Size Based Indicators - a Helcom perspective rjan stman (SLU) with - - PowerPoint PPT Presentation

▶
size based indicators
SMART_READER_LITE
LIVE PREVIEW

Size Based Indicators - a Helcom perspective rjan stman (SLU) with - - PowerPoint PPT Presentation

Dec 24, 2023 179 likes •476 views

Size Based Indicators - a Helcom perspective rjan stman (SLU) with much help of Kristiina Hommik (EMI) & Szymon Smoliski (MIR) Size based indicators of coastal fish Easy to measure for all species Precision & Accuracy

slide-1
SLIDE 1

Size Based Indicators

  • a Helcom perspective

Örjan Östman (SLU) with much help of Kristiina Hommik (EMI) & Szymon Smoliński (MIR)

slide-2
SLIDE 2

Size based indicators of coastal fish

  • Easy to measure for all species
  • Precision & Accuracy
  • Sample sizes needed
  • Is it possible to identify ’regional’

assessment criteria?

  • Spatial consistency?
  • Temporal consistency?
  • Influence of season and gear?
  • (Relation to other reference points)
  • Size based indicators could increase

the spatial resolution of assessments for many species

slide-3
SLIDE 3

Sizer based indicators investigated

Mean and median length Length at 90% quantile (L90) Large Fish Index Size-spectra A minimum size threshold to remove influence of recruitment

0.000 0.025 0.050 0.075 10 20 30 40 50

LengthClass N/(sum(N))

Min size Mean Length (mL) Median length Length at 90% quantile (L90) Large Fish Index (% above threshold length) (LFI) Size spectrum (SS) (slope of log(N)~Length

slide-4
SLIDE 4

Data

  • Data on cod, flounder, perch, pikeperch, and whitefish from around

50 fishery independent surveys from Poland, Estonia, Finland, and Sweden

  • Commercial data of pikeperch from Estonia and Finland
  • Different gears, gillnets dominating but fykenets and trawl data as

well

  • Data over the whole ice-free season, summer dominates
slide-5
SLIDE 5

Pikeperch

  • We have data from:
  • Estonia (commercial + survey)
  • Sweden (survey)
  • Finland (commercial + survey)
  • Threshold values
  • MinSize = 25 cm
  • LFI = 40 cm
  • Q90

Precision generally good at a sample size of 300 individuals. Size-spectra poor accuracy, up to 500 individuals needed

slide-6
SLIDE 6

Estonia ( ) and Finland SD30 ( ), SD29( )

Spring

Estonia Finland

slide-7
SLIDE 7

Estonia ( ) and Finland SD30 ( ), SD29( )

Spring

slide-8
SLIDE 8

Estonia ( ) and Finland SD30 ( ), SD29( )

Autumn

slide-9
SLIDE 9

Estonia ( ) and Finland SD30 ( ), SD29( )

LFI L90

Spring

Estonia Finland

slide-10
SLIDE 10

Åland ( ), Sweden combined ( ), Kvädöfjärden ( ) and Galtfjärden ( )

mL median

*

slide-11
SLIDE 11

Åland ( ), Sweden combined ( ), Kvädöfjärden ( ) and Galtfjärden ( )

LFI L90

*

slide-12
SLIDE 12

mL median

Muskö no-take-zone and reference area,

years 2009-2016

slide-13
SLIDE 13

Muskö no-take-zone and reference area,

years 2009-2016

LFI L90

slide-14
SLIDE 14

Conclusions Pikeperch

  • Mean, median, L90, LFI good precision for 200-300 individuals
  • Differ between gears, commercial data related to fishing regulations
  • Regional differences, largest in Estonia – smallest around Ålands Sea
  • Decreased over time in many areas
  • A couple cm smaller in autumn than in spring
  • Not larger in a no-take area
slide-15
SLIDE 15
  • 0.3
  • 0.2
  • 0.1
50 100 150 200 300 400 500 1000 2000 4000

as.factor(Threshold) IndicatorValue

0.0 0.1 0.2 25 50 75 100 150 200 250 300 400 500 1000 2000 4000

as.factor(Threshold) IndicatorValue

21 23 25 27 25 50 75 100 150 200 250 300 400 500 1000 2000

as.factor(Threshold) IndicatorValue

18 19 20 25 50 75 100 150 200 250 300 400 500 1000 2000

as.factor(Threshold) IndicatorValue

Perch precision

mL L90 LFI SS mL, L90 & LFI good precision at 150 perch, for size spectra > 500 needed (not a major problem as sample size for perch is large).

  • We have data from:
  • Estonia (survey)
  • Sweden (survey)
  • Finland & Åland (survey)
  • Poland (survey)
  • Threshold values
  • MinSize = 15 cm
  • LFI = 25 cm
  • Q90
slide-16
SLIDE 16

18 19 20 21 22 23 Brunskär Finbo Kvädöfjärden Puck Vilsandi

WaterBody mL Period

2000-2010 2011-2016 22 24 26 28 Brunskär Finbo Kvädöfjärden Puck Vilsandi

WaterBody L90 Period

2000-2010 2011-2016

Perch

0.1 0.2 0.3 BrunskärFinbo Kvädöfjärden Puck Vilsandi

WaterBody LFI Period

2000-2010 2011-2016

  • 0.5
  • 0.4
  • 0.3
  • 0.2

BrunskärFinbo Kvädöfjärden Puck Vilsandi

WaterBody SS Period

2000-2010 2011-2016

Different indicators show similar patterns SS stands out a bit

slide-17
SLIDE 17

Perch

Most sites within L90 22-27 cm mL 18-22 cm Relative similar between sites

slide-18
SLIDE 18

Perch

  • 0.6
  • 0.5
  • 0.4
  • 0.3
  • 0.2
  • 0.1

0.1 0.2 0.3 0.4 Pärnu Vilsandi Brunskär Helsinki Tvärminne Puck Vistula Asköfjärden Forsmark Holmön Kinnbäcksfjärden Kvädöfjärden Lagnö Långvindsfjärden Norrbyn Råneå Torhamn Vinö Finbo Kumlinge Lumparn Estonia Finland Poland Sweden Åland 2000-2010 - Medel av LFI > 25 2000-2010 - Medel av SS 2011-2016 - Medel av LFI > 25 2011-2016 - Medel av SS

