Structure in fisheries data: commercial catches and surveys a case history of the Icelandic codEinar Hjrleifsson

Measurements: The basis for any assessmentMeasurements of commercial catch compositionTotal catchLandingsDiscardsCatch compositionSize (length)AgeCatch curve of a year classIndependent measurements (surveys)Total indicesSurvey size compositionLength based indicesAge based indicesSurvey catch curve of a year class

Correlation among commercial data and scientific surveys

iCod: Annual landings

Catches are taken by different gear and in different location

Sampling of catches need to reflect the actual fisheriesAnnual sampling: 500.000 length measures 20.000 age estimationsEach letter refers to a sample from a single fishing activity (150-200 fish measured)

iCod annual length distribution in the fishery30120 cm2001200220032004200520066090length

iCod: Annual sampling from catches and age compositionCatch composition in 2006: Annual landings is known.By sampling the catch composition (length and age) one can split the annual landings into landings by age groups.

Age disaggregated catches 1982-2006 in kt

Sheet1

Age -->

Year01234567891011121314Total

195500043310010249301615518111710545

1956000728689167242115115141720487

195700015364479807326161057514455

19580003156454980948017187339517

1959000207370353254865589215459

1960000164982664740448328727470

19610001736536544442823511016377

19620001346495769285919142544389

19630002347524380532150149143409

196400023504947431164014257516437

1965000224564485041791310518387

196600021515258345218484546353

1967000295165464920431218102336

196800014756064794212216812382

196900012431136663871143100403

19700001068589674699152211475

1971000145610563855633272110444

19720009436874485564249100395

197300038366861622331398200369

19740001610653554741122014310368

197500032521234552251668411365

197600032715610029361162210346

1977000382934975191441000340

1978000830129705028942101330

197900010563613878301232100366

19800006538957142551873200432

198100022289775715437167311465

19820003325588604177174110380

19830004175557714614226311298

1984000954505535432056311282

19850009489167432719113321323

198600030407611153271374211365

198700014122735974261153211390

198800010711446632351043220378

19890003511301233113721100363

1990000721651357917531100335

1991000114838689536721100308

19920001638653844461421000265

199300029624250181720102000251

19940009505025228553100178

1995000151849472110222200169

199600082923514613621110181

199700033150274038841000203

1998000413627231302352110244

1999000334378561181372100260

2000000141268375334953100235

20010001751256627261542100234

2002000836652542141161100208

200300052953642322732000208

2004000234585842151241100227

20050006964583724851100213

2006000321186745231232000196

2007

2008

Total yield and the yield of 5 year olds5 year old fish: 65-75 cm longInterannual changes in catch of 5 year olds much greater than changes in total landings

Age disaggregated yield 1982-2006 in ktThe reason for high interannual variability in catches of 5 year old can be found if one follows catches by cohorts (year classes). Here the catch of the 1984 cohort is highlighted.

Sheet1

Age -->

Year01234567891011121314Total

195500043310010249301615518111710545

1956000728689167242115115141720487

195700015364479807326161057514455

19580003156454980948017187339517

1959000207370353254865589215459

1960000164982664740448328727470

19610001736536544442823511016377

19620001346495769285919142544389

19630002347524380532150149143409

196400023504947431164014257516437

1965000224564485041791310518387

196600021515258345218484546353

1967000295165464920431218102336

196800014756064794212216812382

196900012431136663871143100403

19700001068589674699152211475

1971000145610563855633272110444

19720009436874485564249100395

197300038366861622331398200369

19740001610653554741122014310368

197500032521234552251668411365

197600032715610029361162210346

1977000382934975191441000340

1978000830129705028942101330

197900010563613878301232100366

19800006538957142551873200432

198100022289775715437167311465

19820003325588604177174110380

19830004175557714614226311298

1984000954505535432056311282

19850009489167432719113321323

198600030407611153271374211365

198700014122735974261153211390

198800010711446632351043220378

19890003511301233113721100363

1990000721651357917531100335

1991000114838689536721100308

19920001638653844461421000265

199300029624250181720102000251

19940009505025228553100178

1995000151849472110222200169

199600082923514613621110181

199700033150274038841000203

1998000413627231302352110244

1999000334378561181372100260

2000000141268375334953100235

20010001751256627261542100234

2002000836652542141161100208

200300052953642322732000208

2004000234585842151241100227

20050006964583724851100213

2006000321186745231232000196

2007

2008

The yield of the 1984 year classyc 1984: Total yield: 510 kt

Age disaggregated yield 1982-2006 in kt

Here the yield of the 1984 and 1985 cohort are highlighted.Note that for any particular age group the yield of the 1984 is always higher than in the adjacent 1985 cohort

Sheet1

Age -->

Year01234567891011121314Total

195500043310010249301615518111710545

1956000728689167242115115141720487

195700015364479807326161057514455

19580003156454980948017187339517

1959000207370353254865589215459

1960000164982664740448328727470

19610001736536544442823511016377

19620001346495769285919142544389

19630002347524380532150149143409

196400023504947431164014257516437

1965000224564485041791310518387

196600021515258345218484546353

1967000295165464920431218102336

196800014756064794212216812382

196900012431136663871143100403

19700001068589674699152211475

1971000145610563855633272110444

19720009436874485564249100395

197300038366861622331398200369

19740001610653554741122014310368

197500032521234552251668411365

197600032715610029361162210346

1977000382934975191441000340

1978000830129705028942101330

197900010563613878301232100366

19800006538957142551873200432

198100022289775715437167311465

19820003325588604177174110380

19830004175557714614226311298

1984000954505535432056311282

19850009489167432719113321323

198600030407611153271374211365

198700014122735974261153211390

198800010711446632351043220378

19890003511301233113721100363

1990000721651357917531100335

1991000114838689536721100308

19920001638653844461421000265

199300029624250181720102000251

19940009505025228553100178

1995000151849472110222200169

199600082923514613621110181

199700033150274038841000203

1998000413627231302352110244

1999000334378561181372100260

2000000141268375334953100235

20010001751256627261542100234

2002000836652542141161100208

200300052953642322732000208

2004000234585842151241100227

20050006964583724851100213

2006000321186745231232000196

2007

2008

The yield of the 1985 year classyc 1985: Total yield: 260kt

Yield of 1984 and 1985 year classesyc 1985: Total yield: 260ktyc 1984: Total yield: 510 kt

The yield of the 1996 year classTotal yield: 115 ktThe yield from this year class is at an all time historical low.The sum of the yield from 3 to 10 year old is less than the yield of the 5 year olds from the 1984 year class landed in 1989!

