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Observations on the reproductive biology of the cownose ray rhinoptera bonasus in chesapeake bay usa


, : Observations on the reproductive biology of the cownose ray rhinoptera bonasus in chesapeake bay usa. Fishery Bulletin (Washington D C) 84(4): 871-878

Cownose rays, Rhinoptera bonasus, are abundant in Chesapeake Bay during summer. We made observations on the reproductive biology of specimens collected primarily from commercial pound nets and haul seines from May through October 1976-78. Clasper development suggested that males began to mature at disc widths (DW) of 75-85 cm. Males judged as mature averaged about 90 cm DW. Macroscopic inspection of the oviducts suggested that females began to mature at 85-92 cm DW. Females judged as mature averaged 96 cm DW. Only the left reproductive tract in female cownose rays appeared functional and only one embryo per gravid female was observed. A total of 67 embryos ranging 18-440 mm DW were collected and the sex ratio of the embryos was 1:1. Gravid females carried three-quarter term embryos in May and parturition occurred in late June and July. Full-term embryos averaged about 40 cm DW. Gestation of another group of embryos began by August. Growth of these embryos was rapid and they were relatively large when cownose rays left the Chesapeake Bay in October. Cownose rays exhibited aplacental viviparity. Yolk reserves supplied the initial energy demands of the embryos (up to about 20 cm DW), but histotrophic secretions of uterine villi provided nutrition for the young through the remainder of gestation.


Accession: 006014509

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Related references

Smith, JW.; Merriner, JV., 1986: Observations on the reproductive biology of the cownose ray, Rhinoptera bonasus, in Chesapeake Bay. U S Fish and Wildlife Service Fishery Bulletin, 844: 871-877

Joseph, E.B., 1961: An albino cownose ray, Rhinoptera bonasus (Mitchill) from. Chesapeake Bay. Copeia: 482-483

Blaylock, Robert A., 1993: Distribution and abundance of the cownose ray, Rhinoptera bonasus, in Lower Chesapeake Bay. Aerial surveys were conducted in the lower Chesapeake Bay during 1986-1989 to estimate abundance and examine the distribution of the cownose ray, Rhinoptera bonasus, during its seasonal residence, May-October. Most of the survey effort was concent...

Smith J.W.; Merriner J.V., 1987: Age and growth movements and distribution of the cownose ray rhinoptera bonasus in chesapeake bay usa. Ages were estimated for 115 of 899 cownose rays, Rhinoptera bonasus, collected primarily from commercial fishing gear, in lower Chesapeake Bay and vicinity from May through October, 1976-78. Age determinations were made using sectioned vertebral c...

Smith, JW.; Merriner, JV., 1987: Age and growth, movements and distribution of the cownose ray, Rhinoptera bonasus, in Chesapeake Bay. Ages were estimated for 115 of 899 cownose rays, Rhinoptera bonasus, collected primarily from commercial fishing gear, in lower Chesapeake Bay and vicinity from May through October, 1976-78. Age determinations were made using sectioned vertebral c...

Robert J.Orth, 1975: Destruction of eelgrass zostera marina by the cownose ray rhinoptera bonasus in the chesapeake bay. Chesapeake Science 16(3): 205-208

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Smith, JW.; Merriner, JV., 1985: Food habits and feeding behavior of the cownose ray, Rhinoptera bonasus, in lower Chesapeake Bay. The most important food item of the cownose ray, Rhinoptera bonasus, in the Virginian tributaries of lower Chesapeake Bay is the soft shell clam, Mya arenaria. The Baltic macoma, Macoma balthica, ranks a distant second. Adult rays feed on deep bur...

Blaylock R.A., 1989: A massive school of cownose rays rhinoptera bonasus rhinopteridae in lower chesapeake bay virginia usa. Copeia (3): 744-748

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