نشریه علوم و فنون شیلات
سال دوازدهم شماره 4 (پیاپی 44، پاییز 1402)

This study investigated the Caspian Sea surface temperature fronts from 2015 until 2019 using satellite images (MODIS). The sea surface temperature front, a narrow-width area with a high-temperature gradient, plays a crucial role in various biological, chemical, physical, and agricultural parameters and climate change issues. Detecting sea surface temperature fronts also helps understand other phenomena such as upwelling, eddy, and biological accumulation. The Canny algorithm was used in the MATLAB environment for detecting the fronts, and the results were compared spatially and temporarily. It was observed that the fronts in the north of the Caspian Sea are permanent from September until November and March until May, while they are impermanent and dashed at other times of the year. In the east of the south Caspian Sea, the only detected fronts in March repeat annually, whereas in the west of the south Caspian Sea, fronts were detected in all months except for August, consistently over the five years. The pattern of temperature fronts in the east and west of the Middle Caspian Sea differs. The fronts are clustered in winter but become coherent and clear in summer. Additionally, the southern Caspian Sea temperature fronts are less abundant in the pre-summer period than in other periods. The Caspian Sea surface temperature fronts were mostly detected in the location of internal waves, steep areas near the coast, and eddies.

This research was conducted to determine the effects of garlic extract as feed supplement on the growth performance, body content, blood indicators and culture water quality of rainbow trout (Oncorhynchus mykiss) under stress ammonia. A total number of 156 fish (Average weight 18.37±1.43g and total length 12.27±0.52cm) were reared in twelve 50-L tanks for 60 days (First period: 50 days of feeding with different levels of garlic extract) and (Second period: 10 days under ammonia stress of 0.024 mg /L). Experimental included adding different levels of extract to base food, 0, 0.5, 1 and 1.5% (control, A1, A2 and A3, respectively). The growth performance was significantly higher in fish fed garlic extract supplementation than control. There was a significant difference in feed conversion ratio between different treatments, so that was obtained the lowest in A2 and the highest in control. Protein, immunoglobulin and cortisol concentrations were significantly affected by different levels of garlic. The end of the experiment period, the fish were kept in a close recirculation system for 24 hours. Water sampling was carried out every 4 hours. Water ammonia increased from 16 to 24 hours of the test. At the end of the experiment (time 24), the highest ammonia was obtained in treatment A3 (0.43). In general, the results showed that the addition of 1 to 1.5% garlic extract improved the growth performance and immune response in rainbow trout, while in the recirculation system, the water quality of the rearing environment was better in the control treatment.

The aim of the present study is to evaluate the amount of tilapia fish consumption and the relationship between its consumption amount and some demographic characteristics Such as gender, age, occupation, education, marital status, occupation, number of household members and income.

The statistical population of this research is the whole country. A questionnaire was designed and sent to people electronically through virtual space. Correlation tests were used to evaluate the number of fish purchases per year as well as the amount of each purchase from the output of SPSS software and to investigate the existence of a significant relationship between consumption and demographic characteristics.

The results showed that Most of the female respondents are married, aged 20 to 35, employed and have bachelor's and master's degrees. Most of them are employees and earn between 3 and 6 million tomans. It was also found that most households (54%) buy fish up to 20 times a year. The average number of times of buying fish per year by the households of the consumption community was 45 times. Most households in the consumer society buy 2 kg of fish each time they buy. The number of households that consume more than 10 kg of fish per purchase was 3.3%. According to the obtained information, the average amount of fish per purchase was calculated to be 8 kg. The per capita consumption of tilapia in households consuming this fish was 4.2 kg.

Investigating the trend of temperature changes occurring in the Persian Gulf can be used to determine the pattern of climate change in the region and to study the impact of these changes on aquatic habitats in the Persian Gulf waters.  This study was carried out to investigate the changes in sea surface temperature and sea surface temperature anomaly in Kharg and Hendourabi islands by using Environmental Research Division's Data Access Program (ERDDAP) of National Oceanic and Atmospheric Administration (NOAA) and  daily sea surface temperature and sea surface temperature anomaly  were investigated over a 35-year period.The results showed that the average annual surface temperature increased by about 1 °C over 35 years in Kharg and Hendourabi Islands and the average annual sea surface temperature anomaly in these islands were increased by 2 °C. The slope of this increasing trend on Kharg Island was more severe than Hendourabi Island. The most significant bleaching event in the Persian Gulf occurred in 2016-2017, with the highest increase in temperature in 2017. As water temperatures continue to increase in the coming years, the living conditions of the Persian Gulf corals are likely to deteriorate, and only some resistant species can survive in the Gulf.

