Ecological Archives A018-065-A2

Nick T. Shears, Russell C. Babcock, and Anne K. Salomon. 2008. Context-dependent effects of fishing: Variation in trophic cascades across environmental gradients. Ecological Applications 18:1860–1873.

Appendix B. Analysis of environmental variation among locations, and between reserve and fished sites.

TABLE B1. Results from mixed model analysis of each environmental variable at reserve and fished sites. Variation in environmental variables: (a) across Location and Status, and (b) for Status within each location. Models were back-fitted by removing nonsignificant interaction terms. There was no variation in water clarity measurements among sites at Long Bay, PKI/MKI, and Tuhua so these could not be tested (indicated by “X”). Similarly, as single measurements in water clarity and wave exposure were made at each site we could not test for site-level effects.


Variable

Location

Status

Location × Status

Site(Location × Status)


(a)

       

Sediment

F5,65 = 5.49***

F1,65 = =0.43

-

0.118***

Water clarity

F5,64 = 1022.32***

F1,65 = =0.05

-

X

Wave exposure

F5,64 = 17.92***

F1,65 = =0.79

-

X


(b)

       

   

Sediment

Status

Site(Status)

   
         

Long Bay

F1,9 = 1.11 P = 0.3199

0.297 P = 0.110

   

Tawharanui

F1,8 = 0.43 P = 0.530

0.040 P = 0.327

   

Leigh

F1,12 = 0.09 P = 0.772

0.299 P = 0.044

   

Hahei

F1,8 = 4.25 P = 0.073

0.695 P = 0.054

   

PKIMKI

F1,16 = 0.45 P = 0.514

1.870 P = 0.011

   

Tuhua

F1,6 = 1.43 P = 0.276

0.1379 P = 0.148

   

   

Water clarity

Status

Site(Status)

   

   

Long Bay

X

X

   

Tawharanui

F1,8 = 2.25 P = 0.172

X

   

Leigh

F1,13 = 0.02 P = 0.887

X

   

Hahei

F1,8 = 0.14 P = 0.720

X

   

PKIMKI

X

X

   

Tuhua

X

X

   

   

Wave exposure

Status

Site(Status)

   

   

Long Bay

F1,8 = 0.01 P = .923

X

   

Tawharanui

F1,8 = 1.49 P = 0.256

X

   

Leigh

F1,13 = 0.07 P = 0.795

X

   

Hahei

F1,8 = 1.83 P = 0.213

X

   

PKIMKI

F1,16 = 0.39 P = 0.541

X

   

Tuhua

F1,6 = 2.02 P = 0.205

X

   


 

App. B(ii)
 
   FIG. B1. Environmental variation among locations and between reserve (open bars) and fished (shaded bars) sites: Wave exposure (A), water clarity (B) and sediment (C). Note: secchi depth was >20 m at all offshore sites, but could not be measured accurately beyond 20 m depth. No significant differences in any of the environmental variables were found between reserve and fished sites.

 

App. B(ii)
 
   FIG. B2. Depth related variation in sediment cover (% + SE) among locations and between reserve (open bars) and fished (shaded bars) sites.

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