Aspects of the Reproduction of the Bat Ray, Myliobatis californica, in Central California

Abstract

Reproduction in bat rays collected from Elkhorn Slough in central California appears to follow a well-defined annual cycle in which mature individuals use the Slough in the spring and summer months to give birth and mate. The bat ray's gestation period is estimated to be between 9-12 mo. Embryo number in pregnant females ranged between 2-5. Disc width at birth ranged between 220305 mm. In male bat rays, three indicators of sexual maturity (presence of mature spermatozoa, clasper/disc-width relationship, and internal morphology) showed that at 2-3 yr of age sexual maturity occurs at a disc width of about 450-622 mm. In females, presence of mature ova, ranging from means of 25-279 per female, indicates that 50% maturity occurs at about 881 mm disc width and approx. 5 yr of age.