نشریه پژوهش های ماهی شناسی کاربردی
سال سیزدهم شماره 4 (زمستان 1404)

Medicinal plants are introduced as growth-promoting supplements due to their antioxidant properties. The aim of this study was to investigate the effects of using different levels of nanoemulsions of medicinal plant essential oils (thyme, oregano, and garlic) on growth performance, digestive enzymes, and lipid metabolism in common carp (Cyprinus carpio) larvae. 360 common carp larvae (mean initial weight 2.43±0.37 g) were stocked in 12 tanks at a density of 30 fish. The experiment was conducted in 4 treatments (each with 3 replications) with a mixture of essential oils of three medicinal plants (thyme, oregano and garlic) at concentrations of 0 (control), 3.5, 7 and 14 µl/g (control T0, T1, T2 and T3, respectively) for 8 weeks. The results of this experiment showed that the highest weight performance was obtained in the treatment with 3.5 µl/g of the medicinal plant essential oil nanoemulsion (T1) compared to the control treatment (T0). Feed conversion ratio (FCR) had a statistically significant decrease in T1 and T0 treatments (p<0.05). Digestive enzyme assays showed that the concentration of protease enzymes increased significantly in the T1 and T2 treatments, while the lowest was in the T0 and T3 treatments (p<0.05). Lipase enzyme had a statistical difference between the nutritional treatments with the medicinal plant nanoemulsion combination, so that the highest and lowest were obtained in the T1 and T0 control treatments, respectively. Amylase enzyme increased in the T1 treatment and decreased significantly in the T3 treatment (p<0.05). Analysis of blood lipid metabolism showed that the highest cholesterol and triglyceride levels were observed in treatment T0 and the lowest in treatment T1. HDL levels in T1 increased significantly compared to other experimental treatments (p<0.05). LDL levels in T1 and T2 decreased significantly compared to other treatments (p<0.05). Overall, the results showed that the combination of medicinal plant nanoemulsion (thyme, oregano and garlic), especially the T1 treatment, improved growth performance, digestive enzymes, and fat metabolism compared to the control T0 treatment.

The Caspian Sea, with its brackish water, high species diversity, and exclusive species, hosts a wide range of native and non-native fish in its ecosystem. The present study was conducted to investigate and identify a new species of fish observed in the commercial catch of the cooperative beach seine fisheries in Golestan Province in 2024. In this research, considering the morphological similarity of the new species to the mullet family of the Caspian Sea, 16 specimens of this species were collected along with several Chelon auratus and Chelon saliens from the fish market in Bandar Torkaman, Golestan Province. The morphological characteristics of the new species were examined using identification keys, and dissection was performed to observe the pyloric caeca and compare it with mullet species of the Caspian Sea (Chelon auratus and Chelon saliens). The results indicated that the new species, possessing the main characteristics of mullet fish, particularly the two completely separate dorsal fins (with the first dorsal fin having only 4 spines) and the absence of a lateral line, belongs to the mullet family. However, it is distinguished from the Chelon auratus and Chelon saliens (which have 7-9 pyloric caeca) by having 4 pyloric caeca that are nearly the same size (homogeneous). Based on the results obtained in this study, it appears that the new species of fish observed in the commercial catch of the cooperative beach seine fisheries in Golestan Province is the Biah, Planiliza abu belongs to the Mugilidae.

