فصلنامه بوم شناسی آبزیان
سال یازدهم شماره 1 (پیاپی 40، تابستان 1400)

The environmental effects of rainbow trout cage culture were studied on different physicochemical parameters of water quality in two fish farms, Kiashahr and Abbasabad The concentrations of total phosphorus (TP), total Kjeldahl nitrogen (TKN), nitrate, total organic carbon (TOC), chlorophyll-a, oxygen saturation, and dissolved oxygen (DO) was measured beneath, eastward and westward of the cages. In phase II, a significant increase in the concentrations of TKN, nitrate, TOC, and chlorophyll-a beneath and 50 m east and west of the cages was detected compared to the control and the other stations (P<0.05). A significant higher concentration of these variables was observed in the final sampling campaign in both breeding sites (P<0.05). Unlike other variables, TP concentration in both sites decreased at the end of the breeding period compared to the beginning and also cage station didn’t show a significant difference compared to the control station (P>0.05). In conclusion, rainbow trout cage farming in the southern Caspian Sea can cause a significant increase in water quality parameters up to a radius of 50 m of cages, which indicates an organic enrichment in the water surrounding the cages. Due to the growing trend of fish aquaculture in this region, proper management practices such as high-quality food and low feed conversion ratio are needed to reduce its negative effects on the marine environment.

In order to evaluate the socio-economic indicators of fishing activity of shrimp fleet in Hormozgan province, socio-economic data were collected through a questionnaire (FAO, standard questionnaire form) that includes different variables related to this fishery. From 171 shrimp vessels in three classes 12-18, 18-24 and 24-30, 18, 29 and 10 vessels were randomly selected and while interviewing their owners, the relevant data and information were recorded in a questionnaire and the results of the analysis were extended to the entire fleet. The collected data included employment, literacy level, costs, livelihood dependence, profitability, fuel efficiency and demography in 2018. The number of permanent jobs created by shrimp fishing fleet in Hormozgan provinces was 964.3 jobs. The fixed employment rate of each vessel was 8.5 people per vessel. The total number of job (permanently, temporarily and circulating) created by this fishery was calculated to be 998.3 and the average for each vessel was 8.8 people. The average annual working hours of each crew in shrimp fleet in 2018 in Hormozgan provinces was calculated to be 1938.7 hours. The average ratio of annual working hours of personnel based on the national scale (2107 hours) was /95, and based to international scale (2000 hours), it was calculated as 1.003.  The results of the analysis showed that personnel costs, contributed for more than half of the fishing operating costs of the shrimp catch fleet. Remuneration of crew in shrimp fleet in Hormozgan province is based on fishing share that means personnel receive salaries only in case of fishing activities. Fishermen of Hormozgan province shrimp fleet are young people with an average age of 30.6 years. The analysis of literacy level showed that about 25% of crew had diploma and higher education and the rest (more than 75%) had primary education. The number of people whose livelihood depends on the shrimp fishing fleet in Hormozgan province was estimated to be 4238.3. Data analysis showed that the share of fishing activity in providing livelihood and income of people working in the shrimp fishing fleet in 2018 was 92%. Measurement of fuel consumption efficiency index for the amount of catch, showed that the shrimp fishing fleet of Hormozgan has used 11925.1 tonnes of fuel, for landing of 3324.8 tons of catch (shrimp and other fish species). In other words, fuel efficiency for the entire fleet was calculated to be 0.28 or 28%.

The study of biomass and carbon in mangrove forests is often performed by allometry methods. The allometry models in Mangrove trees are influenced by factors such as species, ecological conditions, and tree age. To study the allometry equation of hara shrub (Avicennia marina) in the Nayband Bay, a complete shrub of Hara from the mentioned area was picked up at 6 stations, and biometry, biomass, and carbon content of the samples were measured. According to the results, the best model for estimating the biomass in mangrove shrubs in Nayband is the power equation using a stem diameter at 30 cm height (ABG = 139.3d301.263). The ratio of the root to the top part (leaf and trunk) is 24%. According to the content of carbon in the biomass samples, the amount of carbon was 42% of the upper part biomass and 39% of the root biomass. The obtained allometry equation in this study is different from mature Avicennia marina in different parts of the world and Iran.

