Bisphenol A (BPA), an important component of the plastics industry, is characterized as an endocrine disrupting toxic substance for aquatic organisms. This study focused on the toxic effects of BPA on endangered Danube sturgeon larvae (Acipenser gueldenstaedtii). In the study, LC50 values for five different BPA concentrations (100, 200, 400, 800, 1200 μg/L) were observed as 803.4 μg/L, 63.1 μg/L, and 39.6 μg/L at 24th, 48th a nd 72nd hours, respectively. Especially, the lethal effect of BPA on the larvae was remarkable after the 24th hour. On the other hand, histopathological changes were examined based on the LC50 value at the 24th hour. Vacuolization symptom was noted in the gills of the larvae. In addition, vacuolization and melanomacrophage centers caused a severe degradation in liver and kidney tissues of BPA group. In the intestine, the number of goblet cells per ville was lower in the BPA group. As a result, it has been proven by LC50 and histopathological studies that BPA has high toxicity in A. gueldenstaedtii larvae.

Providing a sustainable and affordable food supply is one of the most significant challenges facing the global aquaculture industry. Black soldier fly (BSF), Hermetia illucens, meal is a particularly promising alternative to animal-derived protein sources. Following a 90-day feeding experiment with four different diets containing BSF meal with increasing fish meal replacement levels of 25%, 50%, 75%, and 100%, designated as B25, B50, B75, and B100, and a control diet (B0) without BSF meal, the gut microbiota, immune-related gene expression, and Lactococcus petauri resistance of rainbow trout (Oncorhynchus mykiss) were studied. Regardless of diet, rainbow trout intestinal microbiota were different from those in water. In the intestinal mucosa, Fusobacteria, Firmicutes, and Proteobacteria were among the most prevalent taxa. Rainbow trout fed with a BSF-containing diet had a higher bacterial diversity in their gastrointestinal tract than fish fed with a control diet. The abundance of Firmicutes, Actinobacteria, and Proteobacteria increased in tandem with the replacement rate of fish meal with BSF meal. The B75-fed fish were found to be the most resistant group to L. petauri, followed by the groups fed with B100, B50, and B25. Compared to the control group, the expression of cytokines (Tgf, Il-10, Il-1β, , and Il-8) and immune-related genes (IgM, IgT, Mhc-II, and Tlr-5) increased significantly () in all fish groups fed with a BSF-containing diet. Substituting fish meal with BSF meal beyond 50% enhanced the survival rates of fish infected with L. petauri. Furthermore, BSF-containing diets boosted the immune system and cytokine-related genes in fish. Due to improved survival and immunity, rainbow trout may be fed a 50% BSF meal substituted diet without removing chitin or pre-treating BSF meal.

Taxonomic evaluations are needed to accurately determine the host selection of fish parasites. The present study is a multidisciplinary research in the field of basic and fish diseases sciences. The description of the hybrid species of Squalius orientalis and Alburnus derjugini and infection of Ligula intestinalis in these hybrid fish were reported for the first time from the Kürtün Dam Lake in northeast Turkey. A total of 450 fish were sampled in March, August, and October in 2020 using gillnets. Detailed morphological characteristics (n = 24) were compared to determine the difference among ancestors and hybrid species. The prevalence of L. intestinalis between the sampling periods and the size groups of fish (0 – 10, 11 – 15, and ≥16 cm in length) were examined. Moreover, the highest prevalence of the parasite was observed in October (78.94 %), with a size range of 0 – 10 cm in length (77.8 %). In addition, the total prevalence of the parasite was 48.44 %. The results revealed that most of the diagnostic metric and meristic features of hybrid fish were ranging between the data of S. orientalis and A. derjugini. According to previous reports, when hybrid individuals were compared with their ancestors in terms of prevalence, hybrid individuals were more susceptible to L. intestinalis infections. This study was unique as it provided the first record of L. intestinalis in a hybrid fish population.

Duo culture response of Siberian sturgeon (Acipenser baeri) and rainbow trout (Oncorhynchus mykiss) was evaluated in culture tank conditions. Triplicated culture groups were planned as: mono-culture sturgeon (M, n=10), duo-culture sturgeon (DM, n=10) and duo-culture trout (DA, n=10), and mono-culture trout (A, n=10). Examination of mono and duo culture of each species, showed neither sturgeon nor trout, was indicated any significance on specific growth rate (SGR) and condition factor (CF). As for final biomasses among groups, no significant differences were recorded (p<0.05).