NOAA 
National Marine 
Fisheries Service 
Abstract— Demersal sharks and rays 
are common yet vulnerable compo- 
nents of the bycatch in tropical bot- 
tom-trawl fisheries. Little is known 
about the elasmobranch assemblages 
associated with most of these fisher- 
ies, particularly within the eastern 
tropical Pacific. This study charac- 
terized the elasmobranch assem- 
blage associated with the shrimp 
trawl fishery along the Pacific coast 
of Costa Rica. Between August 2008 
and August 2012, 346 trawl hauls 
were conducted at depths of 18-350 
m. These hauls resulted in a sample 
of 4564 elasmobranchs from 25 spe- 
cies and 13 families. The Panam- 
ic stingray (Urotrygon aspidura ), 
rasptail skate (Raja velezi), brown 
smoothhound ( Mustelus henlei ), and 
witch guitarfish (Zapteryx xyster ) ac- 
counted for more than 66% of the 
elasmobranch abundance within the 
bycatch. Depth was the main factor 
influencing the elasmobranch assem- 
blage; species richness was signifi- 
cantly higher at depths <100 m than 
at other depths. Two groups of elas- 
mobranchs were identified: the first 
was found in shallow waters ( <50 
m), and the second was observed 
at depths of 50-350 m. Sex and 
size segregation patterns are also 
influenced by depth. Moreover, we 
documented the shift of the bottom- 
trawl fishery toward shallow-water 
resources — a change that could be 
problematic considering that elasmo- 
branch diversity is higher in shallow 
waters. 
Manuscript submitted 26 August 2014. 
Manuscript accepted 10 September 2015. 
Fish. Bull. 114:1-17 (2016). 
Online publication date: 22 October 2015. 
doi: 10.7755/FB. 114.1 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Fishery Bulletin 
established 1881 -cf. 
Spencer F. Baird 
First U S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Elasmobranch bycatch associated with the 
shrimp trawl fishery off the Pacific coast of 
Costa Rica, Central America 
Tayler M. Clarke 1 - 2 
Mario Espinoza 2 - 3 
Robert Ahrens 4 
Ingo S. Wehrtmann 2 - 3 
Email for contact author: taylermc@gmail.com 
1 Programa Gestion Integrada de Areas Costeras Tropicales (GIACD 
Centro de Investigacion en Ciencias del Mar y Limnologia (CIMAR) 
Universidad de Costa Rica 
11501-2060 San Jose, Costa Rica 
2 Unidad de Investigacion Pesquera y Acuicultura (UNIP) 
CIMAR 
Universidad de Costa Rica 
11501-2060 San Jose, Costa Rica 
3 Escuela de Biologia 
Universidad de Costa Rica 
11501-2060 San Jose, Costa Rica 
4 Fisheries and Aquatic Sciences 
School of Forest Resources and Conservation 
University of Florida 
PO. Box 110410 
Gainesville, Florida 32653 
Overfishing and habitat degradation 
have caused significant declines in 
elasmobranch abundance (Dulvy et 
al., 2008; Ferretti et ah, 2008; Dulvy 
et al., 2014). Most of the global elas- 
mobranch catch is incidental and 
originates from fisheries that target 
higher-valued teleosts or crustaceans 
(Stevens et al., 2000; Walker, 2005; 
Wehrtmann et ah, 2012; Worm et 
ah, 2013). In general, elasmobranch 
bycatch is not regulated or even re- 
ported, especially in developing coun- 
tries (Barker and Schluessel, 2005; 
Cheung et ah, 2005; Walker, 2005). 
Furthermore, sharks and rays tend 
to exhibit slow growth rates, late ma- 
turity, and low fecundity, and, there- 
fore, they have a low resilience to in- 
tense fishing pressures (Cortes, 2000; 
Dulvy and Reynolds, 2002; Frisk et 
ah, 2005). The severity of this issue 
increases in the tropics as a result 
of the interaction between a high 
diversity of elasmobranch species 
and data-deficient fisheries (Barker 
and Schluessel, 2005; Cheung et ah, 
2005; White and Sommerville, 2010). 
Several studies conducted in the 
tropics have reported large declines 
in the abundance of demersal elas- 
mobranchs associated with bottom- 
trawl fisheries (e.g., Thailand: Ste- 
vens et ah, 2000; Australia: Graham 
et ah, 2001; Gulf of Mexico: Shepherd 
and Myers, 2005). Nevertheless, elas- 
mobranch bycatch has been poorly 
studied in many tropical regions, in- 
cluding the Eastern Tropical Pacific 
(ETP; from Mexico to Peru), where 
abundance trends remain unclear 
(Mejla-Falla and Navia 1 ; Lopez-Mar- 
1 Mejia-Falla, P. A., and A. F. Navia (eds.). 
2011. Estadlsticas pesqueras de tibu- 
rones y rayas en el Paclfico Colombiano. 
Documento tecnico Fundacion SQUA- 
LUS No. FS0111, 70 p. [Available at 
website.] 
