Table 2. Predicted and observed population descriptors for different reef manta ray populations.
The population descriptors are: population growth rate (λ, expressed per year), mean lifetime reproductive success (R0), and cohort generation time (Tc, years). Predicted values given are the minimum and maximum values from our demographic analyses (Figs. 2–4); observed values are taken from different locations around the world (locations are indicated).
| Predicted range | Observed value | Explanation of observed value | Location of observation | Reference for observed value | |
|---|---|---|---|---|---|
| λ | 0.64–1.13 | 0.77 | Calculated from the observation of 88% decline between 2005–2011 | Mozambique | Rohner et al. (2013) |
| 0.98 | Calculated from the observation of 80% decline over 75 years | Not specified | Marshall et al. (2011a) | ||
| 1.02 | Estimated using POPAN models covering 1987–2009 | Japan | Kashiwagi (2014) | ||
| R0a | 0.06–6.20 | 0.60 | Calculated using IUCN data (Marshall et al., 2011a)a: Tc = 25 and λ = 0.98 | Not specified | Marshall et al. (2011a) |
| 0.02 | Worst-case scenario calculated using slowest life history valuesa: Tc = 19.4 and λ = 0.77 | Not specified | Marshall et al. (2011a) and Rohner et al. (2013) | ||
| Tc | 3.89–20.40 | 19.4 | Mean of minimum (6.75 years) and maximum (32 years) age of adults | Tropical Eastern Pacific & Atlantic; Hawaii | Ward-Paige, Davis & Worm (2013) |
| 25 | Mean of minimum (10 years) and maximum (40 years) age of adults | Not specified | Marshall et al. (2011a) |
Notes.
a
R0 was calculated by taking the exponent of Tc × log(λ) (Caswell, 2001).