Maertens, I.

Moerman, M.

Torreele, E.

Zenner, A.

Open Marine Archive

Experimental comparison of 4 preparation techniques on 2 structures for
age‐estimation of Rajidae: a case study on Raja clavata
Rajidae in the Belgian fisheries
Belgium’s 2012 quota for skates and rays were the 2nd largest in the North Sea & Eastern Arctic (IIa, IV & VIId) and the 5th largest in the 
North East Atlantic (VIab, VIIa-c & VIIe-k). Rajidae were 3rd in the list of fish landed by the Belgian fleet in 2011 in order of their landed 
weight. This indicates the importance of skates and rays for the Belgian commercial fisheries.
Maertens Ilse, Zenner Annemie, Moerman Martine and Torreele Els
Institute for Agricultural and Fisheries Research,
Unit Animal Sciences - Fisheries
Ankerstraat 1, B-8400 Oostende, Belgium
Management of the stock
In 2011, the Commission and the Council urged 
Member States to improve data availability for 
data limited stocks including all skates and rays.
Insufficient information on the catch-compositions 
of the elasmobranches impede the analyses 
necessary for sustainable management.
Growth rate & Age structure
Growth rate and age structure are important life 
history parameters.
Rajidae are cartilaginous fish and have no otoliths 
for ageing. Both vertebral centra and dermal 
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Natural Stained Burnt
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Institute for Agricultural and Fisheries Research, Animal Sciences – Fisheries
ILVO, Biological Environmental Research, Ankerstraat 1, 8400 Oostende, Belgium 
 +32(0)59/569848 annemie.zenner@ilvo.vlaanderen.be
denticles of elasmobranches show concentric 
band patterning, which probably reflect the 
individual’s growth.
Natural Stained Burnt
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Conclusion:
 Staining → only superficial;
 Vertebrae → are best natural or burnt, both whole and sectioned because angle change (birth mark) more obvious in sections;
 Dermal denticles are best oven burnt and not sectioned.
Further work:
staining after sectioning and saggital sectioning of dermal denticles
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Preparation Methods
Techniques for 
enhancing
contrast between      
opaque & 
translucent bands
Sectioning
Clarification
Staining or burning
Large median dermal denticles and vertebrae from 
R. Clavata were removed and cleaned in 0.5 or 1% 
trypsin.  The whole structures or 0.5 mm thick 
longitudinal sections were either left as such 
(natural), stained with Alizarin red-S or oven-
burned at 200°C for 10 min.  The best results of 2 
individuals are shown here.
All pictures Copyright ILVO, Ilse Maertens.


Experimental comparison of 4 preparation techniques on 2 structures for age‐estimation of Rajidae: a case study on <i>Raja clavata</i>

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