The yield of the 1997 year classTotal yield: 280 kt

The yield of all year classes

Sheet1

Age -->

YclassYieldYear01234567891011121314Total

1955432195500043310010249301615518111710545

19565301956000728689167242115115141720487

1957266195700015364479807326161057514455

195833419580003156454980948017187339517

19592311959000207370353254865589215459

19603051960000164982664740448328727470

196146119610001736536544442823511016377

196240419620001346495769285919142544389

196345019630002347524380532150149143409

1964515196400023504947431164014257516437

19652701965000224564485041791310518387

1966388196600021515258345218484546353

19672861967000295165464920431218102336

1968291196800014756064794212216812382

1969211196900012431136663871143100403

197049819700001068589674699152211475

19712961971000145610563855633272110444

197246419720009436874485564249100395

1973787197300038366861622331398200369

197425019740001610653554741122014310368

1975373197500032521234552251668411365

1976385197600032715610029361162210346

19772251977000382934975191441000340

19782331978000830129705028942101330

1979231197900010563613878301232100366

198038219800006538957142551873200432

1981246198100022289775715437167311465

198224719820003325588604177174110380

198356319830004175557714614226311298

19845191984000954505535432056311282

198526319850009489167432719113321323

1986132198600030407611153271374211365

1987217198700014122735974261153211390

1988167198800010711446632351043220378

198929619890003511301233113721100363

19902691990000721651357917531100335

19911401991000114838689536721100308

199228419920001638653844461421000265

1993281199300029624250181720102000251

199414319940009505025228553100178

19952551995000151849472110222200169

1996113199600082923514613621110181

1997272199700033150274038841000203

19982231998000413627231302352110244

19992721999000334378561181372100260

20001702000000141268375334953100235

20012920010001751256627261542100234

2002272002000836652542141161100208

20033200300052953642322732000208

200402004000234585842151241100227

2005020050006964583724851100213

200602006000321186745231232000196

20072007

20082008

Yield by yearclassesYear class yield is very variable.In recent years (1980 onwards) the largest difference is fivefoldNote: final yield of the most recent year classes is not known until it has passed through the fisheries

The yield of the 2001 yearclass

Yield by year classes what is ahead?

Sheet1

Age -->

YclassYieldYear01234567891011121314Total

1955432195500043310010249301615518111710545

19565301956000728689167242115115141720487

1957266195700015364479807326161057514455

195833419580003156454980948017187339517

19592311959000207370353254865589215459

19603051960000164982664740448328727470

196146119610001736536544442823511016377

196240419620001346495769285919142544389

196345019630002347524380532150149143409

1964515196400023504947431164014257516437

19652701965000224564485041791310518387

1966388196600021515258345218484546353

19672861967000295165464920431218102336

1968291196800014756064794212216812382

1969211196900012431136663871143100403

197049819700001068589674699152211475

19712961971000145610563855633272110444

197246419720009436874485564249100395

1973787197300038366861622331398200369

197425019740001610653554741122014310368

1975373197500032521234552251668411365

1976385197600032715610029361162210346

19772251977000382934975191441000340

19782331978000830129705028942101330

1979231197900010563613878301232100366

198038219800006538957142551873200432

1981246198100022289775715437167311465

198224719820003325588604177174110380

198356319830004175557714614226311298

19845191984000954505535432056311282

198526319850009489167432719113321323

1986132198600030407611153271374211365

1987217198700014122735974261153211390

1988167198800010711446632351043220378

198929619890003511301233113721100363

19902691990000721651357917531100335

19911401991000114838689536721100308

199228419920001638653844461421000265

1993281199300029624250181720102000251

199414319940009505025228553100178

19952551995000151849472110222200169

1996113199600082923514613621110181

1997272199700033150274038841000203

19982231998000413627231302352110244

19991981999000334378561181372100260

20001702000000141268375334953100235

20012920010001751256627261542100234

2002272002000836652542141161100208

20033200300052953642322732000208

200402004000234585842151241100227

2005020050006964583724851100213

200602006000321186745231232000196

20072007

20082008

The information in the commercial catches when agedThe inter-year-class yield can be highly variableThe difference fivefold in recent yearsThe pattern of the catch history among year classes is similarThe yield increase from age 3 to age 5-6 and then declinesThis development is independent of the actual amountThe decline in the catches of older age groups is a proxy for mortalityIndication about likely yield in each year class become apparent right at age 3 and 4If a lot of fish are cought as 3 and 4 year olds, one can expect that future yield from that year class will be high. And vice versa.The pattern observed and the amount give basis for making short term prediction on future catches based on catches alone.

But what about predicting catches of year classes that have yet not appeared in the fisheries?

Scientific surveys: The Icelandic spring bottom trawl survey550 stations taken per yearStandardized approach5000 cod aged and weighted150 thousand cod length measured

iCod: Biomass and abundance indicesTotal biomassBiomass of >55 cmBiomass of >90 cmAbundance < 55 cm

