6 
Fishery Bulletin 1 14(1) 
Table 2 
For the elasmobranch species captured as bycatch in the shrimp trawl fisheries of the Pacific coast of Costa Rica, Central 
America, during 2008-2012, total number of individuals (AO; percentages of the species sample caught in commercial (C), 
monitoring (M), and deepwater (D) surveys; percentages of abundance per depth category (<50 m, with 2279 individuals 
in total; 50-100 m, with 1642 individuals in total; and >100 m, with 643 individuals in total). Data for the most abundant 
species are presented in bold type. 
Survey type Depth range 
Order and family 
Common name (scientific name) 
N 
C 
M 
D 
<50 
m 
50- 
100 m 
>100 
m 
Carcharhiniformes 
Carcharhinidae 
Pacific sharpnose shark (Rhizoprionodon longurio) 
6 
100 
- 
- 
0.26 
- 
- 
Sphyrnidae 
Scalloped hammerhead ( Sphyrna lewini) 
4 
100 
- 
- 
0.18 
- 
- 
Triakidae 
Brown smoothhound (Mustelus henlei) 
696 
55.9 
21.3 
22.8 
0.44 
23.45 
46.81 
Sicklefin smoothhound ( Mustelus lunulatus ) 
122 
99.2 
0.8 
- 
0.26 
7 
0.16 
Squaliformes 
Echinorhinidae 
Prickly shark (Echinorhinus cookei) 
11 
- 
- 
100 
- 
- 
1.71 
Squatiniformes 
Squatinidae 
Pacific angel shark (Squatina californica) 
57 
94.7 
3.5 
1.8 
0.04 
3.23 
0.47 
Myliobatiformes 
Dasyatidae 
Longtail stingray ( Dasyatis longa) 
35 
100 
- 
- 
1.14 
0.55 
- 
Myliobatidae 
Spotted eagle ray (Aetobatus laticeps) 
2 
100 
- 
- 
0.09 
- 
- 
Golden cownose ray ( Rhinoptera steindachneri) 
39 
100 
- 
- 
0.13 
2.19 
- 
Urotrygonidae 
Panamic stingray ( Urotrygon aspidura) 
1178 
100 
- 
- 
51.56 
0.18 
- 
Blotched stingray ( Urotrygon chilensis) 
189 
100 
- 
- 
7.81 
0.67 
- 
Denticled roundray Urotrygon cimar 
1 
100 
- 
- 
0.04 
- 
- 
Spiny stingray ( Urotrygon munda) 
1 
100 
- 
- 
0.04 
- 
- 
Dwarf stingray (Urotrygon nana) 
16 
100 
- 
- 
0.7 
- 
- 
Thorny stingray ( Urotrygon rogersi ) 
143 
100 
- 
- 
6.27 
- 
- 
Gynmuridae 
California butterfly ray ( Gymnura marmorata) 
1 
100 
- 
- 
0.04 
- 
- 
Rajiformes 
Rajidae 
Equatorial skate ( Raja equatorialis ) 
88 
100 
- 
- 
1.97 
2.62 
- 
Rasptail skate (Raja velezi) 
750 
89.6 
3.6 
6.8 
0.04 
34.65 
27.99 
Cortez skate ( Raja cortezensis) 
1 
100 
- 
- 
0.04 
- 
- 
Rhinobatidae 
Whitesnout guitarfish (Rhinobatos leucorhynchus) 
90 
100 
- 
- 
3.91 
0.06 
- 
Witch guitarfish (Zapteryx xyster ) 
393 
96.4 
3.6 
- 
2.63 
19.98 
0.78 
Torpediniformes 
Narcinidae 
Bullseye electric ray (Diplobatis ommata ) 
206 
100 
- 
- 
8.86 
0.24 
- 
Giant electric ray ( Narcine entemedor ) 
152 
100 
- 
- 
6.06 
0.85 
- 
Vermiculate electric ray (Narcine vermiculatus) 
165 
100 
- 
- 
7.24 
- 
- 
Torpedinidae 
Total 
Peruvian torpedo (Torpedo peruana ) 
218 
4564 
59.6 
22.9 
17.4 
0.22 
100 
4.32 
100 
22.08 
100 
in both the lognormal and binomial submodels (Table 
3) . 
Many of the elasmobranch species observed were 
segregated by sex and maturity stage (Table 4). Bino- 
mial GLMs indicated that neither depth nor diel period 
had a significant effect on sex ratios in the catch of 
brown smoothhound, sicklefin smoothhound, blotched 
stingray ( Urotrygon chilensis), thorny stingray (U. rog- 
ersi), rasptail skate, witch guitarfish, bullseye electric 
ray ( Diplobatis ommata), giant electric ray ( Narcine en- 
temedor), or vermiculate electric ray (N. vermiculatus ) 
(Table 4). Conversely, depth had a significant effect on 
the sex ratios of the catch of Panamic stingray (Table 
4) : females of this species dominated at shallow depths 
(<50 m) but were absent from depths >50 m (Fig. 4). 
Diel period had a significant effect on the sex ratios 
of the catch of Peruvian torpedo; more females were 
caught during the day than during the night (Table 4). 
For all depths and diel periods, the proportion of males 
in the catch of brown smoothhound was higher than 
the proportion of females. Sex ratios were skewed to- 
ward females in the catch of species that were distrib- 
uted mainly in shallow waters (depths <50 m): namely 
in the catches of Panamic stingray, thorny stingray, 
bullseye electric ray, giant electric ray, and vermiculate 
electric ray (Fig. 4A). 
Binomial GLMs indicated that depth and diel period 
did not influence maturity ratios of the catch of sick- 
lefin smoothhound, blotched stingray, witch guitarfish, 
bullseye electric ray, vermiculate electric ray, and Peru- 
