Morphometric Evaluations and Yields from Commercial Cuts of Black Pacu Colossoma macropomum (Cuvier, 1818) in Different Body Weights

For the Amazon, it is important to encourage the production of native fish, since there are several species of zootechnical interest. For this, it is necessary to know the species since its acquisition, production, processing, and marketing. Therefore, the aim of this study was to analyze the yield, correlations, and profitability of different cuts of black pacu (Colossoma macropomum) in five weight categories. Data from 220 black pacus were obtained, with a weight range of 2725 ± 1975 g. Yields of commercial cuts and morphometric measurements were evaluated in five weight classes. Kruskal–Wallis test (α = 0.05) was used to compare the average income. And, to verify the correlation between the morphometric measures and the yields, Spearman’s correlation was performed (α = 0.05). To obtain the profit of the weight classes due to the cut produced, an economic analysis was carried out considering the cost of buying the fish. Yields of fillet, ribs, and steak were higher in classes 3 and 4, while in the same classes, the yield of residues was the lowest. Despite classes 1, 2, and 5 showing lower yields, the economic analysis presented that the production of fillet and ribs was profitable. The measures of total length and standard length have a high positive correlation with the yield of meat in all classes, as well as the average circumference and caudal circumference in classes 1, 2, and 4, which can be used to determine the yields of this commercial cut.

A INTRODUÇÃO E DISTRIBUIÇÃO DO TUCUNARÉ-AZUL E DO TAMBAQUI NO PANTANAL CORUMBAENSE

O Pantanal possui características únicas, porém similares à Bacia Amazônica, principalmente no que tange os ciclos de cheias em ambas as regiões. Tais semelhanças permitiram que espécies de peixes introduzidas como o tucunaré-azul (Cichla piquiti) e o tambaqui (Colossoma macropomum) se desenvolvessem na região pantaneira após escape de tanques, escavados na década de 1980. Neste sentido, foi realizada a averiguação da ocorrência de tais espécies nos principais pontos de pesca, no rio Paraguai, partindo da cidade de Corumbá, na planície pantaneira. Nos pontos analisados, foi feita pesca de exemplares com a utilização de apetrechos de pesca permitidos pela legislação vigente para a pesca amadora, considerando o esforço de pesca de oito horas por dia de campanha amostral, totalizando sete campanhas e 56 horas de esforço amostral entre 2018 e 2019. Os resultados apontam que o tucunaré já se encontra amplamente espalhado na planície pantaneira, já o tambaqui ainda se mantém restrito à algumas baías. Sendo assim, é necessário que haja um monitoramento das espécies e estudos comportamentais desses espécimes para compreender e mitigar os impactos da sua introdução em tão importante planície.

Climate change affects the parasitism rate and impairs the regulation of genes related to oxidative stress and ionoregulation of Colossoma macropomum

Global climate change represents a critical threat to the environment since it influences organismic interactions, such as the host-parasite systems, mainly in ectotherms including fishes. Rising temperature and CO2 are predicted to affect this interaction other and critical physiological processes in fish. Herein, we investigated the effects of different periods of exposure to climate change scenarios and to two degrees of parasitism by monogeneans in the host-parasite interaction, as well as the antioxidant and ionoregulatory responses of tambaqui (Colossoma macropomum), an important species in South American fishing and aquaculture. We hypothesized that temperature and CO2 changes in combination with parasite infection would interfere with the host’s physiological processes that are related to oxidative stress and ionoregulation. We experimentally exposed C. macropomum to low and high levels of parasitism in the current and extreme climate scenarios (4.5 °C and 900 ppm CO2 above current levels) for periods of seven and thirty days and we use as analyzed factors; the exposure time, the climate scenario and parasitism level in a 2 × 2 × 2 factorial through a three-way ANOVA as being fish the experimental unit (n = 8). An analysis of gill enzymatic and gene expression profile was performed to assess physiological (SOD, GPx and Na+/K+-ATPase enzymes) and molecular (Nrf2, SOD1, HIF-1α and NKA α1a genes) responses. A clear difference in the parasitism levels of individuals exposed to the extreme climate scenario was observed with a rapid and aggressive increase that was higher after 7 days of exposure though showed a decrease after 30 days. The combination of exposure to the extreme climate change scenario and parasitism caused oxidative stress and osmoregulatory disturbance, which was observed through the analysis of gene expression (Nrf2, SOD1, HIF-1α and NKA α1a) and antioxidant and ionoregulatory enzymes (SOD, GPx and Na+/K+-ATPase) on the host, possibly linked to inflammatory processes caused by the high degree of parasitism. In the coming years, these conditions may result in losses of performance for this species, and as such will represent ecological damage and economical losses, and result in a possible vulnerability in relation to food security.

Modelos matemáticos para estimar o consumo de dieta para Tilápia do Nilo (Oreochromis niloticus) e Tambaqui (Colossoma macropomum)

A tecnologia de precisão a cada dia se insere ao meio rural, e para isso, pesquisas com modelos matemáticos que possam ser adotadas para aperfeiçoar os manejos se fazem necessárias. Essa pesquisa tem o objetivo de elaborar curvas não lineares a partir de equações consolidadas no meio científico para o consumo de dietas para tambaqui e Tilápia do Nilo. Ao obter informações sobre o crescimento ao longo do tempo e tabelas de oferta de alimentos para cada fase de crescimento para a espécie de peixes estudadas, se procedeu à elaboração de curvas de crescimento ao longo do tempo e de seu consumo alimentar. Com base nos dados coletados, os parâmetros das equações de quatro modelos não lineares (Gompertz e Logístico) foram estimados para as duas variáveis estudadas (Crescimento em peso (g) ao longo do tempo e Consumo alimentar (g) ao longo do tempo). Avaliadores de ajustes (interpretação biológica e análise dos resíduos studentizados) foram adotados para selecionar e verificar a qualidade dos modelos. Os dados gerados de oferta ou consumo de ração para tilápias do Nilo e tambaquis se adequaram aos modelos Gompertz e Logístico, respectivamente. Esses modelos podem ser utilizados para estimar consumo ou oferta de ração para tilápia do Nilo e o tambaqui, porém é necessário rigor nos critérios de avaliação e ajustes.