Survey stations and cod catces

Cod: Distribution and abundance of age 115 cm long

Cod: Distribution and abundance of age 225 cm long

Cod: Distribution and abundance of age 340 cm long

Distribution and abundance of selected year classesAge 1 15 cmAge 2 25 cmAge 3 40 cmYearclass 84Yearclass 96Yearclass 97Yearclass 85

iCod: Age based survey indices

Sheet1

Age -->

Year01234567891011121314

195500043310010249301615518111710

1956000728689167242115115141720

195700015364479807326161057514

19580003156454980948017187339

1959000207370353254865589215

1960000164982664740448328727

19610001736536544442823511016

19620001346495769285919142544

19630002347524380532150149143

196400023504947431164014257516

1965000224564485041791310518

196600021515258345218484546

1967000295165464920431218102

196800014756064794212216812

196900012431136663871143100

19700001068589674699152211

1971000145610563855633272110

19720009436874485564249100

197300038366861622331398200

19740001610653554741122014310

197500032521234552251668411

197600032715610029361162210

1977000382934975191441000

1978000830129705028942101

197900010563613878301232100

19800006538957142551873200

198100022289775715437167311

19824110

19836311

19846311

198501711135486423155323321

1986015619622212672114211

19870429103822112123103211

19880377210267866103220

198904162278683441101100

1990061226142732142101100

1991041618301518214101100

19920117331916765101000

19930453136131022102000

19940141592722641003100

19950129259241842002200

199604543291315144101110

19970122145629997101000

19980863016622875312110

199907337421324112112100

20000192855730884103100

200101222373851532102100

20020138414036781101100

200301144639321945102000

200407258623525143301100

2005031539104323116111100

200609723381128104102000

2007061892128910521

2008

Sheet1

Age -->

Year012345678910Samtals121314

195500043310010249301615518111710

1956000728689167242115115141720

195700015364479807326161057514

19580003156454980948017187339

1959000207370353254865589215

1960000164982664740448328727

19610001736536544442823511016

19620001346495769285919142544

19630002347524380532150149143

196400023504947431164014257516

1965000224564485041791310518

196600021515258345218484546

1967000295165464920431218102

196800014756064794212216812

196900012431136663871143100

19700001068589674699152211

1971000145610563855633272110

19720009436874485564249100

197300038366861622331398200

19740001610653554741122014310

197500032521234552251668411

197600032715610029361162210

1977000382934975191441000

1978000830129705028942101

197900010563613878301232100

19800006538957142551873200

198100022289775715437167311

19824110

19836311

198406311

198501711135486423155323321

1986015619622212672114211

19870429103822112123103211

19880377210267866103220

198904162278683441101100

1990061226142732142101100

1991041618301518214101100

19920117331916765101000

19930453136131022102000

19940141592722641003100

19950129259241842002200

199604543291315144101110

19970122145629997101000

19980863016622875312110

199907337421324112112100

20000192855730884103100

200101222373851532102100

20020138414036781101100

200301144639321945102000

200407258623525143301100

2005031539104323116111100

200609723381128104102000

2007061892128910521

2008

Indices by year classes what is ahead?

Sheet1

Age -->

rg.AfliYear01234567891011121314

1955432195500043310010249301615518111710

19565301956000728689167242115115141720

1957266195700015364479807326161057514

195833419580003156454980948017187339

19592311959000207370353254865589215

19603051960000164982664740448328727

196146119610001736536544442823511016

196240419620001346495769285919142544

196345019630002347524380532150149143

1964515196400023504947431164014257516

19652701965000224564485041791310518

1966388196600021515258345218484546

19672861967000295165464920431218102

1968291196800014756064794212216812

1969211196900012431136663871143100

197049819700001068589674699152211

19712961971000145610563855633272110

197244719720009436874485564249100

1973687197300038366861622331398200

197418919740001610653554741122014310

1975237197500032521234552251668411

1976161197600032715610029361162210

1977381977000382934975191441000

1978231978000830129705028942101

197935197900010563613878301232100

198011219800006538957142551873200

198191198100022289775715437167311

198224719824110

198356319836311

198451919846311

1985263198501711135486423155323321

19861321986015619622212672114211

198721719870429103822112123103211

198816719880377210267866103220

1989296198904162278683441101100

19902691990061226142732142101100

19911401991041618301518214101100

199228419920117331916765101000

199328119930453136131022102000

199414319940141592722641003100

199525519950129259241842002200

1996113199604543291315144101110

199727219970122145629997101000

199822319980863016622875312110

1999198199907337421324112112100

200017020000192855730884103100

200129200101222373851532102100

20022720020138414036781101100

20033200301144639321945102000

20040200407258623525143301100

200502005031539104323116111100

20060200609723381128104102000

20072007061892128910521

20082008

The information in the surveys when agedThe inter-year-class abundance is highly variableThe pattern of the catch history among year classes is similarThe abundance increases from age 1 to age 3-4 and then declinesThis development is independent of the actual amountThe decline in the catches of older age groups is a proxy for mortalityIndication about size of the year classes become apparent right at age 1 and 2I.e. year class strength is determined at a relatively young ageScientific measurements of year class strength are obtained before the commercial fisheries know what is aheadThe pattern observed and the amount give basis for making short term prediction on future stock development, independent of the commercial catches.

But what about the link between the catches and the survey?

Development and magnitudes in the survey and the fisheriesYearclass 1984Yearclass 1985IndicesLandings (kt)SurveyFisheriesSurveyFisheries

Development and magnitudes in the survey and the fisheriesYearclass 1996Yearclass 1997IndicesLandings (kt)SurveyFisheriesSurveyFisheries

Survey indices and catchesAge 1Survey indicesyc 84yc 96

Year class yield and indices of 3 year olds

Sheet1

Age -->

YclassYieldYear012345678910Samtals121314

195500043310010249301615518111710

1956000728689167242115115141720

195700015364479807326161057514

19580003156454980948017187339

1959000207370353254865589215

1960000164982664740448328727

19610001736536544442823511016

19620001346495769285919142544

19630002347524380532150149143

196400023504947431164014257516

1965000224564485041791310518

196600021515258345218484546

1967000295165464920431218102

196800014756064794212216812

196900012431136663871143100

19700001068589674699152211

1971000145610563855633272110

19720009436874485564249100

197300038366861622331398200

19740001610653554741122014310

197500032521234552251668411

197600032715610029361162210

1977000382934975191441000

1978000830129705028942101

197900010563613878301232100

19800006538957142551873200

198100022289775715437167311

198224719824110

198356319836311

1984519198406311

1985263198501711135486423155323321

19861321986015619622212672114211

198721719870429103822112123103211

198816719880377210267866103220

1989296198904162278683441101100

19902691990061226142732142101100

19911401991041618301518214101100

199228419920117331916765101000

199328119930453136131022102000

199414319940141592722641003100

199525519950129259241842002200

1996113199604543291315144101110

199727219970122145629997101000

199822319980863016622875312110

1999198199907337421324112112100

200017020000192855730884103100

200129200101222373851532102100

20022720020138414036781101100

20033200301144639321945102000

20040200407258623525143301100

200502005031539104323116111100

20060200609723381128104102000

2007061892128910521

2008

Survey indices at age 3 and consecutive year class yieldSurvey indices at age 3 Year class yield (kt)

Analytical stock assessmentThe assessment if iCod is based on two independent sets of measurements:Age disaggregated information of the commercial catchesAge based survey indices from scientific surveys

There is a relatively good consistency among the two sets of measurements

Predicting the development in the short term can be done almost visually.

