Boletim do Instituto de Pesca

Diversity and similarity in parasitic infracommunities of Mylossoma aureum and Mylossoma duriventre (Characiformes, Serrasalmidae) from the Middle Madeira River Basin, Southern Amazonas, Brazil

Wed, 20 Mar 2024 00:00:00 -0300

A total of 30 specimens of Mylossoma aureum and 30 of Mylossoma duriventre from the Middle Madeira River Basin were examined between October 2020 to March 2021. Eight species of parasites were identified. About 65% of the hosts were parasitized. A total of 386 parasites was collected in M. aureum and 436 in M. duriventre. Species accumulation curves in M. aureum did not reach the asymptote, while in M. duriventre the curves showed tendency to stabilization. Contracaecum sp. larvae was the only endoparasite found. Anacanthorus paraspathulatus was the dominant species in M. aureum. In M. duriventre, the core species with highest parasite indexes was Mymarothecium sp. 3. Margalef’s and Shannon’s diversity indexes were higher in M. aureum. Most of the parasites showed an aggregated distribution pattern. Mymarothecium sp. 1, Mymarothecium sp. 2 and the parasite richness showed a significant positive correlation between its abundance and host length and between Mymarothecium sp. 1 abundance and host weight in M. aureum. All parasites are the first records for the Southern Amazonas. Except A. paraspathulatus, all M. aureum parasites are mentioned for the first time in this host. The three morphotypes of Mymarothecium spp. are probably new species that are in the process of taxonomic description.

Prebiotic, probiotic and marine algae suplementation in juvenile tilapia diet

Wed, 24 Apr 2024 00:00:00 -0300

This study evaluated the probiotic mannan oligosaccharide (MOS), and marine algae for Nile tilapia (Oreochromis niloticus) feeding. The parameters analyzed were fish-growth rate, hematological and immunological parameters, and intestinal microbiota. Also, fish were submitted to experimental infection challenge with Aeromonas hydrophila to evaluate the immune response. Nile tilapia juveniles (weight 8.86 ± 3.22 g) were used in the six treatments with four replicates, for 63 days. The treatments were: control basal diet; PAS-TR: basal diet plus 0.04 g·kg^-1 of the probiotic (Bacillus cereus and Bacillus subtilis); MOS: basal diet plus 4 g·kg^-1 of the prebiotic mannooligosaccharide, 4 g·kg^-1of the prebiotic Kappaphycus alvarezii. Two more diets were formulated by a combination of PAS-TR + MOS (4 +4 g·kg^-1), and PAS-TR + KAP (4 +4 g·kg^-1). For the challenge experiment, the fish were fed for 21 days, infected via intraperitoneal injection with A. hydrophila (1 x 106 UFC·mL^-1), and the mortality rate was registered for 15 days post-infection. Results indicated the capacity of probiotic to remain in the gut for 63 days, and it was inhibited neither by autochthonous microbiota nor by prebiotics used. The feed additives tested for Nile tilapia did not cause a beneficial or adverse effect on growth or hematological variables. However, these treatments protected the fish from A. hydrophyla infection, proved by higher survival rate, and relative protection levels. We concluded that probiotic PAS-TR and prebiotics MOS and KAP, combined or not as symbiotics, may promote immune protection and reduce the mortality rate of A. hydrophyla infection.

Application of biofloc technology in the larval rearing of zebrafish (Danio rerio)

Mon, 05 Feb 2024 00:00:00 -0300

The aim of this study was to investigate the different strategies of biofloc addition to zebrafish (Danio rerio) larviculture, and evaluate their growth and biochemical parameters. Three treatments were used: addition of 200 mL biofloc once at the start of the assay (O1), addition of 100 mL biofloc every seven days (1W), and addition of 100 mL biofloc every four days (2W). The 1W and 2W treatments also received 200 mL biofloc at the start of the assay. Regarding water quality, the only difference was the total suspended solid concentration, because the 2W treatment had a higher concentration in the final assay (127.6 ± 24.3 mg L^-1). The final weight, survival rate, and juvenile percentile did not show statistical differences among the treatments. However, the O1 treatment exhibited a higher total length (11.93 ± 0.45 mm) than those in the 2W treatment. The juveniles in the 2W treatment exhibited lower nonprotein thiols and higher TBARS concentrations than those in the other treatments. Thus, the biofloc system can be a viable alternative to zebrafish larviculture without the use of conventional live food, and the addition of biofloc once (O1) at the beginning of larval rearing achieves good growth and survival results.