Institute of Fisheries and Aquaculture

Varna, Bulgaria

Institute of Fisheries and Aquaculture

Varna, Bulgaria

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Llope M.,University of Oslo | Llope M.,Spanish Institute of Oceanography | Daskalov G.M.,CEFAS Lowestoft Laboratory | Daskalov G.M.,Bulgarian Academy of Science | And 7 more authors.
Global Change Biology | Year: 2011

It is well known that human activities, such as harvesting, have had major direct effects on marine ecosystems. However, it is far less acknowledged that human activities in the surroundings might have important effects on marine systems. There is growing evidence suggesting that major reorganization (i.e., a regime shift) is a common feature in the temporal evolution of a marine system. Here we show, and quantify, the interaction of human activities (nutrient upload) with a favourable climate (run-off) and its contribution to the eutrophication of the Black Sea in the 1980s. Based on virtual analysis of the bottom-up (eutrophication) vs. top-down (trophic cascades) effects, we found that an earlier onset of eutrophication could have counteracted the restructuring of the trophic regulation at the base of the food web that resulted from the depletion of top predators in the 1970s. These enhanced bottom-up effects would, however, not propagate upwards in the food web beyond the zooplankton level. Our simulations identified the removal of apex predators as a key element in terms of loss of resilience that inevitably leads to a reorganization. Once the food web has been truncated, the type and magnitude of interventions on the group replacing the apex predator as the new upper trophic level have no effect in preventing the trophic cascade. By characterizing the tipping point at which increased bottom-up forcing exactly counteracts the top-down cascading effects, our results emphasize the importance of a comprehensive analysis that take into account all structuring forces at play (including those beyond the marine system) at a given time. © 2010 Blackwell Publishing Ltd.


Belabed B.-E.,Annaba University | Laffray X.,University of Franche Comte | Dhib A.,Institute National Des Science Et Technologies Of La Mer Instm | Fertouna-Belakhal M.,Institute of Fisheries and Aquaculture | And 2 more authors.
Marine Pollution Bulletin | Year: 2013

This paper presents the results of a seasonal survey of heavy metals accumulated in sediments and in the soft parts of the body of the mussel Perna perna at four stations in the Gulf of Annaba (Algeria). Pooled soft tissues from 10 mussels representing the entire range of sizes were digested in nitric acid. Statistical analysis reveals a significant seasonal effect on all the measured metals, the highest values being recorded in winter. With the exception of Cr, the levels for all metals were significantly higher in the east, at the outlet of the Seybouse River, than at all other monitoring stations. The study also shows that north-western waters are subject to a significantly lower degree of heavy metal pollution than elsewhere in the gulf. Levels were nevertheless within the limits of public health standards. The results confirm the usefulness of P. perna as a bioindicator for heavy metal pollution. © 2013 Elsevier Ltd.


Hadjinikolova L.,Institute of Fisheries and Aquaculture | Hubenova T.,Institute of Fisheries and Aquaculture | Zaikov A.,Institute of Fisheries and Aquaculture
Bulgarian Journal of Agricultural Science | Year: 2010

The present article surveys the status and the tendencies in the development of the freshwater aquaculture in Bulgaria under the conditions of market economy, and specific attention is paid to the structure and the type compound of the cultivated water organisms, the present state of the production, their actual price for realization, as well as the consumption of fish. Bulgaria possesses a comparatively rich water fund of about 70 000 ha, which accompanied by the climatic conditions in the country creates good conditions for aquaculture development.The main objects for cultivation are the carp (Cyprinus carpio) and the trout (Oncorhynchus mykiss), having in mind that the herbivorous fish species, like silver carp (Hipophthalmichthys molitrix), bighead carp (Aristhichthys nobilis) and grass carp (Ctenopharingodon idella). With good perspectives for increasing the production capacities are the Acipensaridae, the European wels (Silurus glanis) and the channel catfish (Ictalurus punctastus). Fish consumption per capita is 4.6 kg, which ranks Bulgaria among countries with low fish consumption.


Hubenova T.,Institute of Fisheries and Aquaculture | Vasileva P.,Institute of Fisheries and Aquaculture | Zaikov A.,Institute of Fisheries and Aquaculture
Bulgarian Journal of Agricultural Science | Year: 2010

The aim of the study was to establish the sexual maturity, pleopodal egg number and egg size in the stone crayfish from two different biotopes - a dam-lake and a river, at the end of the reproductive period - shortly before larvae hatching. The obtained results are the first data on this species in this country. In both investigated biotopes stone crayfish females seemed to reach sexual maturity at a very closed total length of 62-64 mm and at carapace length of 29 mm. The average egg number of 78 for the females in the Mrachenik River were estimated, while the egg number of the females from Dospat dam-lake are lower - only 29. In Mrachenik River the minimum registered egg number was 21 and the maximum 125. In Dospat dam-lake the minimum registered egg number was 11 and the maximum 66. An average size of 3.2 mm egg diameter and 0.019 mg egg weight for the females from Dospat dam-lake, and an average size of 2.8 mm egg diameter and 0.013 mg egg weight for the females from the Mrachenik River were established. Egg size diameter and weight did not show any significant correlation, neither positive to maternal female size, nor negative to total amount of eggs. The differences in pleopodal egg number and egg size in the both investigated populations are probably in connection with the influence of some environmental factors as temperature, duration of the reproductive period, food and shelters availability and etc.


