Improving the Collection, Management, and Use of Marine Fisheries Data (2000) / Chapter Skim
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Appendix D: Review of Summer Flounder Assessments
Appendix D: Review of Summer Flounder Assessments
Pages 197-222
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From page 197... ...
was used in the 1996 NMFS assessment. Survey data on age classes 5 and older, for example, are typically excluded from the analyses for all but the Northeast Fisheries Science Center (NEFSC)
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From page 198... ...
Information on age classes O and 2 through 4 will therefore have the greatest influence on the overall fit of the model because those data are the most abundant. The log-transformed mean number per tow of summer flounder at age derived from the survey data is the relative abundance measure used by the assessment model.
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From page 199... ...
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. and the assumptions are appropriate, there still might not be enough data to yield accurate and precise estimates.
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From page 200... ...
is available to implement it. The basic idea of the method is that an initial virtual population analysis is conducted from a reasonable but arbitrary starting point to arrive at numbers (Ny a)
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The software requires that the observation month for each survey be listed. Because the data were identified by season rather than month, the observation month was approximated by season (e.g., month 7 was assigned to the Northeast Fisheries Science Center summer series)
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From page 202... ...
APPENDIX D Assessment Results General Results Across Methods The three alternative assessment methods were applied independently by different stock assessment scientists to the same summer flounder data and compared with the NMFS 1999 assessment results. The general trends in spawning stock biomass (Figure D-4)
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From page 203... ...
that would be reflected in all series. 203 NAPS ADAPT CAGEAN VPA I NRC ADAPT — FIGURE D-5 Summer flounder fishing mortality for ages 2-4 as estimated by NMFS and compared with three independently conducted model applications.
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From page 205... ...
As might be expected from groundfish surveys, only a few of the series reach this level: only NEFSC winter survey for ages 2 and 3, the NEFSC autumn survey for age 1, and the Rhode Island fixed station survey for age 0. The significance of the NEFSC winter survey probably results because it is a short time-series with only the downswing of
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From page 206... ...
206 TABLE D-2 Standard Errors of the Natural Log-transformed Survey Catchability Age APPENDIX D Survey 0 1 2 3 NEFSC Spring Survey NEFSC Winter Survey NEFSC Fall Survey Massachusetts Spring Survey Massachusetts Fall Survey Connecticut Spring Survey Connecticut Fall Survey Rhode Island Spring Survey Rhode Island Fall Survey Rhode Island Fixed Station Survey New Jersey Survey Delaware 16-foot Trawl Survey Delaware 30-foot Trawl Survey Virginia Rivers Young-of-the-Year Survey Virginia Bay Young-of-the-Year Survey North Carolina Young-of-the-Year Survey Maryland Young-of-the-Year Survey Massachusetts Young-of-the-Year Survey Shrinkage Mean 0.555 0.625 0.735 0.468 1.024 1.187 0.866 0.607 1.015 0.796 0.707 0.626 0.707 0.921 0.784 0.97 0.427 0.815 1.465 0.532 0.664 0.732 0.599 0.9 0.5 0.52 0.82 0.719 0.82 0.521 0.639 0.628 0.616 0.569 0.609 0.655 0.617 0.507 0.707 0.834 1.131 1.059 0.616 0.479 0.5 0.5 0.5 TABLE D-3 Weightings Applied to Each Age of Each Survey (percentages) Age Survey 0 1 2 3 NEFSC Spring Survey 0% 12% 15% 9% NEFSC Winter Survey 0% 9% 6% 11% NEFSC Fall Survey 6% 16% 8% 9% Massachusetts Spring Survey 0% 3% 6% 8% Massachusetts Fall Survey 0% 3% 15% 9% Connecticut Spring Survey 0% 5% 10% 14% Connecticut Fall Survey 6% 10% 10% 7% Rhode Island Spring Survey 4% 3% 0% 0% Rhode Island Fall Survey 5% 6% 0% 0% Rhode Island Fixed Station Survey 3% 7% 0% 0% New Jersey Survey 18% 9% 6% 3% Delaware 16-foot Trawl Survey 5% 0% 0% 0% Delaware 30-foot Trawl Survey 2% 3% 10% 15% Virginia Rivers Young-of-the-Year Survey 11% 0% 0% 0% Virginia Bay Young-of-the-Year Survey 7% 0% 0% 0% North Carolina Young-of-the-Year Survey 6% 0% 0% 0% Maryland Young-of-the-Year Survey 9% 0% 0% 0% Massachusetts Young-of-the-Year Survey 4% 0% 0% 0% Shrinkage Mean 13% 14% 16% 14%
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From page 207... ...
