Asynchrony and regional differences in the reproductive cycle of the greenback stingaree Urolophus viridis from south-eastern Australia

Determining the periodicity of the reproductive cycle in chondrichthyan species when the population is recruiting asynchronously, as found for Urolopus viridis, can be problematic. The reproductive cycle generally requires distinguishable trends in reproductive indices across the population. The present study utilised other similar and sympatric urolophid species with synchronous reproductive cycles. Through data collected in the present study and comparisons of maximum total length (TL), periodicity of egg and embryo in utero, ovarian cycles, largest ovarian follicle diameter, and matrotrophic contribution (percentage increase from egg to embryo after maternal histotroph supplement) from similar studies, an annual reproductive cycle can be hypothesised. Sampling across two separate regions of Lakes Entrance (LE) and Western Bass Strait (WBS), U. viridis also showed regionality in several of the reproductive indices. Maximum TL and mass for females, mean size-at-birth, and female size-at-maturity and size-at-maternity in LE were markedly smaller than in WBS. In both regions litter size (1–2) increased with TL, with an exception of one female in WBS producing a litter of 3 which could be attributed to the larger TL. The implication of U. viridis producing such few young annually is they have the lowest biological productivity of any urolophid species in south-eastern Australia

Regional differences in the reproductive parameters of the sparsely-spotted stingaree, Urolophus paucimaculatus, from South-Eastern Australia

Whether spatial variation occurs in the life-history traits of chondrichthyan species is important to fisheries modelling and assessments. A study on the reproductive parameters of Urolophus paucimaculatus from four separate regions across south-eastern Australia found regional differences in maximum total length (TL), size-at-maturity, size-at-maternity and litter sizes. Inshore embayments (Port Phillip Bay (PPB) and Corner Inlet (CI)) appear to allow for larger TLs (females and males) than do offshore areas (Lakes Entrance (LE) and Western Bass Strait (WBS)). Size-at-maturity and size-at-maternity decreased across longitude from west (PPB) to east (LE) and seasonality of parturition and ovulation occurred earlier in PPB (August-October) than in LE (September-December). Maximum litter size correlated with maximum TL (six in PPB, five in each of CI and LE, and four in WBS). There was uncertainty in classifying females for maternal condition because the reproductive cycle appears to range from a continuous annual cycle to a non-continuous biennial cycle. Much of the uncertainty arises from the ambiguity of observation of non-pregnant mature females, which have either aborted through capture and handling, or are in a \u27resting year\u27 between pregnancies. Most likely, the majority are reproducing annually with an unknown proportion of females non-continuous and resting between pregnancies

Embryonic diapause in the elasmobranchs

Embryonic diapause is a temporary suspension of development at any stage of embryogenesis, which prolongs the gestation period, allowing parturition to occur in conditions that are more suitable for newborns. This reproductive trait is widespread among all vertebrates, including elasmobranchs. Although it has only been confirmed in two elasmobranchs (Rhizoprionodon taylori and Dasyatis say), evidence indicates that at least 14 species of rays and two sharks undergo diapause, suggesting that this form of reproduction exists within a wide range of elasmobranch reproductive modes, including lecithotrophs and matrotrophs. Where it has been studied, embryogenesis is arrested at the blastodisc stage and preserved in the uterus for periods from four to 10 months. There are still many questions that remain unanswered concerning the knowledge on the biology of most diapausing species but it is clear that species benefit differently from this reproductive trait. As in other vertebrates, it is likely that environmental cues and hormones (especially progesterone and prolactin) are involved in the control of diapause in elasmobranchs, however rigorous testing of current hypothesis remains to be carried out

Prenatal stress from trawl capture affects mothers and neonates:a case study using the southern fiddler ray (<i>Trygonorrhina dumerilii</i>)

Assessing fishing effects on chondrichthyan populations has predominantly focused on 15 quantifying mortality rates. Consequently, sub-lethal effects of capture stress on the 16 reproductive capacity of chondrichthyans are largely unknown. We investigated the 17 reproductive consequences of capture on pregnant southern fiddler rays (Trygonorrhina 18 dumerilii) collected from Swan Bay, Australia, in response to laboratory-simulated trawl 19 capture (8 h) followed immediately by air exposure (30 min). Immediately prior to, and for 20 up to 28 days post trawling, all females were measured for body mass (BM), sex steroid 21 concentrations (17-β estradiol, progesterone, testosterone) and granulocyte to lymphocyte 22 (G:L) ratio. At parturition, neonates were measured for total length (TL), BM and G:L ratio. 23 Trawling reduced maternal BM and elevated the G:L ratio for up to 28 days. Trawling did not 24 significantly affect any sex steroid concentrations relative to controls. Neonates from trawled 25 mothers were significantly lower in BM and TL than control animals, and had an elevated 26 G:L ratio. Our results show that capture of pregnant T. dumerilii can influence their 27 reproductive potential and the fitness of neonates. We suggest other viviparous species are 28 likely to be similarly affected. Sub-lethal effects of capture, particularly on reproduction, 29 require further study, particularly reproduction, to improve fisheries management and 30 conservation of chondrichthyan species.Fil: Guida, L.. Monash University; AustraliaFil: Awruch, Cynthia Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina. University of Tasmania; AustraliaFil: Waker, T.. Monash University; AustraliaFil: Reina. R.. Monash University; Australi