For some time, the rate of non-native fish introductions has been increasing in South America. There are many reasons for introductions: reservoir stocking programs, aquaculture, sport fishing, control of disease vectors, and the pet trade. Accidental escapes also contribute significantly. In Brazil, despite federal and state regulations, there are misunderstandings about such concepts as native, exotic, allochthonous, or autochthonous fishes and introductions, translocations, reintroductions, and transfers of fishes. Known impacts of exotic fishes include native species extinction, changes in competition and predation rates, limnological perturbations, introduction of diseases and parasites, hybridization with native species, and changes in fisheries composition. The few recorded benefits of non-native species introductions are restricted to the improvement of fish production and sport fisheries. In Minas Gerais, Brazil, records of exotic species have increased over the past seven years. In some of the most important river basins of that state, alien fish species might represent up to 40% of the fish fauna. Congeneric species, such as Hyphessobrycon bifasciatus and the exotic H. eques, can be captured from the same water body and the non-native species can be much more abundant than the native species. The recent introduction of Leporinus macrocephalus from the Pantanal may cause the same impact to the native L. copelandii. The widespread introduction of the peacock bass and other piscivorous species is the cause of local extinctions in the central lake of Lagoa Santa and in the Theresa M. Bert (ed.), Ecological and Genetic Implications of Aquaculture Activities, 291-314. ß 2007 Springer.Rio Doce valley lakes. Genetic problems can also be foreseen with the release of hybrids of Pseudoplatystoma corruscans and P. fasciatum in areas where only the first species naturally occurs. Tilapine species, the most widely distributed exotics within the state, have had negative impacts on fisheries and on fish species compositions in reservoirs. Solution to these problems must involve the following: (1) better enforcement of legislation governing the sale and transport of live organisms, (2) development of native-species aquaculture, and (3) public awareness programs on the adverse impacts of exotic species to the native fish fauna.

Informal sales of large-bodied non-native aquarium fishes (known as "tankbusters") is increasing among Brazilian hobbyists. In this study, we surveyed this non-regulated trade on Facebook ® from May 2012 to September 2016, systematically collecting information about the fishes available for trading: species, family, common/scientific names, native range, juvenile length, behavior, number of specimens available in five geographical regions from Brazil. We also assessed the invasion risk of the most frequently sold species using the Fish Invasiveness Screening Test (FIST). We found 93 taxa belonging to 35 families. Cichlidae was the dominant family, and most species were native to South America. All species are sold at very small sizes (< 10.0 cm), and most display aggressive behavior. The hybrid Amphilophus trimaculatus × Amphilophus citrinellus, Astronotus ocellatus, Uaru amphiacanthoides, Osteoglossum bicirrhosum, Cichla piquiti, Pangasianodon hypophthalmus, Datnioides microlepis and Cichla kelberi were the main species available. The southeast region showed the greatest trading activity. Based on biological traits, the FIST indicated that Arapaima gigas, C. kelberi and C. temensis are high-risk species in terms of biological invasions via aquarium dumping. We suggest management strategies such as trade regulations, monitoring, euthanasia and educational programs to prevent further introductions via aquarium dumping.Keywords: Aquarium releases, Aquarium trade, Biological invasions, Invasiveness, Propagule pressure.A venda de juvenis de peixes não-nativos de grandes dimensões, chamados de "peixes jumbo", está aumentando entre aquaristas no Brasil. Neste trabalho, pesquisou-se este comércio informal pelo Facebook ® de maio/2012 a setembro/2016, coletando-se informações sobre espécies, família, nomes vulgares/científicos, origem, tamanho juvenil, comportamento e número/frequência de exemplares disponíveis nas cinco regiões geográficas do Brasil. Também avaliou-se o risco de invasão das espécies mais vendidas usando o protocolo Fish Invasiveness Screening Test (FIST). Foram encontradas 93 espécies pertencentes a 35 famílias. Cichlidae foi a família dominante, e a maioria das espécies é nativa da América do Sul. Todas as espécies foram vendidas como juvenis (< 10.0 cm), e a maioria exibe comportamento agressivo. O híbrido Amphilophus trimaculatus × Amphilophus citrinellus, Astronotus ocellatus, Uaru amphiacanthoides, Osteoglossum bicirrhosum, Cichla piquiti, Pangasianodon hypophthalmus, Datnioides microlepis e Cichla kelberi foram as espécies mais comercializadas. A região sudeste apresentou a maior porcentagem de vendas, e o FIST mostrou que Arapaima gigas, C. kelberi e C. temensis foram consideradas de alto risco para desencadear invasões biológicas mediadas por descarte de aquários. Recomendações como a regulação do comércio, monitoramento, sacrifício das espécies e campanhas educacionais para os aquaristas são sugeridas para evitar futuras introduções de peixes via descarte de aquários. Palavras-chave:Comércio o...

