Iranian Journal of Fisheries Sciences
Volume:23 Issue: 4, Jul 2024

Proteases are the most important industrial enzymes and widespread in nature. In the present work, sardine waste (viscera) was used to optimize the protease production by newly isolated Streptomyces sp. strain. A comparative study of proteolytic activity was first carried out on a synthetic medium, sardine waste broth (in submerged fermentation), and powder of the same waste (in solid-state fermentation). The enzyme production media were optimized according to statistical methods, while using two plans of experiences. The first corresponded to the Plackett-Burman matrices and the second was the Box-Wilson central composite design. The protease characteristics study showed an optimum temperature of 40°C and an optimum pH of 7, which is a typical characteristic of neutral proteases. The results of protease production optimization showed maximum activity on the following fermentation medium: sardine viscera broth (25%), NaCl (7.99 g/L), and gelatin (9.82 g/L). All these results confirmed the high biotechnological potential of this strain for neutral protease production on sardine viscera, which provides an interesting and promising strategy for large-scale enzyme production on fish waste

The present study was conducted to evaluate the effects of three different dietary microalgae on growth, intestinal histology, immune biomarkers, and resistance to a bacterial pathogen (Vibrio anguillarum) in juvenile rainbow trout, Oncorhynchus mykiss. Four experimental diets were prepared, including a basal diet (CON) and three diets containing Chlorella sp. (CHL), Haematococcus sp. (HAE), or Schizochytrium sp. (SCH), at 0.5% for each microalga which was supplemented in the basal diet. A total of 180 juvenile rainbow trout with an initial body weight of 12.16±0.01 g (mean±SD) were randomly distributed into 12 tanks and reared by the semi-recirculation system. After six weeks of the feeding trial, the weight gain (99.4%), specific growth rate (1.92%/day), and myeloperoxidase activity (5.08), of the fish fed the HAE were significantly higher than those of fish fed the other diets (p<0.05). The intestinal villus length of the fish fed the HAE diet (1.34 µm) was significantly higher than that of those fed the CHL (1.13 µm) and CON (1.14 µm) diets. The cumulative survival rates (CSR) were recorded for 27 days after intraperitoneal injection of the bacterial pathogen V. anguillarum. The CSR of the fish fed the HAE diet (75%) was significantly higher than that of those fed the other diets. It is suggested that Haematococcus sp. (0.5% inclusion in the diet) may improve weight gain, specific growth rate, intestinal villus length, and myeloperoxidase activity as well as increase the survival rate of juvenile rainbow trout against the V. anguillarum challenge.

Algae has recently drawn attention due to its strong potential for biological activities as a promising natural antioxidant resource. In this regard, seasonal variations of Sargassum illicifolium antioxidant activities were evaluated in the present study. S. illicifolium was collected from three coastal sites of the Oman Sea from April to May (spring) 2020 and October to November (autumn) 2020, representing pre- and post-monsoon, respectively. The methanolic extract was used to evaluate its antioxidant activities and properties. Regarding antioxidant activity (DPPH), there is a significant difference for the ferric reducing antioxidant power (FRAP), total flavonoids, total anthocyanin, and β-carotene variables analyzed between different sites during pre- and post-monsoon (p>0.05). Meanwhile, IC50 in pre-monsoon was significantly higher than in post-monsoon (p<0.05). However, statistical analysis revealed a strong positive correlation between IC50 and FRAP content in pre-monsoon; total phenolic and anthocyanin contents positively correlated to β-carotene post-monsoon. This study revealed that the seasonal variations lead to alter the biological activities regarding antioxidant contents in S. illicifolium, which need to be considered when considering the seaweed as a commercial antioxidant resource.

A confirmatory method for the determination of tetracycline antibiotics (TCs) in Chinese mitten crab has been developed for the first time. The method comprises two stages: pretreatment of the samples and instrumental analysis. The samples are treated with Na2EDTA–McIlvaine buffer followed by extraction. The extract is then analyzed with ultra-performance liquid chromatography tandem high-resolution mass spectrometry (UPLC-HRMS). Four mostly used TCs, including tetracycline, oxytetracycline, chlortetracycline, and doxycycline, were detected in 10 min. The specificity was confirmed via the retention time and their high-resolution mass spectra. In the range of 50-500 μg/kg, the linear regression coefficients (R2) for all analytes were greater than 0.9985. Recoveries at three concentration levels were between 90.3% and 106.2%. The within-laboratory reproducibility was precise. The decision limit (CCα) and detection capability (CCβ) of the method were determined using the permitted limit (100 μg/kg) of TCs. The detection results of TCs in 12 batches of Chinese mitten crab showed that no target residues were detected. This comprehensive method is compliant with the 2002/657/EC decision. It could be applied for the determination of TCs in Chinese mitten crab samples and potentially in other aquatic products.

