Competitive interactions between non-native and native salmonids and their ecological consequences.

Transcription

1 Competitive interactions between non-native and native salmonids and their ecological consequences. Line Sundt-Hansen (NINA) Julien Cucherousset (Universite Paul Sabatier) Kjetil Hindar (NINA)

2 Introduction Invasive salmonids have been released intentionally or unintentionally by escapes from aquaculture for decades Native salmonid species are often in competition with nonnative species or non-native genotypes Non-native salmonids have reduced the growth and foraging rate of native salmonids (Korsu et al. 2010)

3 Background A competing species cannot invade an ecosystem unless it is sufficiently different in resource use from a native species Limiting similarity concept (MacArthur and Levins 1967)

4 Project Hypothesis Impacts are larger on native species and lower on recipient ecosystems when introducing the same species, but different genotypes. Eg. Farmed salmon vs. wild salmon The competitive effects are smaller and the ecosystem effects stronger when introducing different species, due to a lower level of niche overlap and a broader trophic niche

5 Research questions How will invasive species/genotypes perform relative to native species? Will invasive species and genotypes have an impact on growth and survival of native juvenile Atlantic salmon? Will invasive species in competition with native juvenile Atlantic salmon affect algae biomass and the presence of benthic invertebrates differently than wild salmon alone? Focus on the juvenile stage

6 NINA Research Station Ims

7 Semi-natural stream channel

8 Experiment Performance of invaders +BT +FS Effect on native species No fish +RT + Ecological impact: Benthic invertebrates Algae biomass Ecosystem

9 Experimental juvenile fish Atlantic salmon () Native Farmed Atlantic salmon (FS) Rainbow trout (RT) Brown trout (BT) Invading Native ECOSYSTEM

10 Study design N=5 + N=5+5 +FS N=5+5 +BT N=5+5 +RT N=5+5 No fish x 6

11 Assessments Performance of invaders (growth, mortality) Effect on native species (growth, mortality) Ecological impact: Benthic invertebrates Algae biomass 19 August 30 September 2014

12 RT significantly larger body mass Performance of invaders Inital mass No difference between BT, FS and

13 Condition factor RT significantly higher CF at start Not significant at termination

14 Experimental fish Specific growth rate (d -1 ) (body mass) Farmed salmon (FS) and brown trout (BT): Significantly higher growth rate than wild salmon () and rainbow trout (RT)

15 No significant differences between the experimental fish Survival

16 Specific growth rate (d -1 ), based on body mass Performance of Native species: Atlantic salmon No significant effect of competitor Significant effect of initial mass + + FS + BT + RT

17 Specific growth rate (d -1 ), based on body length * * Significant difference between + and +RT Significant effect of initial length + + FS + BT + RT

18 Survival No significant effect of treatment Wild Atlantic salmon performance + + FS + BT + RT

19 Benthic invertebrates Before start: 0-7 individuals in each sample (Chironomids) 1-10 snails (one channel snails) At termination: Negligible: 0- few individuals Few invertebrates in substrate in stream channels Stomach content: Chironomids Snails

20 Pre-liminary algae biomass In general: low biomass of green algae and diatoms Green algae: Treatment +RT significantly higher biomass than in other fish treatments * * * Diatom Treatment +RT and NO FISH significantly lower biomass than in other fish treatments + + FS + BT + RT No fish + + FS + BT + RT No fish

21 Summary Performance of invasive species/genotypes: Farmed salmon (FS) and brown trout (BT) have a significantly better growth rate compared to wild salmon () and rainbow trout (RT) Effect of invasive species/genotypes on native salmon: No effect on survival Juvenile native salmon in competition with RT higher SGR (length) than alone in same number. Green alge biomass significantly higher biomass in treatment +RT

22 Concluding remarks Support to limiting niche theory? Larger size of RT, an advantage for the native salmon offspring RT were larger and had high CF at start; feeding motivation low? Or sufficiently different in niche use or size difference

23 Thank you! Thanks to: Eli Kvingedal Knut Andreas Eikeland Staff at NINA s Reseach station Ims

24 Performance of invaders and effects on native salmon (and a small piece of the food web) Line Sundt-Hansen Julien Cucherousset Kjetil Hindar

25 We hypothesized that impacts are larger on native species and lower on recipient ecosystems when introducing the same species, but different phenotypes. We then hypothesized that the competitive effects are smaller and the ecosystem effects stronger when introducing different species, due to a lower level of niche overlap and a broader trophic niche, respectively

26 Aim of study hypothesis Will invasive species/groups have an impact on growth and survival of wild salmon parr? How will invasive species perform relative to native species? Will invasive species in competition with wild salmon parr affect the food web differently than wild salmon alone? Focus on the juvenile stage which is particularly vulnerable

27 NINA Ims Research Station

28 Task 1.2 and 2.2: Exp.1 Semi-natural stream channels (2014) Experimental juvenile fish: Wild Atlantic salmon () Farmed Atlantic salmon (FS) Brown trout (BT) Rainbow trout (RT) +RT +BT + +FS ASSESSMENTS: Performance of invaders (growth, mortality) Effect on native species (growth, mortality) Effect of competition on ecosystem: Benthic invertebrates Primary production Diatomes Ecosystem

29 Experiment I: initiated 19 August; terminated September 2014

30 Species Inital length (mm) ± SD Inital body mass (g) ± SD Condition factor± SD Brown trout ± ± ± 0.06 Farmed salmon ± ± ± 0.07 Rainbow trout ± ± ± 0.22 Wild salmon ± ± ± 0.08

31 Inital and final mass

32 Experimental fish Specific growth rate (d -1 ) (SGR.W) BT significantly different from RT, FS significantly different from RT, RT significantly different from BT,FS significantly different from FS,RT

33 Different species growth rate Significant effect of initial mass In rainbow trout and brown trout,

34 Survival

35 Wild Atlantic salmon performance Spesific growth rate (d -1 )

36 Wild Atlantic salmon performance

37 Survival Wild Atlantic salmon performance

38 Algea growth

39 Surber samples Few invertebrates in substrate in stream channels Before start: 0-7 individuals in each sample 1-10 snails (one channel snails) At termination: Negligible: 0- few individuals Stomach content: Chironomids Snails

40 Summary No effect of presence of other species and genotypes on wild salmon growth and survival

41 Previous study

42 Survival and growth: stream channels Imsa Aquage early juvenile stage; n swim up High dens Low dens High dens Low dens Allopatry Allopatry Sympatry Sympatry Substitutive design Density equal effect on growth for farmed and wild offspring No effect of farmed fry on growth of wild fry Reduced survival of wild fry when in sympatry with farmed fry

43 River park 2015