Captive Biology of Pelagic Stingrays,
Dasyatis (Pteroplatytrygon) violacea in the First Year
Randy Wilder
Ann Coleman, Husbandry Division, Monterey Bay Aquarium, California, USA
Fig. 1. Pelagic stingrays of study. Female on left.
Table 1. Pelagic Stingray Reproductive Success and Pup Survival in Captivity
MBA, USA
Steinhart, USA
Sea World SD,
USA
Birth date
Mar 1, 2004
# Litters
(# Pups)
1(2)
Mean size
Disc Width/Weight
19.0cm / 232g
Nov 1, 2003
1(2)
21.5cm / 336g
Sept 7, 1995
Jun 19, 2000
1(3)
1(2)
15.7cm / 122g
22.0cm / 368g
Nov 15, 1995
1(6)
19.0cm / 178g
BSLC, Spain
Oct 20, 1995
1(4)
15.4cm / 143g
Osaka, Japan
Jan 15, Jan 22 (2
litters), Jan 30,
Feb 09, Feb 21,
Mar 11, 1993
Nov 20, 1992
1993
8(46)
19.3cm / 256g
Fondazione
Cetacea
KAMPA, Japan
Mar 4, 19, 1986
1(3)
2(10)
Comments
20.0cm / 233g
Litter in this study.
Stillborn from Outer
Bay exhibit.
Aborted near-term.
Mating in captivity.
Did not survive.
5 survived 3 months,
1 still alive.
17 months growth
data collected.
Survived a few days.
8 litters from 8
females, 15 of 46
pups survived over 3
years. No growth data
collected.
No exact date of birth.
Survived a few days.
2 litters from 2
females. One pup
survived 134 days.
One survived 1.7
years. Growth data
collected.
(Reference for aquaria other than MBA from H. Mollet, personal communication September 2004.)
Both growth and feeding data collected in the first 8
months appear to be as expected when compared to
pelagic stingray growth from the Mollet et al, 2002 paper.
Both pelagic stingray pups grew at the same rate of 30
cm/yr and 2.5 kg/yr, which presents some interesting
questions.
Disk width vs age for two neonate pelagic
stingrays
A
2.5
40
2.0
30
1.5
20
y = 0.0857x + 19.65
R 2 = 0.9519
10
Mass vs age for two neonate pelagic
stingrrays
B
50
y = 0.0067x + 0.1018
R 2 = 0.9773
1.0
0.0
0
30
60
90
120
150
180
210
240
270
0
30
60
90
Age (days)
120
150
180
210
240
270
Age (days)
C
Mean weekly amounts fed for two neonate
pelagic stingrays
D
70.0
References
Mean weekly amounts fed for two neonate
pelagic stingrays
Mollet, H.F. 2002. Distribution of Pelagic stingray, Dasyatis violacea,
off California, Central America, and worldwide. Marine and Freshwater
Research 53, 525–30.
6
60.0
5
50.0
40.0
30.0
20.0
0.0
0
30
60
90
120
150
180
210
240
Mollet, H.F., Ezcurra, J.M., and O’Sullivan, J.B. 2002. Captive biology
of the pelagic stingray, Dasyatis violacea. Marine and Freshwater
Research 53, 531–41.
4
3
2
Acknowledgments
1
0
270
0
30
60
Age (days)
90
120
150
180
210
240
Age (days)
Fig. 5. Food intake of captive pelagic stingrays. Mean weekly food amounts expressed
in (C) g/day and (D)%BM/day.
Conversion factor for neonate pelagic
stingrays based on energy values for squid
and lemon shark
0.2
0.2
0.1
0.1
0.0
0
30
60
90
120
150
180
210
240
I would like to thank Henry Mollet for all his help with compiling the
data and providing background information on pelagic stingrays;
Freya Singer, Jonelle Verdugo, Scott Reid, and Manny Ezcurra for
their help with feedings and measurements; and Christina J.
Slager for her editorial assistance.
Please contact acoleman@mbayaq.org
More information on this and related projects can be obtained at
homepage.mac.com/mollet/
y = -0.0006x + 0.2351
2
R = 0.4208
0.3
270
For Further Information
0.3
Fig. 3. Feeding ray. Note target used for
station training on right side of tank
Since the pups are getting larger, future
measurements will be done using the anesthesia MS-222
for more accurate measurements. This study will continue,
and additional data will be collected on the overall growth
of neonate pelagic stingrays in their first two years.
