Reproductive Biology of the Cownose Ray in the Charlotte Harbor Estuarine SystemPublished on 06. September 2013
Reproductive Biology of the Cownose Ray in the Charlotte Harbor Estuarine System, Florida
Gregg R. Poulakis
The Cownose Ray Rhinoptera bonasus is an abundant species in the western Atlantic Ocean, including the Gulf of Mexico, but its reproductive biology is not completely known because of the difficulty of obtaining year-round samples in large portions of its range where the species is migratory. To address this knowledge gap, Cownose Rays were studied in a subtropical estuarine system where rays are available year-round. Size at maturity and reproductive cyclicity were assessed using 140 females and 151 males. For females, the size at 50% maturity was 701 mm disk width (DW) based on ovary length and weight, maximum follicle diameter, and mating wounds and scars; the size at 100% maturity was 712 mm DW. For males, the size at 50% maturity was 681 mm DW based on clasper morphology, testis length and weight, and epididymis width; the size at 100% maturity was 712 mm DW. Overall testis size (length and weight) and mean testis lobe diameter peaked up to 2 months prior to ovary size and maximum follicle diameter, indicating that males were preparing to inseminate females during the entire parturition and mating period. Mating behaviors and fresh mating wounds were observed mostly between April and June. Ovulation peaked in May, and parturition occurred primarily in March and April after an 11–12 month, single-embryo gestation period, suggesting that females are synchronous in Charlotte Harbor. Size at birth was 202–383 mm DW. Concurrent vitellogenesis and gestation indicated a clearly defined annual reproductive cycle that may be completed within the estuary. Understanding reproductive life history in wide-ranging species such as the Cownose Ray is useful in the short term for making sound management decisions and for future comparison as the effects of global climate change are realized.
Marine and Coastal Fisheries:
Dynamics, Management, and Ecosystem Science
Volume 5, Issue 1, 2013