) Divided by the Standard Error of the Slope Age 207 Survey 0 1 2 3 NEFSC Spring Survey NEFSC Winter Survey NEFSC Fall Survey Massachusetts Spring Survey Massachusetts Fall Survey Connecticut Spring Survey Connecticut Fall Survey Rhode Island Spring Survey Rhode Island Fall Survey Rhode Island Fixed Station Survey New Jersey Survey Delaware 16-foot Trawl Survey Delaware 30-foot Trawl Survey Virginia Rivers Young-of-the-Year Survey Virginia Bay Young-of-the-Year Survey North Carolina Young-of-the-Year Survey Maryland Young-of-the-Year Survey Massachusetts Young-of-the-Year Survey -0.40 -1.31 -0.55 3.33 1.66 0.01 -0.88 -1.23 -0.42 1.90 1.65 1.50 0.44 -1.35 1.29 3.02 0.17 -0.49 0.47 -0.04 -0.15 -0.58 1.50 1.41 -0.83 -6.13 1.72 0.82 -0.75 0.99 0.76 -1.37 -2.34 -0.46 0.14 0.73 0.55 -0.14 0.77 1.31 -1.27 -0.16 -1.31 a cycle included.
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208 APPENDIX D the variability seen in the data may be interpreted as observation error, bias, or a systematic trend in the underlying process (e.g., in fish catchability)
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Figure D-13 summarizes the results of the sequential population analysis. The upper plot is the spawning stock biomass aged ahead (mortality applied)
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From page 210... ...
210 TABLE D-5 Weights Applied for Each Year of Retrospective Analysis APPENDIX D 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Northeast Fisheries Science Center Spring Survey O O O O O O O O O O O O 1 0.0687 0.0624 0.0592 0.0636 0.0504 0.0683 0.072 0.0739 0.0726 0.0782 0.1156 2 0.0369 0.1048 0.1207 0.0796 0.0768 0.0935 0.0971 0.1221 0.113 0.1367 0.1459 3 0.0692 0.0674 0.0696 0.0684 0.0523 0.0812 0.0885 0.0973 0.0556 0.071 0.0928 Northeast Fisheries Science Center Winter Survey O O O O O O O O O O O O 1 0 0 0 0 0 0 0 0 0.0945 0.075 0.0912 2 0 0 0 0 0 0 0 0 0.1951 0.0882 0.0587 3 0 0 0 0 0 0 0 0 0.077 0.0792 0.1087 Northeast Fisheries Science Center Fall Survey 0 0.1199 0.1477 0.1381 0.0889 0.0457 0.0555 0.0512 0.0472 0.0624 0.0621 0.06 1 0.3614 0.5409 0.5504 0.5628 0.4426 0.3331 0.3119 0.2991 0.3145 0.3264 0.1626 2 0.038 0.1406 0.1602 0.1319 0.1243 0.0911 0.1184 0.1008 0.0907 0.0934 0.0763 3 0.2244 0.2216 0.23 0.2237 0.2473 0.2109 0.1959 0.1482 0.0809 0.0862 0.0949 Massachusetts Department of Marine Fisheries Spring Survey O O O O O O O O O O O O 1 0.0375 0.031 0.033 0.0277 0.0246 0.0412 0.0283 0.0274 0.0226 0.0251 0.034 2 0.0112 0.0314 0.0449 0.0274 0.0264 0.038 0.0366 0.038 0.0394 0.0514 0.0587 3 0.0405 0.0433 0.048 0.0446 0.0505 0.0564 0.0609 0.0685 0.0485 0.0653 0.082 Massachusetts Department of Marine Fisheries Fall Survey O O O O 1 0.0216 0.0172 0.0196 0.0225 0.0178 0.0267 0.0241 0.0258 0.0262 0.033 0.0253 2 0.0222 0.082 0.133 0.1386 0.0908 0.1999 0.1604 0.1405 0.1099 0.1318 0.1453 3 0.053 0.0601 0.0627 0.0726 0.0763 0.0978 0.1004 0.1187 0.0668 0.0795 0.0925 Connecticut Department of Environmental Protection Spring Survey O O O O O O O O O O O O 1 0.0188 0.017 0.018 0.0203 0.0171 0.0268 0.0276 0.0291 0.0281 0.0343 0.0475 2 0.0525 0.1358 0.1942 0.1347 0.105 