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Global Change Master Directory (GCMD)
BENEFIT Horse Mackerel age - determination workshops, May 2000 and November 2001
Entry ID: MCM_20020123_91493


Summary
Abstract: MAY 2000 WORKSHOP

All specimens used for age determination in this workshop were sampled
from fish caught between 25 May and 14 June 1998 during the annual
horse mackerel routine survey conducted on board the R/V Dr. Fridtjof
Nansen. The survey area was between 25.00 S and 17.25 S. The area
under investigation was divided into a northern and a southern part
according to catch and size of the fish.

A total of 275 otoliths from Trachurus trachurus capensis ranging
between 6 - 40 cm were examined. However, otoliths from specimens
greater than 31 cm were only discussed and viewed under the Image
Analysing System (IAS).

Otoliths from specimens less than 31 cm were read twice without prior
knowledge of information regarding size, sex and catch locality /
station number. The reason for omitting specimens above 31 cm was
because of difficulties reading the larger otoliths regarding the
current method of otolith preparation. Slides were prepared for
otoliths from specimens larger than 31 cm, but due to difficulties in
slicing the otoliths with the present single bladed saw we decided not
to include these otoliths in the individual reading exercise. Otoliths
from specimens greater than 21 cm were burned in order to enhance the
contrast between the opaque and hyaline zones (annuli) (Christensen,
1964). Each pair of otoliths (the burned one and the unburned one)
were then viewed; immersed in glycerin or water, with a stereo
dissection microscope under reflected light (figure 4.1).

In addition, two readers (reader 1 and reader 4) read 28 otoliths from
Cunene horse mackerel (Trachurus trecae). The specimens were caught by
commercial vessels in Angolan waters in 1991 Whole otoliths were
immersed in glycerine and viewed through a dissection microscope under
reflected light. At first, the otoliths were not treated before the
age reading and they were read unburned. For the second reading one of
the otoliths from each pair was burned over an alcohol flame until
dark brown in appearance.

NOVEMBER 2001 WORKSHOP
*report currently in process

Related URL
Link: View Related Information
Description: Benefit home page

Geographic Coverage
 N: -17.25 S: -25.0  E: 25.0  W: 17.25

 Min Depth: 30M  Max Depth: 600M

Data Set Citation
Version: Not provided


Temporal Coverage
Start Date: 1998-05-25
Stop Date: 1998-06-14


Location Keywords
OCEAN > ATLANTIC OCEAN > SOUTH ATLANTIC OCEAN


Science Keywords
AGRICULTURE >AGRICULTURAL AQUATIC SCIENCES >FISHERIES    [Definition]
OCEANS >AQUATIC SCIENCES >FISHERIES    [Definition]
BIOLOGICAL CLASSIFICATION >ANIMALS/VERTEBRATES >FISH >WEIGHT    [Definition]
BIOLOGICAL CLASSIFICATION >ANIMALS/VERTEBRATES >FISH >LENGTH    [Definition]
BIOSPHERE >ECOSYSTEMS >MARINE ECOSYSTEMS >PELAGIC    [Definition]
BIOSPHERE >ECOLOGICAL DYNAMICS >SPECIES/POPULATION INTERACTIONS >SPECIES LIFE HISTORY >AGE    [Definition]
BIOSPHERE >ECOLOGICAL DYNAMICS >SPECIES/POPULATION INTERACTIONS >SPECIES LIFE HISTORY >OTOLITH RING COUNTS    [Definition]
BIOSPHERE >ECOLOGICAL DYNAMICS >SPECIES/POPULATION INTERACTIONS >SPECIES LIFE HISTORY    [Definition]


Platform
SHIPS    [Information]


Instrument
Cameras    [Information]
MICROSCOPES    [Information]


Project
GLOBEC >Global Ocean Ecosystem Dynamics, IGBP    [Information]
IGBP >International Geosphere-Biosphere Programme    [Information]
BENEFIT >Benguela Environment Fisheries Interaction and Training Programme    [Information]


Quality
Data results obtained from MAY 2000 not recommendated for use
see recommendations (pages 8 and 9).


Access Constraints
Release with permission of the appropriate parties


Use Constraints
Contact Principal Investigator for access to data


Keywords
Midwater Habitat
Image Anylising system
burned, resisn cast, sliced
Dr. Fridtjof Nansen


Data Set Progress
ACTIVE


Data Center
Marine and Coastal Management, Department of Environmental Affairs and Tourism, South Africa    [Information]
Data Center URL: http://www.environment.gov.za/

Data Center Personnel
Name: DEON DURHOLTZ
Phone: Ph: + 27 21 430 7037 (office)
Fax: Fax:+ 27 21 434 2899
Email: durholtz at mcm.wcape.gov.za
Contact Address:
Deon Durholtz
c/o MCM (Research Aquarium)
Private Bag X2
Roggebaai
8012
Cape Town
Ph: + 27 21 430 7037 (office)
+ 27 21 430 7002 (s/board)
Email: durholtz@mcm.wcape.gov.za
durholtz@webmail.co.za
Postal Code: 434
Country: SOUTH AFRICA



Distribution
Distribution_Media: CD-ROM
Distribution_Format: EXCEL > Microsoft Excel

Distribution_Media: Not Known
Distribution_Format: MS Word > Microsoft Word

Distribution_Media: Not Known
Distribution_Format: Not Known

Distribution_Media: CD-ROM
Distribution_Format: Not Known


Personnel
DEON DURHOLTZ
Role: INVESTIGATOR
Role: TECHNICAL CONTACT
Phone: Ph: + 27 21 430 7037 (office)
Fax: Fax:+ 27 21 434 2899
Email: durholtz at mcm.wcape.gov.za
Contact Address:
Deon Durholtz
c/o MCM (Research Aquarium)
Private Bag X2
Roggebaai
8012
Cape Town
Ph: + 27 21 430 7037 (office)
+ 27 21 430 7002 (s/board)
Email: durholtz@mcm.wcape.gov.za
durholtz@webmail.co.za
Postal Code: 434
Country: SOUTH AFRICA


Extended Metadata Properties
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Creation and Review Dates
DIF Creation Date: 2002-01-23
Last DIF Revision Date: 2018-11-08



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