The gametogenesis and reproduction of the matrinxã, Brycon orthotaenia in the São Francisco river, Pirapora Region, Minas Gerais, were studied from December, 1998 to November, 1999. The matrinxã B. orthotaenia is an endemic species in the São Francisco river basin in Brazil and important for commercial fishing. The size of the 1 st gonadal maturation, indicated by the total length of the smallest spent males and spawned female, was 32.0 and 40.5 cm respectively. Reproduction occurred from October to January, when high frequencies of females and males at an advanced ripening/mature stage and spawned females were found. The short spawning period and histological characteristics of spawned ovaries containing only oocytes in stages of initial development, along with post-ovulatory and atresic follicles, indicated that Brycon orthotaenia presents total spawning.Keywords: teleost fish, oogenesis, spermatogenesis, reproductive cycle. RESUMO Gametogênese e reprodução do matrinxã Brycon orthotaenia (Günther, 1864) (Pisces: Characidae) do rio São Francisco, Minas GeraisEstudaram-se a gametogênese e a reprodução de Brycon orthotaenia do rio São Francisco, na região de Pirapora, Minas Gerais, no período de dezembro/1998 a novembro/1999. O matrinxã B. orthotaenia é uma espécie endêmica da bacia do rio São Francisco, Brasil e importante na pesca comercial. O tamanho de 1ª maturação gonadal, indicado pelo comprimento total do menor macho espermiado e da menor fêmea desovada, foi de 32,0 e 40,5 cm, respectivamente. A reprodução ocorreu de outubro a janeiro, quando observam-se altas freqüências de fêmeas e machos no estádio maturação avançada/maduro e fêmeas desovadas. O curto período de desova e as características histológicas de ovários desovados, contendo somente ovócitos nos estádios iniciais de desenvolvimento ao lado de folículos pós-ovulatórios e atrésicos, indicam que a desova de B. orthotaenia é do tipo total.Palavras-chave: peixe teleósteo, ovogênese, espermatogênese, ciclo reprodutivo.

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The reproductive biology of the surubim, P. coruscans of the São Francisco River, in the Pirapora region was studied from December/98 to November/99. Reproduction occurred between October and January with high frequency of fishes in the advanced ripening/mature and spawned/spent stages along with higher values of the gonadosomatic index. Macroscopic and microscopic analyses indicated that P. coruscans presents total spawning. The reproductive period coincided with highest rainfall and water turbidity values in the region. The smallest male captured had a total length of 63.3cm and the smallest female 92.0cm in total length. The largest male in the maturation stage was recorded to be 97.0cm and the largest female 144.1cm in total length. Surubim were more frequently captured than females, at a proportion of approximately one female to three males. The gonadosomatic, hepatosomatic, stomach repletion, and coelomic fat indexes, as well as the condition factor were related to stages of the reproductive cycle.

The testes of the catfish Conorhynchus conirostris(n = 67) from the São Francisco River, Minas Gerais, Brazil were of the fringed type, similar to those of some Pimelodidae. The germ, Sertoli and Leydig cells showed characteristics which are general for all vertebrates although the spermatozoa had a peculiar morphology, with an ovoid head without an acrosome, inverted U‐shaped nucleus, a short midpiece and a long tail, typical of teleosts showing external fertilization. The spermatic duct and genital papilla performed a secretory function.

The composition and antibacterial properties of indigenous intestinal microbiota from Prochilodus argenteus were studied during reproductive (alimentary restriction) and nonreproductive (normal feeding) periods. Dilutions of intestinal contents from 21 specimens of P. argenteus captured from Sa˜o Francisco Basin, Minas Gerais State, Brazil, were used for enumeration, isolation, identification and determination of in vitro antibacterial properties of predominant components of the intestinal microbial ecosystem. Predominant species recovered for both periods were: Aeromonas hydrophila, Plesiomonas shigelloides, Lactococcus lactis and an unidentified Gram-positive rod for facultative anaerobes and Bacteroides stercoris/ eggerthii and Fusobacterium mortiferum for obligate anaerobes. Gram-positive components of this microbiota showed high antagonistic activity against gram-negative species. Coagulasenegative Staphylococcus sp., Enterococcus durans, Enterococcus faecium and the unidentified gram-positive rod had wider range of antagonism properties. The indigenous intestinal microbiota of P. argenteus was quite similar to that of other fishes and the reproductive and alimentary status has few influences on its composition. # 2005 The Fisheries Society of the British Isles

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