New Zealand Journal of Marine and Freshwater Research abstracts
Shore-level induced variations in condition and feeding of the mussel
Perna canaliculus from the east coast of the South Island, New
Zealand
ISLAY D. MARSDEN
MARK A. WEATHERHEAD*
Zoology Department
University of Canterbury
Private Bag 4800
Christchurch, New Zealand
*Present address: National Institute of Water &
Atmospheric Research Ltd, P. O. Box 8602, Christchurch, New
Zealand.
Abstract Mussels (Perna canaliculus) (Gmelin, 1791)
collected from mid and low tide rocky platforms along the east coast of the
South Island of New Zealand differed in dry weight condition index between
shore levels. Mussel condition was c. 15% lower at mid tide level than the low
tide level and there was greater variation between shore level than between
sites. Feeding experiments were conducted at 15deg.C with mussels collected
from mid and low tide levels using Isochrysis galbana as the food.
Clearance rate depended upon body size, shore level, and season. During summer
clearance rates of mid and low tide mussels were similar. However in winter,
increased filtration rates were recorded in mussels from the mid tide level
compared with those from the low tide. In addition, for mussels from both shore
levels, winter rates were higher than those recorded in the summer. Nitrogen
excretion by mussels also showed seasonal and shore level differences. High
values for ammonia excretion of mussels collected from the mid tide during
winter suggests they utilise metabolic reserves to maintain their basal
metabolism. Although our results suggest that increased filtration rates for
mid tide mussels might compensate for reduced feeding time, in the winter,
larger mussels from the mid tide level would be unlikely to obtain sufficient
energy for maintenance or growth. Large mussels were infrequent in the mid tide
population, where the mean length was 62.5 mm compared with 75.1 mm
from the low tide. It is concluded that nutrient limitation, as a result of
reduced feeding time can act as a significant stress factor limiting the growth
potential of mussels settled at the mid tide level.
Keywords mussel; Perna canaliculus; clearance rate;
condition index; nitrogen excretion; tidal level
M98077
Received 30 October 1998; accepted 29 April 1999
PDF file of entire paper: medium quality (893K); (scanned from paper original: notes about this process)
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