نشریه آبزیان زینتی
سال دهم شماره 1 (بهار 1402)

Oscar fish (Astronotus ocellatus), is one of the most popular aquarium fish, which needs more attention to provide health in breeding conditions. Due to the expansion of the use of probiotic bacteria in the aquaculture industry this research was conducted to evaluate the effects of Lactococcus lactis and Bacillus subtilis on digestive enzymes and hematology as health indices of Oscar. The experiment was set up with 300 juveniles with an average weight of 8.96 ± 0.03 (gr) and a length of 8.23 ​​± 0.02 (cm) during 70 days with a diet containing the two mentioned bacteria in 9 treatment groups of CFU/g 1010 bacterial ​​concentration as 150, 300 and 450 mg added bacteria per kg of food and equal mixtures of both bacteria as 75, 150 and 225 mg per kg of food and were compared with control treatment. At the end of rearing period the results of the blood indices showed an increase in red blood cells, hemoglobin and hematocrit values ​​in treatment 3 (LL450) (P<0.05). Also, the results of the activity of digestive enzymes, including amylase, lipase and protease, in the treatments receiving bacterial added diets, especially in treatment 3 (LL450), statistically was differing from control (P<0.05).

Lactobacillus casei probiotic is one of the probiotics used in aquaculture industry. The aim of this study was to evaluate the effect of Lactobacillus casei probiotic on the growth performance, blood parameters, and intestinal microbial flora in goldfish (Carassius auratus) for 60 days. In this study, 180 fish with an average weight of 10.11± 0.16 g were randomly distributed into two treatments with three replicates (n= 30) including commercial diet (control treatment) and diet containing L. casei probiotics at 107 CFU / g (experimental treatment).The results showed that the final weight, weight gain, specific growth rate (SGR) and condition factor (CF) in the treatment containing L. casei had a significant increase compared to the control group (P <0.05). The results also showed that the inclusion of L. casei probiotic to the goldfish diet resulted in increase the number of white blood cells compared to the control group (P<0.05). Moreover, a significant increase in total number and intestinal lactic acid bacteria in the treatment containing probiotic Lactobacillus was observed compared to the control group (P<0.05). Therefore, addition of L. casei probiotic enhanced growth performance and intestinal lactic acid bacteria in goldfish (C. auratus).

Biodiversity includes the composition, abundance and richness of species and is studied at genetic diversity within species, between species and ecosystem level. Species diversity is vital for maintaining the flexibility of an ecosystems results in greater stability. The presence of more species in an ecosystem makes natural ecosystems more complex and therefore ecosystems are more resistant to unfavorable environmental changes with their stable communities. The Caspian Sea is poorer in biodiversity than other seas such as the Baltic and Black Seas, and due to growing pressure of environmental challenges, the population of valuable aquatic species has declined radically including all sturgeon representing the Caspian Sea and are in danger of extinction. On the other hand, rivers and lagoons leading to the Caspian Sea, which are suitable spawning grounds for spawners and safe nursery grounds for offsprings of several bony fishes often do not have appropriate conditions due to irresponsible fishing and heavy loads of various pollutants. Therefore, practically there is no sound spawning migration into these water bodies by bony fishes which means the stocks of anadromous species are severely threatened. Restoration of stocks of these bony fish species should be practiced in large scale similar to that of Kutum (Rutilus kutum). Appropriate river management and restoration and providing conditions for migration to at least some of these rivers and providing conditions for natural reproduction will play a key role in rehabilitation of stocks of these fish and preserving the biodiversity of the Caspian Sea.

Ornamental fish is one of the most important industries in the aquaculture industry, which has international reputation compared to other aquatics. Breeding of ornamental fish has been successful in terms of using internal resources, high profitability, low investment, relative simplicity of production technology, and the possibility of spreading innovation and participation of young people for direct and indirect employment generation. Polypterus fish which is known as Azarakhsh fish in Iran, is one of our prehistoric fish whose history goes back to more than 200 million years ago. In addition to water breathing, this fish has air breathing and is resistant to many diseases and unfavorable environmental conditions. The birthplace of this fish is Africa and the catchment areas of the Nile River, Senegal, Niger, and other countries. The weight of this fish is reported to be about two hundred grams. In nature, these fish use insects, small fish, crustaceans, frog larvae and some molluscs, although some polypterous species are insectivorous and their lifespan reaches 34 years. Although it is very difficult to reproduce polypterus fish inside the aquarium, it can be done using techniques. The best age for polypterus fish reproduction is over 7 years and 30 cm long, otherwise these fish will not spawn. In order to stimulate the spawning of these fishes, it is necessary that the place of the aquarium is quite large and covered with hiding places.

Number of attempts has been made to cryopreserve fish and shellfish gametes. Success has been achieved to establish only sperm banks in case of some commercially important fish. In shellfish, also particularly in shrimps, though the sperm cryopreservation was successful; no attempts were made to develop sperm banks. As far as cryopreservation of egg and embryos of fish and shellfish is concerned, less research efforts were made with limited success. Number of reasons have been given for the failure of egg/embryo cryopreservation and the main barriers speculated are low membrane permeability in the eggs, the large yolk mass of the oocyte, and the presence of compartments in early developing embryos. These factors result in ice crystal formation during the freezing process. In addition, the oocytes and embryos are prone to chilling injuries unrelated to ice crystal damage. There are number of other problems reported by several researchers in the egg/embryo cryobanking protocols which are elaborately discussed in the present paper. There is an urgent need to develop a viable cryobanking technology for fish egg/embryos to enhance fish production in captive condition. Attempts to cryopreserve larvae of aquatic animals are another challenge occurring in the recent past. The aim of the present review is to collect comprehensive information on the efforts so far made on fish and shellfish egg and embryo cryobanking; and to assess the challenges in the development of viable technology and plan for future research for making this technology viable and cost effective.

Zebrafish are one of the creatures that have been increasingly considered in neurophysiological studies of pain as well as pharmacological and toxicological research. As the popularity of zebrafish grows in biomedical studies, the legal aspects of its applications have not grown at the same time and lagged behind. It seems that the evaluation of the legal aspects of Zebrafish applications in pharmaceutical and neuroscience research is important. The aim of this study was to investigate the ethical aspects of working with zebrafish in experiments such as the neurophysiology of pain and the effect of various drugs, and stress-related studies. Therefore, in this study, we will introduce the methods that have been considered in scientific research to reduce the pain and stress caused by experiments in zebrafish, including anesthesia and euthanasia techniques in this species.