and the assumptions are appropriate, there still might not be enough data to yield accurate and precise estimates.

TABLE D-1 Number of Surveys by Year and Age Class for Which Relative Abundance Measures are Available. (Surveys include NEFSC winter, spring, and autumn surveys, MADMF spring and fall surveys, CTDEP spring and fall surveys, RIDFW fall and fixed surveys, an NJDFW survey, and a DEDFW survey.)

Year

Age 0a

Age 1

Age 2

Age 3

Age 4

Age 5+

1982

4

1

2

3

3

0

1983

4

1

3

4

4

0

1984

4

1

4

5

5

0

1985

5

1

5

6

6

0

1986

5

1

5

6

6

0

1987

6

1

5

6

6

0

1988

7

2

6

6

6

0

1989

6

2

6

6

6

0

1990

7

3

7

6

6

0

1991

7

3

8

7

6

0

1992

7

4

9

8

7

1

1993

7

4

9

8

7

1

1994

7

4

9

8

7

1

1995

7

4

9

8

7

1

1996

7

4

9

8

7

1

1997

7

4

9

8

7

1

1998

6

4

9

8

7

1

1999

0

2

5

6

6

1

a Information on young-of-the-year fish (age 0) is available from a separate set of surveys and include data from Connecticut, Virginia, North Carolina, Maryland, New Jersey, Massachusetts, and the NEFSC.

NOTE: CTDEP = Connecticut Department of Environmental Protection; DEDFW = Delaware Department of Fish and Wildlife; MADMF = Massachusetts Department of Marine Fisheries; NEFSC = Northeast Fisheries Science Center; NJDFW = New Jersey Department of Fish and Wildlife; and RIDFW = Rhode Island Department of Fish and Wildlife.

Assessment Methodology

Three modeling approaches were applied to the summer flounder data to examine the influence of the data, model structure, and model assumptions on key assessment outputs. The approaches taken were based on the LaurecShepherd VPA method (Laurec and Shepherd, 1983; Darby and Flatman, 1994), the ADAPT method (Gavaris, 1988), and an AutoDifferentiation (AD) Model Builder implementation (Fournier, 1996) of a CAGEAN method (Deriso et al., 1985). Results from these methods were compared with results from the 1999 NMFS ADAPT assessment.

Laurec-Shepherd Virtual Population Analysis (VPA)

The Laurec-Shepherd method is an example of an ad hoc VPA tuning procedure. A number of these procedures are described in the literature and used in actual fisheries. The main characteristic of these procedures is that they accept the



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