Early life history of two Neotropical Triportheidae fish (Characiformes)

The early ontogeny of Triportheus albus and T. angulatus, two fish species of Triportheidae, is described using morphological, meristic, and morphometric characters. These species are exploited by subsistence fisheries and have potential as an alternative source of fish, given the decline in the natural stocks of other commercially important fish species in the Amazon. The specimens were collected in the open water limnetic zone, under of the macrophyte stands, and in subsurface areas near sandbars in the Amazon basin. Intra and interspecific morphometric analyzes were performed to evaluate growth models between species. The combination of color pattern, body morphology, morphometric proportions and myomeres number distinguishes the species from each other and from other congeners. Some morphometric relationships related to head as snout length and eye diameter as well as length from the snout to the origins of anal and length from the snout to the origins of pelvic, related with standard length were different between the two species of Triportheus, reflecting different growth models between them. An identification key for larvae and juveniles of some species of Triportheus from the Eastern Amazon is presented.(AU)

A ontogenia inicial de Triportheus albus e T. angulatus, duas espécies de peixes pertencentes a Triportheidae, é descrita usando caracteres morfológicos, merísticos e morfométricos. Essas espécies são exploradas pela pesca de subsistência e têm potencial como fonte alternativa de pescado, dado o declínio nos estoques naturais de outras espécies de peixes comercialmente importantes na Amazônia. Os espécimes foram coletados na zona limnética de águas abertas, sob bancos de macrófitas e em áreas subsuperficiais próximas a bancos de areia na bacia amazônica. Análises morfométricas, intra e interespecíficas, foram realizadas para avaliar modelos de crescimento entre as espécies. A combinação do padrão de coloração, morfologia corporal, proporções morfométricas e número de miômeros distingue as espécies entre si e de outras congêneres. Algumas relações morfométricas relacionadas à cabeça, como comprimento do focinho e diâmetro do olho, assim como o comprimento do focinho à origem da nadadeira anal e o comprimento do focinho à origem da nadadeira pélvica, relacionadas ao comprimento padrão foram diferentes entre as duas espécies de Triportheus, refletindo modelos distintos de crescimento entre elas. Uma chave de identificação para larvas e juvenis de algumas espécies de Triportheus da Amazônia Oriental é apresentada.(AU)

Early development of two commercially valuable fish from the lower Amazon River, Brazil (Characiformes: Serrasalmidae)

We described the early development of Myloplus asterias and M. lobatus, two fish species of the Serrasalmidae using morphological, meristic, and morphometric characteristics. These herbivores serrasalmids are heavily fished because of their commercial importance in the Amazon. The individuals were collected between 2016 and 2020 in the limnetic zone of open water and macrophyte stands in the Lower Amazon River floodplain. We tested different growth models to identify the development pattern of these species. During the initial ontogeny, these two species can be differentiated mainly by the myomeres total number, 37 to 39 in M. asterias vs. 40 to 41 in M. lobatus, the pigmentation pattern, and dorsal-fin ray numbers. These characteristics are effective in distinguishing these species from other serrasalmids. The morphometric relationships were also different between these two species, showing distinct patterns in growth between the analyzed features. An identification key for larvae of some sympatric Serrasalmidae species from the Amazon basin is presented. Our expectation is that this study will contribute to the knowledge of the initial ontogeny and the biology of fish species in the Neotropical region.(AU)

