Metal cross-contamination relationships between sediments and loricariidae species (siluriform) in a neotropical riverine system.

Human activities have changed the natural rates at which metals are moved and accumulated in both land and water environments, resulting in negative impacts on local wildlife. In this study, concentrations of Cr, Ni, Cd, Pb, Cu, Mn, Co, and Zn were evaluated in water and riverbed sediment samples collected from the Verde River basin (VR), as well as in tissue samples from five native Loricariidae species. Sediment samples collected from the central section of the VR riverbed indicated the presence of metal concentrations, which were primarily attributed to scattered pollution sources linked to rural activities in the surrounding areas. The bioconcentration factor in the Loricariids liver presented the highest average values for Zn (1.27-58.21), Co (0.48-14.91) and Cu (1.15-11.14). The same pattern was observed in the muscle, but in a lower proportion. Regarding the bioaccumulation factor, Co (1.54-34.84), Cu (5.85-25.22) and Zn (0.64-18.08) attained the highest average values in the liver. The co-inertia analysis examined the spatial distribution of metal concentrations in riverbed sediments and in tissues of Loricariids from the upper, middle, and lower stretches of the river, including the river mouth. The analysis revealed varying patterns, with samples from some regions showing higher bioaccumulation levels. This suggests that riverbed sediments are a primary source of metal contamination in Loricariids from these areas. The pollution has had a significant impact on the bioaccumulation of metals in the VR' Loricariids, which are good indicators of sediment-associated metal bioaccumulation. The metal concentrations recorded in both the riverbed sediments and Loricariids surpassed international and Brazilian limits set for aquatic health and safe human consumption. Given the importance of the Verde River in terms of its ecological, social, cultural, and economic roles, it is essential to implement biomonitoring and control measures to safeguard both terrestrial and aquatic resources.

Bioaccumulation and bioconcentration of metals in Characidae from a Neotropical river basin under anthropic activities.

Natural rates of metal mobilization and deposition in terrestrial and aquatic environments have been changed due to anthropic activities, exposing the native biota to dangerous effects related to bioconcentration and bioaccumulation of metals. This study assessed the concentrations of Cr, Ni, Cd, Pb, Cu, Mn, Co, and Zn in the water and riverbed sediment samples from the Verde River basin (VR), and in tissue samples from two native fishes, the Psalidodon paranae, a VR inhabitant, and the Psalidodon aff. fasciatus, a migratory species. Arithmetic mean values of metal concentrations recorded in waters were Cr: 46.16, Ni: 40.29, Cd 43.19, Pb: 57.74, Cu: 63.72, Mn: 98.36, Co: 64.53, Zn: 81.19, while for riverbed sediments were Cr: 11.84, Ni: 10.52, Cd: 7.14, Pb: 15.00, Cu: 22.16, Mn: 334.77, Co: 24.62, Zn: 434.44. For several analyzed samples, metal concentrations found were higher than Brazilian and international limits set for healthy aquatic life and human uses. Analyzed fish tissues also presented metal concentrations higher than Brazilian and international limits set, indicating a high ecological and health risk for the region. Psalidodon paranae showed affinity to bioconcentrate Pb, Zn, and Cd, while Psalidodon. aff. fasciatus tended to bioconcentrate Ni, Zn, and Cr. Multivariate analyses revealed spatial and temporal patterns in the metal contaminations in VR. These patterns were associated with rural and urban activities developed along VR, which practice inadequate soil handling, indiscriminate use of agrochemicals, and the dumping of domestic garbage and untreated and treated sewage into the river. The implementation of public policies for biomonitoring and pollution control by metals in VR is essential to safeguard regional water resources and their biota.

Sexual dimorphism in the catfish Genidens genidens (Siluriformes: Ariidae) based on otolith morphometry and relative growth

Genidens genidens is a species susceptible to population declines in view of their reproductive biology peculiarities. Morphometric differences between sexes are observed in the literature, and these differences should also be evident in otolith development. Growth patterns are one of the most important biological characteristics regarding population dynamics and management. In this context, the aim of the present study is to describe this species relative growth and identify differences between sex life cycles. Somatic growth-otolith growth relationships and somatic length-weight relationships were estimated based on two methodologies; the Huxley and the polyphasic allometric models. Both models demonstrated different growth patterns between sexes. The three axes of otolith growth were adequate descriptors of growth, and the results of the Huxley model demonstrated distinct growth patterns between sexes, with male otoliths larger in all three measured axes. In the polyphase model, male otoliths were thicker, while female otoliths were longer and higher. Both sexes presented similar length-weight relationships, which may indicate that oocyte production and parental care lead to similar costs for this species.(AU)

