Current Status of Fish Communities in the Danube

Author(s):  
Vladimír Kováč

1976 ◽  
Vol 33 (8) ◽  
pp. 1822-1857 ◽  
Author(s):  
K. H. Loftus

A brief, generalized review of the current status of salmonid fisheries on the west and east coasts, and of selected representative waters in the freshwater area is presented. It is concluded that many fish communities and/or fish stocks are depressed, collapsed, or extinct as a result of severe stresses imposed directly, or indirectly, by man’s activities. Rehabilitation of fish stocks and fish communities to levels approximating those of early years, and to levels capable of supporting more stable yields to meet growing client requirements appears practical. The need for explicit policy decisions with regard to sea ranching and rehabilitation as options for approaches to increasing fish abundance is stressed. Rehabilitation of stocks and communities will require additional science in areas such as hatching, rearing and selective breeding, fisheries engineering, and in the more precise definition of natural productive capacity of waters. Effective fisheries rehabilitation programs, and fisheries management generally, require: development of fisheries information systems; an adaptive or experimental approach; more social and economic data; synthesis and communication of science available; and fundamental reconsideration of the traditional institutional arrangements for fisheries work. Some important fisheries rehabilitation programs, carefully planned and assessed, can proceed immediately with confidence in their success; others must await improvement in water quality.



Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1534
Author(s):  
Daniela Giannetto ◽  
Deniz Innal

Due to its peculiar geographical position and its environmental heterogeneity, Turkey represents an important biodiversity hotspot for freshwater fish fauna. Unfortunately, native fish communities of Turkey, mainly from lentic ecosystems, have been massively altered in the past decades. Furthermore, these species, especially the endemic species, are now threatened by several human activities in addition to the global issue of climatic changes. The aim of this paper is to provide an updated review on the current status of endemic fish species from main lakes of Turkey including major threats affecting fish assemblages. By gathering data from the literature and authors’ personal observations, 62 endemic fish species were reported to occur in the considered 37 Turkish Lakes. The presence of non-native species, agriculture activities, climatic drought, and decreasing water level were found to be the threats that most affect the fish communities of the considered Turkish Lakes.



2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Masaki Miya

Environmental DNA (eDNA) is genetic material that has been shed from macroorganisms. It has received increased attention as an indirect marker for biodiversity monitoring. This article reviews the current status of eDNA metabarcoding (simultaneous detection of multiple species) as a noninvasive and cost-effective approach for monitoring marine fish communities and discusses the prospects for this growing field. eDNA metabarcoding coamplifies short fragments of fish eDNA across a wide variety of taxa and, coupled with high-throughput sequencing technologies, allows massively parallel sequencing to be performed simultaneously for dozens to hundreds of samples. It can predict species richness in a given area, detect habitat segregation and biogeographic patterns from small to large spatial scales, and monitor the spatiotemporal dynamics of fish communities. In addition, it can detect an anthropogenic impact on fish communities through evaluation of their functional diversity. Recognizing the strengths and limitations of eDNA metabarcoding will help ensure that continuous biodiversity monitoring at multiple sites will be useful for ecosystem conservation and sustainable use of fishery resources, possibly contributing to achieving the targets of the United Nations’ Sustainable Development Goal 14 for 2030. Expected final online publication date for the Annual Review of Marine Science, Volume 14 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.



1966 ◽  
Vol 25 ◽  
pp. 266-267
Author(s):  
R. L. Duncombe

An examination of some specialized lunar and planetary ephemerides has revealed inconsistencies in the adopted planetary masses, the presence of non-gravitational terms, and some outright numerical errors. They should be considered of temporary usefulness only, subject to subsequent amendment as required for the interpretation of observational data.



Author(s):  
Martin Peckerar ◽  
Anastasios Tousimis

Solid state x-ray sensing systems have been used for many years in conjunction with scanning and transmission electron microscopes. Such systems conveniently provide users with elemental area maps and quantitative chemical analyses of samples. Improvements on these tools are currently sought in the following areas: sensitivity at longer and shorter x-ray wavelengths and minimization of noise-broadening of spectral lines. In this paper, we review basic limitations and recent advances in each of these areas. Throughout the review, we emphasize the systems nature of the problem. That is. limitations exist not only in the sensor elements but also in the preamplifier/amplifier chain and in the interfaces between these components.Solid state x-ray sensors usually function by way of incident photons creating electron-hole pairs in semiconductor material. This radiation-produced mobile charge is swept into external circuitry by electric fields in the semiconductor bulk.



2021 ◽  
Author(s):  
Yuanhong Ma ◽  
Shao-Jie Lou ◽  
Zhaomin Hou

This review article provides a comprehensive overview to recognise the current status of electron-deficient boron-based catalysis in C–H functionalisations.







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