Table 1. Demographic characteristics of mobulid rays landed in Sri Lanka.
| Mobula birostris | Mobula mobular | Mobula tarapacana | Mobula thurstoni | Mobula kuhlii | |
|---|---|---|---|---|---|
| Specimens recorded | |||||
| Females | 107 | 1,598 | 388 | 41 | 18 |
| Mature males | 22 | 670 | 115 | 8 | 18 |
| Immature males | 73 | 1,077 | 224 | 32 | 11 |
| Unknown males | 1 | 3 | 0 | 0 | 0 |
| Unsexed | 96 | 1,550 | 387 | 12 | 12 |
| Total a | 299 (4.6%) | 4,898 (75.2%) | 1,114 (17.1%) | 93 (1.4%) | 59 (0.9%) |
| Size range (including pups) | |||||
| Females | 180–478 cm | 60–252 cm | 132–326 cm | 72-168cm | 35–138 cm |
| Mature males | 396–449 cm | 184–242 cm | 212–314 cm | 138–160 cm | 101–124 cm |
| Immature males | 136–375 cm | 62–222 cm | 98–244 cm | 65–145 cm | 63–104 cm |
| Unsexed | 168–308 cm | 71–236 cm | 115–300 cm | 98.5-115.5 cm | 75 cm |
| Size at 50% maturity (Fig. 4) | |||||
| Males | 385.53 cm | 202.51 cm | 239.99 cm | 142.78 cm | 102.87 cm |
| Proportion of immature | |||||
| % of males immature | 76% of 96 specimens | 62% of 1,750 specimens | 66% of 339 specimens | 80% of 40 specimens | 38% of 29 specimens |
| % of males smaller than DW50 | 86% of 56 specimens | 67% of 431 specimens | 75% of 112 specimens | 79% of 34 specimens | 32% of 28 specimens |
| % of females smaller than DW50b | 96% of 53 specimens | 83% of 406 specimens | 87% of 117 specimens | 97% of 31 specimens | 56% of 18 specimens |
Notes.
a
This excludes 53 specimens (0.8%) that were not identified to species level.
b
DW50 for females from Rambahiniarison et al. (2018): M. birostris: 448.0 cm; M. mobular: 217.8 cm; M. tarapacana: 264.8 cm; M. thurstoni: 163.6 cm and the size of the one recorded pregnant female specimen of M. kuhlii from Notarbartolo di Sciara et al. (2017): 116.8 cm. These figures are expected to be higher as they are based on DW50 and not the DW of the smallest pregnant individual, however previous studies have shown delayed onset between maturity and pregnancy (Rambahiniarison et al., 2018).