Most sites within LFI 5-30% Size spectra -0.1 -- -0.5

slide-19
SLIDE 19

Conclusions Perch

  • Mean, median, L90, LFI good precision for 150 individuals
  • No major difference between gears and seasons, commercial data not

included

  • Relative small regional differences, largest in Estonia – smallest in

Puck?

  • Should be possible to set regional assessment criteria
slide-20
SLIDE 20

Whitefish precision

32 33 34 35 36 50 100 150 200 300 400 500 600 700 800

as.factor(Threshold) IndicatorValue

36 38 40 42 44 46 50 100 150 200 300 400 500 600 700 800

as.factor(Threshold) IndicatorValue

0.1 0.2 0.3 50 100 150 200 300 400 500 600 700 800

as.factor(Threshold) IndicatorValue

  • 0.2
  • 0.1
0.0 50 100 150 200 300 400 500 600 700 800

as.factor(Threshold) IndicatorValue

mL L90 LFI SS mL, L90 & LFI good precision at 200 ind., for size spectra > 400 needed (which is a high sample size for whitefish).

  • We have data from:
  • Estonia (survey)
  • Sweden (survey)
  • Finland & Åland (survey)
  • Poland (survey)
  • Threshold values
  • MinSize = 25 cm
  • LFI = 40 cm
  • Q90
slide-21
SLIDE 21

32 36 40 Brunskär Kinnbäcksfjärden Kumlinge Kvädöfjärden NorrbynVilsandi

WaterBody mL Period

2000-2010 2011-2016 40 44 48 52 Brunskär Kinnbäcksfjärden Kumlinge Kvädöfjärden NorrbynVilsandi

WaterBody L90 Period

2000-2010 2011-2016

Whitefish

0.2 0.4 0.6 Brunskär Kinnbäcksfjärden Kumlinge Kvädöfjärden NorrbynVilsandi

WaterBody LFI Period

2000-2010 2011-2016

  • 0.15
  • 0.12
  • 0.09
  • 0.06

Kinnbäcksfjärden Kumlinge Kvädöfjärden Norrbyn Vilsandi

WaterBody SS Period

2000-2010 2011-2016

Southern sites Northern sites

Different indicators show similar patterns

slide-22
SLIDE 22

Whitefish

slide-23
SLIDE 23

Conclusions Whitefish

  • Mean, median, L90, LFI good precision for 200 individuals
  • No major difference between gears and seasons, commercial data not

included

  • Smaller in Gulf of Bothnia than Baltic Proper
  • Should be possible to set assessment criteria per basin
slide-24
SLIDE 24

Cod

28.0 28.5 29.0 29.5 30.0 50 100 150 200 250 300 400 500 600 700 800 1000 1400

as.factor(Threshold) IndicatorValue

30 32 34 36 38 50 100 150 200 250 300 400 500 600 700 800 1000 1400

as.factor(Threshold) IndicatorValue

0.00 0.05 0.10 0.15 0.20 50 100 150 200 250 300 400 500 600 700 800 1000 1400

as.factor(Threshold) IndicatorValue

  • 0.3
  • 0.2
  • 0.1
50 100 150 200 250 300 400 500 600 700 800 1000 1400

as.factor(Threshold) IndicatorValue

  • We have data from:
  • Estonia (survey)
  • Sweden (survey)
  • Lithuania?
  • Threshold values
  • MinSize = 25 cm
  • LFI = 40 cm
  • Q90

Good precision at around 300 individuals

slide-25
SLIDE 25

Cod

26 28 30 32 34 Hoburgsbank Litauen Torhamn Vilsandi

WaterBody mL Period

2000-2010 2011-2016 35.0 37.5 40.0 42.5 45.0 Hoburgsbank Litauen Torhamn Vilsandi

WaterBody L90 Period

2000-2010 2011-2016 0.05 0.10 0.15 0.20 Hoburgsbank Litauen Torhamn Vilsandi

WaterBody LFI Period

2000-2010 2011-2016

Similar pattern between indicators

slide-26
SLIDE 26

Cod

Evident differences between sites, smaller at the Swedish west coast (likely a gear effect)

slide-27
SLIDE 27

Conclusions cod

  • Mean, median, L90, LFI good precision for 300 individuals
  • Difference between gears and seasons, commercial data not included
  • Smaller in Kategatt & Skagerrak than Baltic Sea, but likely a gear effect
  • Larger in the Sound (SD 23)
  • Not an evident decrease during 2010’s
slide-28
SLIDE 28

Flounder – On Kristiina’s computer 

  • Very good precision
  • Difference between areas, smallest along Swedish and Polish coast,

largest in central Baltic (SD 25)

  • Relatively similar from the Strait to Skagerrak (SD21-23)
  • I think…
slide-29
SLIDE 29

Next

  • What do spatial/temporal changes in size-based indicators reflect?