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Abstract

In the present study, Salmonella spp. was successfully isolated from Asian clam Corbicula fluminea by using Xylose Lysine Deoxycholate (XLD) selective agar. A total of 200 bacterial colonies from live Asian clams were isolated and subjected to antimicrobial sensitivity test by using disc diffusion method. A total of 18 antibiotics was applied in the present study, namely oxolinic acid, nalidixic acid, erythromycin, tetracycline, doxycycline, oleandomycin, oxytetracycline, spiramycin, ampicillin, kanamycin, fosfomycin, florfenicol, lincomycin, novobiocin, chloramphenicol, amoxycillin, flumequine and sulphamethoxazole. The findings of the present study showed that total antibiotic sensitive case for Salmonella spp. isolated from C. fluminea sample was 50% or 1800 cases. This was followed by antibiotic resistance case 45% or 1620 cases and intermediary antibiotic sensitive case (5% or 180 cases). Based on the results of the present study, tetracycline, doxycycline, oxytetracycline and flumequine showed the highest inhibition of isolated Salmonella spp. The multiple antibiotic resistance (MAR) index was 0.36, indicating the sampled clams were highly exposed to the tested antibiotics.

Abstract

Accessory respiratory is generally accepted to have evolved independently on numerous occasions in adaption to aquatic hypoxia in freshwater habitats. In general, the air-breathing organ in fish is believed to be structurally modified to supplement respiration. In this study, intuitive evidence for elaborate structural modifications of the intestine, an air-breathing organ in mud loach (Misgurnus anguillicaudatus), compared with two other obligate aquatic breathers, grass carp (Ctenopharyngodon idellus) and yellow catfish (Pelteobagrus fulvidraco), were directly provided by histological and morphometric methods. As a result, a sharply decreasing height of mucosal folds and thickness of muscularis were manifested in loach intestine from its anterior to posterior region. Compared with grass carp and yellow catfish, loach had the smallest ratios of mucosal fold height/muscularis thickness to intestinal lumen radius in the posterior intestine. These suggested that the posterior intestine is the air-breathing location for the loach. Furthermore, length density of capillary (0.46±0.05 μm−2) in the posterior intestine of the loach was significantly higher than those of grass carp and yellow catfish. Meanwhile, diffusion distance of air-blood barrier (1.34±0.04 μm) in the posterior intestine of the loach was significantly smaller than those of the other two fish species. In summary, the characteristics of highly vascularized, short diffusion distance of air-blood barrier, thinned and flattened made the posterior intestine a perfect air-breathing location for the loach.

Abstract

In Mexico, studies of octopus Paroctopus digueti are scarce, thus the objective of this research is to evaluate some of its biological aspects in Ohuira Bay, Ahome, Sinaloa, Mexico. From autumn 2016 to autumn 2017, a total of 217 organisms of P. digueti were collected, from which 166 were females, 31 ovigerous females and 20 males. The lengths of the mantle (ML), tentacles or arms (AL) and total length (TL) were recorded as well as the total weight (TW) of each organism. The software FiSAT II was used to obtain the growth parameters by mediating seasonal size frequencies. Considering both sexes, the average registered mantle length was 40.31±2.5 mm. For the analysis of ML-TL y ML-AL, the data were adjusted to a linear-type model. For the relationship between ML-TL, the minimum determination coefficient was observed during spring R2 = 0.335, and the highest was registered in winter R2 = 0.6452. With regards to the allometry coefficient (b), it was different among the 4 climatic seasons. The theoretical ML growth curve showed both sexes of ML= 73.50 mm, K = 1.30 year−1 and t0= 0.10. The estimated values from the growth equation revealed faster growth (ML= 63 mm) within the 1.2 years of their lives, reaching a maximum length at 2.5 years of age. The total weight growth curve of P. digueti octopus was formed by an exponential first stage up to six months and the second logarithmic stage from seven months to approximately 1.8 years. In the summer there were slightly lower coefficients and percentages of instantaneous growth coefficients (IGC) for the lengths and total weight of octopus P. digueti. The highest Fulton’s condition index (k) was recorded in winter. The sex ratio was significant in a proportion of 9.85 F:1 M.

