Altitudinal distribution and body condition of migratory fish juveniles Megaleporinus obtusidens (Valenciennes) and Salminus brasiliensis (Cuvier) in the main channel of the Uruguay River, Southern Brazil.

In this study, we analyzed the altitudinal distribution and body condition of the juvenile migratory fish Megaleporinus obtusidens and Salminus brasiliensis in the Uruguay River, a South American subtropical river. We used the presence/absence data and condition factor (K) of juveniles as indicators to try to characterize some recruitment patterns of migratory fish in the main channel of the Uruguay River. Gillnet sampling was conducted during two reproductive years, 2015-2016 and 2016-2017 (November and March of each reproductive year), in three Uruguay River stretches at different levels of altitude. The nets remained in the water for 10-12 hours per night or day for 10 days during each field trip (NOV-15, MAR-16, NOV-16, and MAR-17). The abundance of M. obtusidens juveniles were similar between the two reproductive years, whereas S. brasiliensis capture was higher during the 2015-2016 reproductive year. The probability of finding M. obtusidens juveniles in the Uruguay River was negatively correlated (p < 0.05) with the altitudinal gradient of the sampling points, as shown by the GLM model. For S. brasiliensis, the logit model indicated a non-significant probabilistic relationship (p > 0.05) between the presence of juveniles of this fish species and the altitude gradient. Regarding the body condition of juveniles, the water quality of the sampling points did not affect the juvenile condition factor for either species; however, a positive relationship (p < 0.05) was found with the water level for both species, even with an adjusted R2 of 0.13 for M. obtusidens and 0.48 to S. brasiliensis. Altitude gradient and water level were factors that may affect the juvenile distribution and body condition of these species, respectively, in the Uruguay River. Therefore, this information can be used in hydropower generation policies to conserve migratory fish populations in the Uruguay River Basin.

Reproductive dynamics of Lycengraulis grossidens (Clupeiformes: Engraulidae) and Platanichthys platana (Clupeiformes: Clupeidae) in a subtropical coastal lagoon / Dinâmica reprodutiva de Lycengraulis grossidens (Clupeiformes: Engraulidae) e Platanichthys platana (Clupeiformes: Clupeidae) em uma lagoa costeira subtropical

Abstract We evaluated the reproductive dynamics of two fish species, Lycengraulis grossidens and Platanichthys platana, in a subtropical freshwater coastal lagoon (Peri Lagoon) in Brazil. Samples were collected from nine sites every two months from June 2008 to April 2012. Different fishing methods were used to capture larvae, juveniles, and adults. Limnological variables were obtained using multiparameter probe. More females than males were collected of both fish species and the chi-square test (χ2) was used to confirm that the sex ratio was female-biased. Large numbers of maturing and mature fishes were observed in almost every sampling month. The gonadosomatic index (GSI) of L. grossidens was the highest in August, October, and December for females and in October for males, and no significant difference was found across years. The GSI of P. platana showed no significant difference across months for either sex; however, significant differences were recorded in year three (June 2010-April 2011) and year four (June 2011-April 2012) for females and in year three (June 2010-April 2011) for males. For both species, GSI was negatively correlated with temperature and water level. L. grossidens larvae were more abundant in October 2010, showing a positive correlation with water transparency, whereas P. platana larvae were more abundant in June 2011, showing a positive correlation with water transparency and negative correlation with temperature and precipitation. Both species were represented by different stages, including larvae, which confirm that these species reproduce in Peri Lagoon. Reproduction was more pronounced in autumn and winter; however, reproductive activity was evident throughout the sampling period. In conclusion, our results show that abiotic factors strongly influence the temporal pattern of reproductive activity and larval assemblages of both L. grossidens and P. platana in Peri Lagoon, Brazil.

