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Distribution and abundance of the cownose ray, Rhinoptera bonasus, in Lower Chesapeake Bay






Estuaries. 16(2): 255-263

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 concentrated in the lower and mid-bay regions. Cownose rays appeared uniformly distributed across the bay during mid-summer, but were more abundant in the eastern portion of the bay during migration. North-south distribution varied and reflected the general seasonal migration pattern. Mean abundance increased stepwise monthly from June through September and declined dramatically in October with their emigration from the bay. Abundance estimates from individual surveys varied. The greatest range of individual survey abundance estimates occurred in September (0-3.7 times 10-7 cownose rays) due to high variation in school size and abundance between surveys. Monthly mean cownose ray abundance ranged from 0 in May and November to an estimated maximum of 9.3 times 10-6 individuals in September. The magnitude of the population suggests that the cownose ray plays an important role in the trophic dynamics of the Chesapeake Bay ecosystem. The historical data were insufficient to determine whether the population has increased, but these surveys provided the baseline data which would allow future investigation of cownose ray population dynamics in lower Chesapeake Bay.

Accession: 008488535

DOI: 10.2307/1352498

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Related references

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...

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...

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Rogers, C.; Roden, C.; Lohoefener, R.; Mullin, K.; Hoggard, W., 1990: Behavior, distribution and relative abundance of cownose ray schools Rhinoptera bonasus in the northern Gulf of Mexico. Northeast Gulf Science 11(1): 69-76

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