In this study,the immunogenicity of streptococcosis/lactococcosis and yersiniosis vaccine in rainbow trout was investigated in farm.900 fish with an average of 50±5 g were divided into three treatments and three replications (injection treatment, immersion treatment and control group).Fish were kept for 60 days and samples were taken on the 30th and 60th days.Then the fishes were challenged for 14 days with three bacteria, Streptococcus iniae, Lactococcus garvieae, and Yersinia ruckeri.Sampling was done to evaluate lysozyme activity,complement, antibody titer and survival rate. The results indicated a significant increase in serum complement and lysozyme activity on the 30th and 60th days of sampling in the vaccinated groups compared to the control group (P<0.05).Antibody titers against S. iniae, L. garvieae and Y. ruckeri on the 30th and 60th days of sampling in the vaccinated groups had a significant increase compared to the control group (P < 0.05).The  relative percentage survival after 14 days of challenge with S. iniae, L. garvieae and Y. ruckeri in the injected group was (70, 60, and 76.6%),respectively, which was significant compared to the control group (P<0.05).Also, the relative percentage survival in the immersion group with S. iniae, L. garvieae and Y. ruckeri was(30, 36.6 and 53.3%),respectively, which was significant only in the group immersed with S. iniae (P<0.05).In general,it can be concluded that the use of polyvalent vaccine by injection and immersion has significant effects on the immunity and survival rate of rainbow trout. However, the injection method is more effective and suitable than the immersion method.

The objective of this study was to evaluate the performance of nutritional programming on growth and hematological indices of sterlet sturgeon (Acipenser ruthenus) during the larval stage by partial replacement of fish meal (FM) with soybean meal (S). Sterlet sturgeon with initial mean weight of 0.32 ± 0.01 g were randomly distributed into twelve circular concrete tanks (260 fish per each tank) and fed four experimental diets with substitution levels of 0 (control/FM), 15% (S15), 30% (S30) and 45% (S45) of fish meal with soybean meal during three phases in three replicates. In phase 1 (programming), fish were fed four different diets for 28 days. All the groups were then fed with FM during phases 2 (intermediate) and S45 at phase 3 (challenge) for 28 days. At the end of each phase, growth indices were measured. Hematological indices including red blood cell, hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration were assessed at the end of the challenge phase. The growth performance was not significantly different in either phases 1 or 2 (P > 0.05); however, final weight, weight gain, specific growth rate, and average daily growth were significantly higher in S45 than FM during phase 3 (P < 0.05). Moreover, no significant difference was indicated among the groups in hematological indices (P > 0.05). According to the obtained results, early nutritional programming could effectively enhance the adaptation of sterlet sturgeon to plant-based protein later in life.

Trichiurus lepturus is one of the most important and commericial species in the Persian Gulf and Oman Sea.In order to come up with the responsible fishing pattern,there was a need to identify  reproduction characteristics. Data were collected randomly from April 2019 to February 2020 from six major artisanal fish-landing sites in Hormuzgan Province (Bandar Parsian, Bandar Kong, Qeshm Island, Bandar Abbas, Bandar Sirik and Bandar Jask). In the detection of sexual stages, the 5-stage key of sexual maturity was used at the macroscopic level. In determining the spawning season, the gonado-somatic index(GSI) was used and its comparison in different months. The lowest GSI of female fish was in September (1.2). The highest GSI of male fish was determined in December with a value of 3.1 and after that in May 2.6. Examination of the GSI and reproductive stages showed two main spawning periods in the middle of spring and late autumn. Different sexual stages were seen in all months of the year, which indicated the batch spawning strategy in T. lepturus. During different months, significant differences in the sex ratio were observed, but during the investigation and in total, no significant difference was observed between the female: male sex ratio in the expected ratio of 1:1.The length at first maturity obtained 78.7 cm total length. It is necessary to ban fishing during the spawning season in order to protect the stocks of this species.