Demographic Analysis of the Pelagic
stingray Pteroplatytrygon (Dasyatis) violacea (Bonaparte, 1832)


A) Using Captive data (Mollet et al. 2002)  B) Using guesstimates for field data 
Ageatfirst reproduction
(α) 3 years ; Longevity (ω) about 10 years ,; Mortality, M = 0.4605 yr1 (S = 0.6310) based on longevity of 10 years and using M = ln(0.01)/10 ; Llitter of 6 every year, i.e. fecundity of 6/2 =3; Abar/α = 1.3 (using low value of range 1.31.5 because species
is relatively short lived), thus Abar = 3.9 yr. 
Ageatfirst reproduction
(α) 5 years ; Longevity (ω) about 15 years,; Mortality, M = 0.3070 yr1 (S = 0.7356) based on longevity of 15 years and using M = ln(0.01)15; Litter of 6 every year, i.e. fecundity of 6/2 =3; Abar/α = 1.3 (using low value of range 1.31.5 because species is relatively short lived), thus Abar = 6.5 yr. 
Elasticities from α = 3 yr, Abar = 3.9 yr Normalized elasticities: E1 = 20.4%, E2 = 61.2%, E3 = 18.4% 
Elasticities from α = 5 yr, Abar = 6.5 yr Normalized elasticities: E1 = 13.3%, E2 = 66.7%, E3 = 20.0% 
Solution using life history table or 10x10
Leslie matrix (Mollet and Cailliet 2002) with alpha = 3 yr: Lambda = 1.1739, growth rate of stable population (r = ln (λ) = 0.1604 yr^{1}); Net reproductvie rate Ro = 1.9901, Generation "times": Abar = 4.105 yr (an age), T = ln(Ro)/r = 4.29 yr, μ_{1} = 4.50 yr (an age) (Abar/α = 1.368); Elasticities E1 = 0.2436, E2 = 0.7308 E3 = 0.2692 Normalized elasticites E1 = 19.6%, E2 = 58.8%, E3 = 21.7%. 