A formal analytical model should be just a summary of the observations, where model assumption should have minimum influence.For the iCod, the assessment results are mostly data driven.In many cases, where data may be poorer, the results may be largely assumption driven.

Length distribution of S. marinus catches

Age distribution of S. marinus catches

S. marinus long lived, slow growing

north-east arctic saithe assessment performance

FIN

Einar HjrleifssonEinar HjrleifssonMefylgjandi mynd snir heilarafla orsks eftir almanaksrum runum 1955-2006. Upplsingagildi rsafla einu og sr er mjg takmarkaar. Ein af grunnstoum fiskifrinnar er a skoa samsetningu aflans og fyrst og fremst samsetningu eftir aldri.Einar HjrleifssonEinar HjrleifssonEinar Hjrleifssonessi myndi snir stasetningu sna r afla sem teknar voru einu ri (2005). Afli r mismunandi veiarfrum er tknaur me mismunandi lit. rlega eru teknar um 500000 orskar lengdarmldir og um 20000 af eim eru greindir til aldurs me v a lesa rhringi kvrnum. Me v a taka tillit til afla eftir veiarfrum og rstma m nota essar mlingar til ess a meta hlutfallslegan fjlda og hlutfallslegt magn sem veitt er af hverjum aldursflokki hverju ri. myndinni er snt hlutfallslegt magn sem veitt var r hverjum aldurflokki ri 2006. Ef a heildaraflinn er ekktur er auvelt a umreikna essa hlutfallstlu eiginlegt magn sem a veitt er r hverjum aldursflokki (sj nstu glru).Einar Hjrleifsson essari tflu hefur heildaraflanum (dlkur lengst til hgri) veri skipt upp afla eftir aldri fisksins og er skipting bygg snatku r afla (sj fyrri glru). annig m sj a 196 sund tonna heildarafla rinu 2006 (lrtti raui kassinn) samanst 3 sund tonna afla 3ja ra fisks, 21 sund tonna afla 4ja ra fisks, 18 sund tonna afla 5 ra fisks, o.s.fr. Athugi a afli fisks eldri en 10 ra er ekki sndur tflunni ( er hann reiknaur) enda verulegur sustu rum.Eins og sj m samanstendur aflinn hverju ri r nokku mrgum aldursflokkum. En ur en a vi skoum a nnar skulum vi fyrst skoa rsafla kveins aldurshp og er hr teki dmi af afla 5 ra fiski(lrtti raui kassin) og til a gera hlutina einfaldari skulum vi skoa a myndrnt (sj nstu glru).Einar HjrleifssonHr tkna gru slurnar heildarrsaflann og hringirnir tkna afla 5 ra fisks.Breytingar heildarafla er flestum tilfellum ekki mjg miklar milli einstakra ra. Hinsvegar geta breytingar afla einstakra aldursflokka milli ra veri umtalver. Sem dmi m taka a heildaraflinn runum 1989 og 1990 fer r 360 sund tonnum niur um 330 sund tonn. Hinsvegar fellur aflinn 5 ra fiski um meira en helming essum tveimur rum, r 130 kt ri 1989 65 kt ri eftir (1990). Anna dmi um essar breytingar afla 5 ra fiska milli ra m t.d. sj runum 2001 til 2002, .e. r 25 kt ri 2001 65 kt ri 2002. Heilaraflinn lkkar hinsvegar essum tveimur rum, r um 230 kt ri 2001 rm 200 kt ri 2002.essar breytingar afla 5 ra fisks milli aliggjandi ra geta ekki stafa af takmrkun heildarafla enda er kvtinn sem betur fer ekki gefinn einstakann aldursflokk Breytingar mealyngd (ekki snt hr) geta ri hr einhverju en r eru hinsvegar ekki randi ttur essum sveiflum milli einstakra ra. Til ess a leita skringa arf a horfa til aflarunar eftir einstkum rgngum. En ur en a vi skoum aflarun eftir rgngum nnar (nsta glra) vil g bija menn a geyma bak vi eyra a afli 5 ra fisks ri 2006 er i sgulegu lgmarki, ea rtt um 18 kt.Einar HjrleifssonBreytileikinn afla 5 ra fisks skrist me v a skoa afla eftir rgngum. Hr skulum vi fyrst skoa afli rgangsins fr 1984. Fyrst er a taka a fram a engar teljandi veiar eru orski fyrr en a hann hefur n 3ja ra aldri. annig verum vi ekki vr vi 1984 rganginn veium a neinu marki fyrr en ri 1987, en voru veidd 14 sund tonn r essum rgangi. ri eftir egar essi rgangur hefur n 4ja ra aldri voru veidd 71 sund tonn og svo vi 5 ra aldur ri 1989 ni aflinn 130 sundum tonna. Hmarkinu er n vi 6 ra aldur ri eftir (130 sund tonn). Vi 7 ra aldur er aflinn hins vegar 45 sund tonnum minni. Nstu rj rin fellur aflinn fram og n um meira en helming milli ri og er vi 10 ra aldur einungis 5 sund tonn. Eitthva er svo veitt af essum rgangi eftir a en a er verulegt og v ekki snt hr. En skoum aeins nnar ennan afla r rgangi 1984 og gerum a myndrnt (nsta glra).Einar Hjrleifssonfram eru tkna gru slurnar heildarafla rsins, grleitu hringirnir tkna afla 5 ra fisks hverju ri (sem a vi vorum bin a skoa hr undan) og blu hringirnir tkna aflann r 1984 rganginum. Tlurnar hringjunum tkna aldur fisksins.Eins fram hefur komi fyrri glru var afli 5 ra fiski ri 1989 um 130 sund tonn og a hann hafi komi undan klaki rsins 1984. Mefyljandi mynd