English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Systematic acoustic surveys to estimate the Spanish fraction of the Atlantic Sardine Stock werebegun in 1983. Since 1991, with the use ofthe new Sirnrad EK-500 echosounder-echointegrator,the covered area has been extended to 1000 m isobath to observe the distribution of the mainpelagic species in the area. The last three surveys, from spring 1991 to 1993, had a range of 20to 1000 m isobath. They were first analysed using the traditional methodology proposed in Pastorel al (1986) which do es not give any estimation ofthe variance. Therefore, the data was thenanalysed using geostatistic techniques, and the resulting relative abundance estimates werecompared.Sardine showed high variability between years and zones in both distribution area and density,expressed as number of fish per square nautical mile. The two methods of analysis gave differentbiomass estimates by zone, especially in 1993. Variograms computed over areas of fish presencedid not show, in general, a clear spatial structure and sills were reached at 3 n.m. of range. Theprecision ofthese variograms was low, ranging from 23% to 40 %, expressed as relative standarderror.In order to improve precision it seems necessary to increase the sampling intensity and changethe survey grid. For sardine, a systematic parallel with random start survey design, with 6 n.m.between transects, would be more appropriate

Analysis of Spanish acoustic surveys for sardine, 1991–1993: abundance estimates and inter-annual variability