0.0949 0.075 0.088 0.0786 0.0923 0.0966 3 0.1624 0.1934 0.214 0.2199 0.1966 0.189 0.1862 0.2259 0.1163 0.1368 0.1369 Connecticut Department of Environmental Protection Fall Survey 0 0 0 0.0889 0.0939 0.0392 0.0454 0.0611 0.0542 0.0569 0.0674 0.0648 1 0.1574 0.054 0.0537 0.0541 0.0444 0.0663 0.067 0.0668 0.0597 0.0683 0.0967 2 0.792 0.3854 0.1651 0.3176 0.2123 0.1646 0.1884 0.1538 0.0919 0.0966 0.1 3 0.2244 0.2076 0.1801 0.1733 0.1565 0.1252 0.1351 0.1207 0.057 0.0624 0.0704 Rhode Island Department of Fish and Wildlife Spring Survey 0 0.0211 0.019 0.022 0.0222 0.0155 0.0182 0.0196 0.0216 0.0264 0.0325 0.0382 1 0.0308 0.0265 0.0283 0.0332 0.0269 0.0439 0.0475 0.0485 0.0279 0.0282 0.0346 2 0 0 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0
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APPENDIX D TABLE D-5 Continued 1988 1989 1990 1991 1992 1993 211 1994 1995 1996 1997 1998 Rhode Island Department of Fish and Wildlife Fall Survey 0 0.0359 0.0324 0.0333 0.0308 0.018 0.025 0.0257 0.028 0.0401 0.0458 0.0527 1 0.0816 0.0665 0.0664 0.0455 0.039 0.0582 0.0611 0.0597 0.0494 0.0503 0.0562 2 0 0 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 Rhode Island Department of Fish and Wildlife Fixed-station Survey 0 0 0 0 0 0 0 0 0 0.0283 0.0338 0.0344 1 0 0 0 0 0 0 0.0884 0.0813 0.0585 0.0518 0.0713 2 0 0 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 New Jersey Department of Fish and Wildlife Survey 0 0 0 0 0 0.2307 0.0739 0.1222 0.079 0.1536 0.1417 0.1777 1 0 0 0 0 0.2136 0.158 0.1014 0.1101 0.0969 0.0882 0.0909 2 0 0 0 0 0.2345 0.1479 0.1349 0.1058 0.0604 0.0531 0.0567 3 0 0 0 0 0.0324 0.031 0.034 0.0327 0.0217 0.0239 0.0275 Delaware Department of Fish and Wildlife 16-Foot Trawl Survey 0 0.1819 0.1225 0.0987 0.0823 0.0351 0.0439 0.0363 0.0357 0.0465 0.046 0.0488 1 0 0 0 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 Delaware Department of Fish and Wildlife 30-Foot Trawl Survey 0 0 0 0 0 0 0 0 0.0112 0.0164 0.014 0.0151 1 0 0 0 0 0 0 0 0.0301 0.0297 0.022 0.0318 2 0 0 0 0 0 0 0 0.0715 0.0749 0.0951 0.104 3 0 0 0 0 0 0 0 0 0.3614 0.2607 0.1534 Virginia Rivers Young-of-the-Year Survey 0 0.126 0.1787 0.1649 0.1421 0.0779 0.0815 0.0899 0.0989 0.1099 0.1106 0.1145 Virginia Institute of Marine Sciences Survey, including Chesapeake Bay Young-of-the-Year 0 0 0 0 0 0.2 0.0786 0.083 0.0723 0.0736 0.0717 0.0735 North Carolina Young-of-the-Year Survey 0 0 0 0 0.1599 0.1042 0.281 0.2438 0.2946 0.0692 0.0666 0.0605 Maryland Young-of-the-Year Survey 0 0.1267 0.1185 0.1125 0.1019 0.0714 0.1029 0.0926 0.0849 0.1238 0.1164 0.0903 Massachusetts Young-of-the-Year Survey 0 0.0715 0.0792 0.0748 0.0671 0.0392 0.0508 0.0403 0.0402 0.0489 0.0536 0.04 Shrinkage Mean 0 0.317 0.302 0.2668 0.2108 0.1229 0.1432 0.1342 0.1322 0.1439 0.1378 0.1296 1 0.2221 0.1845 0.1714 0.1703 0.1234 0.1775 0.1708 0.1482 0.1194 0.1191 0.1425 2 0.0472 0.12 0.182 0.1702 0.1298 0.17 0.1892 0.1794 0.1463 0.1613 0.1578 3 0.2262 0.2067 0.1956 0.1976 0.188 0.2084 0.1991 0.1879 0.1149 0.1351 0.1408
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From page 212... ...
