Wyniki wyszukiwania - Biblioteka Nauki

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Past and recent lake eutrophication evidenced by microfossil (over 160 years) diatom succession in sediments, Lake Xingyun (Southwest China)

100%

Ji M. , Li Y. , Shen J.

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tom 61

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nr 4

EN

Eutrophication, disappearance of aquatic vegetation and fish introduction are important disturbances of aquatic ecosystems, especially in plateau lakes, which are generally considered to be very vulnerable. This study investigated the effects of eutrophication, aquatic vegetation and fish introduction on the diatom community of Lake Xingyun by examining the changes of microfossil diatom assemblage. Results showed that diatom assemblages changed with increasing trophic level, decreasing aquatic vegetation and fish introduction. A mesotrophic, alkaliphilous species, Aulacoseira ambigua, was dominant in Lake Xingyun before 1950, which indicated the lake was mesotrophic in the period. Epiphytic diatom species (Achnanthes minutissima, Denticula sp., Gomphonema pumilum) presented high relative concentration between 1950–1980, which indicated aquatic vegetation had a higher cover in this period. The number of diatom species varied from 20 to 66, and to 52 with the change of aquatic vegetation from the past to present. Epiphytic diatoms except Achnanthes minutissima disappeared with the decrease of aquatic vegetation after 1980. Since 1980, with the sharply rising of TP and TN concentration, mesotrophic species (Aulacoseira ambigua) disappeared and eutrophic species (Cyclostephanos dubius, Fragilaria crotonensis, Aulacoseira granulata, Nitzschia palea) were dominant. It indicates the lake has evolved towards eutrophication after 1980. Our study indicated that change of trophic status and aquatic vegetation are important driving factors affecting diatom community composition in Lake Xingyun, but that fish introductions have also been an additional factor.

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Fish biological control of the Israeli National Water Carrier and dual-purpose reservoirs (fish culture/crop irrigation): the Israeli concept

84%

Rothbard S.

Archives of Polish Fisheries

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2008

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tom 16

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nr 1

3

Histoarchitecture and scanning electron microscopic studies of the olfactory epithelium in the exotic fish Puntius javanicus (Bleeker)

84%

Chakrabarti P. , Ghosh S. K.

Archives of Polish Fisheries

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2010

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tom 18

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nr 3

4

Patterns of fish communities along a mountain river: the Upper Coruh River [Turkey]

67%

Yildirim A. , Arslan M. , Pegg M. A.

Polish Journal of Ecology

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2008

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tom 56

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nr 4

731-736

EN

Distribution of fish communities along the submountain river (upper Coruh River, Northeastern of Turkey) was assessed to evaluate course of the longitudinal pattern in fish species diversity. The watershed area of Coruh Basin is 21.000 km², river length 376 km and it flows into Black Sea in northeastern Turkey at average discharge of 149 m³ s⁻¹ (range: 45.2–1215 m³ s⁻¹). Fixed-site electrofishing sampling at five sites located 15–210 km from river source at 2100–950 m a.s.l (Q values ranged 5–200 m³ s⁻¹) was conducted from March 2001 to March 2002. A total of 12 species were collected. Number of species (8–10) did not differ among sites suggesting no longitudinal changes, but Shannon-Wiener biodiversity index (H`) increased downstream from 1.23 to 1.82. Two distinct fish assemblages were identified. Most abundant species were Leuciscus cephalus and Alburnoides bipunctatus. Both Oncorhynchus mykiss and Cyprinus carpio collected rarely are exotic fishes for Coruh River.

5

Invasion of an exotic fish - common carp, Cyprinus carpio L. (Actinopterygii: Cypriniformes: Cyprinidae) in the Ganga River, India and its impacts

67%

Singh A. K. , Pathak A. K. , Lakra W. S.

Acta Ichthyologica et Piscatoria

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2010

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tom 40

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nr 1

EN

Background. The Ganga River (Ganges) is known of its rich fish diversity which is adversely affected by degrading environmental and ecological conditions. There are more than 300 exotic fish species in India. Many of them (particularly Cyprinus carpio) escaped from confinement and are now present in the Ganga River, challenging its ecological equilibrium. The aim of this project was to study the population characteristics of Cyprinus carpio (i.e., the abundance, size range, food and feeding, gonado-somatic index (GSI), gonad maturity stage, maturity and breeding) and the altered fishery dynamics. Materials and Methods. The commercially caught fishes, including the exotic ones, were identified, examined and measured. Important indices such as: the abundance index of exotic fishes, the gonado-somatic index (IG), as well as the gonad maturity stage of the escapee C. carpio were determined. The gut content was also analyzed to identify food items and thereafter the food richness, diet breadth, and gut repletion index (GRI%) were calculated using the Simpson’s diversity index. Results. C. carpio introduced about sixty years ago for aquaculture has now been found to invade into the Ganga, the largest river of the country contributing significantly to the fishery. The abundance index of C. carpio ranged from 12.2% to 45.5 % in 250 km long river stretch of the Ganga River flowing along Kanpur to Varanasi in the state of Uttar Pradesh. The gut content analysis revealed the presence of Eichhornia (9.8%), Pistia (11.6%), Nymphaea (8.5%), annelids worms (7.8%), algae (20.2%), mud and detritus (14.8%). The calculated diet breadth ranged from 0.82% to 0.91%; food richness ranged from 12 to 16, and the gut repletion index (GRI%) was 100% at different sampling sites. Mature females represented all the six reproductive stages with varying gonadosomatic index (IG) (0.5 to 30) in different catches. Presence of spent, ripe, and mature females was recorded. Conclusion. Abundance of exotic fish primarily C. carpio and Oreochromis niloticus in the fishery of the Ganga River was observed. The gonado-somatic index (IG) and the presence of all the six gonadal stages confirmed that C. carpio established its breeding population. The dominant catch of exotic fishes negatively impacted on the important indigenous fishes particularly Indian major carps (Catla catla, Labeo rohita, and Cirrhinus mrigala). The change in dynamics of the fishery due to the presence of common carp attracted attention to conserve rich indigenous germplasm facing threats of shifting from their natural habitats.