Assessing the effects of the Sand Engine on essential nursery - - PowerPoint PPT Presentation

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Assessing the effects of the Sand Engine on essential nursery - - PowerPoint PPT Presentation

Oct 25, 2023 291 likes •460 views

Assessing the effects of the Sand Engine on essential nursery habitat conditions for juvenile plaice (Pleuronectes platessa) and sole (Solea solea) Marjolein Post , Ralf van Hal , Chen Chun, Martin Baptist Introduction Coastal sea is an

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Assessing the effects of the Sand Engine on essential nursery habitat conditions for juvenile plaice (Pleuronectes platessa) and sole (Solea solea)

Marjolein Post , Ralf van Hal , Chen Chun, Martin Baptist

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Introduction

  • Coastal sea is an important flatfish nursery
  • Increase in sand nourishments
  • Direct effect on nursery habitat
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Sand nourishment strategies

  • Placing sand on the

beach

  • Sediment supply at

5-8m depth

  • Concentrated mega-

nourishment

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SLIDE 4

Dutch coastline

Sand Engine: mega-nourishment

How does this affect important habitat conditions for juvenile flatfish?

Sand Engine

  • 21.5 million m3 sand
  • 1.5 km wide
  • 2 km long
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SLIDE 5

Fish in a Sand-box

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SLIDE 6

Sampling design

2012 2013 2015

SOUTH SAND ENGINE NORTH

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Methods

  • 0-group plaice and sole
  • Fish sampling season

2012: August/September 2013: October 2015: October

  • Selected prey species based on diet studies
  • Percentage of medium sand (250-500µm)
  • Depth
  • Statistics

– Zero inflated glmm’s

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SLIDE 8

Sediment grain size

Figure 3. Changes in median grain size in 2012 (a), 2013 (b) and 2015 (c). Maps were made by kriging in ArcGis.

Aimed grain size nourished sand

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Benthic prey

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Fish abundance

  • Annual difference in numbers

– Substantially higher catch in 2012

638 plaice in 2012, 248 (2013) and 331 (2015) 790 sole in 2012, 138 (2013) and 132 (2015)

  • Variation in distribution

– Generally the highest numbers around the Sand Engine – Seemingly associated with prey abundance

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Analysis - Sole

  • Annual and spatial variability
  • Positive association with benthic abundance
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Analysis - Plaice

  • Annual and spatial variability
  • Increased abundance with higher prey biomass
  • Negative relation with medium sand
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Discussion

  • Sediment coarsening

– Resulting in decreased abundance of plaice

  • Local variability in prey biomass

– Initial benefit for opportunistic species – Related to plaice and sole abundance – Indication of community recovery after 4 years

  • Lack of seasonal data

– Baseline is necessary

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SLIDE 14
  • Sediment grain size

– Grain size of the Dutch coast went from 210 µm to 320 µm

  • Seasonal timing of nourishment

– Allow for recovery with a nourishment in winter

Theoretical modelling

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Any questions?

marjolein.post@wur.nl