Descrevemos o desenvolvimento inicial de Myloplus asterias e M. lobatus, duas espécies de peixes da família Serrasalmidae usando características morfológicas, merísticas e morfométricas. Esses serrasalmídeos herbívoros são fortemente pescados devido à sua importância comercial na Amazônia. Os indivíduos foram coletados entre 2016 e 2020 na zona limnética de águas abertas e em bancos de macrófitas na planície de inundação do baixo rio Amazonas. Testamos diferentes modelos de crescimento para identificar o padrão de desenvolvimento dessas espécies. Durante a ontogenia inicial, essas duas espécies podem ser diferenciadas pelo número total de miômeros; 37 a 39 em M. asterias vs. 40 a 41 em M. lobatus; pelo padrão de pigmentação e número de raios da nadadeira dorsal. Essas características são eficazes para distinguir essas espécies de outros serrasalmídeos. As relações morfométricas também foram diferentes entre as duas espécies, com distintos padrões de crescimento entre as características analisadas. Uma chave de identificação para larvas de algumas espécies simpátricas de Serrasalmidae da bacia amazônica é apresentada. Nossa expectativa é que este estudo contribua para o conhecimento da ontogenia inicial e da biologia das espécies de peixes da região Neotropical.(AU)

Larvae of migratory Characiformes species in an archipelago in the Lower Amazon River

In the Amazon basin, most of the migratory Characiformes species represent an important fishing resource for local people. However, the lack of information about the main areas and periods of reproduction and the importance of certain environments for the maintenance of species may jeopardize the renewal of fish stocks. Thus, the aim was to examine the spatial and seasonal variation in the density of larvae of migratory Characiformes species in an archipelago in the Lower Amazon River and to assess the importance of this environment for the biological recruitment of the studied species. The capture of larvae was carried out in places close to restinga swamps, steep ruts,and inlet areas with a plankton net (300 μm) in monthly sampling from January to December 2013. An analysis of variance was used to verify differences in larval density between seasons and sampling months. A total of 30,997 larvae were captured and showed no significant differences in their distributions between habitats. However, a variationbetween the phases of the hydrological cycle was evident, in which the highest larval concentrations were observed during the flooding (17.72 larvae.10m-3) and the drought (1.33 larvae.10m-3). The study area has a great capacity to assist in the maintenance and renewal of regional fish stocks, as it is an important retention and nursery site for larvae of Characiformes that drift along the main channel of the Amazon River.

Larvae of migratory Characiformes species in an archipelago in the Lower Amazon River

In the Amazon basin, most of the migratory Characiformes species represent an important fishing resource for local people. However, the lack of information about the main areas and periods of reproduction and the importance of certain environments for the maintenance of species may jeopardize the renewal of fish stocks. Thus, the aim was to examine the spatial and seasonal variation in the density of larvae of migratory Characiformes species in an archipelago in the Lower Amazon River and to assess the importance of this environment for the biological recruitment of the studied species. The capture of larvae was carried out in places close to restinga swamps, steep ruts,and inlet areas with a plankton net (300 μm) in monthly sampling from January to December 2013. An analysis of variance was used to verify differences in larval density between seasons and sampling months. A total of 30,997 larvae were captured and showed no significant differences in their distributions between habitats. However, a variationbetween the phases of the hydrological cycle was evident, in which the highest larval concentrations were observed during the flooding (17.72 larvae.10m-3) and the drought (1.33 larvae.10m-3). The study area has a great capacity to assist in the maintenance and renewal of regional fish stocks, as it is an important retention and nursery site for larvae of Characiformes that drift along the main channel of the Amazon River.(AU)

Length-weight relationship of the six most abundant fish species in prawn fishery semi-fixed trap bycatches in the lower amazon region (Pará, Brazil) / Relação peso-comprimento das seis espécies de peixes mais abundantes na pesca de camarão em armadilhas semifixas na região do baixo amazonas (Pará)

In this study, the length-weight relationships (LWR) were estimated for six fish species captured during prawn fishing in the Lower Amazon region (Pará, Brazil). Prawn fishing boosts the socioeconomic development of riverine communities and is a relevant activity as a source of income and subsistence in this region. In addition, we registered new LWRs for the species Ossancora punctata and Hypoptopoma elongatum. The samplings were performed in prawn catches monthly from February 2018 to January 2019, using a “matapi”, which consists of a semi-fixed trap that has a galvanized iron structure (2.5 m height by 2.0 m in length) and nylon mesh (1.40 x 1.60 mm mesh), and has two tapered openings to facilitate the entry and trapping of the prawn. The results show that 75% of the fish caught as prawn bycatches had not yet reached sexual maturity. Thus, it is clear that fisheries need to develop fishing gear that allow small fish to escape from the traps during the prawn fishery.