Abstract

Effects of dietary supplementation of Pleurotus pulmonarius stalk meal on growth, gut microflora and intestinal morphology of Clarias gariepinus were assessed in this study. The stalk meal was incorporated at 0.0 g/100 g (Control), 2.5 g/100 g (PSM 2), 5.0 g/100 g (PSM 3), 7.5 g/100 g (PSM 4) and 10.0 g/100 g (PSM 5). Clarias gariepinus (n=375), with an initial weight of 10.84±0.04 g, were allotted at 25 fish/60 litres of water in a completely randomised design for each diet treatment in triplicate. Feeding trial was conducted for eight weeks. Weight gain, specific growth rate, survival rate, feed intake and feed conversion ratio were not significantly different across all diet treatments. However, the production performance index of the fish and protein efficiency ratio were higher in fish fed PSM 3 diet than other treatments. Total viable bacteria count in the gut ranged from 7.56 (PSM 2) to 8.34 log10 cfu/g (PSM 4), while lactic acid bacteria count was between 5.00 (control) and 7.03 log10 cfu/g (PSM 3). Escherichia coli were identified in the gut of the control group but were not detected in those fed supplemented diets. More colonies of Salmonella and Vibrio species were observed in the control but fewer colonies in the diets supplemented groups. The proximal, middle and distal villus length, proximal, middle and distal cryptal depth, proximal and distal absorption area of fish fed supplemented diet were higher than those of the control. Conversely, proximal, middle and distal villus width and middle absorption area were not significantly different. In spite of observable favourable gut microflora and gut histomorphology of fish fed supplemental P. pulmonarius stalk meal diet, these attributes did not manifest in growth performance indices.

Abstract

Buško Blato Reservoir, the third largest hydro accumulation in Europe, is situated in the south-eastern part of the karstic Livanjsko Polje Valley. This aquatic ecosystem is distinguished by a very rich ichthyofauna and the presence of four endemic fish species. Numerous studies focus on ichthyological researches of Buško Blato Reservoir. Its ichthyofauna has been exposed to changes in ecological factors, which in turn reflected on the structure and composition of fish populations. The main objective of this paper was to assess the current state and predict future trends in the ichthyofauna structure and dynamics based on the field data and comprehensive analyses of literature data. The results of the research indicated the presence of 11 fish species from four families, which is the largest number of fish species ever recorded in this ecosystem. Sander lucioperca, Lepomis gibbosus, Pseudorasbora parva and Tinca tinca were recorded for the first time in this ecosystem, while some previously recorded species were not found. The results of the analyses clearly indicate the presence of natural interspecific competition and significant level of threats to the endemic fish species caused by human activities.

Abstract

A total of 558 specimens of black-bellied anglerfish Lophius budegassa (Spinola, 1807) were collected by the vessels engaged in commercial trawl fishing in the Central Aegean Sea between September 2017 and August 2018 in order to determine age and growth. Ageing was based on growth ring counts of transverse sections of the illicium (first ray of the dorsal fin). By reading the illicium, individuals were found within II-XI age groups. Total lengths and weights ranged between 12.0 – 65.0 cm and 24.5 – 4682.0 g, respectively. Von Bertalanffy growth parameters were estimated for males, females and combined sexes of L. budegassa. The results are compared with previous studies.

Abstract

There is a significant lack of data for the biological parameters of beluga or great sturgeon, the largest fish in the Caspian Sea. The age, growth and fisheries indices for the stock status of beluga was investigated in the south Caspian Basin of Iran between 1990 and 2011. Fork lengths ranged between 113-420 cm and weights from 8.0 to 725.0 kg. The growth parameters were L = 440 cm, K = 0.027 year−1, t 0 = − 5.8 years. The age at first capture (t c) was 13.1 years. The long-term age composition data showed age up to 63 years, and the ages 12-19 years comprised 76.7% of the total catch. The generation length was 33 years. The values of “KF” were close to 1 or >1, indicating that beluga sturgeon is in a favorable condition in the southern Caspian Sea. The length distribution showed that 24.2% of the catch is comprised of juveniles. Based on the age structure and age at first maturity, recruitment and growth overfishing occurred in beluga stocks. Therefore, increased length or age at first capture in future fishery policies should be implemented. The mega-spawners represented 4.4% of the fish captured and revealed an unhealthy population structure.