snir aflann r essum rgangi fr nll til 14 ra aldurs. run aflabrgum rgangsins m lsa me v a fram a riggja ra aldri er aflinn v sem nst nll. Fr riggja ra aldri fram til 5-6 ra aldurs eykst aflinn, en eftir a fellur aflinn mjg hratt me aldri og eftir 10 ra aldur er aflinn r rganginum vart mlanlegur. sta ess a aflinn eykst fr 3ja ra til 5-6 ra aldurs er a essu aldursbili er fiskurinn a koma inn veiina og einnig eru einstaklingarnir a auka verulega vi yngd sna hverju ri. Falli eftir 6 ra aldurs m rekja til ess a er vxtur ekki lengur eins hraur og svo fer eli mlsins samkvmt fjldinn r rganginum stugt fkkandi. Falli aflanum eftir a hmarkinu er n er v nokkurskonar gildi ess hve hratt fiskar rganginum tna tlunni. fskifrinni er etta fall vanalega meti t fr fjlda fiska afla og er tala um a fkkun fiska afla s gildi heildardaua en hr skulum vi fram til einfldunar halda okkur vi yngd fisks afla.Eins og fram kemur myndinni var rgangurinn fr 1984 hluti af rsaflanum runum 1987 til 1994 og var vgi hans heildarveiinni mestur 5 og 6 ra. Me v a leggja saman aflann r einstkum aldurshpum er hgt a reikna heildaraflann sem a tekinn var r hverjum rgangi. Aflinn r 1984 rganginum nam tpum um 510 sundum tonna. Ef a aflarun allir aliggjandi rgangar, bi og eldri og yngri, hefu veri me sama htti a magni til hefi rsaflinn essum rum a llu jfnu tt a vera um 510 sund tonn. En af hverju var s ekki raunin (sj nstu glru)?Einar HjrleifssonEins og fram hefur komi fll afli 5 ra fisks r 130 sund tonnum ri 1989 65 sund tonn ri 1990. Fyrrgreindi aflinn kom r 1984 rganginum, s sargreindi r rgangi sem kom r klakinu ri eftir, ea r 1985 rganginum. tflunni hr a ofan er aflinn r 1985 rganginum sndur me rauum tlum. Eins og 1984 rgangurinn kemur 1985 rgangurinn fyrst fram veii einhverju magni sem 3ja ra fiskur. Aflinn r rganginum eykst me aldri og nr hmarki vi 5-6 ra aldur. Efir a fellur aflinn mjg hratt og er orinn nsta ltill vi 10 ra aldur. Eftirtektarvert er hinsvegar a aflinn r 1985 rganginum er a alltaf lgri en aflinn r rganginum 1984. Og a rtt fyrir a essir tveir rgangar voru meira og minna a ganga gegnum veiina sama tma. Lkkun afla 5 ra fisks milli ranna 1989 og 1990 sr v skringar v a aflinn r essum aldursflokki kemur r tveimur rgngum sem a greinilega eru mjg mismunandi a str.En skoum run afla 1985 rgangsins eftir aldri aeins betur me myndrnum htti (sj nstu mynd).Einar HjrleifssonEins og ur sna gru slurnar heildarafla rsins, grleitu hringirnir tkna afla 5 ra fisks hverju ri (sem a vi vorum bin a skoa hr undan) og rauu hringirnir tkna aflann r 1984 rganginum. Tlurnar hringjunum tkna aldur fisksins.Mefyljandi mynd snir run afla ess rgangs eftir aldurshpum. Hr kemur berlega fram a nokku svipu run er afla eftir aldri og vi sum me 1984 rganginn. annig eykst aflinn fr 3ja ra aldri fram til 5 ra aldurs, en fellur san hratt eftir a. Heildarafli rgangsins er hinsvegar um helmingi minni en r 1984 rganginum. Vi skulum skoa etta nnar myndrnt nstu mynd.Einar HjrleifssonSamanburur veii r 1984 og 1985 rganginum. Nnari skringar sj fyrri glrur.Einar HjrleifssonFrum aeins nr tma og skoum aflann r 1996 rganginum. Enn og aftur m sj svipaan run aflanum, aukningu fr 3 til 5-6 ra aldurs en san fellur aflinn eftir a. Samanlagur afli r essum rgangi var hinsvegar ekki nema 115 sund tonn og essi afli rgangs s lgsti sem a um er vita og einungis um tpur fimmtungur af afla 1984 rgangsins. Taki eftir a essi samanlagi afli fr 3ja til 10 ra r 1996 rganginum er minna en veitt var r rgangi 1984 vi 5 ra aldur ri 1989! Taki einnig eftir a vsbendingar um ennan llega afla koma strax fram llegum aflabrgum 3ja og 4ja ra fisks.Sem betur fer voru nstu rgangar eftir 1996 rganginn ekki af sama flokki. Eins og fram var komi upphafi erindisins, egar vi skouum afla 5 ra fisks eftir rum jkst aflinn essum aldurshpi r 25 sund tonnum ri 2001 (1996 rgangurinn) 65 sund tonn ri 2002 (1997 rgangurinn). Og a rtt fyrir a heilaraflinn hafi falli milli essara tveggja almanaksra. g vonast til a horfendur s fari a renna grun um hvers vegna essu standi. Skoum v aflarun 1997 rganginum (nsta mynd).Einar HjrleifssonSemsagt, eftir llegasta rgang slandssgunnar, rgangi 1996, kemur rgangur fr 1997. run afla rgangsins eru r smu og ur. Taki eftir a magn 3ja og 4ja ra fisks afla eru strax mun hrri en fram kom afla r smu aldursflokkum 1996 rgangsins. Heildaraflinn r rgangi 1997 verur endanum meira en tvfallt hrri en aflinn r 1996 rganginum, ea samtals um 280 sund tonn. ekki veri hr fari nnar a a skoa afla r rgngum sem eftir koma, vil g bija horfendur a hugsa