauna and in the habitat of both rivers. Nevertheless, it points to the need for the development of studies concerning the trophic relations and the possible effects of this introduction in the aquatic biota.

Activity patterns of South American silver catfish (Rhamdia quelen).

The South American silver catfish (Rhamdia quelen) is a widely distributed species in Central and South America in areas east of the Andes between Venezuela and the northern parts of Argentina. The bottom dwelling species occurs in lakes and reservoirs as well as in rivers. Between June 2000 and December 2001, sixteen silver catfish were tracked during fourteen 24-h cycles in two-hour-intervals, with the aim of investigating daily movements and habitat use. Covered distances varied between 0 m/2 h and 326 m/2 h and the mean distance covered in 2 h was 25.6 m. The mean activity of individual silver catfish varied between 5.6 m/2 h and 81.4 m/2 h. The swimming activity was linearly related to the total fish length. The highest mean swimming activity occurred in the morning and at nightfall. Silver catfish concentrated in three areas of frequent use. All of them were characterized by steep banks providing shelter in the form of rip-rap or large woody debris. Vertically, silver catfish preferred the upper 2 m layer where tracked fish encountered higher temperatures and higher dissolved oxygen concentrations.

Activity patterns of South American silver catfish (Rhamdia quelen)

O jundiá sul-americano (Rhamdia quelen) é uma espécie amplamente distribuída na América do Sul e Central, ao leste dos Andes e entre a Venezuela e o norte da Argentina. A espécie é um peixe de fundo que ocorre tanto em lagos e reservatórios como em rios. Entre junho de 2000 e dezembro de 2001, 16 jundiás foram monitorados durante 14 ciclos de 24 h, em intervalos de duas h, com o objetivo de investigar movimentos diários e uso de habitat da espécie. Os deslocamentos verificados variaram entre 0 m/2 h e 326 m/2 h, a distância média medida em 2 h foi de 25,6 m. A atividade média dos indivíduos oscilou entre 5,6 m/2 h e 81,4 m/2 h. Os picos de maior atividade ocorreram, principalmente, durante a manhã e no vespertino. Os jundiás se concentraram em três áreas de uso freqüente. Todas as áreas caracterizavam-se por apresentar barrancos muito inclinados com abrigos em forma de seixos grandes ou troncos submersos. Verticalmente a espécie mostrou preferência por profundidades entre 0 m e 2 m, onde encontravam temperaturas e concentrações de oxigênio mais altas.

Growth and mortality of black bass, Micropterus salmoides (Pisces, Centrachidae; Lacapède, 1802) in a reservoir in southern Brazil.

The black bass, Micropterus salmoides, was introduced to Brazil from North America in 1922. Since then the species has been reared in aquaculture facilities intended to stock reservoirs as additions to native stocks available for angling. At present no scientific information on the biology of black bass in Brazilian waters is available. Since black bass dispersion may cause severe impacts on native Brazilian fish fauna, information on the basic biological parameters of this species is necessary. The objective of the present study is to provide information on the growth, age structure, and mortality of the species in a small reservoir in southern Brazil, where the species reproduces regularly. Based on scale readings, the von Bertalanffy growth curve was calculated and compared to the length-frequency distribution of the population. Both methods showed similar results. Maximum length was about 44 cm. The mean length at the end of the first year was 23.1 cm (s.d. = 13.88); at that of the second, 37.3 cm (s.d. = 12.52); and 41.4 cm (s.d. = 9.92) at the third. Oldest fish were three years old. The growth performance index phi' was 3.28 cm year(-1). Mortality increased from 0.16 year(-1) between the first and the second cohort, to 0.8 year(-1) between the second and third. The results show that black bass in Brazil grows faster than in its area of origin, but longevity is shorter and body shape, stouter. The cause of high mortality at a relatively early age may be connected with the loss of genetic diversity due to inbreeding of the Brazilian stocks, which originated from few introduced individuals a long time ago. The fact that black bass reproduces in reservoirs and grows rapidly may be considered a threat to conserving fish diversity in Brazilian ecosystems.

Growth and mortality of black bass, Micropterus salmoides (Pisces, Centrachidae; Lacapède, 1802) in a reservoir in southern Brazil