Abstract

This study investigated the efficacy of Tamarind Leaves (TL) and Mango Leaves (ML) with Oxytetracycline (OXY) on growth performance, haematoimmunological and disease resistance of Clarias gariepinus juveniles against Aeromonas hydrophila. Experimental diets consist of control (0%), TL2 (1%), TL3 (2%), ML4 (1%), ML5 (2%), OXY6 (30mg/kg diet), (TL+ML) 7, (TL+OXY) 8, (ML+OXY) 9 and (TL+ML+OXY) 10. The fish (3.02±0.01g) were replicated twice with 20 fish per replicate and were fed twice daily at 3% body weight of 40% crude protein for twelve weeks (8 weeks for feeding trial and 4 weeks for challenge test). Mean Weight Gain (MWG), Specific Growth Rate (SGR), Packed Cell Volume (PCV), Haemoglobin (Hb), Lymphocytes (LYM), Globulin (GLO), Amino Alanine Transferase (ALT) and Aspertate Amino Transferase (AST) contents were ascertained using standard technique. The fish were infected with A. hydrophila at 5.94 log10 CFU/ml interperitoneally and fed different diets to evaluate their Relative Percent of Survival (RPS). Data was subjected to descriptive statistics and one-way analysis of variance at P=0.05. Clarias gariepinus juveniles fed treated diets had higher growth rates than the control diet but C. gariepinus fed (TL+ML+OXY) 10 had a significantly higher MWG and SGR of 7.74±0.69 g and 0.97±0.01 g, respectively. The PCV (44.0±2.00%), Hb (14.7±2.00 g/dl), LYM (37.0±2.00), GLO (42.0 ±2.00 g/dl) were higher in the C. gariepinus fed (TL+ML+OXY) 10 than the control diet. The AST and ALT values among the treated groups were lower than the values in the control at the post-challenge test. The RPS against A. hydrophila was higher in the treated groups (100%) than in the control (0%). Fish fed tamarind and mango leaves had enhanced mean weight gain and were more resistant to A. hydrophila infection.

Abstract

Loss of fish biodiversity, especially in the inland and coastal areas, is a major concern in sustainable fish production. Indiscriminate fish catch, climate change and many other anthropogenic activities synergistically affect fish biodiversity. To formulate a sustainable fish biodiversity conservation plan, fish biodiversity in the Andharmanik River, a 40-km-long Hilsa shad sanctuary in the southern part of Bangladesh, was assessed. The study was conducted to understand the status of fish species diversity through sampling in three sampling stations between December 2014 and November 2015. A total of 93 fish species were found belonging to 66 genera, 45 families and 14 orders. Perciformes (27.65%) was found to be the most dominant order, followed by Cypriniformes (20.21%), Siluriformes (21.28%) Clupeiformes (7.45%) Mastacembeliformes (4.26%) and Channiformes (4.26%). Out of the 93 fish species of the river, the percentage compositions of the vulnerable, endangered, critically endangered and not threatened were found to be 14%, 11%, 6% and 59%, respectively. Four population indices viz. Shannon-Wiener’s diversity index (H), Simpson’s dominance index (D), Simpson’s index of diversity (1-D) and Margalef’s index (d) were applied to demonstrate species diversity, richness and evenness of fish species in sampling areas, and the overall values of the indices were 2.70-3.51, 0.10-0.12, 0.88-0.90 and 7.84-8.19, respectively. The main threats to fish biodiversity were reviewed and the measures for fish biodiversity conservation of the river recommended. Indiscriminate fishing using biodiversity destructive gears, as well as losing hydrological and ecological connectivity with the surrounding habitats, were identified as major threats to biodiversity in the Andharmanik River. Effective sanctuary-based co-management, immediate actions for habitat enhancement to conserve and improve fish biodiversity in the river were recommended. Necessary steps to improve hydrological and ecological connectivity for habitat protection and elimination of all destructive fishing gears in order to conserve biodiversity in the Andharmanik River were also suggested.

Abstract

The aim of this paper is to provide an overview of bluefin tuna, with special regard to its farming challenges. Tuna is one of the most prominent species in fisheries worldwide. The high market value of tuna stocks has led to intensified fishing pressure that resulted in drastic population reductions in every ocean where these fish are found. It is very difficult to obtain the necessary data for the appropriate stock assessment analysis, and there is a very high degree of uncertainty in the models used to evaluate Atlantic bluefin tuna stocks. Tuna-farming could help reduce pressure on the tuna population, but the problem is that the majority of cage-farmed fish is caught in its natural environment (wild population), and thus is fattened or farmed to a certain size. Additionally, the challenges in tuna farming are numerous. Tuna is a fast swimmer, a large energy and oxygen consumer, therefore consuming a large portion of available food to maintain its metabolism. However, due to its delicious taste, high market price and a large demand for this species, pressure will probably continue to grow in the future. Therefore intensive farming, which implies the full breeding cycle in captivity, remains one of the possible solutions that could help reduce the pressure on the tuna population.