Effect of protein and lipids levels in a growth diet on adult whitebait Galaxias maculatus (Jenyns 1842)

Galaxias maculatus aquaculture objectives is to produce millions of eggs. Wild females are small (2 g), have quick sexual maturity and low mean fecundity (500 eggs/female), requiring larger fishes with higher fecundity. This study aim is to evaluate experimentally the effect of the levels of protein, lipid and dietary energy on weight increases in adults. Five independent experiments were performed at different sequential time periods at the UCT hatchery, Chile. Specimens were obtained from a) Crystalline sea return specimen catches in the Tolten estuary (4 -6 cm, 0.3-0.4 g.). b) Hatchery cultured fish. Fish were fed by hand ad libitum. In experiments 1 to 4, pelleted diets were prepared with 3 to 5 levels of protein (treatments 27 up to 57%), crumble size, three 100 L fibre ponds replicates. In experiment 5 the effect of two lipid levels (8 and 21%) was evaluated with commercial extruded Salmon Nutra Starter isoproteic crumble 1 diet at 63%, replicated in 4 ponds. The results show: A tendency to increased weight in all sizes with an increased protein level in the pelleted diet.A maximal adult growth is obtained with a diet containing a minimum of 37% crude protein, with 40% the optimal value. A higher % protein in the diet or growth in weight lower feed conversion ratio. The feed conversion ratio in the extruded diet reaches up to 0.5 and in the pelleted vary from 0.7 to 1.5. Fish 0.6 g fed with 63% protein, extruded commercial diet with two different lipid levels (8 and 21%, 20.40 and 23.84 MJ kg-1, PE/TE 0.62 and 0.71) increased weight the first month 67 and 105% each. It has been established that high-energy diets with optimal levels of protein and lipid are a good short-term solution to obtain G. maculatus of higher weight.

Dietary incorporation of Sweet Potato Ipomoea batatas shoots improved growth performance and haematological profile of Tilapia Oreochromis niloticus in Hapa Nets

This study was conducted to evaluate the potential of sweet potato Ipomoea bata-tas powder (IbSPP), hot-water extracts (IbSPHWE) and crude ethanolic extracts (IbSPCEE) as growth pro-moter and immunoenhancer for tilapia cultured in hapa nets. Fish were divided ran-domly into four Treatments: T1 (control group) was fed a practical diet (PD) while T2, T3 and T4 were fed PD + IbSP powder (P), PD + IbSP hot-water extract (HWE), PD + IbSP Crude Ethanol Extracts (CCE), respective-ly. The growth indices and haematological profile of cultured fish were recorded after four months of feeding experiment. The final weight, weight gain, specific growth rate, condition factor, FCR, PER, FER were significantly higher in fishes that re-ceived PD +IbSPHWE than those that received either PD, PD + IbSPCEE or PD+ IbSPP only. The same trend was observed with the RBC, Hb, HCT, WBC and the PLT and its indices. The study has demonstrated that in-corporation of the hot-water extracts of I. batatas could improve the growth perfor-mance and increase immu-nocompetence of O. nilot-icus as evidenced by im-proved haematological pro-file.

Complete Genome Sequences and Pathogenicity Analysis of Two Red Sea Bream Iridoviruses Isolated from Cultured Fish in Korea

In Korea, red sea bream iridovirus (RSIV), especially subtype II, has been the main causative agent of red sea bream iridoviral disease since the 1990s. Herein, we report two Korean RSIV isolates with different subtypes based on the major capsid protein and adenosine triphosphatase genes: 17SbTy (RSIV mixed subtype I/II) from Japanese seabass (Lateolabrax japonicus) and 17RbGs (RSIV subtype II) from rock bream (Oplegnathus fasciatus). The complete genome sequences of 17SbTy and 17RbGs were 112,360 and 112,235 bp long, respectively (115 and 114 open reading frames [ORFs], respectively). Based on nucleotide sequence homology with sequences of representative RSIVs, 69 of 115 ORFs of 17SbTy were most closely related to subtype II (98.48–100% identity), and 46 were closely related to subtype I (98.77–100% identity). In comparison with RSIVs, 17SbTy and 17RbGs carried two insertion/deletion mutations (ORFs 014R and 102R on the basis of 17SbTy) in regions encoding functional proteins (a DNA-binding protein and a myristoylated membrane protein). Notably, survival rates differed significantly between 17SbTy-infected and 17RbGs-infected rock breams, indicating that the genomic characteristics and/or adaptations to their respective original hosts might influence pathogenicity. Thus, this study provides complete genome sequences and insights into the pathogenicity of two newly identified RSIV isolates classified as a mixed subtype I/II and subtype II.

