Reproductive Strategy of the Giant Electric Ray in the Southern Gulf of California

Abstract

The objective of the present study was to describe and characterize macroscopic and microscopic aspects of the reproductive biology of the Giant Electric Ray Narcine entemedor, a viviparous elasmobranch targeted by commercial fishers in Mexico. A total of 305 individual rays were captured (260 females, 45 males); all males were sexually mature. The median size at maturity for females was estimated to be 58.5 cm TL, the median size at pregnancy was 63.7 cm TL, and the median size at maternity was 66.2 cm TL. The range of ovarian follicles recorded per female was 1–69; the maximum ovarian fecundity of fully grown vitellogenic oocytes was 17, and uterine fecundity ranged from 1 to 24 embryos per female. The lengths of the oblong ovarian follicles varied significantly among months, and the largest ovarian follicles were found in July, August, and September. Median embryo size was largest in August, and the size at birth was between 12.4 and 14.5 cm TL. Histological evidence of secretions from the glandular tissue of the uterine villi indicate that this species probably has limited histotrophy as a reproductive mode. Vitellogenesis in the ovary occurred synchronously with gestation in the uterus. The Giant Electric Ray has a continuous annual reproductive cycle; a period of ovulation occurs between May and September and two peaks of parturition, one in January and one in August, occur, suggesting that embryonic diapause occurs in some individuals. These results provide useful information for the management of this important commercial species in Bahía de La Paz, Mexico, and will allow possible modification of the current Mexican regulations to enable better protection of this species.

Reproductive biology of the Brazilian blind electric ray Benthobatis kreffti (Chondrichthyes: Narcinidae)

“…Rincon (1997) observed only one functional ovary in specimens of B. kreffti from southern Brazil. Torpediniformes present, however, usually present two functional ovaries, as observed in this study and for Torpedo torpedo (Linnaeus, 1758) (Capapé et al, 2000), Tetronarce californica (Ayres, 1855) (Neer, Cailliet, 2001), Narcine bancroftii (Griffith & Smith, 1834) (Moreno et al, 2010) and Narcine entemedor Jordan & Starck, 1895(Burgos-Vázquez et al, 2017. Differences in reproductive functionality have been reported between species for the genus Squatina (Vooren, Da Silva, 1991), however, differences in the number of gonads between populations was never reported for elasmobranchs.…”

Spatial pattern of distribution and reproductive strategy of vermiculate electric‐raysNarcine vermiculatus

“…adult females grow longer in L T (9.8%). Sexual dimorphism has been observed in other species of Narcine genus such as N. brasiliensis and N. entemedor (Burgos‐Vázquez et al ., 2017; Rolim et al ., 2015a; Villavicencio‐Garayzar, 1993). The advantage of reaching greater L T is that it allows adult females to have more space available in the body cavity for the growth of oocytes or embryos (Klimley, 1987; Parsons et al ., 2008) and a larger liver to cover energetic costs during vitellogenesis, oocyte maturation and gestation (Klimley, 1987; Lucifora et al ., 2002; Mabragaña et al ., 2002; Oddone & Velasco, 2006).…”

Growth Modeling of the Giant Electric Ray Narcine entemedor in the Southern Gulf of California: Analyzing the Uncertainty of Three Data Sets

“…The organisms were captured using monofilament gill nets (200–300 m long, 1.5 m high, 20–25 cm stretch mesh) set in the afternoon at depths between 10 and 30 m over sandy bottoms and recovered the next morning. Individuals were measured for total length (TL in cm), and the sex was determined by the presence of copulatory organs in males (claspers; [ 28 ]). Vertebrae were collected from the abdominal region of each specimen and placed in a freezer.…”

“…The birth band was defined as the angle change on the centrum side [ 29 ]. Additionally, a centrum of a 12.4 cm TL near-term embryo [ 28 ] was polished and compared with a thin section of an adult. The size of the embryo’s centra and the birth band coincided; furthermore, no pre-birth bands were observed.…”

“…The giant electric ray N. entemedor is an endemic batoid of the eastern tropical Pacific Ocean distributed from southern Baja California and the Gulf of California to Peru. While the diet and feeding ecology [ 27 ] and reproductive biology [ 24 , 28 ] of the giant electric ray have been investigated, there is little information on the age and growth of this species. Moreover, information on the species is limited to the Pacific coast of Mexico, while life-history traits could vary in Central and South America.…”