Free radical scavengers, which act as antioxidants, have the potential to prevent oocyte aging and preserve fertilization capacity. The microalgae are an important source of antioxidants in the environment. This study examined the protective effects of methanol extracts derived from Chlorella sp. microalgae on the viability and maturation of oocytes obtained from mice under in vitro conditions. The microalgae were collected from the Persian Gulf region and cultured in Bold's Basal medium. The antioxidant capacity of the extracts was assessed using the ferric reducing ability of plasma (FRAP) and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) methods. Oocytes from female Naval Medical Research Institute (NMRI) mice were treated with the microalgae extracts for 16 h. The viability and maturity of the oocytes were evaluated using inverted microscopy. The expression levels of SIRT-3, BMP-15, and GDF-9 genes in the treated oocytes were analyzed using real-time PCR. Both extracts showed antioxidant properties, according to the findings of FRAP and DPPH analyses. Untreated oocytes had a survival percentage of 58% without maturation. However, oocytes treated with either extract at a dosage of 150 µg/ml had a survival rate of over 70%. The gene expression levels of SIRT-3 and BMP-15 were significantly higher in the treatment groups compared to the control group. In conclusion, Chlorella sp. extracts demonstrated protective effects on oocyte survival, but they did not significantly impact oocyte maturation. This study emphasizes the potential therapeutic uses of microalgae extracts from the Persian Gulf for disorders associated with infertility.

The main purpose of this research was to design a model that meets the educational needs of Iranian fisheries researchers in developing fisheries entrepreneurship ecosystems. In this research, educational needs were identified using a mixed research approach (qualitative-quantitative). In the first stage, semi-structured interviews and grounded theory were used to develop a model of fisheries researchers entrepreneurship education. The results indicated that casual conditions include coordination and communication challenges, applied research needed by the private sector, teaching general entrepreneurship skills, background conditions including the personal characteristics of researchers, the difficulties of carrying out organizational and research activities and financing challenges were intervening conditions. Supporting commercialization and establishing business acceleration centers, and presenting commercialization models as part of strategic conditions, promoting sustainable production and harvest, and recognizing the advantages of knowledge and income for researchers were identified as the positive effects of entrepreneurship education on Iranian fisheries researchers in the development of fisheries entrepreneurship ecosystems. In the quantitative section a questionnaire was compiled and given to a statistical sample which included researchers and faculty members of the Iranian Fisheries  Science Research Institute, Sampling was done through Cochran's formula (n=135). The identification of educational need items was accomplished through the employment of confirmatory factor analysis. Educational needs were categorized into seven components consist of 1) management and planning of applied research projects, 2) startup and entrepreneurship, 3) communication, 4) teamwork and networking, 5) fisheries Innovation ecosystem, 6) extension activities, principles and 7) rules and commercialization.

Numerous techniques are used in aquaculture to stripped eggs from fish broodstocks. The most common is the manual method, where the abdomen of the fish is gently massaged to extract the eggs. Alternatively, injecting gas pressure into the abdominal cavity can facilitate the release of eggs with potentially fewer negative impacts on the welfare and egg quality. This study compared the pneumatic stripping methods and the manual spawning method in rainbow trout (Oncorhynchus mykiss) spawners. The study focused on the effects of these techniques on the quality of the harvested eggs, relative fertility, stripping duration, and pH of the ovarian fluids. The findings revealed that maintaining a gas flow rate at 1.5 L min-1 during stripping is crucial to prevent post-stripping mortality of the broodstocks. The pneumatic method demonstrated a shorter duration of egg retrieval (39.5 s) compared to the manual method (42 s). Notably, there were no significant differences observed in ovarian fluid pH across the various methods (p<0.05). Overall, pneumatic egg extraction leads to higher-quality eggs with a greater hatching rate compared to the manual method. Considering the positive results of the pneumatic stripping and its high level of repeatability and efficiency, it can be used instead of the traditional method in rainbow trout hatcheries.