um hver lklegur afli og rgangastyrkur rganganna fr 1998-2000 s/geti ori, svona ljsi ess a essi rgangar gfu af sr svipaan afla sem 5 ra fiskur og umrddur 1997 rgangur.Einar Hjrleifssonur en a vi snum okkur a ru skulum vi gera upp afla allra rganga sem a hafa a mestu gengi gegnum veiina. tflunni er kemur fram afli rganganna (dlkur lengst til vinstri) og eru eir sem vi hfum til essa veri a skoa srstaklega tknair me litum. Eins og fram hefur komi er afli rgangs fengin me v a leggja saman aflan r einstkum aldursflokkum tflunni summum vi v einfaldlega tlurnar hverri sklnu. Skoum etta myndrnt (nsta mynd)Einar HjrleifssonHr kemur fram a heildarafli aliggjandi rganga getur veri nokku jafn en er hinsvegar mrgum tilfellum mjg mismikill. Eftirtektarvert sj a eftir tvo milungsrganga fr 1981 og 1982 koma tveir risargangar fr 1983 og 1984. Eftir a skiptast milungs rgangar (1985, 1989, 1990, 1992, 1993, 1995 og 1997) og llegir rgangar (1986, 1988, 1991, 1994, 1996). ekki veri ger grein fyrir v hr srstaklega eru rgangarnir fjrir fr 1997 til 2000 allir taldir milungsrgangar, eir tveir sustu reyndar enn tluverur hluti af heildaraflanum r. En hva er hinsvegar vndum (sj nstu mynd).Einar HjrleifssonMia vi sgulega reynslu, hva er lklegt a rgangurinn fr 2001 gefi af sr??Einar Hjrleifssona sem gert hefur veri glrunum hr undan er ekkert anna en a fylgja eftir run afla eftir einstkum aldurflokkum.Fram hefur komi a aflinn r einstkum aliggjandi rgngum getur veri mjg breytilegur.Fram hefur komi a vsibendingar um vntanlegt aflamagn r hverjum rgangi koma fram afla strax 3ja og 4ja aldursflokki.Fram hefur komi a eftir a kvenum aldri er n (5-6 ra tmabilinu sem a er til athugunar) fellur aflinn alla jafna. Ef a meiri tmi hefi gefist til hefi veri hgt a skra t a hr sum vi kominn me mlikvara heildardaua, eftir v sem a aflinn rgangi fellur hraar me aldri, v hrri er heildardauinn. ljsi ess mynsturs sem a vi hfum s eru vi einnig kominn me grunn a v a gera sp um vntanlegan afla hverjum rgangi sem a vi hfum egar fengi einhverjar upplsingar um. Sem dmi m nefna a aflinn r 2000 rganginum hefur veri nokku gur fram til rsins 2006, orinn sex ra. ljsi essa er ekki varlegt a tla a aflinn r essum rgangi ri 2007 og 2008 haldist fram hlutfallslega gur. A magni til m hinsvegar bast vi, mia vi fyrri reynslu um aflarun rgangs a aflinn r 7 ra (ri 2007) og 8 ra aldurflokkinum (ri 2008) veri mun minni en a sem veiddist r honum 6 ra (ri 2006). a sama vi um eldri rganga sem a enn eru veium. Aflinn r rgangi 2001 hefur hinsvegar veri mjg llegur, bi sem 3ja, 4ja og 5 ra fiskur aflasagan minnir um margt llega rganginn fr 1996.. a er engin sta til a tla anna en a hann haldist fram slakur nstu rum. En hr kynni einhver a spyrja eirra elilegu spurningar hvaa hrif umtalver takmrkun heildarafla hefur essa mynd. .e.a.s. ef a heildarafli er takmarkaur, eins og veri hefur undangengin einn og hlfan ratug leiir a til ess a aflatlur endurspegli ekki lengur str rganganna. Til ess a komast a v hvort a s er raunin er elilegt a kynna til leiks Ralli.Einar Hjrleifssona sem gert hefur veri glrunum hr undan er ekkert anna en a fylgja eftir run afla eftir einstkum aldurflokkum.Fram hefur komi a aflinn r einstkum rgngum getur veri mjg breytilegur.Fram hefur komi a vsibendingar um vntanlegt aflamagn r hverjum rgangi koma fram afla strax 3ja og 4ja aldursflokki.Fram hefur komi a eftir a kvenum aldri er n (5-6 ra tmabilinu sem a er til athugunar) fellur aflinn alla jafna. Ef a meiri tmi hefi gefist til hefi veri hgt a skra t a hr sum vi kominn me mlikvara heildardaua, eftir v sem a aflinn rgangi fellur hraar me aldri, v hrri er heildardauinn. ljsi ess mynsturs sem a vi hfum s eru vi einnig kominn me grunn a v a gera sp um vntanlegan afla hverjum rgangi sem a vi hfum egar fengi einhverjar upplsingar um. Sem dmi m nefna a aflinn r 2000 rganginum hefur veri nokku gur fram til rsins 2006. ljsi essa er ekki varlegt a tla a aflinn r essum rgangi ri 2007 og 2008 haldist fram hlutfallslega gur. Aflinn r rgangi 2001 hefur hinsvegar veri mjg llegur, bi sem 3ja, 4ja og 5 ra fiskur aflasagan minnir um margt llega rganginn fr 1996.. a er engin sta til a tla anna en a hann haldist fram slakur nstu rum. En hr kynni einhver a spyrja eirra elilegu spurningar hvaa hrif umtalver takmrkun heildarafla hefur essa mynd. .e.a.s. ef a heildarafli er takmarkaur, eins og veri hefur undangengin einn og hlfan ratug leiir a til ess a aflatlur endurspegli ekki lengur str rganganna. Til ess a komast a v hvort a s er raunin er elilegt a kynna til leiks Ralli.