Resumo O objetivo do estudo foi avaliar a dinâmica reprodutiva de Lycengraulis grossidens e Platanichthys platana, na lagoa do Peri, uma lagoa costeira de água doce subtropical do Brasil. As amostras foram coletadas a cada dois meses, de junho/2008 a abril/2012 em nove pontos de amostragem. Para a captura de larvas, juvenis e adultos foram utilizados diferentes apetrechos de pesca. As variáveis limnológicas foram obtidas com sonda multiparâmetro. Estatisticamente, mais fêmeas do que machos foram capturadas para as duas espécies baseado no teste de qui-quadrado (χ2). Grande número de peixes em maturação e maduros foram comuns em quase todos os meses de coleta. O índice gonadossomático (RGS) de L. grossidens variou significativamente apenas entre os meses, sendo mais elevada em agosto, outubro e dezembro para as fêmeas e em outubro para os machos; e não foram encontradas diferenças significativas entre os anos. Não foi encontrado diferença significativa para o RGS de P. platana entre os meses para cada sexo; entretanto, diferenças significativas foram obtidas para as fêmeas no ano três (junho 2010-abril 2011) e quatro (junho 2011-abril 2012) e no ano três (junho 2010-abril 2011) para os machos. Para as duas espécies, o RGS apresentou uma correlação negativa com a temperatura e o nível de água. A distribuição das larvas apresentou variação temporal. As larvas de L. grossidens foram mais abundantes em outubro/2010, apresentando correlação positiva com a transparência da água. As larvas da espécie P. platana foram mais abundantes em junho/2011, apresentando correlação positiva com a transparência da água e negativa com a temperatura e a precipitação. A presença de L. grossidens e P. platana em diferentes estádios de maturação e a ocorrência de larvas confirmou que essas espécies se reproduzem na lagoa do Peri. O período reprodutivo foi mais pronunciado no outono e no inverno, porém a atividade reprodutiva ocorreu durante todo o período de coleta. Em conclusão, nossos resultados mostraram que os fatores abióticos influenciam fortemente o padrão temporal da atividade reprodutiva e a assembleia de larvas da L. grossidens e da P. platana na lagoa do Peri, Brasil.

Fish parasites as indicators of organic pollution in southern Brazil.

Increasing urbanization along riverbanks is a constant source of stressors to the aquatic community, and the use of bioindicators is suitable to detect and monitor the effect of each stressor. We investigated the parasites of the 'cará' fish (Geophagus brasiliensis) as potential bioindicators in a river whose banks are subject to increasing anthropogenic pressure. Samples were taken at four points of the Sangradouro River, in Florianópolis, southern Brazil, bimonthly for 12 months. Water temperature, pH, dissolved oxygen, conductivity and salinity were measured at each point and water samples were taken for nutrient analysis (total nitrogen, nitrite, total ammonia nitrogen, total phosphorus, phosphate), and total and faecal coliforms. A generalized linear model (GLM) was constructed using the abundance of each parasite species as the response variable and biometric characteristic of the fish and water variables as possible predictors. Among the 137 fish examined, 114 (83.2%) were parasitized by at least one parasite species. Two species of ectoparasites (Sciadicleithrum guanduensis and Neascus-type metacercariae) and two species of endoparasites (Pandosentis aff. iracundus and Homalometron pseudopallidum) were observed. This is the first record of the genus Pandosentis in Brazilian waters and the first record of the species G. brasiliensis as a host for this parasite. Among the analysed groups of parasites, monogeneans and acanthocephalans proved to be the most sensitive to the concentrations of dissolved oxygen, faecal coliforms and total ammonia nitrogen in the water. Our study suggests that the abundance of both monoxenic and heteroxenous parasites can be negatively affected by organic pollution in the aquatic environment, reinforcing the potential of fish parasites as indicators of water quality.

Reproductive dynamics of Lycengraulis grossidens (Clupeiformes: Engraulidae) and Platanichthys platana (Clupeiformes: Clupeidae) in a subtropical coastal lagoon.

We evaluated the reproductive dynamics of two fish species, Lycengraulis grossidens and Platanichthys platana, in a subtropical freshwater coastal lagoon (Peri Lagoon) in Brazil. Samples were collected from nine sites every two months from June 2008 to April 2012. Different fishing methods were used to capture larvae, juveniles, and adults. Limnological variables were obtained using multiparameter probe. More females than males were collected of both fish species and the chi-square test (χ2) was used to confirm that the sex ratio was female-biased. Large numbers of maturing and mature fishes were observed in almost every sampling month. The gonadosomatic index (GSI) of L. grossidens was the highest in August, October, and December for females and in October for males, and no significant difference was found across years. The GSI of P. platana showed no significant difference across months for either sex; however, significant differences were recorded in year three (June 2010-April 2011) and year four (June 2011-April 2012) for females and in year three (June 2010-April 2011) for males. For both species, GSI was negatively correlated with temperature and water level. L. grossidens larvae were more abundant in October 2010, showing a positive correlation with water transparency, whereas P. platana larvae were more abundant in June 2011, showing a positive correlation with water transparency and negative correlation with temperature and precipitation. Both species were represented by different stages, including larvae, which confirm that these species reproduce in Peri Lagoon. Reproduction was more pronounced in autumn and winter; however, reproductive activity was evident throughout the sampling period. In conclusion, our results show that abiotic factors strongly influence the temporal pattern of reproductive activity and larval assemblages of both L. grossidens and P. platana in Peri Lagoon, Brazil.

