2 
Fishery Bulletin 1 14(1) 
tinez et al., 2010; Clarke et al., 2014). The best infor- 
mation available is obtained from the Pacific coast of 
Colombia, where significant changes in elasmobranch 
species composition and abundance have been detected 
since the 1990s (Mejia-Falla and Navia 1 ). Other coun- 
tries, such as Mexico (Lopez-Martlnez et al., 2010), 
have basic information that is limited to species lists 
and short-term relative abundance. In the remaining 
countries of the ETP, even this basic information is not 
available. Scarcity of published data has hindered at- 
tempts to estimate the effect of shrimp trawl fisheries 
on the elasmobranch assemblage in the ETP (Espinoza 
et al., 2012; Espinoza et al., 2013; Clarke et al., 2014). 
The commercial shrimp trawl fishery of Costa Rica 
operates exclusively along the Pacific coast, in shallow- 
water and deepwater areas (Wehrtmann and Nielsen- 
Munoz, 2009). The shallow-water (<100 m) fishery 
began in the 1950s, but the rapid depletion of coastal 
resources forced the fleet to expand their oprations 
toward deeper waters by the 1980s (Wehrtmann and 
Nielsen-Munoz, 2009). The shrimp trawl fishery in Cos- 
ta Rica has elevated bycatch rates of up to 93% of the 
total biomass catch (Wehrtmann and Nielsen-Munoz, 
2009; Arana et al., 2013). Moreover, the results of a 
long-term (2004-2012) fishery-independent monitoring 
program indicate that a shift has occurred in the over- 
all structure of the demersal community of Costa Rica 
(Wehrtmann and Nielsen-Munoz, 2009; Hernaez et al., 
2011; Wehrtmann et al., 2012; Espinoza et al., 2012, 
2013). Changes in elasmobranch abundance associated 
with this shift remain poorly understood, given that 
this monitoring program was designed to study deep- 
water shrimp resources and the crustacean bycatch as- 
sociated with the fisheries that target them. 
Together, the lack of biological information and 
the unreliability or nonexistence of landing statistics 
have limited the development of sustainable manage- 
ment practices and conservation strategies for elasmo- 
branchs in Costa Rica. Given the fishery’s current man- 
agement framework is poorly enforced, the sustainabil- 
ity and environmental impacts have become a serious 
concern. Concern regarding the effect of this fishery 
culminated in a constitutional judgment (Sentence No. 
2013-10540), enacted by the government of Costa Rica 
and that prohibited the Costa Rican Institute of Fish- 
eries and Aquaculture (INCOPESCA) from granting or 
renewing commercial shrimp trawl licenses. All current 
licenses for this fishery are set to expire in 2018, and 
an ongoing national decision process will eventually 
define the legal framework requirements for any sus- 
tainable shrimp trawling in Costa Rica. 
According to the Code of Conduct for Responsible 
Fisheries, the effects of a fishery on an ecosystem 
should be accounted for in management policies (FAO, 
1995). In data-deficient situations, information on by- 
catch may provide estimates of a fishery’s effects on 
an ecosystem. We aimed to characterize the relative 
composition of elasmobranch bycatch associated with 
the data-poor shrimp trawl fishery of Costa Rica. More 
specifically, we examined 1) elasmobranch distribution 
patterns in relation to geographic position, depth, year, 
season, and diel period; 2) the relationship between 
depth and number of elasmobranch species; 3) sex and 
size segregation patterns of the most common elasmo- 
branch species; 4) the effects of latitude, depth, season, 
year, and sampling type on elasmobranch species com- 
position; and 5) and a comparison of our results of spe- 
cies composition with those from historical data. This 
baseline information on the demersal elasmobranch 
assemblage of Costa Rica will enable an examination 
of the effects of management strategies to be imple- 
mented in the near future. 
Materials and methods 
Study area 
The Pacific coastline of Costa Rica is highly irregular 
and is approximately 1254 km long, borders 3 large 
gulfs and a continental shelf that together cover an 
area of 15,600 km 2 (Fig. 1; Wehrtmann and Cortes, 
2009). Costa Rica has pronounced rainy (May-Novem- 
ber) and dry (December-April) seasons (Fiedler and 
Talley, 2006). Although temperature remains relatively 
constant across seasons (27-30°C), coastal productivity 
along most of the central and southern Pacific coast 
increases during the rainy season as a consequence of 
nutrient input from the largest rivers in this country: 
the Tempisque, Tarcoles, and Terraba rivers (Fiedler 
and Talley, 2006; Wehrtmann and Cortes, 2009). 
The northern Pacific coast is characterized by strong, 
seasonal upwelling between December and February 
and by a limited freshwater input resulting from the 
absence of large rivers (Jimenez, 2001; Fiedler, 2002). 
The coast of the central Pacific region is influenced by 
2 large estuarine systems, the Golfo de Nicoya and the 
Terraba-Sierpe delta; both estuaries have large man- 
grove forests in close proximity to coral communities 
or rocky reefs (Quesada-Alpizar and Cortes, 2006). 
The southern Pacific coast has a very steep continen- 
tal slope and includes the Golfo Dulce tropical fjord 
(Quesada-Alpizar and Cortes, 2006). 
Sampling 
Sampling effort was concentrated near the main fishing 
port, Puntarenas, located in the northern Pacific region 
(Fig.l). Data for this study were collected from 3 types 
of surveys: 1) deepwater, 2) monitoring, and 3) com- 
mercial (Fig. 1). Sampling depth range was divided into 
shallow (<50 m), intermediate (50-100 m).and deep 
(>100 m). Bottom trawls were carried out exclusively on 
soft sand or mud because of sampling gear limitations. 
Deepwater surveys were conducted annually along 
the entire Pacific coastline of Costa Rica to examine 
the bycatch associated with the deepwater shrimp 
trawl fishery. A total of 4 deepwater surveys were con- 
ducted, 2 during the rainy season (August 2008 and 
May 2009) and 2 during the dry season (March 2010 