Genidens genidens é uma espécie suscetível a declínios populacionais, tendo em vista as peculiaridades de sua reprodução. Diferenças morfométricas entre os sexos são observadas na literatura, e essas diferenças também devem ser evidentes no desenvolvimento dos otólitos. O padrão de crescimento é uma das características biológicas mais importantes no que diz respeito à dinâmica populacional e manejo. Assim, nosso objetivo é descrever o crescimento relativo da espécie e identificar diferenças entre os ciclos de vida dos sexos. A relação crescimento somático-crescimento do otólito e a relação comprimento-peso somáticos foram estimados com base em duas metodologias, os modelos alométricos de Huxley e polifásico. Ambos os modelos demonstraram diferentes padrões de crescimento entre sexos. Os três eixos dos otólitos descreveram adequadamente o crescimento, e os resultados do modelo de Huxley demonstraram padrões de crescimento distintos entre os sexos, com os otólitos dos machos sendo maiores em todos os três eixos medidos. No modelo polifásico os otólitos dos machos foram maiores em espessura, enquanto os otólitos das fêmeas exibiram maior comprimento e altura. Ambos os sexos apresentaram relações de comprimento-peso semelhantes, o que pode indicar que a produção de ovócitos e o cuidado parental apresentam custos semelhantes para essa espécie.(AU)

Management proposal based on the timing of oral incubation of eggs and juveniles in the sentinel species Genidens genidens (Siluriformes: Ariidae) in a tropical estuary

Ariids such as Genidens genidens are particularly susceptible to overfishing because of their complex reproductive mechanisms, which result in slow replenishment of stocks. In this study, we obtained data about the reproductive ecology of the catfish G. genidens in the Guanabara Bay estuary, Rio de Janeiro, Brazil, providing supporting information for management of its fishery. The sex ratio, mean size of each sex at first sexual maturation, and female fecundity were determined and the reproductive period was characterized. The males:females ratio was 1:2. The fecundity is low and increases proportionally to the females' growth in total length and weight. The breeding season occurs during the warmest months of the year, with spawning extending from October through March and incubation from December through April. Sexual maturation is late, with males maturing at a larger size than females. Skipping spawning was also identified in females. Based on the reproductive biology, it is suggested that the catch be restricted to individuals larger than 20 cm, considering the L75 of the males, and that fishing be prohibited from December through March, to include the main period of spawning season by females and oropharyngeal incubation by males.(AU)

Ariídeos, como Genidens genidens, são particularmente suscetíveis à sobrepesca devido a seus complexos mecanismos reprodutivos, que resultam em uma reposição lenta dos estoques. Neste estudo, obtivemos dados sobre a ecologia reprodutiva do bagre G. genidens no estuário da Baía de Guanabara, Rio de Janeiro, Brasil, fornecendo subsídios para seu manejo pesqueiro. A proporção sexual, o tamanho médio de primeira maturação sexual de cada sexo e a fecundidade das fêmeas foram determinados e o período reprodutivo caracterizado. A proporção machos:fêmeas foi de ١:2. A fecundidade é baixa e aumenta proporcionalmente ao crescimento das fêmeas em comprimento total e no peso. O período reprodutivo ocorre durante os meses mais quentes do ano, com a desova se estendendo de outubro a março e a incubação de dezembro a abril. A maturação sexual é tardia, com machos amadurecendo em tamanho maior que as fêmeas. Também foi identificado nas fêmeas adiamento da desova. Com base na biologia reprodutiva, sugere-se que a captura seja restrita a indivíduos maiores que 20 cm, considerando a C75 dos machos, e que a pesca seja proibida de dezembro a março, para incluir o período principal de época de desova das fêmeas e incubação orofaríngea dos machos.(AU)

Acute Toxicity of Nitrite to Various Life Stages of the Amazon River Prawn, Macrobrachium amazonicum, Heller, 1862.

This study determined the effects of nitrite on different life stages of the Amazon river prawn Macrobrachium amazonicum. Prawns of each life stage (postlarvae, juveniles and adults) were stocked in 24 experimental units (n = 10 prawns), under a complete randomized design. Individuals were exposed to nitrite (0, 1, 2, 4, 8 and 16 mg L-1). The median lethal concentration after 96 h (96 h LC50) was calculated through the Weibull I. The mortality results showed that M. amazonicum is slightly less tolerant to nitrite than other species of Macrobrachium. The 96 h LC50 for postlarvae, juveniles and adults of M. amazonicum were of 1.49, 2.36 and 2.34 mg nitrite/L, respectively. Nitrite intoxication risk quotient suggest moderated risk to low risk to the species. Usually in production systems nitrite values are lower than safe levels suggested in this study (0.1 mg L-1 to postlarvae and 0.2 mg L-1 nitrite to juvenile and adults), which makes our results appropriate for the production of this species.