Structure and diversity of fishes in a freshwater and coastal subtropical lagoon.

This study examined the fish communities of Peri Lagoon in southern Brazil to aid in the development of an effective management plan because the area is under threat from human activities. Sampling of fish fauna, ichthyoplankton and limnological data were compared between sites, differing by habitat type and characteristics such as depth, substratum composition and vegetation type. Results were significantly related to site, with the highest diversity and abundance recorded at shallow vegetated sites. A total of 14 fish species were recorded throughout the lagoon, with the most abundant being Hyphessobrycon luetkenii. Of the 14 species, half were sampled at their larval stage, suggesting a healthy and protected system. Significantly more larvae and eggs were collected during colder months (autumn to winter) and at sites closer to stream flow, possibly owing to increased food sources and habitat protection. This study highlights the importance of Peri Lagoon as a nursery ground for a wide range of fish species, providing essential information for incorporation into the future protection of fish stocks throughout Brazil.

Water pH and Prochilodus lineatus larvae survival.

The present study aimed to determine the influence of water pH on survival of curimbatá, Prochilodus lineatus, larvae. Forty-five 2-l glass aquaria with artificial aeration and no water exchange were stocked at a density of 10 larvae l(-1). The pH values used as treatments were 3.7 +/- 0.0, 4.0 +/- 0.0, 4.4 +/- 0.2, 4.6 +/- 0.2, 4.8 +/- 0.2, 5.1 +/- 0.2, 5.3 +/- 0.2, 5.6 +/- 0.2, 7.2 +/- 0.2, 8.7 +/- 0.4, 9.0 +/- 0.4, 9.2 +/- 0.4, 9.4 +/- 0.6, 9.7 +/- 0.5 and 10.0 +/- 0.5 in a completely random experimental design with three repetitions. Water pH was maintained by the addition of NaOH or H(2)SO(4) solutions. After 72 h of experiment, no survival was registered at pH below 4.6, 1.5% survival at pH 4.6, and about 50% survival at pH 9.4 and above. Survival rates between 70 and 80% were registered at pH 4.8-5.6 and at pH 7.2, whereas over 90% survival was registered at pH between 8.7 and 9.2.

Survival and growth of Pseudoplatystoma corruscans (Pisces - Pimelodidae) larvae: effect of photoperiod / Sobrevivência e crescimento de larvas de surubim, Pseudoplatystoma corruscans (Pisces, Pimelodidae): efeito do fotoperíodo

The survival and the growth of Pseudoplatystoma corruscans larvae exposed to four photoperiods: light:dark (LD) 0:24, LD 10:14, LD 14:10, and LD 24:0, in a brackish water (5ë) culture were analyzed. Larvae were fed with Artemia sp. nauplii at a 500 nauplii/larvae/day ratio. Survival on day 5 was inversely related to the length of photoperiod. From days 5 to 10, intermediate photoperiods resulted in a better survival, although LD 0:24 and LD 14:10 resulted in similar survival on day 10. Larvae presented higher weight at intermediate photoperiods. The results suggested that photoperiod requirements shifted during early development of P. corruscans larvae.

A sobrevivência e o crescimento de larvas de surubim, Pseudoplatystoma corruscans, submetidas a quatro fotoperíodos: luz:escuro (LE) 0:24, LE 10:14, LE 14:10 e LE 24:0 em água salinizada (5ë) foram avaliadas. As larvas foram alimentadas com náuplios de Artemia sp. na proporção de 500 náuplios/larva/dia. Após cinco dias de experimento, a sobrevivência apresentou relação inversa ao aumento do fotoperíodo. Entre o quinto e o 10º dia, houve tendência de maior sobrevivência nos fotoperíodos intermediários, mas foram registradas sobrevivências semelhantes no intervalo entre LE 0:24 e LE 14:10 no 10º dia. As larvas apresentaram maior peso nos fotoperíodos intermediários. Os resultados sugerem que a exigência de fotoperíodo das larvas de P. corruscans sofre mudanças durante o cultivo.

