Table 1.
The nine species of shovelnose rays in this study.
Listed is their threat status according the International Union of Conservation of Nature’s (IUCN) Red List of Threatened Species, and whether the species are listed on the appendixes of CITES, and/or CMS, and the CMS Sharks MOU (MOU). IUCN categories are CR, Critically Endangered; EN, Endangered; VU, Vulnerable; LC, Least Concern; DD, Data Deficient.
Table 2.
Life-history values and sources used to estimate rmax for the nine species of shovelnose rays.
Including the maximum size (Lmax in centimetres total length, cm TL), lower, upper and mean (standard deviation, S.D.) values of the age at maturity (αmat, years), lower and upper values for litter size, breeding interval (i, years), lower and upper annual reproductive output of females (b), lower and upper values for von Bertalanffy growth coefficient (k, year-1), the observed, and lower (Tlower) and upper (Tupper) and mean (S.D.) values of theoretical maximum age (αmax, years). See Table 1 in S1 Appendix for re-estimated k results for R. australiae and G. typus.
Table 3.
Natural mortality (M) methods used to estimate maximum intrinsic rate of population increase.
Where αmat is age at maturity in years, αmax is maximum age in years, and k is the von Bertalanffy growth coefficient in year-1.
Fig 1.
Incorporating uncertainty in the model parameters when predicting values of rmax (year-1) for nine shovelnose rays species.
When including uncertainty in age at maturity (αmat, first/orange boxplot), annual reproductive output (b, middle/blue boxplot), and reciprocal of the lifespan natural mortality estimator (M, last/grey boxplot). Species are (A) R. australiae, (B), G. cemiculus, (C) G. typus, (D) A. annulatus, (E) P. horkelii, (F) P. productus, (G) R. rhinobatos, (H) Z. brevirostris, and (I) Z. exasperata. Boxes indicate median, 25 and 75% quantiles, whereas the lines encompass 95% of the values (2.5 and 97.5% quantiles). For plots incorporating uncertainty with other natural mortality methods, see S2 Appendix.
Fig 2.
Values of rmax (year-1) for nine shovelnose ray species vary with different methods of estimating natural mortality.
Which are Jensen’s First Estimator (red), modified Hoeing & Hewitt’s Estimator (yellow), Frisk’s Estimator (green), and Reciprocal of lifespan (blue). Means (triangle) and standard deviation (black line) are presented for each method. Species are (A) R. australiae, (B), G. cemiculus, (C) G. typus, (D) A. annulatus, (E) P. horkelii, (F) P. productus, (G) R. rhinobatos, (H) Z. brevirostris, and (I) Z. exasperata. Values below the black dashed line indicate implausible rmax estimates.
Table 4.
Estimates of rmax (year-1) for nine species of shovelnose rays using four methods of estimating natural mortality.
The mean (± standard deviation S.D.) and 25% and 95% quantiles of rmax values are reported for each species and natural mortality estimator.
Fig 3.
Predicted value of rmax for the nine species of shovelnose rays in relation to their (A) age at maturity (amat, years) and (B) annual reproduction rate of females (b). The black lines encompass 95% of the values (2.5 and 97.5% quantiles). The reciprocal of lifespan natural mortality estimator to estimate rmax. The shapes represent the four families; black circles represents the giant guitarfishes, Family Glaucostegidae; black triangles signifies the wedgefishes, Family Rhinidae; black squares represents guitarfishes, Family Rhinobatidae; and black crosses are banjo rays, Family Trygonorrhinidae.
Fig 4.
Maximum size(cm TL) for the nine species of shovelnose rays in relation to the (A) median maximum intrinsic rate of population increase (rmax, year-1) using the reciprocal of lifespan to estimate natural mortality, (B) annual reproduction rate of females (b), and (C) size at birth (cm TL). The black lines encompass 95% of the values (2.5 and 97.5% quantiles). The shapes represent the four families; black circles represents the giant guitarfishes, Family Glaucostegidae; black triangles signifies the wedgefishes, Family Rhinidae; black squares represents guitarfishes, Family Rhinobatidae; and black crosses are banjo rays, Family Trygonorrhinidae.
Fig 5.
The frequency of the rmax values predicted for 115 chondrichthyans, including the nine shovelnose ray species.
The reciprocal of lifespan natural mortality estimator was used to estimate rmax and species are grouped by their rmax values. Black line denote the mean (rmax = 0.30) and blue line represents the median (rmax = 0.23). The nine shovelnose rays species are displayed on the figure and species illustrations are from Last et al. [75].
Fig 6.
Estimates of rmax for 115 chondrichthyans, including the nine shovelnose rays species, compared with life history parameters.
(A) maximum size (cm TL/DW), (B), age at maturity (αmat years), (C) maximum age (αmax, years), (D) annual reproductive output b, (E) the von Bertanlaffy growth coefficient (k, year-1). The nine shovelnose ray species labelled are: RA, R. australiae; GC, G. cemiculus; GT, G. typus; AA, A. annulatus; PH, P. horkelii; PP, P. productus; RR, R. rhinobatos, ZB, Z. brevirostris; ZE, Z. exasperata. The black lines encompass 95% of the values (2.5 and 97.5% quantiles). The median rmax value is reported, using the reciprocal of the lifespan method to estimate natural mortality. All axes are on a logarithmic scale. Species that are listed on CITES Appendix I or II are represented in blue, species listed on CMS Appendix I or II are represented as triangles. Species that are listed on neither CITES or CMS are indicated as grey circles.