14 
Fishery Bulletin 1 14(1) 
that were absent in the study conducted during 1983- 
1984 (Campos, 1986). Conversely, the whitenose shark 
( Nasolamia velox) and scalloped bonnethead ( Sphyrna 
corona ) were caught during 1983-1984 but were absent 
in our surveys. The overall lower abundance of elas- 
mobranchs reported by Campos (1986) may be related 
to differences in the sample size or to actual changes 
in demersal elasmobranch diversity, changes that prob- 
ably were due to the loss of top predatory fishes (Dulvy 
et al., 2014; Stevens et al., 2000). 
The elasmobranch assemblage at depths of 100-350 
m comprised only 6 species, among which the most 
abundant were the rasptail skate, brown smoothhound, 
and Peruvian torpedo. The prickly shark, which inhab- 
its depths up to 1100 m, was the only true deepwater 
elasmobranch in this assemblage (Compagno et al., 
2005). Only one previous study has examined deep- 
water elasmobranches within the ETP (Puentes et al., 
2007), and that study reported 8 elasmobranch species 
at depths between 72 and 360 m in Colombia. Addi- 
tional studies are necessary to broaden our knowledge 
about deepwater communities of elasmobranchs in this 
region and about their relation to physical and biologi- 
cal features. 
Because of the inherently slow growth of deepwater 
elasmobranchs, future studies should also focus on the 
interaction between deepwater species and fisheries 
(Simpfendorfer and Kyne, 2009). These emergent deep- 
water fisheries are rarely subjected to management 
or scientific monitoring. In Costa Rica, shrimp trawl 
fisheries expanded into deeper waters in the 1980s. As 
the deepwater shrimp stocks became rapidly depleted, 
the fishing fleet shifted operations to shallow waters, 
where they now target several economically important 
teleosts, such as the Pacific bearded brotula ( Brotula 
clarkae) (senior author, unpubl. data). This change is 
problematic; for example, one of the main findings in 
our study was the high species richness of elasmo- 
branchs associated with shallow waters. This shift in 
the target species of shrimp fisheries may increase the 
effects of this fishery on coastal demersal ecosystems. 
A few elasmobranch bycatch species, including 
smoothhounds ( Mustelus spp. ) and the longtail sting- 
ray, are commonly retained in Costa Rica because of 
their commercial value. The sicklefin smoothhound is 
an important source of affordable protein in local mar- 
kets in Costa Rica, and there is a growing demand 
for longtail stingray in both Mexico and Costa Rica 
(Rojas et al., 2000). In addition to noting that these 
species are caught by shrimp trawlers, Lopez Garro 
et al. (2009) reported that the sicklefin smoothhound 
and longtail stingray composed 16.7% and 3.5%, re- 
spectively, of the landings of elasmobranchs in the ar- 
tisanal fishery of Tarcoles, in the central Pacific region 
of Costa Rica during 2006-2007. Although current re- 
cords are insufficient for an evaluation of long-term 
trends in abundance of elasmobranchs in Costa Rica, 
catch data from Colombian commercial shrimp fisher- 
ies indicate that abundances of the sicklefin smooth- 
hound and longtail stingray have declined consider- 
ably since the 1990s. 1 Therefore, it seems advisable 
to closely monitor trends in the relative abundance of 
these 2 species. 
Our results indicate that a large number of elas- 
mobranchs interact with the demersal trawl fishery of 
Costa Rica and, therefore, may be vulnerable to high 
levels of exploitation. Comparisons with historical data 
(Campos, 1986) revealed that the species composition 
of elasmobranchs might have changed since the 1980s. 
Yet, given the lack of continuous sampling throughout 
the period 1980-2010, it is difficult to identify the driv- 
ers behind these changes. 
The creation of independent observer programs 
would allow monitoring and assessment of long-term 
trends of bycatch, as well as prediction of potential 
changes in fish assemblages. In addition, knowledge 
of the feeding ecology and trophic interactions of 
elasmobranchs is critical to understanding food web 
dynamics and trophic cascades that may occur as a 
result of the loss of top predatory fishes from coast- 
al ecosystems (Ferretti et al., 2008; Heithaus et al., 
2008). This information is also essential for defining 
the role of mesopredators in demersal ecosystems and 
for developing ecosystem-based management strate- 
gies (Espinoza et al., 2015). Future research on the 
life history traits of these species is also necessary 
and will allow us to identify vulnerable species and 
redirect conservation efforts. The interaction between 
the shrimp trawl fishery and the elasmobranch as- 
semblage may be comparable within the different 
countries of Central America (Lopez-Martlnez et al., 
2010; Clarke et al., 2014). Therefore, the results of 
this study may serve as biological information that 
can support the development of management strate- 
gies in Central America. 
Acknowledgments 
This research was supported financially by Conserva- 
cion Internacional, MarViva, the Universidad de Costa 
Rica (VI project no. 808-B0-536; 111-A4-508), and the 
Rainbow Jewels S. A., Puntarenas, Costa Rica. We are 
grateful for the collaboration of Onuva crewmembers D. 
Petete, J. Nivia, J. S. Vargas, N. Sandoval, V. Sanabria, 
J. C. Azofeifa, M. Herrera, F. Vargas, A. Chacon, A. Lan- 
yon, A. Alvarado, and F. Villalobos-Rojas. G. Avalos and 
H. Molina provided constructive ideas at an earlier 
stage of the manuscript. 
Literature cited 
Allen, A. P., J. H. Brown, and J. F. Gillooly. 
2002. Global biodiversity, biochemical kinetics, and the 
energetic-equivalence rule. Science 297:1545—1548. 
Arana, P. M, I. S. Wehrtmann, J. C. Orellana, V. Nielsen-Mu- 
noz, and F. Villalobos-Rojas. 
2013. Bycatch associated with fisheries of Heterocarpus 
vicarius (Costa Rica) and Heterocarpus reedi (Chile) 