Fig. 4. Growth of captive pelagic stingrays from 1 Mar –1 Nov 2004. (A) DW, (B) Mass.
10.0
Fig. 2. Taking DW measurement of female
Mollet et al, 2002, determined that males are thought
to mature at around 35–40 cm in the wild and females at
45–55 cm. This indicates that both pups will reach the size
for maturity within one year. This may mean that in captive
situations, captive-born rays could reach sexual maturity
before 2 years of age.
In the future, we will start collecting data on clasper
length for the male. We will also be looking for an increase
in growth rate for the female in the next year, as well as
any mating activity.
0.5
0
Conversion factor, K1
Aquarium
The growth data for the 2 pups showed a large growth rate of 30 cm/yr
and 2.5 kg/yr for both sexes within the first 8 months (Fig. 4). Typically,
females grow to a larger size than males (Mollet et al, 2002). This was not
found to occur within the first 8 months of the neonate stage. The pups had
an initial DW of 18.5–19.5 cm and mass of 0.23 kg. At 8 months, they
reached a DW of 38–39 cm and a mass of 1.7–2.0 kg. As the rays aged, the
mean weekly amounts of food in grams per day increased, however mean
weekly food intake as a % Body Mass decreased slightly (Fig. 5). The
conversion factor for the neonate pelagic stingrays is based on energy
values for squid and lemon sharks (Fig. 6).
Mass (kg)
During a collecting trip on the NOAA research vessel, R/V David Starr
Jordan, in June 2003, 2 female pelagic stingrays and 1 male were collected
and brought back to the MBA. All three were kept in a holding tank together
where mating was observed and where fertilization most likely occurred.
A litter of 2 pups, 1 male and 1 female were born on 1 March 2004 in the
parent holding tank. Holding tank temperature was kept at 20C (68F). The
pups were moved to a separate 4’x 8’ (27.174foot2) holding tank kept at a
higher temperature of 23.8C (75F). Both rays were held in the same 4’x 8’
holding tank for the first 7 months then transferred to a larger cylindrical tank
(10’ diameter, 78.54foot2) kept at the same temperature.
The male is easily distinguishable from the female due to the presence of
claspers and a white birthmark on the dorsal side. Measurements were
conducted using the metric system so DW was measured in centimeters and
weight was measured in grams.
Once a month (every 4 weeks after initial measurement) each ray’s DW
was measured accurately by hand using a measuring tape over the curve of
the dorsal side from widest wing-tip to wing-tip. The first measurement was
taken at one-week-old after the rays had started to feed.
Weight was measured once a month (every 4 weeks after initial
measurement) by placing each ray in a large tub of seawater and then
subtracting the weight of the tub and water. The first weight and
measurement was taken at 1-week-old after the rays had started to feed.
Both pups showed no signs of stress after initial measurements, so
accurately weighing and measuring once a month was considered feasible
without anesthesia (Fig. 2).
Since the rays are easily identifiable from one another, the feeding study
was conducted by weighing out individual amounts of squid for each ray and
feeding to satiation on a daily basis. Feeding was done by hand at the side
of the tank. At 3 months, a feeding target was introduced to this same area to
start training the pups to come to a feeding station when moved to a larger
tank (Fig. 3).
Mean weekly food intake
(%BM/day)
The pelagic stingray, Dasyatis (Pteroplatytrygon) violacea is
a common ray species found in aquaria worldwide. It is a
species that has been displayed for over a hundred years,
beginning in Naples, Italy. However, there has been little data
collected on the growth and feeding of this species in a captive
environment, especially in the neonate stage of 0–2 years. This
is due to the low reproductive success and low pup survival in
aquaria (Mollet et al, 2002). Table 1 shows all known pelagic
stingray reproductive success in aquaria.
Monterey Bay Aquarium (MBA) had its first successful
pelagic stingray births on 1 March 2004. The litter of two, one
female and one male, provided the opportunity for an age,
growth, and feeding study (Fig. 1). The results presented here
represent the first eight months of a two-year study. It includes
disc width (DW) and mass versus age, and mean weekly
amounts fed for both rays.
Discussion
DW (cm)
Materials and Methods
Results
Amount fed (g/day)
Introduction
270
Age (days)
Fig. 6. Conversion factor for the rays.