Isolation and Identification of Pathogenic Bacteria from Baime Fish (Mystus armatus) and Evaluation of Antibiotic Susceptibility

Aquaculture products (fish) can harbor pathogenic bacteria which are part of the natural micro-flora of the environment. The current study was carried out for the extraction and identification of fish pathogenic microbes from Baime fish (Mystus armatus). Diseased fresh-water fishes were collected from different water bodies and fish landing centers of two study areas, namely the City area, Jhenaidah region. Bacteria are one of the important causative agents of fish diseases in both wild and cultured fish and are responsible for serious economic losses. Pathogenic bacteria strain was isolated from the infected area of Baime (M. armatus) fish skin. After isolation, isolates were finally identified by their desired morphological, characteristics, and biochemical test. They were gram-negative, rod-shaped bacteria that showed positive reaction for catalase, able to ferment glucose and one is citrate negative and another is citrate positive. After being persuaded above-mentioned test isolates were identified as genus Aeromonas and Pseudomonas. The ulcer type disease of M. armatus, the isolate was tested against several antibiotics’ treatment. Pseudomonas strains isolated from M. armatus is susceptible to penicillin G (10 μg), amoxicillin (10 μg), erythromycin (15 μg), Tetracycline (30 μg), Kanamycin (30 μg), moderately susceptible to Co-trimoxazole (25 μg), and Resistance to ceftazidime (10 μg). Aeromonas strains isolated from M. armatus is susceptible to amoxicillin (10 μg), erythromycin (15 μg), Tetracycline (30 μg), moderately susceptible to ceftazidime (10 μg), and Resistance to Co-trimoxazole (25 μg), penicillin G (10 μg), Kanamycin (30 μg). The results of the present study constitute an advance in the available diagnostic and bacterial pathogens in fish farms.

Effect of rearing system and sex on the composition and fatty acid profile of Andinoacara rivulatus meat from Ecuador

This study evaluated the influence of rearing system (cultured vs. wild rearing systems), and fish sex on carcass and flesh traits of A. rivulatus, raised in Ecuador. Three hundred mature specimens from A. rivulatus were captured, 150 from each origin. Slaughter yield and dress-out resulted similar for both rearing system, and average fillet yield for cultured fish was significantly higher than for wild fish, while cooking loss was significantly lower. Dress-out was significantly higher in females. Significant differences were found in wet percentage, ash, fat and protein content in both rearing systems, but only wet percentage was significantly affected by sex. Palmitic, oleic and arachidonic acids had the maximum percentage of saturated (SFA) and mono/poly unsaturated (MUFA/ PUFA) fatty acids, respectively. In cultured and wild fish, differentiations were also found in PUFA/SFA, docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA), atherogenicity (IA), and thrombogenicity (IT) indices, along with P, K, Mg, Cu and Fe. Sex and rearing system significantly influenced most of the analyzed characteristics of carcass and flesh of A. rivulatus. Fillet high yield and its proximate composition categorize A. rivulatus as a suitable food. These results provide valuable nutritional information about native species for consumers in Ecuador. Highlights: The rearing system (cultured vs. wild rearing systems), and fish sex affect the carcass and flesh traits of A. rivulatus. Fillet high yield and its proximate composition categorize A. rivulatus as a suitable food. The proximate composition of fillet from cultured A. rivulatus is more adequate than those of wild A. rivulatus. The cultured A. rivulatus contains higher n-3 and n-6 PUFA percentages and adequate n-3/n-6 ratio.

Cupriavidus in the intestinal microbiota of Tibet endemic fish Glyptosternum maculatum can help it adapt to habitat of the Qinghai Tibet Plateau

Background Gut microbes play an important role in the growth and development of fish. The Tibetan Plateau fish Glyptosternum maculatum is a unique species of sisorid catfish living in the river up to 4200 m altitude. Results To understand the mechanisms underlying the ability of G. maculatum to adapt to the high-altitude habitat, the intestinal microbiota of G. maculatum was studied. We used high-throughput sequencing of the 16S ribosomal RNA gene of intestinal microorganisms of wild and cultured G. maculatum to explore the characteristics of intestinal microorganisms and compared the gut microbial community of wild and cultured G. maculatum. The results showed that the α-diversity and richness of the intestinal microbiome were higher in wild G. maculatum than in cultured fish. The most abundant phylum in both G. maculatum were Fusobacteria, Proteobacteria, Firmicutes, and Bacteroidetes; Cetobacterium and Cupriavidus are the most dominant genus. The membership and structure of intestinal bacterial communities in wild G. maculatum are similar to the cultured fish, suggesting that a core microbiota is present in both G. maculatum intestinal bacterial communities. Metastats analysis showed that six genera were differentially represented between the wild and cultured G. maculatum. Conclusions The most interesting characteristic of the intestinal microbial communities of G. maculatum is that there were large numbers of Cupriavidus, which may play an important role in the adaptation of G. maculatum to the water of the Yarlung Zangbo River with a high Cu content. This result, in turn, can guide us on breeding G. maculatum.