Since the Persian Gulf is a semi-closed water ecosystem, climate change has more severe impacts on organisms, especially on non-motile ones. The harmful effects on organisms can be studied at all biological levels of morphology, anatomy, physiology, to cellular and molecular levels. The collapse of the symbiotic relationship between coral and its symbiont algae can result in bleaching and it is the first effect of changing favorable conditions on hard coral. The cells produce Heat Shock Proteins (hereinafter referred to as HSP) in response to heat stress. The rate and way of HSP production in corals depend on the expression of the genes encoding these proteins. In this study, we investigated the expression of heat shock gene HSP70 in response to elevated temperature in Acropora downingi (Wallace, 1999) coral reef. After sampling hard corals in March 2018 and adapting them to laboratory conditions, their ambient water temperature increased to 9 °C (from 25 °C to 34 °C). The samples were adapted to laboratory conditions for 2 weeks after being transferred to the laboratory. The water temperature was 25 °C under control conditions, which was increased to 34 °C to create thermal stress. The expression of the gene Hsp70 was evaluated at control time and also 24 h and 48 h after temperature rise. The study showed that gene expression was significantly increased 24 h after stress and it decreased at 48. However, the corals were bleached, which could be due to the deterioration and reduced resistance to heat shock.

This research was aimed to investigate the concentration of heavy metals (including copper, vanadium, lead, and nickel) in water, sediment, muscle, and liver tissues of Sillago sihama living in the Khour-e-Mousa, Khuzestan province. Samples were picked randomly from three stations during winter and summer and the concentration of heavy metals was measured using atomic absorption spectrometry (flame and flameless GF AAS). Based on the results, the bioaccumulation index (BI) of liver tissue for these four elements was measured 183.33, 0.05, 0.29, and 2.35 in winter, and 21.7, 0.07, 0.25, and 1.05 in summer, respectively. Moreover, the BI for muscles was measured 130, 0.02, 0.07, and 1.45 in winter and 18.3, 0.02, 0.07, and 0.49, in summer, respectively. The results showed that there was a significant linear relationship between the concentration of heavy metals in sediment with their accumulation rate in muscle and liver tissues of Silver sillago. According to the results of this study, the ecological risk potential index (RI) was however rated low at the ecological risk range, since, Khour-e-Mousa is known as one of the most sensitive ecological and environmental areas and there are signs of an increasing trend of metal pollution. It raises serious concerns for the region in terms of ecology and public health.

The Future projection models (FPMs) were used to assess some shrimp fisheries management strategies (11 strategies and 2 Reference procedures) in a data-poor and uncertain situation in Hormozgan province, Persian Gulf. Data were collectedby scientific observers onboard traditional shrimp trawlers during October to December 2018, and reviewing the literatures. Data analysis revealed that maximum relative performance was related to Catch by shrimp size controlling strategy. Against, Delay-difference management strategy has the lowest relative performance, in terms of remaining stock and yield, and is never recommended to shrimp fisheries management in the region. Strategy of the controlling fishing effort through target species length frequency (LtargetE) has also the best outputs than others for conserving the shrimp stock.To achieve the maximum protection from spawning stock biomass,strategy of regulating the fishing effort through target species optimum length (EtargetLopt)has an acceptable performance.Effort searching strategy has also the highest performance forarriving the maximum sustainable yield (MSY) in a depleted stock, and disclosed that forty percent of the stock should be harvested as an optimum effort. The findings of the present paper could help to promote sustainable fisheries management in the Persian Gulf.

The aim of this study was to a histological investigation of zebrafish ovary and the process of ovulation under the effect of various intensities of the static electromagnetic field. 80 adult female fishes with an average weight of 0.4-0.7 g were selected and exposed to different intensities of electromagnetic field (2.5، 5 and 7.5 mT) for one hour per day for 7 days. On the 7th day, the ovaries were removed, after fixation and embedding; tissue sections were prepared with a thickness of 5 microns. The results showed that during the development of oocytes, six phases are observed. Comparison of the effects of different doses of the static electromagnetic fields on ovarian tissue of zebrafish showed that oocytes enter the atresia phase at intensities of 7.5 mT. These oocytes will not have normal fertilization if they are released. At low intensities of electromagnetic field (2.5 and 5 mT), most oocytes are observed in cortical alveolar phases, vitellogenesis, and mature phases. The percentage of atretic oocytes is low, and the rest of the oocytes will have normal fertilization. In conclusion, it seems that high-intensities of the static electromagnetic field have negative effects on the reproduction of zebrafish and could reduce their regeneration.