مجله علوم و فنون دریایی
سال بیست و یکم شماره 2 (تابستان 1401)

This study estimated the discarded catch of the Moshta gear and the length at maturity parameter (Lm50) of two species of discard aquatics Arius maculatus and Plicofollis dussumieri. Sampling carried out in the city of Bandar Abbas since December 2014 for one year. After specifying the maturity of samples by the Biswas (1993) method, to calculate the length at maturity the least-squares technique under the king (2007) method was performed in Data Analysis Solver of Excel 2013. Discard catch included 65.23% of the weight and 74.93% of the number while commercial catch included 34.77% of the weight and 25.07% of the number. According to the results, the length at maturity of Arius maculatus was 28.2 cm, 51.50% were below puberty. The length at maturity of Plicofollis dussumieri was 32 cm, 62.3% were below puberty. The results of this study showed that Moshta with a high diversity of trapped aquatics, while some of these aquatics are caught immature, was a threat to fisheries stocks in Hormozgan province and the Iranian waters of the Persian Gulf.

In this paper, free vibration of the ship with Timoshenko beam model is investigated and natural frequencies and mode shapes are obtained. Since the frequency equations of Timoshenko beam are nonlinear, for obtaining the frequencies and mode shapes, numerical method, differential quadrature method with discretization is used. Frequencies of some vessels with different geometers such as length, height and width are obtained and versus length, height and width are compared and effect of these parameters on the frequencies are investigated. These investigations show that by increasing these parameters the frequencies are decreased and for the vessels that have a large ratio of height to length, the Timoshenko beam model should be used for vibration investigation that the shear effect is considered.

The purpose of this study was to investigate the population of benthic invertebrates and their relationship with environmental factors of Gorgan Bay Inlet. The abundance of benthic invertebrates during 2017 in three seasons from 9 stations in three sites, bay mouth, Ashuradeh coast and sturgeon culture area was studied using three replicates (225 cm2). In this study, in total, fauna was identified: 3 phyla, 6 classes, 12 families and 12 Genus. Streblospio gynobranchiata (2347±177, 47%) and Hediste diversicolor (873±101, 17%) had the highest abundance. The highest species abundance was observed in spring and the lowest species abundance in autumn. The lowest Shannon (1.12) and Pielu index (0.62) were obtained in the sturgeon culture area. Also, the dbRDA graph based on DistLM model showed that temperature, salinity and clay temperature variables and sand, silt and dissolved oxygen variables were responsible for causing abundance of fauna among different stations in the sampling seasons. According to these results, it can be concluded that macrobenthos in different seasons and areas have many changes in abundance and diversity index. Therefore, when using these communities to assess the impact of environmental factors, their natural changes should be considered.

The liver is one of the most important organs of animals that know as a detoxifying and filtering toxin in the body and the most studies was used the target organ. In peresent study, hepatocytes were isolated from 8 immature grouper fish (equal to the number of male and female). Then, anesthetized fish and the head was separated from the body. The fish wiped with 70% etanol alchol. The liver was removed was cuted with scissors. Finally, the cells digested by collagen type 4. Then, the cells incubated in 30^C and 20% FBS+ITS during two weeks. The doses of pollutant (100 µM, 2*100 µM, 3*100 µM) added to samples, then were studied in 0, 6, 12 and 24 time. The morphological analysis exhibited that the cell death incubated by B[a]P polluted by concentration of 100 µm results in 50% of apoptosis cell death. Our finding from this study showed that using lower dosage of B[a]P during 24h treatment period cause inhibition of proliferation in time and dose dependent manner and higher doasage cause lysis and necrosis.

