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The aim of this study was to evaluate the influence of different stunning methods on the meat quality of Arapaima gigas fillets from fish farming. A total of 48 specimens of A. gigas in the weight class 11.1 to 14.0 kg were investigated; these fish were subjected to different stunning methods for slaughter: ice asphyxia (IA), air asphyxia (AA), electronarcosis (EE) and hypothermia followed by bleeding (HB). Then, data were obtained from the analysis of pH, rigor mortis index (RI), water activity (Aw), instrumental texture (compression strength, firmness and adhesiveness) and blood glucose and via instrumental colourimetry. During the study, for up to 15 days of refrigerated storage, the methods provided pH values below 6.0. A. gigas submitted to EE and HB remained longer in the pre-rigor status. In addition, they expressed lower percentages of Aw. The EE method resulted in better texture assignments in the fillets. The blood glucose values indicated that the fish subjected to EE were less stressed. Concerning instrumental colourimetry, the fillets submitted to EE and HB showed greater luminosity; the fillets subjected to AA showed greater red-green colour intensity, while the fillets subjected to EE showed greater yellow-blue colour intensity. Therefore, the fish did not suffer stress with electronarcosis, and the fillets showed better preservation, juiciness, and tenderness.

The main aimed of this study was to evaluate the physicochemical parameters, abundance and density of cyanobacteria, determine their blooms and the ecotoxicological risk of their cyanotoxins in fish ponds water. This study was conducted out in 20 fish farms in Rondônia state (Brazilian Amazon), samplings were carried out in the rainy and dry seasons. The experiment was developed in a completely randomized factorial design 20 × 3 x 3 (20 fish farms, 3 ponds and 3 replications). Regarding the composition of qualitative samples, horizontal and vertical hauls were carried out on the water surface, quantitative samples was obtained using a plankton net (50 μm mesh opening). Meanwhile, with the use of a multiparametric probe, physicochemical analyzes in fish ponds water were carried out. Furthermore, the cyanobacteria found were classified taxonomically and its blooms were recorded. Finally, blood was collected from 60 Colossoma macropomum . Concerning the higher averages in the rainy season 6.13 mg L ⁻1 of dissolved oxygen, 40.02 cm of transparency, 0.35 NO 3 1⁻ of nitrate, 0.15 NO 2 1⁻ of nitrite, 44.55 mg L ⁻1 CaCO 3 of alkalinity and 50.10 mg L ⁻1 CaCO 3 of hardness, while higher averages of pH, phosphate and phosphorus were found in the dry season. A total of 15 families and 29 species of cyanobacteria were identified in the different seasons. The families that showed the highest densities (rainy and dry seasons) were Microcystaceae (356 and 760 cells mL ⁻1 ), Leptolyngbyaceae (126 and 287 cells mL ⁻1 ) and Microcoleaceae (111 and 405 cells mL ⁻1 ). The species that showed the highest densities were Microcystis aeruginosa (356 and 697 cells mL ⁻1 ), Planktolyngbya limnetica (98 and 257 cells mL ⁻1 ) and Planktothrix sp. (111 and 239 cells mL ⁻1 ). There were significant Pearson's correlations ( r  > 0.85; p  < 0.05) between family abundances and cyanotoxin volume between physicochemical water variables and seasonality. A total of 20 cyanobacteria blooms were recorded, all of which in the dry season showed an ecotoxicological risk. Concerning the assessment mutagenicity in fish blood cells, a total of 78 abnormalities per slide were observed. In the dry season, the expected volume of cyanotoxins in the ponds from fish farms F1 and F4 were above the quantification limit (>QL). Abundance and density of cyanobacteria and their blooms and cyanotoxins can be used as bioindicators of eutrophication and/or water quality and ecotoxicological risk in fish ponds., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

The main aimed of this study was to provide information on microplastics present in the freshwater of fish farm ponds. In addition, the study showes a relationship between the seasonal, spatial distribution and the amount of microplastics found. This study was conducted in 35 fish farms located in the Rondônia state, Brazil, the sample collects were carried out in the two Amazonian hydrological seasons (dry and rainy). The study was developed in a completely randomized factorial scheme 35 × 3 x 3 (35 fish farms, 3 ponds and 3 repetitions per ponds). Microplastic sampling was performed following a modified method based on National Oceanic and Atmospheric Administration (NOAA). Samples of 250 mL freshwater collected, which were deionized and pre-filtered through 6.0 mm mesh granulometric sieves. The average abundances of the different hydrological seasons were compared by Student's t -test, with differences statistically significant at p < 0.05. The microplastics were morphological categorized into fibers and colors blue, red or transparent. Microplastic contamination was confirmed in freshwater of 9 fish farming, with greater abundance of blue fibers and greater quantification in the rainy season. Fish farms P3, P4 and P6 had the highest quantifications of blue fiber in the two seasons (6 and 43, 19 and 56, 11 and 88 items mL -1 , respectively). Almost all fish farms had a higher abundance of microplastics in the rainy season. It is important to highlight the prominence of microplastics in the blue fiber rainy season (286 items mL -1 ) compared to the dry season (58 items mL -1 ). Fish farms P3, P4 and P6 showed a strong positive correlation between the factors distance from the nearest urban area (r = 0.94, 0.79 and 0.97, respectively) and seasonality (r = 0.98, 0.77 and 0.96, respectively). Rainfall variations influenced the abundance of microplastics, especially of blue fibers. Fish farms are supplied with fresh water by rivers or streams, so it is possible that microplastics originate outside the fish farm, perhaps they were introduced due to high soil occupation, although surface runoff (of water contaminated by sewage) caused by heavy rains the most important factor. Therefore, one factor must be considered, surface runoff and groundwater contaminated by urban, agricultural and urban effluents may have contaminated rivers and streams and then contaminated the water in the fish farm ponds., Competing Interests: The authors declare no conflict of interest., (© 2023 The Authors.)