The introduction of various pollutants into lakes leads to eutrification, algal blooms, and the development of unpleasant taste and odor in the water. This study aimed to investigate the effect of silver carp (Hypophthalmichthys molitrix) on controlling algal communities in the Qeshlagh reservoir and reducing the taste and odor of drinking water in Sanandaj. To this end, the planktonic composition of both the environment and the digestive system of silver carp was examined. Water and fish samples were collected from two dam stations, followed by laboratory analyses of plankton composition, biometric parameters, nutritional indices, reproductive status, and digestive system contents. The environmental planktonic population analysis revealed that the Bacillariophyta phylum (70%) and the Arthropoda phylum (54%) had the highest densities of algae and zooplankton, respectively. Fish from four age groups (3+ to 6+ years) had an average weight of 1130.4 g and an average total length of 482.7 mm. The average relative intestine length index and condition factor were 4.3 and 0.98, respectively, with an intestinal emptying index of zero. Examination of the digestive contents identified 54 genera and species of phytoplankton and 11 genera and species of zooplankton, compared to 37 genera and species of phytoplankton and 16 genera and species of zooplankton in the environment. Within the digestive system, Bacillariophyta (54%) and Chrysophyta (43.8%) predominated among phytoplankton, while Rotifera (59%) and Ciliophora (40%) were the most abundant zooplankton. The genera Dinobryon and Melosira were predominant in the diets of fish from both stations, with Melosira also having the highest density in environmental phytoplankton samples. The Ivlev selectivity index indicated that Bacillariophyta (45%) was the most frequently consumed phytoplankton group by silver carp. Melosira demonstrated the highest prey abundance at both stations (100%), while Fragillaria, Cyclotella, and Dinobryon showed high frequencies of 100% in station 1 and 94%, 88.9%, and 88.9%, respectively, in station 2. The sexual maturation index suggested that environmental conditions in Gheshlagh reservoir are not conducive to the growth and development of silver carp gonadal tissues, indicating likely absence of natural spawning and ovulation for this species. Overall, silver carp appears to be an effective species for controlling algal biomass in lake ecosystems. This study provides valuable insights into the biocontrol potential of silver carp for managing algal blooms and improving water quality in reservoir ecosystems.

this research aimed to evaluate and compare several mathematical models for describing the growth trajectory of the sharpnose shark (Carcharhinus macloti) within the coastal waters of Hormozgan Province, situated in the northwestern Persian Gulf and northeastern Gulf of Oman, between 2019 and 2022. A total of 265 individuals, including 156 females and 109 males, were sampled for morphometric measurements and age estimation through vertebral band counts. Five growth models—second-degree polynomial, von Bertalanffy, Gompertz, logistic, and Schnute—were fitted using Python programming tools in a Jupyter environment.For females, logistic, Gompertz, and Schnute models provided the best fit according to the Bayesian Information Criterion (BIC), while the von Bertalanffy model failed to accurately represent growth in either sex. Although the polynomial model demonstrated statistical fit, its biological interpretability remains limited. Among males, the polynomial model showed the best numerical fit, followed closely by Gompertz and logistic models. The estimated asymptotic length (L∞) and growth rate (K) for females were 106.11 cm and 0.34 year⁻¹, respectively, with an inflection point at 1.7 years. In males, these values were 103.9 cm, 0.40 year⁻¹, and -0.46 (t₀).Overall, the study emphasizes the necessity of model selection based on empirical data quality and biological plausibility, rather than defaulting to traditional models.

Nile tilapia (Oreochromis niloticus) is one of the most important aquaculture species in the world, which is sometimes incorrectly identified as an invasive species. This article, based on scientific evidence from reputable international sources, analyzes the views related to the non-invasiveness of this species and the management conditions necessary for its control and sustainable use in Iran. The findings show that in closed and monitored ecosystems, tilapia can play the role of a harmless economic species. Although many ecological studies have described this species as invasive in Iran, recent studies show that in native habitats and managed environments, Nile tilapia cannot be considered an invasive species. This analytical article aims to examine the scientific views on the invasiveness or non-invasiveness of Nile tilapia, analyzing the conditions in which this species is considered to be non-invasive. The main focus will be on distinguishing between the effects of accidental release in non-native environments and the role of this species in natural ecosystems and controlled agriculture.

Common carp, Cyprinus carpio is one of the most important and commericial species in Caspian Sea. In this study, for surveying some biological parameters, 679 specimens were collected from beach seine cooperative firms in southeast of Caspian Sea (Golestan Province) since October 2014 to March 2015. The individuals range from 15 to 75 cm fork length and 1to 10 age. Common carp has negative allometric growth model. The Von-Bertalanfi growth equation was assessed Lt =78.23 ( 1-e-0.2t+0.64) . Total mortality, natural mortality, fishing mortality coefficients and exploitation ratio were estimated 0.872, 0.364, 0.49 year-1 and 0.58, respectively. According to Thampson and Bell model, biomass and maximum sustainable yield were estimate 16641 Kg and 2151 Kg. Results determine common carp stock has unsuitable situation in southeast of Caspian Sea.