Length-weight relationships of the ichthyofauna from a coastal subtropical system: a tool for biomass estimates and ecosystem modelling / Relações comprimento-peso da ictiofauna de um sistema costeiro subtropical: uma ferramenta para estimativas de biomassa e modelagem de ecossistemas

Aiming to analyse the growth pattern, to allow biomass estimates and consequently to subsidize the ecosystem modelling, the length-weight relationships (LWR) of 39 fish species from the Araçá Bay, a subtropical coastal area chosen as model for a holistic study comprising environmental, social and economic aspects have been estimated. The objective of this study was to provide LWR for the fishes from the area itself, accurately based on the life stages of fish populations present there. Particularly for Albula vulpes, Trachinotus carolinus, T. falcatus, Archosargus rhomboidalis and Kyphosus sectatrix these are the first records of LWR in Brazil.

Com o objetivo de analisar o padrão de crescimento e viabilizar estimativas de biomassas e, consequentemente, subsidiar a modelagem ecossistêmica, foram estimadas as relações comprimento-peso (RCP) de 39 espécies de peixes da baía do Araçá, uma área costeira subtropical escolhida como modelo para um estudo holístico compreendendo aspectos ambientais, sociais e econômicos. O objetivo deste estudo foi fornecer RCP para os peixes da própria área, baseadas nas estágios de vida das populações ictiícas ali presentes. Especialmente para Albula vulpes, Trachinotus carolinus, T. falcatus, Archosargus rhomboidalis e Kyphosus sectatrix estas são as primeiras estimativas de RCP no Brasil.

Reproduction of the silver John dory Zenopsis conchifer (Actinopterygii: Zeiformes) based on virgin stock condition / Reprodução do peixe galo-de-profundidade Zenopsis conchifer (Actinopterygii, Zeiformes) baseada em um estoque virgem

This study describes the reproduction of the silver John dory, Zenopsis conchifer, based on data collected before its fishery exploitation in the southwestern Atlantic, Brazil, in the early 2000s. Biological material was collected through bottom-trawl surveys in 2001 and 2002 from depths of 100 to 600 m. A total of 1,056 individuals ranging from 57 to 504 mm Ls were analyzed. A sex ratio analysis showed that males were predominant among the shorter fishes (< 240 mm Ls) and females among the longer ones (> 320 mm Ls). Between 240 mm and 319 mm Ls sex-ratio was 1:1. The silver John dory is a multiple spawner. Spawning is protracted and more intensive during August and November, when both females and males in spawning capable actively spawning and in regression/regeneration stages were predominant. In this period average values of gonadosomatic index were also higher. For both sexes, the first maturation occurs at 220 mm Ls and at 240 mm Ls all fish can be considered adult. The recruitment apparently takes place from February to May. The length-weight relationships fitted to all specimens and for both sexes yieldedb coefficients of ∼2.7. The virgin stock ofZ. conchifer here characterized, may serve a basis for future studies on the effects of fisheries on the reproduction of the species.

O presente estudo descreve a reprodução do peixe galo-de-profundidade,Zenopsis conchifer, a partir de dados pretéritos a sua explotação pesqueira no Atlântico Sudoeste, Brasil, iniciada nos anos 2000. As coletas foram realizadas durante cruzeiros de prospecção pesqueira com arrasto-de-fundo em 2001 e 2002, em profundidades entre 100 e 600 m. Um total de 1056 exemplares (comprimento padrão entre 57 mm e 504 mm) foi examinado. A proporção sexual mostrou que machos predominam em comprimentos inferiores a 240 mm, que entre 240 mm e 319 mm a proporção é de 1:1 e que fêmeas predominam a partir de 320 mm. O peixe galo-de-profundidade apresenta desova múltipla, mais intensa entre agosto e novembro, quando predominam fêmeas e machos desovantes ativos e em regressão/regeneração. Neste período foram registrados os maiores valores do índice gonadossomático. Para ambos os sexos a primeira maturação se dá aos 220 mm de comprimento padrão e com 240 mm os indivíduos são considerados adultos. O recrutamento de jovens para o estoque adulto foi mais intenso entre fevereiro e maio. Os valores dos coeficientes b das relações comprimento peso ajustadas para todos os peixes e por sexo ficaram em torno de 2,7. As condições do estoque virgem de Z. conchiferaqui caracterizadas podem servir como um referencial para futuros estudos sobre os efeitos da pesca na reprodução da espécie.