Dochin K.,Institute of Fisheries and Aquaculture | Ivanova A.,Institute of Fisheries and Aquaculture
Bulgarian Journal of Agricultural Science | Year: 2015

Taxonomic structure of phytoplankton community and dynamics of hydrochemical regime as determining factors of trophic conditions were studied in Bistrica Dam Lake. Seventy seven taxa in six divisions of planktonic algae were found: Cyanoprokaryota (8 species, 10.38%), Chlorophyta (34 species, 44.15%), Euglenophyta (6 species, 7.79%), Streptophyta (3 species, 2.59%), Pyrrhophyta (3 species, 3.88%), Ochrophyta (24 species) including class Synurophyceae (3 species, 3.89%) and class Bacillariophyceae (21 species, 27.27%). Dominant and sub-dominant species were identified and seasonal dynamic of phytoplankton community was established of Bistrica Dam Lake. Diatoms Synedra acus Kützing, Aulacoseira granulata (Ehrenberg) Simonsen and Stephanodiscus hantzschii Grunow predominated in May Scenedesmus communis (Breb.) Hegewald, Scenedesmus acuminatus (Lagerheim) Chodat and Hyaloraphidium contortum Pascher and Korshikov were the majority in the summer-time populations, while diatoms Asterionella formosa Hassall Stephanodiscus hantzschii Grunow and Synedra ulna (Nitzsch) Ehrenberg were the sub-dominant species. Stephanodiscus hantzschii Grunow and Aulacoseira granulata (Ehrenberg) species increased their numbers again in the autumn. The average phytoplankton biomass for the studied period (0.333 mg.l-1) determined the oligothrophic status of the Bistrica Dam Lake. © 2015, National Centre for Agrarian Sciences. All rights reserved.


A comparative slaughtering analysis has been carried out at the Institute of Fisheries and Aquaculture, Bulgaria upon two-summer old silver carp, reared in polyculture (H. molitrix 300 p-ces.ha-1 and C. carpio - 2000 p-ces.ha-1) under the conditions of integrated with ducks (Peking ducks and mule ducks) and non-integrated technologies. The fish in all experimental ponds have grown well and no considerable difference has been observed between the separate variants as regards the final live weight. The integration has exercised a positive (F=4.182; P<0.005) effect upon the slaughtering output, however, this effect has not been preserved as regards the relative fillet share within the fish carcass (F=0.096; P<0.05).


An investigation upon the daily dynamics of the separate elements of mule ducks behavior has been carried out at the Institute of Fisheries and Acuaculture Plovdiv, Bulgaria, applying the schedule of feeding with full-ration factory-made mixtures, at conditions of integrated fish-ducks technology. Ducks used to enter the water for a short time, and the time for swimming reported has been 9.63 min.h1 while the time spent at rest in the water has not surpassed 2.5 min.h-1. Age differences concerning behavior have been observed. With the advance of the fattening period, in general, the motion activity has decreased, ducks have reacted weaker to forage supply, and the forages have been consumed more actively during the morning hours. The tested technology has ensured good rearing conditions of mule ducks, however, the influence of ducks upon fishpond ecosystem was minimal.


Nikolova L.,Institute of Fisheries and Aquaculture
Bulgarian Journal of Agricultural Science | Year: 2013

The study was conducted in two consecutive years in the Fisheries and Aquaculture Institute - Plovdiv. For the needs of ecologo- and bio-friendly fish farming, the impact of some factors on the growth of carp fish reared in polyculture, based on a natural nutritive basis, have been investigated. Rearing in autochthonous polyculture led to satisfactorily fish growth. The polyculture structure is a significant source of common carp growth variation, as the impact decreases when taking into account intense vegetation in the pond, and increases when taking into account the size of the pond. Common carp had better growth in one-year polyculture. The polyculture structure had no impact on bighead carp growth. One-year old grass carp grew more intensively compared to two-year old grass carp. Fertilization is a significant source for growth variation, but the impact is specific for the different species. Positive effect of the factor is established only for bighead carp. Significant sources for growth variation in all studied species are pond size and macrophytes density level.


An investigation upon the daily dynamics of the separate elements of mule ducks behavior has been carried out at the Institute of Fisheries and Acuaculture Plovdiv, Bulgaria, applying the schedule of feeding with partial restriction, at conditions of integrated fish-ducks technology. Our investigation has shown that the fishponds have been suitable for mule ducks rearing - the birds have had a good plumage status without demonstrations of cannibalism and aggressiveness. Together with the fattening period advance, ducks have spent less time for feeding and have reacted rather weakly to forage supply; the dry land stay time has been on the account of the fish-pond stay, having in mind that the swimming time has increased, as well as the rest time in the fish-pond together with the advance in age.


Nikolova L.,Institute of Fisheries and Aquaculture
Journal of Environmental Protection and Ecology | Year: 2012

Loading of fishponds with organic matter in integrated rearing offish and ducks of the Peking breed and mule ducks was studied at the Institute of Fisheries and Aquaculture - Plovdiv. The stocking density of ducklings was 340 pes ha-1 The coefficient of loading (M) was used for establishing the pond loading: Mathmatical Equation Repersented where N is the mean number of ducks in the rotation; t - rotation length in days; W-average live weight of the ducks for the growing period, kg; 96 g - the amount of the manure released for a day by 1 duck per kg of live weight; P - pond surface area, ha; r- relative stay of the ducks in water out of the active time of days. It was established that using ducks of different genotypes had a significant effect (P<0.05) on the levels of the organic matter accumulated in the pond. The ducks of the Peking breed gained in weight more intensively and in 3 out of the 4 periods of study they had a higher live weight than the mule ducks. However, the time the ducks spent in water played a significant role for pond loading. In the period of study the Peking ducks spent in water 2 times more time compared to the mule ducks. That caused the release of twice bigger amount of manure in the fishpond.

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