Einar HjrleifssonEinar HjrleifssonEinar Hjrleifssonur en a vi gngum lengra skulum vi samt skoa aeins rallstvarnar samhengi vi dreifingu heildarafla orsks. essum myndum eru rallstvarnar sndar sem bltt strik og rauu litirnir sna orskaflann sem tonn fermlu skv. afladagbkum runum 1991, 1995, 2000 og 2006. Eftir v sem a raui liturinn er dekkri, eim mun meira magn var teki per fermlu. megindrttum m segja a ltil breyting hafi ori hvar v hvar orskurinn er tekinn essu tma. Og megindrttum virist stvarneti vera a tt a a dekki ll helstu veiisvi orsk svo a finna megin einstk svi ar sem einhver afli er sem a ekki er dekkaur vel rallinu. En a er einnig athyglisvert a a svi ar sem eru tluverur fjldi togstva en a alla jafna engin orskveii. Hvernig m a vera? J a stafar m.a. af v a markmii me rallinu er ekki einungis a mla veianlegan fisks heldur einnig ungan sman fisk, fisk sem enn er ekki kominn fram veii. Skoum etta nnar og byrjum a skoa dreifingu 1 rs fisk rallinu (nsta mynd).Einar HjrleifssonMyndin snir magn af 1 rs fiski einstkum stvum ralli eftir rum, nema hva rgangar 1984, 1985, 1996 og 1997 eru merktir srstaklega sem slkir. Eftir v sem a blu hringirnir eru strri eim mun meiri fiskur fannst stoinni. 1 rs fiskur er um 10 cm langur og v kemur hann ekki fram afla. myndinni kemur fram a fjldinn getur veri mjg breytilegur milli einstakra aldurshpa. annig er miki magn af 1 rs fiski ri 1985 (1984 rgangurinn) og 1986 (1985 rgangurinn). ri 1987 er magn 1 rs fisk (1986 rgangurinn) hinsvegar mun minna. essu samhengi vil g bija menn um a minnast hver var aflareynslan r essum rgngum, skv. glrunum hr undan.Ef a vi skoum sveiflurnar nr tma m er virist vera eitthva til af 1 rs fiski ri 1996 (1995 rgangurinn). ri 1997 er hinsvegar 1 rs fiskur vart mlanlegur, fyrsta vsbendingin um hinn hrmulega 1996 rgang er hr strax komin. ri 1998 er svo aftur tluvert af 1 rs fiski, fyrstu vsbendingar um a rgangurinn fr 1997 gti veri smilegur. essari mynd og eim nstu munum vi fyrst og fremst beina sjnum okkar a rgngum 1984, 1985, 1996 og 1997, rgngunum sem a vi fylgdum eftir egar vi vorum a lsa run afla og heildarmagni afla raganga. Skoum nst magn tveggja ra fisks rallinu.Einar HjrleifssonHr er snd tbreisla og magn af 2ja ra orski rallinu. essi fiskur er a jafnai um 20 cm langur. Svipa mynstur kemur upp og var um eins rs fisk, miklar breytingar geta tt sr magni milli aliggjandi ra. Mlingar eim rgngum sem a vi erum a fylgja eftir eru n nttrulega mldir einu ri sar en egar eir voru mldir sem 1 rs.Vi sjum a magn 2ja ra fisks ri 1986 (rgangur 1984) er htt og er a samrmi vi magni sem a vi sum af 1 rs fiski rallinu ri ur. Me sama htti er mlist lti af 2ja ri fiski ri 1998 (1996 rgangurinn) og svo er okkalegt magn af fiski ri 1999 og er 1997 rgangurinn hr aftur fer.Einar HjrleifssonHr er snd vsitala riggja ra fisks, fiskur sem a er um 30 cm langur. Mynstri er svipa og ur, rgangar sem a mldur strir, milungs og smri bi sem 1 og 2 ra mlast fram me svipuum htti. Hr er fiskur binn a n eirri str a hans fer a vera vart veii. Fyrir hvern rgang eru vi v rallinu bnir a mla magni risvar sinnum ur en a hann kemur fram veii. a sem meira er um vert virist vsbending um hva s vndum koma fram mjg snemma hverjum rgangi, ea strax 1st aldursrinu. Skoum etta nnar (nsta mynd).Einar HjrleifssonHr er magn og tbreisla rgngunum fjrum sem a vi hfum veri a fylgja eftir glrunum undan teknar saman eina mynd. Fram kemur a strax vi eins rs aldur erum vi komnir me vsbendingu um hva er vndum magni ralli vi 2ja og svo 3ja ra aldur. egar miki er mlt af eins rs fiski mlist miki magn af riggja ra fiski tveimur rum sar og fugt. a mtti v tla a rgangastyrkurinn rist mjg snemma lfskeii orsks. En sta ess a skoa etta myndrnt, skoum treikningana tlulegu formi (nsta mynd).Einar HjrleifssonHr eru sndar fjldavsitlur orsks ralli. Vsitalan endurspeglar magn fisks af kvenum aldurshpi ralli hvers rs, ar sem tlugildi a endurspegla dreifingu og magn fiska llum rallstvunum til samans. sinn einfldustu mynd m tkla essar vsitlur sem mlikvara fjldann veitt var rallinu af hverjum aldursflokki um sig hverju ri. Taflan er v annig s sambrileg og s sem a vi hfum egar skoa fyrir afla, nema a ar hldum vi okkur vi yngdareiningu en ekki fjldaeiningu. Rtt er a taka a fram a vsitalan er einungis sambrileg innan hvers aldurshps, ekki milli aldurshpa. stan er s a vegna strarmunar, a.m.k. yngri fiski er veianleikinn mjg mismunandi eftir aldri. Hr er vert a vekja athygli fernu: Fjldi fiska kvenum aldurflokki (t.d. 5 ra) getur veri mjg breytilegur milli einstakra ra, nokku sem a vi vorum egar bin a sj egar vi skouum aldursgreindan afla. Ef fylgt er eftir rgngum er greinilegt samband milli magn fiskjar yngri aldurhpum og ess sem a kemur fram ralli sar eldri aldurflokkum sama rgangs. H vsitala yngri fiski ir a llu jfnu a vsitalan eldir aldurshpum helst einnig h, og fugt. Hlutirnir eru nttrulega ekki 100% samrmi. annig m sj a vsitala 1999 rgangsins sem 1 rs fisk er sgulegu hmarki. Vi tveggja ra aldur er vsitalan r sama rgangi hinsvegar ekki nema rtt milungs. En slkt samrmi er undantekning megin mynstrinu sem a fram kemur. Ralli nr til yngri aldurflokka en eirra sem a eru afla. annig m nefna a ri 2007 hfum vi fengi fyrstu magnmlingu rgangi 2006 (1 rs fiskur 2007), 2 mlingar rgangi 2005 (1 rs rallinu 2006, 2ja ra rallinu 2007) og rjr mlingar 2004 rganginum (1 rs rallinu 2005, 2ja ra rallinu 2006, 3ja ra rallinu 2007). Ralli nr einnig til aldurflokka sem a eru veium.

