Speaker:Jianhu

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Seasonal Changes in the Ecological
Characteristics of Pelagic Molluscs in the
Changjiang Estuary

• 
  SpeakerJianhu
• East China Sea Fisheries Research Institute
• Dalian 10.31

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Outline

• Purpose and Significance
• Study area and sampling methods
• Results
• Conclusion

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• There are two species belong to pelagic
  mollusks.One is Pteropoda, the other is
  Heteropoda. Pteropoda is a group of marine
  pelagic molluscs,which belongs to Opisthobranchia
  of Gastropoda. Heteropoda belong to Prosobranchia
  subclass, Gastropoda order.

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Study area and time
The investigation was carried out in the East
China Sea (28303230N?1213012330E).
Four sampling cruises are conducted separately in
spring(May), summer(August), autumn(November) and
winter(February-March) in 2002.
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Data Processing

• Index of clumping
• Dominance (Y)
• Shannon-Wiener ( )

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Horizontal distribution of the total abundance
In spring, pelagic molluscs aggregated in north
nearshore where the Yellow Sea Coastal Current
meets the Changjiang Diluted Water. Numerically,
Limacina trochiformis and Peraclis reticulata
were found to be the main component of the
pelagic Molluscs. In summer, high abundance
distribution area was located in the nearshore of
Changjiang Estuary. Atlanta peroni and Creseis
acicula were the main component of the pelagic
Molluscs.
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Horizontal distribution of the total abundance
In autumn, pelagic molluscs were abundant in the
water off Chowshan. where the Taiwan Warm Current
met the Changjiang Diluted Water. Pelagic
Molluscs were composed of Creseis acicula and
Cavolinia tridentata. Species number was low in
winter because most of the pelagic molluscs are
warm water species.
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Seasonal variation of pelagic molluscs
abundance,temperature, salinity
Temperature(?) Salinity()
Abundence(ind/m3)
spring
winter
autumn
summer
According to Fig, there was a obviously
seasonally variation of average abundance. The
abundance peaked in summer (7.11ind/m3), declined
in autumn and reached the lowest in winter(0.05
ind/m3).
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Contribution of dominant species to total
abundance of pelagic mollusks
Seasons dominant species Y ß t P
Spring Limacina trochiformis 0.27 0.86 22.56 0.0001
Spring Peraclis reticulata 0.02 0.56 14.82 0.0001
Summer Atlanta peroni 0.16 0.92 12.11 0.0001
Summer Creseis acicula 0.10 0.01 0.17 0.8627
Autumn Creseis acicula 0.16 0.21 21.00 0.0001
Autumn Cavolinia tridentata 0.10 0.80 89.81 0.0001
Autumn Agadina stimpsoniji 0.04 0.14 19.75 0.0001
Autumn Pneumodermopsis ciliata 0.02 0.05 7.76 0.0001
Winter Agadina stimpsoniji 0.03 0.99 gt100 0.0001
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Relationship of pelagic mollusc abundance,
surface salinity and temperature
T?
S
Limacina trochiformis
Creseis acicula
Limacina trochiform was sensitive to temperature
and it was more abundant at the sea surface
temperature 17.5?. As to Creseis acicula, it
reached the peak of 4.2ind/m3 where the surface
water temperature at 18.4 ?, salinity at 15.4, in
the other hydrological environment, the abundance
is relatively low.
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Atlanta rosea
Agadina stimpsoniji
The total abundance of Atlanta rosea have the
highest value where the surface water temperature
25.7?, salinity in 7.7. The highest abundance of
Agadina stimpsoniji occurred in the area with the
surface water temperature 18.43?, salinity in
9.14.
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Species Spring Summer Autumn Winter
Agadina stimpsoniji
Abranchaea chinensis
Atlanta lesueuri
Atlanta rosea
Atlanta peroni
Atlanta inflata
Cavolinia longirostris
Cavolinia tridentata
Corolla ovata
Creseis sp.
Creseis acicula
Creseis virgula
Creseis virgula v.comica
Desmopterus papilio
Limacina inflata
Limacina bulimoides
Limacina trochiformis
Notobranchaea macdonaldi
Oxygyrus eraudreni
Paraclione longicaudata
Peraclis reticulata
Pneumodermopsis ciliata
Pneumoderma atlanticum
Protatlanta souleyeti
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Conclusion

• Temperature was a major factor influencing the
  seasonal changes of the total abundance. The
  distribution was mainly affected by salinity.
• Numerically, Limacina trochiformis was the
  dominant species in spring, which we attribute to
  its low temperature adaptation. Atlanta peroni
  was the dominant species in summer and Creseis
  acicula was the dominant species in autumn. These
  species are adapted to relatively high
  temperature. Agadina stimpsoniji, adapted to low
  temperature,was the dominant species in winter.
• Abundance and species number were lower nearshore
  than offshore in the East China Sea because most
  pelagic molluscs are offshore species.

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• Thanks