Neste estudo, as relações de peso-comprimento (RPC) foram estimadas para seis espécies de peixes capturadas durante a pesca do camarão de água doce na região da Baixa Amazônia (Pará, Brasil). A pesca do camarão promove o desenvolvimento socioeconômico das comunidades ribeirinhas, sendo uma atividade de fonte de renda e subsistência nesta região. Além disso, registramos novas RPCs para as espécies Ossancora punctata e Hypoptopoma elongatum. As amostragens foram realizadas mensalmente em capturas de camarão, entre fevereiro de 2018 e janeiro de 2019, com o uso de “matapi”, que consiste em uma armadilha semifixa, com estrutura de ferro galvanizado (com altura de 2,5 m por 2,0 m de comprimento) e tela de náilon (malha de 1,40 mm x 1,60 mm), com duas aberturas afuniladas para facilitar a entrada e aprisionamento do camarão. Os resultados mostraram que 75% dos peixes capturados como fauna acompanhante de camarão ainda não tinha atingido a maturidade sexual. Assim, é evidente que as pescarias precisam desenvolver equipamentos de pesca que permitam que os peixes menores escapem da captura durante a pesca do camarão.

Length-weight relationship of the six most abundant fish species in prawn fishery semi-fixed trap bycatches in the lower amazon region (Pará, Brazil) / Relação peso-comprimento das seis espécies de peixes mais abundantes na pesca de camarão em armadilhas semifixas na região do baixo amazonas (Pará)

In this study, the length-weight relationships (LWR) were estimated for six fish species captured during prawn fishing in the Lower Amazon region (Pará, Brazil). Prawn fishing boosts the socioeconomic development of riverine communities and is a relevant activity as a source of income and subsistence in this region. In addition, we registered new LWRs for the species Ossancora punctata and Hypoptopoma elongatum. The samplings were performed in prawn catches monthly from February 2018 to January 2019, using a “matapi”, which consists of a semi-fixed trap that has a galvanized iron structure (2.5 m height by 2.0 m in length) and nylon mesh (1.40 x 1.60 mm mesh), and has two tapered openings to facilitate the entry and trapping of the prawn. The results show that 75% of the fish caught as prawn bycatches had not yet reached sexual maturity. Thus, it is clear that fisheries need to develop fishing gear that allow small fish to escape from the traps during the prawn fishery.(AU)

Neste estudo, as relações de peso-comprimento (RPC) foram estimadas para seis espécies de peixes capturadas durante a pesca do camarão de água doce na região da Baixa Amazônia (Pará, Brasil). A pesca do camarão promove o desenvolvimento socioeconômico das comunidades ribeirinhas, sendo uma atividade de fonte de renda e subsistência nesta região. Além disso, registramos novas RPCs para as espécies Ossancora punctata e Hypoptopoma elongatum. As amostragens foram realizadas mensalmente em capturas de camarão, entre fevereiro de 2018 e janeiro de 2019, com o uso de “matapi”, que consiste em uma armadilha semifixa, com estrutura de ferro galvanizado (com altura de 2,5 m por 2,0 m de comprimento) e tela de náilon (malha de 1,40 mm x 1,60 mm), com duas aberturas afuniladas para facilitar a entrada e aprisionamento do camarão. Os resultados mostraram que 75% dos peixes capturados como fauna acompanhante de camarão ainda não tinha atingido a maturidade sexual. Assim, é evidente que as pescarias precisam desenvolver equipamentos de pesca que permitam que os peixes menores escapem da captura durante a pesca do camarão.(AU)