En skoum einnig run afla rgangs rallinu (nsta mynd).

Einar Hjrleifssonur hefur komi fram a mynstri sem fram kemur ggnum um aldursgreindan afla egar fylgt er eftir rgngum megi nota til ess a sp fyrir um afla nsta og jafnvel arnsta rs. Me sama htti m nota mlingar vsitlum til a sp fyrir um framhaldi. Munurinn ggnunum felst fyrst og fremst v a rallinu erum vi me mlingar fiskinum strax vi eins rs aldurs (samanbori vi 3ja ra aldur afla) og vi erum einnig me mlingu sem nr einu ri nr tma (2007 ralli, 2006 r afla).ur en vi segjum skili vi essa tflu er vert a benda a rgangarnir fr 1997 til 2000 mlast allir mjg svipair af str og a a eru essir rgangar sem a hafa fyrst og fremst bori upp veiina undangegndum rum. ar sem allir esir rgangar eru n essu ri ornir 7 ra ea eldri m bast vi v a tillegg eirra heildaraflanum fara minnkandi. Vi taka v yngri rgangar, .m.t. rgangurinn fr 2001. egar hefur komi fram a veii r eim rgangi er mjg ltil, nokku sem a lg fyrir skv. mlingu r rallinu egar ri 2002. Annar slkur rgangur er einnig farvatninu skv. rallmlingu, rgangurinn fr 2004 en hans tti fyrst a fara a gta afla rinu 2007. rgangarnir tveir ar milli virast vera nokku skrri.

Einar HjrleifssonEinar HjrleifssonHr er myndrnt snd run veii rganga 1984 og 1985 rallinu og svo sjlf runin veii flotans. Fram kemur a runin er mjg svipu bum tilvikum nema hva a mlingar rallinu r hverjum rgangi eru alltaf tveimur fleir en r afla af eirri einfldu stu a fyrsta mlingin rallinu er vi 1 rs aldur, r aflanum vi 3ja ra aldur. Einnig kemur fram a sjlft magni rallinu endurspeglar svo sjlft magni sem a veitt er r rganginum. etta kemur einnig fram nstu mynd.Einar HjrleifssonEinar HjrleifssonHr er raun veri a skoa smu ggn me svolti annarri framsetningu. Tekin sem dmi rgangur 1984 og 1996. Fram kemur a rallvsitlur strax vi eins rs aldurs gefa vsbendingu um framhaldi, bi rallmlingum egar fiskurinn er orinn eldri sem og sjlfum aflanum framhaldinu. Vi skulum nstu tveimur glrum skoa samhengi milli rallvsitlu allra rganga sem a gengi hafa gegnum veiina og svo heildaraflann r hverjum rgangi (.e.a.s. summun af aflanum fr 3 ra aldri og upp r) skoum etta fyrst tfluformi Einar HjrleifssonDlkurinn lengst til vinstri snir summu afla hvers rgangs og hefur hann veri sndur ur essum fyrirlestri. Til vinstri eru aldursgreindar rallvsitlur. a sem vi tlum a gera er a plotta vsitlu 3ja ra fiski r hverjum rgangi x-s mti afla rgangsins y-s. Vert er a vekja athygli v a veiar rganginum sr sta nstu 7 rin eftir rallmlinguna.Einar Hjrleifsson x-s er vsitala 3ja ra fisks rallinu og y-s er aflinn r rganginum framhaldinu i tonnum tali. Tlurnar tkna rgang. Rauu deplarnir sna rganga sem a eru gengnir r veii. Fram kemur mjg sterkt lnulegt samband, .e. ef a vsitala 3ja ra fisks er h er afli rgangins hr og fugt. etta samband snir fyrsta lagi hve gott samrmi er raun milli rallmlinga og afla. ru lagi m tla mia vi fyrri reynslu a nota mtti etta samhengi til a sp fyrir um afla eirra rganga sem a ekki eru a fullu gengnir gegnum veiina.Svrtu hringirnir tkna rganga sem a mestu eru a ganga r veii enn enn eftir a veia nokku r. Aflatlurnar essum rngum eiga v enn eftir a hkka eitthva (srstaklega r 2000 rganginum) vsitalan x-snum breytist nttrulega ekki! rhyrningarnir sna rganga sem a eru ekki a fullu komnir veii og v aflinn (gildi y-snum) eftir a hkka umtalsvert. Samkvmt essu eru vsbendingar um a rgangarnir fr 2001 til 2004 su ekki mjg sterkir.Einar HjrleifssonHr a framan hafa mliggnin sem eru grunnvllur stofnmats orsks skou me nokku einflduum htti. Fram hefur komi a upplsingagildi gagnanna kemur fyrst og sast fram me v a fylgja eftir hverjum rgangi. Einnig hefur komi a miki samrmi er aflaggnum og rallggnum og a nota megi essi ggn ein og sr til a sp fram tmann um strargruna stofn- og aflarun. Meginlnurnar liggja v nokk fyrir sjlfum mliggnunum. Vissulega eru essi mliggn hinsvegar ekki fullkomin og n ekki utan um alla tti ra stofnrun orski. Einar HjrleifssonEinar Hjrleifsson