The study aimed to compare the growth performance and physiological responses of bester (B) and backcrossed bester ♀ × beluga ♂ (BB) in response to crowding stress under different stocking densities, as well as to establish a threshold stocking density for rearing BB in a recirculating aquaculture system (RAS) without welfare impairment. For this purpose, in the first trial (T1), B (181.15 ± 21.21 g) and BB fingerlings (181.98 ± 28.65 g) were reared in two stocking densities of 2 kg/m2 and 4 kg/m2 in fiberglass tanks (1 m3) for 6 weeks. In a parallel trial (T2), the BB hybrids (335.24 ± 39.30 g) were kept in four initial stocking densities, ranging from 5 kg/m2 to 12 kg/m2. The results of T1 revealed better growth indices (i.e., final mean weight, weight gain, specific growth rate) at lower stocking densities for both hybrids; however, in terms of growth performance, the BB hybrid showed better results when compared with the B hybrid. BB hybrids registered significantly (p < 0.05) lower serum cortisol and MDA and higher lysozyme than B hybrids, showing higher tolerance to crowding stress. Nevertheless, at higher densities, selected serum parameters (i.e., hematological indices, cortisol, glucose, protein, malondialdehyde, lysozyme) and growth performance indices used to evaluate the hybrids indicate that high stocking density could affect the growth and welfare of BB hybrids, and that the selected serum parameters could be used as good indicators for chronic stress caused by overcrowding conditions.
The Black Sea sturgeons are anadromous fish species [1], which migrate upstream on the Danube River for breeding. The distance traveled in the migration process varies depending on each species, from tens to hundreds of kilometers [2]. After breeding, the anadromous sturgeons return to the Black Sea and go back to the Danube after a time that varies depending on the species between 3 and 5 years [3]. All sturgeon species that migrate in the Danube basin are on the IUCN Red List of Threatened Species [4]. Considering that sturgeon migration is a condition of the existence of species [5], INCDPM developed in 2011-2017 extensive research studies of their behavior. Using ultrasonic telemetry, unique information volumes have been obtained on the behavior during sturgeon migration in different hydrodynamic conditions and under the pressures caused by anthropogenic activities. The intensity of poaching was also analyzed, resulting in that this pressure represents a real threat to the existence of sturgeon species. Over 70% of the total specimens monitored in research studies, developed by INCDPM during the over 7 years of research, were poached. The research was conducted in Ml compliance with the provisions of the EU Biodiversity Strategy for 2030 [6], which aims to conserve endangered habitats and species, including by reducing and eliminating by-catches.
Construction of the dams in Lower Danube River (LDR- rkm 0 Sulina – rkm 1075 Baziasi) without fish passages, as well as illegal fishery and river bottom modification due to navigation had negative impact on sturgeon’s populations. Beluga Sturgeon, Stellate Sturgeon and Russian Sturgeon still migrate to spawn in LDR but there is lack of information relating to sturgeons long distance migration in this area. Tagging with Vemco V16 TP acoustic tags, equipped with temperature and depth sensors involved 36 adult Beluga and 44 Stellate Sturgeons provide new data about sturgeon migration. Their migrations are monitored by VR2W receivers, deployed on between rkm 71 and rkm 864. Analysis of data showed that 17% of Beluga and 30% of Stellate Sturgeon never recorded and 30% and 11% of Beluga and Stellate Sturgeon recorded in period more than 30 days after tagging. Only 5% of Beluga and 7% of Stellate Sturgeon have been recorded after a period of more than 1 year. During 2013-2016 4 adult Beluga and 1 adult Stellate Sturgeon were recorded in the IGII Dam area. Results of this investigation showed that sturgeons still approached the IG2 dam and construction of fish passage on this dam is needed.
The hydrotechnical works (bottom sills, banks protections, and guiding wall) performed during 2011 -2017 period on the Danube river, between Calarasi and Braila (km 375-175), aimed to improve the fluvial navigation, and have imposed a continuous monitoring of biotic and abiotic environmental factors. The aim of these hydraulic works is to identify the possible negative effects which might appear and find the alternative solutions to eliminate the risks. The sturgeons, which are migratory species protected by Romanian law and closely monitored by international organizations, can be affected by these works, in the sense that the newly constructed bottom sills would prevent the migration to the breeding habitats. For the migration monitoring, ultrasonic receiver stations and ultrasonic transmitters developed by the Vemco Canada Company were used. The novelty of this work is attributed to the characteristics and efficiency of two monitoring systems developed and patented by the National Institute for Research and Development in Environmental Protection and applied along the Danube River.
The swimming ground speed and swimming depths of beluga sturgeon (Huso huso) and stellate sturgeon (Acipenser stellatus) were investigated using ultrasonic telemetry between 2011 and 2017 in the Lower Danube River (river kilometer (rkm) 0 Sulina-rkm 1075 Baziaș). Acoustic telemetry receivers VR2W and V16TP tags (Vemco, Canada) were used to collect data about sturgeon migration behavior in the Lower Danube River between the Black Sea and the Iron Gate II dam. The tags, equipped with depth and temperature sensors, provided data about beluga and stellate sturgeon migration periods, swimming speeds, and depths. Twenty-three beluga sturgeon (184-245 cm TL) and twenty-one stellate sturgeon (92-135 cm TL) were ultrasonically tagged and passively tracked using hydrophone receivers installed in the river between rkm 71 and rkm 860. Three tagged beluga sturgeon returned after 2 and 5 years and two stellate sturgeon returned after 2 years since the time of their initial release in the river. This study provides, for the first time, further details concerning beluga sturgeon and stellate sturgeon migratory behavior patterns, traveled distances, swimming depths, and their swimming ground speeds during spawning migration.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.