O black bass, Micropterus salmoides, proveniente da América do Norte, foi introduzido no Brasil em 1922. A partir dessa data, a espécie foi criada na piscicultura brasileira para fins de soltura em açudes e reservatórios com o objetivo de sustentar a pesca amadora. Atualmente não há informações sobre a biologia da espécie em águas brasileiras. Como a dispersão da espécie em águas naturais pode causar impactos imprevisíveis, é necessário levantar dados sobre parâmetros básicos de sua biologia. O objetivo do presente trabalho é investigar o crescimento, a estrutura etária e a mortalidade da espécie num pequeno reservatório no sul do Brasil, onde ela se reproduz todos os anos. Por meio da leitura de escamas foi calculada a curva de crescimento von Bertalanffy e comparada à distribuição do comprimento. Ambos os métodos chegaram a resultados similares. O comprimento máximo foi de aproximadamente 44 cm. No primeiro ano de vida, o comprimento médio foi de 26,1 cm (d.p. = 13,88); no segundo, 37,3 cm (d.p. = 12,52); e no terceiro, 41,5 cm (d.p. = 9,92). O índice de performance de crescimento foi º' = 3,28 cm anoù1. A mortalidade Z aumentou aproximadamente quatro vezes, de 0,16 anosù1 entre a primeira e a segunda coorte para 0,8 anosù1 entre a segunda e a terceira coorte. Os resultados mostram que o black bass cresce mais rapidamente no Brasil e tende a ser mais enxuto que em sua área de origem, mas não atinge a longevidade dos espécimes nos Estados Unidos. A causa dessa mortalidade elevada é vista na provável diminuição da diversidade genética dos estoques brasileiros, originados de poucos indivíduos introduzidos muito tempo atrás. O fato de a espécie se reproduzir e crescer rapidamente em sistemas seminaturais pode ser considerado uma ameaça para a conservação dos ecossistemas brasileiros.

Effects of surgically implanted dummy transmitters on the South American catfish Jundiá (Rhamdia quelen).

High water temperatures and low water quality may negatively influence wound healing, growth and transmitter retention in radio-tagged fish of tropical and subtropical water bodies which in turn may hamper radio tracking studies. For a period of 90 days, we compared growth of an experimental group of ten Rhamdia quelen, which were submitted to intraperitoneal dummy transmitter implantation, with that of a control group. Additionally, wound healing and transmitter expulsion were observed in the experimental group. Water temperature varied between 24 degrees C and 30 degrees C during the study. Experimental group and control fish decreased in body weight during the investigation period, but the differences between the mean individual weight loss in both groups were not significant (Student t-test, p = 0.64). Wound healing in experiment group fish was advanced after 14 days, while after 70 days eight out of ten incision wounds were closed and cicatrized. One fish had its dummy transmitter expulsed through the ventral body wall. After 90 days two more fish had the dummies expulsed, one through the ventral body wall and the other through the antenna exit. One experimental group fish died with visible signs of infection. The results encourage the use of surgically implanted radio transmitters for long-term tagging studies at high water temperatures.

Effects of surgically implanted dummy transmitters on the South American catfish Jundiá (Rhamdia quelen)

High water temperatures and low water quality may negatively influence wound healing, growth and transmitter retention in radio-tagged fish of tropical and subtropical water bodies which in turn may hamper radio tracking studies. For a period of 90 days, we compared growth of an experimental group of ten Rhamdia quelen, which were submitted to intraperitoneal dummy transmitter implantation, with that of a control group. Additionally, wound healing and transmitter expulsion were observed in the experimental group. Water temperature varied between 24ºC and 30ºC during the study. Experimental group and control fish decreased in body weight during the investigation period, but the differences between the mean individual weight loss in both groups were not significant (Student t-test, p = 0.64). Wound healing in experiment group fish was advanced after 14 days, while after 70 days eight out of ten incision wounds were closed and cicatrized. One fish had its dummy transmitter expulsed through the ventral body wall. After 90 days two more fish had the dummies expulsed, one through the ventral body wall and the other through the antenna exit. One experimental group fish died with visible signs of infection. The results encourage the use of surgically implanted radio transmitters for long-term tagging studies at high water temperatures

Astyanax fasciatus as bioindicator of water pollution of Rio dos Sinos, RS, Brazil

The effects of an increasing downriver pollution gradient on the reproductive system of Astyanax fasciatus were investigated in the Rio dos Sinos, RS. The comparison of mean oocyte diameters, gonadal indices and gonado-somatic relationships of specimens captured in polluted areas with individuals from unpolluted reference sites revealed a significant decrease of these parameters with increasing water pollution. High loads of organic and industrial sewage are considered responsible for these effects. Condition factors showed an inverse relationship, and increased significantly in downriver polluted areas. The declining gonadal indices showed that energy was allocated to somatic growth. The results of the study recommend the use of A. fasciatus in biomonitoring essays

Astyanax fasciatus as bioindicator of water pollution of Rio dos Sinos, RS, Brazil.

The effects of an increasing downriver pollution gradient on the reproductive system of Astyanax fasciatus were investigated in the Rio dos Sinos, RS. The comparison of mean oocyte diameters, gonadal indices and gonado-somatic relationships of specimens captured in polluted areas with individuals from unpolluted reference sites revealed a significant decrease of these parameters with increasing water pollution. High loads of organic and industrial sewage are considered responsible for these effects. Condition factors showed an inverse relationship, and increased significantly in down-river polluted areas. The declining gonadal indices showed that energy was allocated to somatic growth. The results of the study recommend the use of A. fasciatus in biomonitoring essays.