Docstoc

Population increment of native and alien fish species in the Dutch

Document Sample
Population increment of native and alien fish species in the Dutch Powered By Docstoc
					Population increment of native and alien fish species
       in the Dutch rivers Rhine and Meuse




               Dr. Martijn Dorenbosch
               Department of Animal Ecology
Introduction
                                            First records of non-native fish in Dutch waters

During the centuries, Dutch rivers changed:
   25


          → Rapid increment in alien species richness
→ from natural dynamic large floodplain-systems
   20
→ to strictly man-regulated narrow rivers
          during last decennium
  Number of species




                      15
                           • charactererized by groins & quarrystones
                      10

In this new homogeneous landscape,
                                                                      2
                            R = 0.69
alien5 fish species settled

                       0
                       1500 1525 1550 1575 1600 1625 1650 1675 1700 1725 1750 1775 1800 1825 1850 1875 1900 1925 1950 1975 2000

                                                                          Year
Central questions:


1)    Which types of settlement-patterns can be
      distinguished of alien fish species?

2)    Which environmental factors may explain the
      successful settlement-patterns of these species?


3)    How is the rapid increment of alien fish
      species related to population development of
      native fish?
Firstly: identification of settlement-patterns of alien
fish species in Dutch rivers



1) Are they deliberately introduced, escaped or truly
invasive?
   Three types of ‘settlement-patterns’ of alien fish species
      Types of introduction        Wanted introduction (n=12)
  non-native fishes Dutch rivers   Escaped (n=5)                Deliberately
        (Ntot = 22 species)        Unwanted invasion (7)
                                                                introduced
                                                                e.g. Pikeperch,
                                                                Grass carp
                                                           Most species no
                                                           steady populations
                                                                Escaped
                                                                e.g. Guppy,
                                                                Pumpkinseed,
                                                                Pseudorasbora

Invasive species, predominantly gobid fishes: e.g. Tubenose
                                → rapid population
goby, Rounded goby, Pontian bighead
                                increment
2) When did alien fish species settle in Dutch rivers?
                                              First records of non-native fish in Dutch waters

                     14             Wanted introduction
                                    Escaped
                                    Unwanted invasion
                                                                                      Deliberately introduced
                     12



                     10
 Number of species




                     8
                            Strong invasive species settled only very recently
                     6



                     4



                     2                                      Escaped
                                                                                             Invasive
                     0
                     1875    1885     1895    1905   1915    1925   1935    1945   1955   1965   1975   1985   1995   2005
                                                                           Year
3) Where do alien fish species come from?

                                                                           Settlement pattern
                                                                      Non-native fishes Dutch Rhine
                                        All origins
                     16                 Ponto Caspian origin

                     14
 Number of species




                     12
                     10
                      8                 Recent rapid increase of invasive species:
                      6                 → Gobid fishes from the Ponto-Caspian region
                      4
                      2
                      0
                          1825

                                 1835

                                          1845

                                                 1855

                                                        1865

                                                               1875

                                                                       1885

                                                                              1895

                                                                                     1905

                                                                                            1915

                                                                                                   1925

                                                                                                          1935

                                                                                                                 1945

                                                                                                                        1955

                                                                                                                               1965

                                                                                                                                      1975

                                                                                                                                             1985

                                                                                                                                                    1995

                                                                                                                                                           2005
                                                                                            Year
4) How is this related to other invasive species: crustaceans?
                                                     Settlement pattern
                                               Comparison settlement pattern
                                             Ponto Caspian species Dutch Rhine
                                             Non-native crustaceans Dutch Rhine

                        100
                        25         All origins
                         90            Crustaceans
                                   Ponto Caspian origin
 %Number ofof species




                        20
                         80            Fishes
  of max. # species




                         70      However: invasive gobids
                        15
                         60
                         50      arrive later than crustaceans a similar pattern
                                            Crustaceans show
                        10
                         40
                         30
                         5
                         20
                         10
                         00
                          1825

                                 1835

                                 1845

                                 1855

                                          1865

                                                 1875

                                                        1885

                                                               1895

                                                                      1905

                                                                             1915

                                                                             1925

                                                                             1935

                                                                                    1945

                                                                                           1955

                                                                                                  1965

                                                                                                         1975

                                                                                                                1985

                                                                                                                       1995

                                                                                                                              2005
                          1961

                                 1964

                                 1967

                                          1970

                                                 1973

                                                        1976

                                                               1979

                                                                      1982

                                                                             1985

                                                                             1988

                                                                                    1991

                                                                                           1994

                                                                                                  1997

                                                                                                         2000

                                                                                                                2003

                                                                                                                       2006

                                                                                                                              2009
                                                                             Year
                                                                             Year
Which variables may explain these patterns?
1) Man-made rivers provide ideal habitat for bottom-dwelling
species: both gobid fishes and crustaceans

→ Homogeneous habitat: groins & quarrystones

2) Opening of Main-Donau channel (1992) strongly facilitates
settlement of Ponto-Caspian species. Crustaceans may be
faster colonizers than fishes

