Date Awarded

1995

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Virginia Institute of Marine Science

Abstract

A total of 12,323 summer flounder were tagged and released in Chesapeake Bay, the coastal waters off Virginia Beach, and the Eastern Shore during 1987-89. Excluding immediate recaptures, a total of 675 were recaptured for an overall return rate of 5.5%. Returns from the commercial fishery (56.2%) outnumbered those from the recreational fishery (35.7%). The majority of returns (47.1%) came from either Virginia waters or areas to the south, while only 12.8% were from areas to the north of Virginia. offshore returns accounted for 8.5% of the total. Returns with insufficient location data made up the remaining 31.5%. of the returns with sufficient recapture location data, 69% were from Virginia waters or areas to the south. Differences in length at tagging were noted between these groups with smaller fish accounting for a larger proportion of the returns from northern waters. The returns from Virginia waters and areas to the south were more representative of the entire size range of fish tagged. No behavioral differences were noted between tagged and untagged summer flounder held in the laboratory. No tag losses were noted in fish held over the course of one year. Scales were used to age summer flounder and were found to be adequate for ages 0-3, older fish were more difficult to age with scales. Percent agreement between scale and otolith determined ages (n = 170) was 100% for ages 0-5. Length frequencies of summer flounder were used to validate scale determined ages during 1987-89. Prominent modes in length frequencies represented ages 0-2, afterwards, differential growth between the sexes obscured the modes. Marginal increment analysis proved that the marks formed on scales were annular for ages 1-4 and that annulus formation occurred in May-June, at sizes ranging from 179-367 mm TL. Overall mean backcalculated length and the mean observed length in May for age-1 fish were 262 vs 265.4 mm. Mean backcalculated lengths for males were 249, 337, 393, and 455 mm TL for ages 1-4. Mean backcalculated lengths for females were 273, 379, 470, and 550 mm TL for ages 1-4. Backcalculated lengths at ages 1-7 for the pooled sexes were 262, 377, 473, 546, 600, 655, and 696 mm TL. Length-weight relations were calculated by sex for 2,172 fish. Overall sex ratio was 1:1.32, males to females. The sex ratio was approximately 1:1 for length groups up to 360 mm TL. Females outnumbered males at sizes greater than 360 mm TL. Male summer flounder reached 50% maturity at 261-270 mm TL, while females attained 50% maturity at 361-370 mm TL. Overall catch per unit effort decreased from 1.65 fish caught per minute to 0.4 from 1987 to 1989. Instantaneous rates of mortality for summer flounder caught in Chesapeake Bay and coastal waters ranged from 0.964 in 1988, to 1.655 in 1987. Instantaneous rates of mortality for summer flounder caught at Wachapreague ranged from 0.844 in 1989, to 3.608 in 1987.

DOI

https://dx.doi.org/doi:10.25773/v5-vdr9-cn07

Rights

© The Author

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