Sutton Stream and Stony Creek
Sutton Stream and Stony Creek are moderate-gradient headwater streams in the
Lammerlaw Range of the South Island of New Zealand. The river valleys are
incised and rugged with schist bedrock. Vegetation is largely exotic pasture
grasses and native tussock grasses that are extensively grazed by livestock. The
400-metre study reaches selected at each site have no canopy, although there
are shrubs along the stream margins. Mean daily water temperature ranged from
0.0 to 17.4 8 C (annual mean¼5.6 8 C) in Sutton Stream, and from 0.0 to 16.4 8 C
(annual mean¼6.0 8 C) in Stony Creek. Mean annual discharge of Sutton Stream
is 568 L s^1 ; discharge of Stony Creek is 461 L s^1. Sutton Stream is inhabited
by introduced brown trout (Salmo trutta); Stony Creek is inhabited by native
river galaxias (Galaxias eldoni). These fish species are the top predators in both
systems.
Production was estimated for a one year period during 1991–1992 for 37 taxa
in Sutton Stream and 42 taxa in Stony Creek (Huryn,1996a, 1996b, 1998).
Samples used to estimate invertebrate production were collected from each
stream approximately monthly during 1991–1992. Sixteen benthic samples
were taken from random locations approximately monthly using a 900 cm^2
Surber sampler fitted with a 232mm net. Samples were processed using a
250 mm sieve. Individual growth studies were done for many of the small fast-
growing taxa (Leptophlebiidae) and slow-growing taxa (Potamopyrgus) so that
accurate taxon-specific estimates of biomass turnover (annual P/B) could be
obtained. Fish production was also estimated using standard methods (Huryn,
1996a, 1998). Annual primary consumer production for Sutton Stream was
11.2 g ash-free dry mass m^2 , secondary consumer production was 2.1 g m^2 ,
and trout production was 2.1 g m^2. Primary, secondary andGalaxiasproduction
in Stony Creek were 7.7, 0.9 and 0.2 g m^2 yr^1 , respectively. Trout predation in
Sutton Stream exerted strong top-down control on prey production. In compar-
ision,Galaxiaspredation in Stony Stream had minor energetic consequences for
prey production (Huryn, 1998 ).
Tests of predictions
The average individual mass for each taxon was estimated as B/N¼M(mg indi-
vidual^1 ) for each stream community. Two basic approaches were used. The
first approach consisted of summing production statistics for taxa occurring
within discrete body-size classes. M was log 10 transformed and each taxon
assigned to the appropriate body-size class (log 10 M¼0.5–0.99, 1.0–1.49 ...
6.5–7.49). The N, B and P values for each taxon in each size class were then
summed as suggested by Brownet al.(2004). A P/B was then calculated for each
size class using summed values. Plots of body-mass category versus log 10 trans-
formed N, B, P and P/B were then prepared and least-squares regression was used
to fit a linear model to the plots. The second approach assessed the relationship
BIOMASS TURNOVER AND BODY SIZE 59