The production of fish flour is an alternative for better use of the raw material, although it is rarely used in instant food. Thus, the aimed of this study was to evaluate Oreochromis niloticus (Nile tilapia) and Cynoscion virescens (croaker) fillets and the elaboration of flour with filleting by-products for inclusion in food products. Carcasses and heads of the two fish species were cooked, pressed, ground, subjected to drying and re-grinding to obtain standardized flours. These carcass flours were seasoned (sweet and salted). This study was organized into two experimental tests: Test 1: Yield, physicochemical and microbiological analyzes of fillets and flours made from carcass and head of Nile tilapia and croaker; Test 2: Seasoned flours made from Nile tilapia carcasses. There was a difference in fillets yield, where the croaker demonstrated 46.56% and the Nile tilapia 32.60%. Nile tilapia fillets had higher protein content (17.08%) and lower lipid content (0.89%) compared to croaker fillets (14.21 and 4.45%). Nile tilapia backbone flour had the highest protein content (55.41%) and the croaker the highest ash (45.55%) and the lowest Nile tilapia (28.38%). The head flours had lower protein contents (39.86%). Flours produced with croaker backbone had higher levels of calcium and phosphorus (9.34 and 9.27%). However, Nile tilapia backbone flour showed higher contents of essential amino acids. These flours demonstrated a fine granulometry (0.23 to 0.56 mm). Seasoned flours demonstrated interaction between fish species and flavors for moisture, ash, carbohydrates, calcium and phosphorus. The highest protein content (29.70%) was for Nile tilapia flour sweet flours (31.28%) had higher protein content, while salted lipids (8.06%). Nile tilapia has a lower fillet yield, although with a high protein content and low lipid content. Comparing the flours made from filleting by-products, the backbone flour has better nutritional quality, with Nile tilapia being superior to that of croaker, especially in terms of protein and amino acids., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Santos Corrêa et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

With the intensification of fish farming, the amount of residues also increased. One of the by-products generated is leather. However, several factors influence its quality, among them, the types of tanning used. Paiche (Arapaima gigas) is the largest freshwater fish in the world, and therefore has great potential in the use of leather, in addition to being one of the most cultivated fish in the Rondônia state. The aimed was to evaluate the physicomechanical resistance, histological and morphological aspects in different directions of the fibers of the paiche to evaluate the tanning with chromium oxide and vegetable tannin. Paiches with an average weight of 12.0 kg were used, skins were made and tanned using chromium and vegetable tannin as techniques. After tanning, 20 specimens were removed in longitudinal, transverse and diagonal directions to the fish body, to determine resistance in dynamometer and leather for histological analysis, scanning electron microscopy and physical-chemical analysis. The average thickness of the specimens of the leathers ranged 1.79mm to 2.82mm, in addition, there was no interaction between the type of tanning agent and the directions obtained for strength, traction and elongation. Regarding the progressive tearing test, there was also no interaction effect. However, the defined factors had relevant differences for the maximum and average amount applied, and the leathers tanned with vegetable tannin expanded to larger dimensions 110.19 and 85.52 N. According to the images obtained by histology and scanning microscopy, they presented that in the longitudinal and transverse direction the collagen fibers are presented in layers parallel to the leather surface and in the diagonal direction the interlacing is more intense, that is, in addition to the overlapping layers intercalated thinner, close to the surface, fiber bundles can also be seen crossing each other. It is concluded that leathers tanned with vegetable tannin have less resistance than leathers tanned with chromium salts for traction to rupture and greater resistance to tear., Competing Interests: The authors have declared that no competing interests exist.

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., Competing Interests: The authors declare that there are no conflicts of personal, financial, commercial, political, or academic interest., (Copyright © 2021 Jucilene Cavali et al.)

The aim of this study was to evaluate the physiological, zootechnical, and environmental benefits of the use of growth-promoting virginiamycin in the pirarucu diet. The research was conducted at the Carlos Eduardo Matiazze Fish Center, Federal University of Rondônia. In this study, 96 pirarucu fish were distributed in excavated nursery, divided into two treatment groups, control (0.0 mg kg -1 ) and treatment (75.0 mg kg -1 ) of feed with virginiamycin, with 8 replications in a completely randomized design. With virginiamycin being incorporated into commercial feed, for 107 days of cultivation, the fish were slaughtered with an average weight of 9.18 kg. Carcass weight, flesh, residues, and internal organs/guts were evaluated to calculate slaughter yields, Spearman's correlation, and subsequently regression. For the quantification of micronuclei, a count of 1,000 cells per blade was determined. The means of the results obtained were contrasted by the Student's t -test ( α  = 0.05). Virginiamycin did not cause oscillations in the limnological variables of the nursery but could reduce micronucleated erythrocytes. The average yields in carcass, flesh, and waste were 67.43, 53.4, and 43.14%, respectively. Virginiamycin provided strong correlations ( ρ 2 ) for better productive yields and lower slaughter residue. The hepatosomatic index indicated a strong relationship between liver weight and fat. Virginiamycin may be recommended for fish farming in pirarucu fattening because it contributes to the productive efficiency and sustainability of the fish farm system., Competing Interests: The authors declare that there are no conflicts of personal, financial, commercial, political, or academic interest., (Copyright © 2020 Jucilene Cavali et al.)