ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 57 (2000), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Lavnun Mirogrex terraesanctae have a dual-chambered swimbladder and are the dominant fish species in Lake Kinneret, Israel. Bi-monthly acoustic assessments are used to monitor lavnun abundance but the relation between the amount of reflected sound and organism morphology is not well described. Predictions from Kirchho.-ray mode (KRM) backscatter models show a sensitivity of echo amplitude to fish length and fish aspect. Predicted mean KRM target strengths matched maximum in situ target strength measurements of eight tethered fish within 2·5 dB at 120 kHz and within 7 dB at 420 kHz. Tilt and roll of lavnun during tethered measurements increased variance of backscatter measurements. Accurate abundance and length frequency distribution estimates cannot be obtained from in situ acoustic measurements without supplementary net samples.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 416 (1999), S. 33-40 
    ISSN: 1573-5117
    Keywords: community structure; size spectra ; invariant ; ecosystem area ; Lake Kinneret
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aim of the study was to analyze the influence of aquatic ecosystem size on community structure. Analysis is based on quantitative indices, describing integral communities and comparison of their biomass size spectra with standard patterns. Comparative analysis of widely differing aquatic communities shows that certain characteristics of the community structure withstand considerable changes of many important parameters of the abiotic environment and taxonomic composition of the community. At the same time, there are some changes in fine structure of the community size spectra, which can now be documented and measured with relatively high precision due to development of modern automated means of data acquisition. In this study, application of spectral descriptions is discussed as applied to communities of River Jordan-Lake Kinneret aquatic system. It follows from the theoretical scheme developed that, for analysis, the most important part of the community size spectrum is its right extreme, i.e. body size of the largest species of the ecosystem. In the case of Lake Kinneret, that is fish. The fish biomass size spectra were obtained using dual-beam hydro-acoustics techniques. The parameter comparison shows that for riverine systems (i.e. ecological systems with a high role of allochtonous organic matter in the total energy influx of the community), both the water area and the watershed basin (including its terrestrial part) deserve attention as the appropriate scaling parameter.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Publication Date: 2016-10-08
    Description: A comprehensive evaluation of the uncertainty of acoustic-trawl survey estimates is needed to appropriately include them in stock assessments. However, this evaluation is not straightforward because various data types (acoustic backscatter, length, weight, and age composition) are combined to produce estimates of abundance- and biomass-at-age. Uncertainties associated with each data type and those from functional relationships among variables need to be evaluated and combined. Uncertainty due to spatial sampling is evaluated using geostatistical conditional (co-) simulations. Multiple realizations of acoustic backscatter were produced using transformed Gaussian simulations with a Gibbs sampler to handle zeros. Multiple realizations of length frequency distributions were produced using transformed multivariate Gaussian co-simulations derived from quantiles of the empirical length distributions. Uncertainty due to errors in functional relationships was evaluated using bootstrap for the target strength-at-length and the weight-at-length relationships and for age–length keys. The contribution of each of these major sources of uncertainty was assessed for acoustic-trawl surveys of walleye pollock in the eastern Bering Sea in 2006–2010. This simulation framework allows a general computation for estimating abundance- and biomass-at-age variance–covariance matrices. Such estimates suggest that the covariance structure assumed in fitting stock assessment models differs substantially from what careful analysis of survey data actually indicate.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Publication Date: 1985-03-01
    Print ISSN: 0024-3590
    Electronic ISSN: 1939-5590
    Topics: Biology , Geosciences , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...