A Transcriptomic Analysis of Gonads from the Low-Temperature-Induced Masculinization of Takifugu rubripes

The phenotypic sex of fish is usually plastic. Low-temperature treatment induces the masculinization of Takifugu rubripes, resulting in pseudo-males (PM) with the physiological sex of a male (M) and genetic sex of a female (F). For a comparison of gonadal transcriptomes, we collected gonads from three groups of T. rubripes (F, M, and PM) for high-throughput transcriptome sequencing. The results provided 467,640,218 raw reads (70.15 Gb) and a total of 436,151,088 clean reads (65.43 Gb), with an average length of 150 bp. Only 79 differentially expressed genes (DEGs) were identified between F and PM, whereas 12,041 and 11,528 DEGs were identified between F and M, and PM and M, respectively. According to the functional annotation of DEGs, 13 DEGs related to gonadal development were screened (LOC101066759, dgat1, limk1, fbxl3, col6a3, fgfr3, dusp22b, svil, abhd17b, srgap3, tmem88b, bud4, and mustn10) which might participate in formating PM. A quantitative PCR of the DEGs confirmed the reliability of the RNA-seq. Our results provide an important contribution to the genome sequence resources for T. rubripes and insight into the molecular mechanism of masculinization in a cultured fish subject to low-temperature treatment.

Heavy Metal Concentrations and Human Health Risk Assessment of Selected Wild and Cultured Fishes of Bangladesh

This study was conducted to estimate the concentration of selected heavy metals such as chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) as well as the possible risk to consumer health from the flesh of three wild and cultured fishes (Labeo rohita, Mystus cavasius, and Heteropneustes fossilis) collected from the Meghna river, Narayangonj and Rajoir fish farm, Madaripur district respectively. Heavy metal concentrations were determined using Atomic Absorption Spectrometric method. The average concentration of heavy metals were found in the wild fish samples in the range as Cr (0.295-1.647), Mn (0.900-1.294), Ni (0.063-0.198), Cu (0.179-0.529), Zn (5.487-8.343), Cd (0.004-0.009) and Pb (0.193-0.290) mg/kg dry weight while in the cultured fish samples in the range as Cr (0.043-0.315), Mn (0.975-2.36), Co (BDL), Ni (0.005-0.095), Cu (0.238-0.978), Zn (5.487-8.305), Cd (0.004-0.009), and Pb (0.238-0.286) mg/kg dry weight respectively. The hierarchy of mean concentration of heavy metals in wild fishes was Zn> Mn> Cu> Pb> Cr> Ni > Cd and in the cultured fishes, the order was found Zn> Mn> Cr> Pb> Cu> Ni > Cd. The present study showed that the wild fish accumulated higher concentration of heavy metals in their muscles than the cultured fish. The analyzed Ni, Cu, Zn, Cd, and Pb were below the allowable level specified by international agencies (FAO, WHO, EU, CE, USEP). In order to assess the human health risk, the Target Hazard Quotient (THQ), Hazard Index (HI), and Target carcinogenic Risk (TR) were calculated. The TR values suggested that the fishes posed low to moderate carcinogenic risk from Cr, Ni and Cd. Consequently, continuous and excessive consumption of these fish species over a lifetime will increase the possibility of causing cancer. Bangladesh J. Zool. 49 (2): 189-203, 2021

Sublethal Effects of The Toxic Alga Karlodinium Veneficum On Fish

Dinoflagellates of the genus Karlodinium are ichthyotoxic species that produce karlotoxins. Karlotoxins show hemolytic and cytotoxic activities and have been associated with fish mortality. This study evaluated the effect of toxins released into the environment of Karlodinium veneficum strain K10 (Ebro Delta, NW Mediterranean) on the early stages of Danio rerio (zebrafish). Extracts of supernatant of K10 contained KmTx-10, -11, -12, -13, and a sulfated form of KmTx-10. Total egg mortality was observed for karlotoxins concentration higher than 2.69 µg L−1 and the 1.35 µg L−1, 87% of development anomalies were evidenced (concentrations expressed as KmTx-2 equivalent). Larvae of 8 days post-fertilization exposed to 1.35 µg L−1 presented epithelial damage with 80% of cells in the early apoptotic stage. Our results indicate that supernatants with low concentration of KmTxs produce both lethal and sublethal effects in early fish stages. Moreover, apoptosis was induced at concentrations as low as 0.01 µg L−1. This is of great relevance since detrimental long-term effects due to exposure to low concentrations of these substances could affect wild and cultured fish.