Aquac. J., Volume 5, Issue 3 (September 2025) – 4 articles

The emergence and spread of pathogens pose significant challenges to the sustainability and productivity of aquaculture globally. For the Chilean salmon farming industry, salmonid rickettsial septicemia (SRS), caused by the facultative intracellular bacterium Piscirickettsia salmonis, constitutes one of the main disease challenges. In this study, the efficacy of various oral doses of florfenicol (FFC) (5, 7.5, and 10 mg/kg BW/day) against SRS was assessed in Atlantic salmon, when treatment was initiated at an early stage of infection. Since salmonids infected with P. salmonis typically lose appetite as the disease progresses, and the therapeutic FFC dose is dependent on a normal specific feeding rate (SFR), the treatments were administered 5 days post-challenge (DPC5). On the day of challenge, experimental fish were intraperitoneally (IP) injected with 0.2 mL of P. salmonis genogroup LF-89 inoculum (9.07 × 10⁷ CFU mL⁻¹). Fish mortality, behavior, clinical signs of disease, feed intake and SFR were monitored throughout the study. Conclusions: An important finding in this study was that all tested antibiotic doses halted disease progression and prevented mortality in fish challenged with P. salmonis when administered DPC5. In the control group, mortality reached 32.2% with fish displaying clinical signs of SRS. Full article

This study investigated the effects of integrating biofloc with microalgae on growth performance and immune gene expression in red tilapia (Oreochromis sp.). The experiment consisted of four treatments: C (Biofloc), T1 (Chlorella vulgaris and Nannochloropsis sp.; 1:1), T2 (Biofloc + Chlorella vulgaris and Nannochloropsis sp.; 1:1), T3 (Biofloc + Chlorella vulgaris and Nannochloropsis sp.; 2:1) in 500 L plastic tanks for 60 days. T2 and T3 exhibited the lowest ammonia and nitrite levels, respectively. T3 exhibited the highest chlorophyll a and chlorophyll b levels, while T2 showed the highest carotenoid content. T2 showed the highest weight gain (142 ± 0.7 g) and SGR (1.61 ± 0.02) and the lowest FCR (1.79 ± 0.009). T2 exhibited the highest gene expression levels in the intestine, with 7.8-fold upregulation of the cathepsin L (ctsl) gene, 3-fold upregulation of toll-like receptor 7 (tlr7), 6.7-fold upregulation of interleukin-1 b (il-1b), 4.7-fold upregulation of tumor necrosis factor-alpha (tnf-a), and 2.8-fold upregulation of metallothionein (mt). In the head kidney, the mt upregulation was highest in T3 (7.2-fold), while tnf-a and tlr7 upregulations were highest in T2 (5.9-fold and 5-fold, respectively). In the liver, the gene expressions were highest in T3, with 6.4-fold upregulation of mt, 5-fold upregulation of ctsl, 2.7-fold upregulation of tlr7, 3-fold upregulation of il-1b, and 5.4-fold upregulation of tnf-a. These results suggest a synergistic effect of algae and bacteria on immune and antioxidative capacity in red tilapia. Full article

Selenium nanoparticles (SeNPs), with their high absorption and antioxidant properties, hold promise as feed additives in aquaculture, enhancing growth and reproductive health in fish. This review evaluates how selenium nanoparticles influence growth and reproductive traits in Asian seabass (L. calcarifer). Using the PRISMA approach, we examined the impacts of selenium nanoparticles (SeNPs) on the growth performance and gonadal development of Asian seabass (L. calcarifer) by synthesizing findings from the existing literature. Meta-analysis explored that selenium nanoparticles (SeNPs) supplementation significantly improved specific growth rate (SGR) (pooled effect size = 3.97; 95% CI: 3.68–4.26) and feed conversion ratio (FCR) (pooled effect size = 0.81; 95% CI: 0.75–0.86), with low heterogeneity. Regarding reproductive outcomes, SeNPs enhanced gonadal development, sperm quality, and steroidogenesis. Significant improvements were observed in gonadosomatic index (effect size = 0.5), fertilization rate (0.6), and testosterone levels (0.5), along with a reduction in abnormal embryogenesis (−0.3) (p < 0.05). While an optimal level of SeNPs is effective for enhancing aquaculture performance, excessive use may lead to toxicity; therefore, their economic viability, environmental impact, and sustainability in large-scale aquaculture warrant further investigation. This review provides insights for researchers, policymakers, and industry stakeholders on the potential of SeNPs in advancing sustainable aquaculture through fish productivity and reproductive performance. Full article

The objective of this work was to evaluate the effects of three commercial diets for ornamental fish (BIOMAA Spiruflake^® (T1), Tetra TetraMin Tropical Flakes^® (T2), LOMAS tropical fish flakes^® (T3)) compared to a balanced feed for trout (Silver Cup TM (T4)) on the growth, survival, digestive enzyme activity, and intestinal and liver morphology of guppy (Poecilia reticulata) fry after 31 days of feeding. The highest growth was in T2 (0.101 ± 0.004 g) and T4 (0.084 ± 0.008 g) (p < 0.05). Fish fed with T1, T2, and T4 presented the greatest total length. T4 (98 ± 2.828%) and T1 (96 ± 5.656%) had the highest survival. Fish fed with T2 and T4 showed the best growth index values (AWG, SGR, FCR). T4 showed greater alkaline protease, trypsin, and chymotrypsin activity and better in vitro digestibility. The fish fed the T4 diet had the lowest intestinal fold height and the smallest hepatocyte diameter. A cheaper aquaculture diet (T4) significantly improved guppy juvenile nutrition compared to ornamental feeds. Further research should focus on developing species-specific ornamental diets for enhanced fish welfare. Full article