Stress in Salminus brasiliensis fingerlings due to different densities and times of transportation / Estresse em alevinos de dourado (Salminus brasiliensis) em diferentes densidades e tempos de transporte

The stress in dorado fingerlings (Salminus brasiliensis) caused by transportation at densities of 5, 10, and 15g/l after 4, 8, and 12h was evaluated by the concentration of tissue cortisol measured by ELISA. The conditions of transportation were simulated on an orbital table shaker with horizontal movements, inside 15 litres plastic bags filled with 4 litres of water and pure oxygen. Cortisol concentrations increased in all densities after 4h of transportation converging to a common concentration at the end of the tested times. Electrical conductivity of water increased with density and transportation time. The transportation caused stress on fish, but the increase on density and in times of transportation did not cause mortality to fingerlings. The transportation of S. brasiliensis fingerlings can be done without mortality or apparent injuries to animals until the maximum analyzed density of 15g/l and up to 12h.

O estresse em alevinos de dourado (Salminus brasiliensis) causado pelo transporte nas densidades 5, 10 e 15g/l após 4, 8 e 12h, foi avaliado por meio dos níveis de cortisol tecidual quantificado por ELISA. O transporte foi simulado em uma mesa agitadora com movimento orbital, em sacos plásticos de 15 litros, contendo 4 litros de água e oxigênio puro. As concentrações de cortisol aumentaram em todas as densidades após 4h de transporte e convergiram para uma mesma concentração ao final dos tempos de transporte. A condutividade elétrica da água aumentou com a densidade e com os tempos de transporte. O transporte causou estresse aos peixes, mas o aumento da densidade e do tempo de transporte não causou mortalidade nos alevinos. O transporte de alevinos de S. brasiliensis pode ser realizado até a densidade máxima avaliada de 15g/l e o tempo máximo de 12h sem que haja mortalidade ou danos aparentes aos animais.

Feed transition in larval rearing of bocudo, Steindachneridion scripta (Pisces, Pimelodidae), using Artemia spp. nauplii and artificial diet

Feed transition of Steindachneridion scripta larvae was investigated using seven treatments in which the reference diet, Artemia spp. nauplii, was totally substituted for a 56 percent crude protein artificial diet in two-day intervals. Initially, all treatments were fed with Artemia spp. nauplii and, subsequently, during the transition period, feed was equally composed by Artemia sp. nauplii and artificial diet. Everyday, one of the treatments began the feed transition, which was implemented between the second and the eighth days of culturing. Two treatments were used as control: one exclusively fed Artemia spp. nauplii and another only with artificial diet. Total weight, total length, and survival rate were not influenced by the day in which feed transition was implemented (P>0.05), and their mean values (± SD) were 31.1±25.0mg, 13.3±1.5mm and 58.8±12.0 percent, respectively. This suggests that Steindachneridion scripta larvae adapted well the transition to artificial diet

A transição alimentar de larvas de Steindachneridion scripta foi investigada utilizando-se sete tratamentos, nos quais a dieta básica, composta por náuplios de Artemia spp., foi integralmente substituída, em intervalo de dois dias, por uma dieta artificial contendo 56 por cento de proteína bruta. Inicialmente, todos os tratamentos receberam náuplios de Artemia spp. No período de transição alimentar, metade da alimentação foi formada por náuplios de Artemia spp. e metade por dieta artificial. A cada dia, um dos tratamentos entrou na fase de transição, que foi implementada entre o segundo e o oitavo dia de cultivo. Utilizaram-se dois tratamentos como controle; em um as larvas foram alimentadas, exclusivamente, com náuplios de Artemia spp. e em outro, somente, com dieta artificial. Peso total, comprimento total e sobrevivência não foram influenciados pelo dia de implantação da transição alimentar (P>0,05) e, apresentaram valores médios iguais a (± desvio padrão) 31,1±25,0mg, 13,3±1,5mm e 58,8±12,0 por cento, respectivamente, sugerindo que as larvas Steindachneridion scripta aceitaram bem a transição alimentar para a dieta artificial