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
Filter
Collection
Keywords
Years
  • 1
    Publication Date: 2007-06-12
    Description: Burwen, D. L., Nealson, P. A., Fleischman, S. J., Mulligan, T. J., and Horne, J. K. 2007. The complexity of narrowband echo envelopes as a function of fish side-aspect angle. – ICES Journal of Marine Science, 64: 1066–1074. High-frequency, narrowband acoustic signals may contain more information on fish size and orientation than previously thought. Our observations of dual frequency identification sonar (DIDSON) images of fish orientation paired with split-beam echo envelopes helped clarify why metrics such as echo duration have performed better than target strength measurements when predicting salmon lengths at side aspect. Fish orientation has a pronounced effect on the duration and shape of split-beam echo envelopes from large (80–130 cm) salmon insonified at side aspect. At near-normal aspect angles, echo envelopes are unimodal, symmetrical, and resemble echo envelopes from calibration spheres. With increasing oblique-aspect angle, echo shapes become less symmetrical as the number of peaks increases, and echo duration and amplitude become more variable. Using angle and range coordinates, peaks in an echo envelope can be traced to their origin on a DIDSON image. At oblique-aspect angles, discrete peaks develop that are reflected from regions close to the head and tail. In addition, the distance between peaks increases with increasing aspect angle and is larger than can be explained by swimbladder length.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    facet.materialart.
    Unknown
    NOAA | Seattle, WA
    In:  http://aquaticcommons.org/id/eprint/2481 | 403 | 2011-09-29 18:56:17 | 2481 | United States National Marine Fisheries Service
    Publication Date: 2021-07-13
    Description: Red hind (Epinephelus guttatus) have been overfished in the Caribbean and were included with seven other regional grouper species deemed vulnerable to risk of extinction. The Puerto Rico Department of Natural and EnvironmentalResources desired to map spawning red hind aggregations within commonwealth waters as part of their resource management program for the species. Mobile hydroacoustic surveys were conducted over 3-day periods in 2002 and 2003,indexed to the full moon phase in February or March when red hind were known to aggregate. Four vessels concurrentlysampled the southwest, south, and southeast coasts of Puerto Rico in 2002. In 2003, three vessels conducted complementary surveys of the northwest, north, and northeast coasts of the island, completing a circuit of the coastal shelf-spawning habitat. These surveys indicated that red hind spawning aggregations were prevalent along the south and west coasts, and sparse along the north coast during the survey periods. Highest spawning red hindconcentrations were observed in three areas offshore of the west coast of Puerto Rico, around Mona and Desecheo islands(20,443 and 10,559 fish/km2, respectively) and in the Bajo de Cico seasonal closed area (4,544 fish/km2). Following both 2002 and 2003 surveys, a series of controlledacoustic measurements of known local fish species in net pens were conducted to assess the mean target strength(acoustic backscatter) of each group. Ten species of fish were measured, including red hind (E. guttatus), coney (E. fulvus), white grunt (Haemulon plumieri), pluma (Calamus pennatula), blue tang (Acanthurus coeruleus), squirrel fish (Holocentrus spp.), black durgeon (Melichtyhs niger), ocean file fish (Canthidermis sufflamen), ocean surgeon fish (Acanthurus bahianus), and butter grouper (Mycteroperca spp.). In general, the mean target strength results from the caged fish experiments were in agreement with published target strength length relationships, with the exception ofwhite grunt and pluma.
    Keywords: Management ; Ecology ; Fisheries
    Repository Name: AquaDocs
    Type: book_section , TRUE
    Format: application/pdf
    Format: application/pdf
    Format: 10-17
    Format: 124
    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...