Nepal has a diverse geography, ranging from an altitude of 60 m to the world's highest peaks at 8849 m. Fish diversity has been observed to extend up to an elevation of 3600 m. With its intricate topography, fluctuating climatic conditions, and abundant water resources, the region exclusively comprises freshwater habitats spanning 745,000 ha. These habitats include rivers, lakes, ponds, marshes, reservoirs, and irrigated rice fields. There are roughly 6,000 rivers and creeks in the country (194,471 km² drainage area). Four major river systems, namely Koshi, Gandaki, Karnali, and Mahakali, originate from the upper Himalayas at an altitude greater than 5000 m above sea level and drain about 75% of the country. Freshwater fishes are often overlooked in biodiversity conservation efforts, leading to a significant decrease in fish diversity, particularly in densely populated urban areas and wetlands in the southern plains of Nepal. The decrease in fish diversity is likely linked to inadequate prioritization, funding, and human resources allocated to fish conservation. According to the literature and FishBase database records, the freshwater river system in Nepal contains a total of 255 fish species from 12 orders, 41 families, and 124 genera. This includes 15 fish species that are unique to Nepal and 15 that are not native to the region. Additionally, 34 fish species in this system are considered threatened and have been listed under the IUCN Red List. These fish have pronounced vertical dispersion throughout the country and horizontal distribution within the area and continent, displaying diverse adaptations. This research specifically examines the fluctuations in water quality and the range of fish species, together with their conservation status in the rivers of Nepal.

European anchovy (Engraulis encrasicolus) is one of the most important commercial species in the Mediterranean Sea. 4310 studied records were reported from the Google Scholar database between 1980 and 2022. A search with the keywords "Engraulis encrasicolus" or "European anchovy" and "growth" and "sex" and "length" and "length-weight relationship" returned 201 results, of which only research articles were included in the compilation. A total of 20 studies were evaluated in the present study. In the studies on the growth and length-weight relationship of anchovy species, pooled random effect meta-analysis, subgroup analysis, and moderator analysis were carried out. It was found that sex had a significant effect on the mean and standard deviation of length of male and female individuals. The results showed that there was a positive correlation between male and female individuals. The moderator analysis was carried out to examine this high heterogeneity. Accordingly, L∞ and K values and b coefficients of male and female individuals in different regions of the Mediterranean Sea should not be considered equivalent. The results of the study are generalizable to the reviewed studies except for the b coefficients of males and females.

Aquaculture represents a pivotal economic sector worldwide, meeting the escalating food demands of the expanding global population. Consequently, this research aimed to assess the incidence of fatty liver in Asian sea bass (Lates calcarifer) subjected to a diet enriched with lactic acid bacteria and evaluate their survival against Streptococcus iniae infection. The present study examined 240 sea bass (109 ± 10.5 g average weight) that were randomly assigned into four treatments with three replicates (25 specimens per treatment) for 60 days. The treatments comprised the following: First treatment: fish were fed with commercial feed. Second treatment: fish were provided with feed containing 109 CFU/g of Lactobacillus plantarum bacteria. Third treatment: fish were fed with feed containing 109 CFU/g of Lactobacillus pentosus bacteria. Fourth treatment: fish were provided with feed having 109 CFU/g of L. pentosus bacteria combined with L. plantarum in equal proportions. At the end of the experiment, the growth performance, the survival rate against the pathogenic bacteria S. iniae and the amount of fatty liver were evaluated. The findings disclosed enhanced growth indicators in the second treatment (strain 140) during the initial 30 days. Furthermore, statistically significant disparities were noted in the third treatment (2P) concerning PER, SGR, WG, RGR, and DWG during the subsequent 30-day period (P<0.05). Liver pathology examination demonstrated that most treatments resulted in the development of fatty liver. However, the third treatment (L. pentosus) exhibited the lowest incidence of fatty liver when endogenous probiotics were incorporated into the diet. Post-challenge with S. iniae, the mortality rate in the probiotic treatments L. pentosus (P2) and L. plantarum (140) significantly surpassed that of the control group (P<0.05). The findings underscore the absence of synergistic interactions between the two experimental probiotics on the 60th day, as the combined group displayed diminished growth performance compared to the individual groups. Moreover, the use of L. plantarum and L. pentosus bacteria, particularly the latter, has been shown to significantly improve several growth indicators, as well as the food conversion ratio. Consequently, these probiotics are recommended as dietary supplements for Asian sea bass.