NOTE: CTDEP = Connecticut Department of Environmental Protection; CTYOY = Connecticut Young-of-theYear Survey; MADMF = Massachusetts Department of Marine Fisheries; MDYOY = Maryland Young-of-theYear Survey; NCYOY = North Carolina Young-of-the-Year Survey; NEFSC = Northeast Fisheries Science Center; NEYOY = New England Young-of-the-Year Survey; NJBMF = New Jersey Bureau of Marine Fisheries; NJYOY = New Jersey Young-of-the-Year Survey; RIDFW = Rhode Island Department of Fish and Wildlife; VAYOY = Virginia Young-of-the-Year Survey. f = fall survey; s = spring survey; w = winter survey.
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From page 213... ...
. ~ I 1985 1990 1995 Ye~ FIGURE D-12 Predicted population size and data from each survey.
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From page 214... ...
estimates of F and biomass from ADAPT base run using data shown in Figure D-1. The biomass has been aged ahead to August and weighted by a maturity ogive (a continuous cumulative frequency curve)
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APPENDIX D 1 ¢ _' 1.5— cat ·_.
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The estimates in Figure D-15 have been divided by the longest time series to obtain the values shown above.
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Figure D-16 recasts Figure D-15 as relative retrospective patterns. Each line in Figure D- 15 was scaled relative to the longest series.
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When the CAGEAN model was used with varying selectivity at age O and age 1, the spawning stock biomass estimates more closely follow that derived under the 1999 NMFS assessment (Figure D- 18 )
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From page 220... ...
All these results point to the rather tenuous nature of the estimates available for the most recent years. SUMMARY Three analyses of summer flounder data by three different individuals using three different stock assessment models yielded the same general decadal trends indicated by the 1999 National Marine Fisheries Service assessment (see Figures D-4 and Dab.
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From page 221... ...
To explore and address this issue, a modification was made to the CAGEAN model to allow for some variation in selectivity over time.2 When the CAGEAN model was used with varying selectivity at age O and age 1, the spawning stock biomass estimates more closely followed those derived under the 1999 NMFS assessment (Figure D-18. This indicates that the selectivity assumption caused at least some of the differences in the outputs of the NMFS ADAPT and CAGEAN models.
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From page 222... ...
In the summer flounder case, the NMFS assessment could be improved by analyzing the APPENDIX D same data using different models. The differences obtained should help analysts learn about problems in the data, problems in using the ADAPT model with these data, or problems with the assumptions used in the NMFS ADAPT model (e.g., related to shrinkage and changes in selectivity over time)
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