The use of caudal thorns for ageing Raja undulata from the Portuguese continental shelf, with comments on its reproductive cycle

Abstract

The present study focuses on age estimation, with reproductive information contributing to the better understanding of the growth and the biology of Raja undulata. In the age and growth study, two calcified structures were used: caudal thorns and central vertebra. Results of readings showed that there were no significant differences in age estimates between the two structures. Both von Bertalanffy and Gompertz growth models were fitted to size-at-age data by sex and geographical area. No significant differences were found between sexes for the two models but significant differences were found between geographical areas (P = 0.05). The Gompertz growth function was selected as the best model to describe R. undulata growth because it presented the best fit and the most reasonable biological estimates. Reproductive analysis indicates one annual breeding season for R. undulata. The differences found in the estimates of length at first maturity between geographical areas (TL50% = 838 mm in Peniche and 762 mm in Algarve for females and TL50% = 781 mm in Peniche and 736 mm in Algarve for males), together with the regional differences found between growth parameters estimates (P = 0.05), may reflect the existence of different local populations of R. undulata on the Portuguese continental shelf.

Using biological variables and reproductive strategy of the undulate ray Raja undulata to evaluate productivity and susceptibility to exploitation

“…seasonal occurrence of each reproductive phase), and other reproductive variables, including fecundity, remain unknown. Raja undulata is an oviparous species that is known to lay eggs between February and May (Moura et al ., ). Size at hatching is estimated to be c .…”

“…According to Portuguese fishing records, R. undulata is relatively frequent off Setúbal and along the inshore waters off the Algarve coast (Coelho et al ., ; Baeta et al ., ). Inshore areas, namely estuaries and coastal lagoons, were identified as being associated with egg laying and as nursery sites (Prista et al ., ; Moura et al ., ; Ellis et al ., ).…”

“…To date, there are no published studies on the population genetics of this species, although tagging studies carried out in south‐western Ireland and the eastern English Channel indicate high site fidelity (Ellis et al ., ; ICES, ). Geographical differences in life‐history variables from south and central Portugal (Moura et al ., ) may also be indicative of patchy population distributions. These studies suggest that there is little exchange between discrete areas where R. undulata is locally abundant.…”

“…In Portuguese waters, there is published information on the growth and diet of R. undulata (Table ; Coelho & Erzini, ; Moura et al ., , ). Some information is also available on reproductive biology (Table ; Coelho & Erzini, ; Moura et al ., ), although the reproductive dynamics ( i.e . seasonal occurrence of each reproductive phase), and other reproductive variables, including fecundity, remain unknown.…”

A review of longnose skates Zearaja chilensis and Dipturus trachyderma

“…While caudal thorns and other dermal denticles have been used for species identification of some extant and fossilised rajids (Stehmann & Bürkel 1984, Gravendeel et al 2002, few studies have been used dermal denticles morphology for taxonomic and phylogenetic purposes (Deynat & Séret 1996, McEachran & Konstantinou 1996, Deynat 1998. Caudal thorns have also been sectioned and used to determine the age of some skates and rays (Gallagher & Nolan 1999, Henderson et al 2004, Gallagher et al 2006, Davis et al 2007, Matta & Gunderson 2007, Moura et al 2007). The body surfaces of Z. chilensis are relatively smooth (excluding the rostral area), with sparse prickles on the dorsal surface and without obvious denticles on the ventral surface.…”