→ e.g. high densities, fast reproduction, easy drifters

3) Waterquality of the Dutch rivers was for decades very poor,
inhibiting settlement of invasive species

→ Crustaceans may have higher resistance than fishes
Waterquality hypothesis: decline of zinc (Zn) pollution Rhine
                     Zn concentration (ug / l) Rhine
              Zinc tolerance of Ponto - Caspian gobids unknown
       120

              However, for similar ground-dwelling sculpins
       100
              (Cottidae), LC50 values are known

              → Ponto - Caspian gobids with comparable
       80


                          life history most likely also sensitive
              ecology and R = 0.69
  Zn




       60                         2




       40


       20


        0
         78

                80

                       82

                       84

                                86

                                88

                                           90

                                                  92

                                                  94

                                                            96

                                                            98

                                                                   00

                                                                          02

                                                                          04

                                                                                 06
       19

              19

                     19

                     19

                              19

                              19

                                         19

                                                19

                                                19

                                                          19

                                                          19

                                                                 20

                                                                        20

                                                                        20

                                                                               20
                                                   Year
 Waterquality hypothesis: decline of zinc (Zn) pollution Rhine:
                                       Arrival of Ponto – Caspian gobids fits
                      Zn concentration (ug / l) Rhine
                                       with Zn tolerance
        120


        100
                                       → Waterquality inhibiting factor

        80
   Zn




        60                         2
                                  R = 0.69


        40
                                                                         LC50 6 days

         No effect conc. 31 days
        20
On the opposite: crustaceans (e.g., Gammarus) have
higher0tolerance than fish
(Zn > 100 ug /l)
          78

                 80

                        82

                        84

                                 86

                                 88

                                            90

                                                   92

                                                   94

                                                             96

                                                             98

                                                                    00

                                                                           02

                                                                           04

                                                                                  06
        19

               19

                      19

                      19

                               19

                               19

                                          19

                                                 19

                                                 19

                                                           19

                                                           19

                                                                  20

                                                                         20

                                                                         20

                                                                                20
                                                    Year

→ Early colonizers of rivers that are too polluted for gobids
How is settlement of invasive species related to native species?
       River Meuse: no Ponto – Caspian gobids present
       → 1990 – 2007 recovery of native sculpins
       Cottus perifretum and C. rhenanus (bullheads)
       As in Rhine, most likely related to improvement
       of waterquality: Zn

               Zn concentration Meuse (ug /l)

       35
       30
       25
       20
ug /




       15
                                                        2
                                                       R = 0.72
       10
        5
        0
        1970   1975   1980     1985    1990     1995    2000      2005
                                   Year
  Situation in the river Rhine
  No increase of native bullheads observed
  Since 1997 there are yearly fish surveys in the river Rhine
                                          35
                                          60000
                                                  Total observations native fish
                                                    1997-2006 yearly surveys
                                          30
                                          50000

                                          25                                                      2
                                                                                               2 R = 0.11
                                                                                              R = 0.0009
                     Total observations

                                          40000
                      Species richness



                                          20
                                          30000
                                          15

                                          20000
                                          10

                                          10000                       Species richness all native fishes
                                           5
                                                                         1997-2006 yearly surveys
                                           0  0
                                                                                                  2008
                                           1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
                                              1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
                                                                         Year
                                                                          Year
→ Surveys indicate relative stabile native fishfauna
 Situation river Rhine
 However, instead of increase of bullheads:

               → Rhine shows increase of Ponto-Caspian gobids
                                            600
                                                  Species richness Ponto-Caspian fishes
                                                   # records invasive gobids
                                                        1997-2006 yearly surveys
                                                   1997-2006 yearly surveys
                                            500
                                             8

→ Ponto-Caspian gobids may increase,
                       7
                       Total observations


                      400
                                                                                            2
                                                                                           R = 0.89
at the cost of native bullheads
                       6
                   Species richness




                                            300
                                             5

                                            4
                                            200
                                             3

                                             2
                                            100
                                            1

                                            00
                                              1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
                                             1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
                                                                            Year
                                                                            Year
Distribution 2006 - 2009
                           Since 2000 bullheads greatly
                           declined

                            Ponto – Caspian gobids
                            Everywhere since 2007
Distribution around 2000
Synthesis
       Opportunities for Ponto – Caspian gobids
       are nowadays ideal:

       1) Waterquality greaty improved

       2) Widely available habitat:

              Montonous landscape of groins and
              quarrystone → rapid distribution
  Impact of Ponto – Caspian gobids:
         • Likely competition and exclusion with native fish
                species → example bullheads
  Can we diminish the impact of Ponto – Caspian gobids?
   Possibly by creating a heterogeneous river landscape
      → construction of secondary river channels

• No groins and quarrystones
• Lower waterdynamics

→ Native species have an
advantage on Ponto – Caspian
gobids

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:12
posted:2/22/2011
language:English
pages:17