De Backer, A.

Depestele, J.

Hostens, K.

Vincx, M.

Willems, T.

Open Marine Archive

70 
 
14. By-catch in a tropical shrimp fishery: are TEDs effective in excluding rays?    
 
Tomas Willems1,2, Jochen Depestele1,2, Annelies De Backer1, Kris Hostens1 & Magda Vincx2   
 
1. Institute for Agricultural and Fisheries Research – Fisheries and Aquatic Production, 
Ankerstraat 1, 8400 Oostende, Belgium  
2. Ghent University, Department of Biology, Marine Biology Section, Krijgslaan 281/S8, 9000 
Gent, Belgium   
Corresponding author: Tomas Willems   
 
Tropical shrimp trawling generally produces significant amounts of by-catch, including 
endangered marine species. To avoid incidental capture of marine turtles, Turtle Excluder 
Devices (TEDs) are now widespread. TEDs are effective in avoiding turtle by-catch and 
theoretically exclude all organisms large enough not to pass in between the TED’s vertical 
bars. Rays (Batoidea; Chondrichthyes: Elasmobranchii) are particular in this respect, because 
even large sized individuals might pass through a TED as a result of their flattened body 
shape. Several ray species are listed as threatened and they are very vulnerable to fishing 
mortality due to their life-history characteristics. By-catch of rays in tropical shrimp trawling 
is thus highly undesirable. The current study assessed the potential of TEDs in reducing ray 
by-catch in the seabob shrimp (Xiphopenaeus kroyeri) fishery in Suriname. Sixty-five catch-
comparison hauls were conducted, comparing ray by-catch in trawls fitted with TEDs (test-
net) and without TEDs (control-net). Overall, catch rate of rays was reduced by 36% in the 
test-net. Rays caught in the test-net were on average 21% smaller than those in the control-
net meaning larger ones were indeed able to escape, while smaller individuals passed 
through the TED, ending up in the codend. As such, TEDs were most efficient in excluding 
Dasyatis geijskesi, the largest ray species, while no significant reduction was observed for 
the small-sized Urotrygon microphalmum. A GLMM was fitted to calculate exclusion-at-size 
for the two most abundant species. Exclusion of Dasyatis guttata reached 100% for 
individuals over 50cm (body width), while Gymnura micrura only approached 80% exclusion 
even for the largest individuals (70cm).  
 
Keywords: seabob shrimp, trawling, Turtle Excluder Device, by-catch, rays   


By-catch in a tropical shrimp fishery: are TEDs effective in excluding rays?

http://www.vliz.be/imisdocs/publications/311322.pdf

By-catch in a tropical shrimp fishery: are TEDs effective in excluding rays?

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