Exploitation of marine living resources, especially fish, has long been one of the most important ways of providing human food and has been considered a lucrative economic activity. In the past, the view has been that marine species are endless resources, but gradually, with increasing knowledge and awareness in this field, the view of countries about their infinity has changed and the need to protect them has become apparent. International law has considered the protection of marine species in recent decades, especially with the ratification of numerous international conventions and instruments. It should be noted that although there is a wide range of international and regional rules and regulations in the field of protection of marine species, but their overfishing continues, which shows the lack of adequate government support for such documents and non-implementation. Complete their regulations. Accordingly, it is necessary for governments to make every effort to exploit and protect marine living resources responsibly, and it is clear that responsible exploitation and optimal protection of marine living resources is in the interests of all nations. And governments need cooperation at the international level. There is also a need to develop and develop rules on various aspects of the protection of marine species, in which governments should take appropriate action at the international level, including through relevant international organizations.

The extensive development and design of multihull ships began in the second half of the twentieth century. Nowadays, many of these ships are built with different designs. However, less numerical and experimental studies have been conducted on their behavior compared to single hull ships. The length and distance of the two hulls are the factors influencing the wave pattern created around and between the hulls and, consequently wavemaking resistance. In this study, the effect of geometric parameters including length to diameter ratio and body spacing on the hydrodynamic performance of a vessel with a small water plane area surface has been studied using computational fluid dynamics. To investigate the effect of L/D on the wave pattern around the body, towing test is simulated for two models with different ratios in a wide speed range. Furthermore, to evaluate the effect of two-hull distance on the interference of waves between two bodies, two models have been simulated at different distances at different speeds in the computational fluid dynamics environment. Simulations are performed for two different draft. The effect of Froude number, length to diameter ratio and draft on hydrodynamic behavior of the model has also been studied. The pressure, friction and interference resistance of the two bodies are calculated and the wave pattern surrounding the body and between the two bodies is extracted and compared with experimental data, which indicates the reasonable approximation of numerical and laboratory results.

This study aimed to investigate the effect of two species of Lactobacillus probiotics (Lactobacillus acidophilus and Lactobacillus bulgaricus) and button mushroom (Agaricus bisporus) extract singular and combined on digestive enzyme activities, body composition, survival, growth and microbial flora in Zebrafish (Danio rerio). For this purpose, 7 experimental diets were evaluated in 3 replications. One-month-old aged zebrafish (D. rerio) (75.9±1 mg) were fed with experimental diets including: diet without probiotics and prebiotic as the control diet (diet 1), diet with 1% button mushroom extract as prebiotic (diet 2), diet with 107 CFU g-1 Lactobacillus acidophilus as probiotic (diet 3), diet with 107 CFU g-1  Lactobacillus bulgaricus  as probiotic (diet 4), diet with 107 CFU g-1  Lactobacillus acidophilus in combination with 1% button mushroom extract as synbiotic1 (diet 5), diet with 107 CFU g-1  Lactobacillus bulgaricus in combination with 1% button mushroom extract as synbiotic2 (diet 6) and diet with 107 CFU g-1  Lactobacillus acidophilus, 107 CFU g-1  Lactobacillus bulgaricus and 1% button mushroom extract as synbiotic3 (diet 7) for 60 days. At the end of the experiment, Sampling was performed randomly to evaluate those mentioned factors. The results showed that the highest growth rate, specific growth rate and the lowest feed conversion ratio were observed in the synbiotic treatments, which were significantly different from the control group (P <0.05). However, there was no significant difference in the survival rate of all treatments with the control group (P <0.05). Also, the highest activity of digestive enzymes was observed in the group which fed with diet 7, which was significantly different from other treatments and control group (P <0.05). In addition, the highest amount of protein was observed in the treatment which fed with diet 7, which was significantly different from control group (P <0.05). However, this difference in fat, ash content and body moisture between control group and other treatments was not significant (P <0.05). The total number of intestinal microbial flora bacteria and lactic acid bacteria that was examined at the end of the period was significantly different from the control group in all treatments (P <0.05). But, there was no significant difference between all treatments with the control group 10 days after stopping feeding with the experimental diets (P <0.05). According to the results, feeding with synbiotics containing these probiotics in combination with button mushroom extract as a prebiotic had a positive effect on growth performance and digestive enzymes in Zebrafish (D.rerio), therefore, it can be recommended as a functional synbiotic in zebrafish (D. rerio) farming.