174 
Fishery Bulletin 117(3) 
Table 1 
Parameters and statistical criteria for the von Bertalanffy growth model (VBGM), two-phase growth model (TPGM), 
Gompertz growth model (GGM), and logistic growth model (LGM) used to describe the growth of female Panamic sting¬ 
rays (Urotrygon aspidura) (sample size [n]=124) collected in the central zone of the Pacific coast of Colombia in 2006-2009 
and 2015. Two data sets are presented; the adjusted data set considers the months with peaks of reproduction and the 
unadjusted data set does not consider them. The parameters and criteria are asymptotic disc width (DW„, in centimeters), 
birth size ( DW 0 , fixed to 7.5 cm for models with 2 and 4 parameters), annual growth rate (k), theoretical age at zero (£ 0 ), age 
at transition between 2 phases or inflection point (f h ), maximum difference in DW at age between the VBGM and TPGM 
at the t h (h), Akaike information criterion (AIC;), difference in AIC ; between models (Aj), and Akaike weight (w^). Weighted 
averages from the TPGM are given with standard errors of the mean (SEs). Numerals after the model abbreviation indi¬ 
cate the number of parameters used in that model. Dashes indicate that data were not available because variables were 
not included in a model. 
Model 
DW„ 
k 
^0 
h 
DW 0 
AIC ; 
A ; 
Wi 
Unadjusted data 
VBGM-3 
29.32 
0.24 
-1.80 
10.28 
556.61 
1.65 
0.17 
VBGM-2 
25.46 
0.42 
- 
- 
- 
7.50 
615.64 
60.68 
0.00 
GGM-3 
26.82 
0.40 
-0.12 
- 
- 
10.33 
556.02 
1.06 
0.22 
GGM-2 
23.91 
0.69 
- 
- 
- 
7.50 
618.25 
63.29 
0.00 
LGM-3 
25.60 
0.57 
0.67 
- 
- 
10.38 
555.95 
0.99 
0.23 
LGM-2 
20.40 
0.79 
- 
- 
- 
12.50 
628.75 
73.79 
0.00 
TPGM-5 
24.93 
0.47 
-1.21 
1.93 
0.31 
10.31 
554.96 
0.00 
0.38 
TPGM-4 
24.03 
0.68 
- 
2.14 
0.46 
7.50 
614.67 
59.71 
0.00 
Adjusted data 
VBGM-3 
29.60 
0.22 
-1.53 
- 
- 
8.63 
536.69 
6.84 
0.02 
VBGM-2 
26.64 
0.31 
- 
- 
- 
7.50 
542.49 
12.65 
0.00 
GGM-3 
26.89 
0.38 
0.26 
- 
- 
8.91 
537.30 
7.45 
0.01 
GGM-2 
24.51 
0.54 
- 
- 
- 
7.50 
549.79 
19.94 
0.00 
LGM-3 
25.62 
0.55 
1.08 
- 
- 
9.13 
538.23 
8.38 
0.01 
LGM-2 
20.07 
0.60 
- 
- 
- 
12.34 
652.41 
122.56 
0.00 
TPGM-5 
24.71 
0.47 
-0.91 
2.32 
0.36 
8.18 
530.01 
0.16 
0.46 
TPGM-4 
24.02 
0.57 
- 
2.24 
0.53 
7.50 
529.85 
0.00 
0.50 
Weighted 
average from 
24.35 
0.52 
2.28 
0.45 
TPGM (SE) 
(0.59) 
(0.09) 
(0.07) 
(0.15) 
validated through the use of tetracycline for the round 
stingray ( Urobatis halleri), white-blotched river stingray 
(Potamotrygon leopoldi), and little skate (Leucoraja eri- 
nacea ) (Hale and Lowe, 2008; Cicia et al., 2009; Charvet 
et al., 2018). This validation does not imply a general¬ 
ized pattern for batoids, but it does allow inference that 
yearly periodicity occurs regularly in this group, regard¬ 
less of the taxonomic classification, habitats, or latitudi¬ 
nal distributions of the species. 
Although band pairs may begin to form during the 
first trimester of the year, starting with the opaque 
band, the reduced sample size during those months 
limited our capacity to determine with precision in 
which month this process starts. Several studies have 
also reported on the difficulty in validating band for¬ 
mation in sharks and rays (O’Shea et ah, 2013; Cailliet, 
2015); therefore, it has been assumed that 1 pair is 
formed each year. Carlson et al. (1999) and Lessa et al. 
(2006) attribute this difficulty to a bias of MI val¬ 
ues and inconclusive analyses due to long sampling 
periods (several years) during which births occur over 
a long time span and organisms from the same cohort 
are born at different times of the year. Such multiple 
births could be the case for the Panamic stingray, as 
the reproductive information available for this species 
(P. Mejfa-Falla et al., unpubl. data) and for a sympatric spe¬ 
cies, the thorny stingray {Urotrygon rogersi) (Mejfa-Falla 
et al., 2014), indicates that there is continuous reproduc¬ 
tion throughout the year with 2-3 reproductive events 
per year. 
In female and male Panamic stingrays, differences in 
age and growth parameters were observed. The maximum 
estimated female age was 7.5 years, whereas the maxi¬ 
mum estimated male age was 5.5 years. Similar values 
have also been recorded for other species of this family, 
such as the smalleyed round stingray (U microphthal- 
mum ) with 8.5 years for females of and 5.5 years for males 
(Santander-Neto, 2015) and the thorny stingray with 
8 years for females and 6 years for males (Mejfa-Falla et al., 
2014). In contrast, the blotched stingray (U chilensis) has 
