New Zealand Journal of Marine and Freshwater Research abstracts
M98040Received 14 July 1998; accepted 6 July 2000
Size-specific clearance, excretion, and respiration rates, and phytoplankton
selectivity for the mussel Perna canaliculus at low levels of natural
food
M. R. JAMES
National Institute of Water & Atmospheric
Research Ltd
P. O. Box 11 115
Hamilton, New Zealand
email: m.james@niwa.cri.nz
M. A. WEATHERHEAD
A. H. ROSS
National Institute of Water & Atmospheric
Research Ltd
P. O. Box 8602
Christchurch, New Zealand
Abstract Clearance, respiration, and ammonia excretion rates,
and phytoplankton selectivity were measured for the Greenshell
TM
mussel
Perna canaliculus (Gmelin) in Beatrix Bay, Marlborough Sounds,
New Zealand. Functional equations were developed describing the relationship
between body size (length and weight) and clearance and metabolic rates for
this species feeding on natural food assemblages in New Zealand waters.
Relationships with shell length were described by allometric power curves but
the relationship with chlorophyll
a concentrations in the water for a
particular size of mussel suggested there was a threshold between 0.2 and 0.3
μg Chl.
a litre
-1 and an exponential decline in clearance
rate from c. 0.5-0.6 μg Chl.
a litre
-1 with increasing
chlorophyll concentrations. Under these field conditions ingestion rate would
increase linearly with increasing chlorophyll concentrations up to c. 0.5 μg
Chl.
a litre
-1 then remain constant at higher chlorophyll
levels. Food levels, as measured by chlorophyll
a or particulate carbon,
were very low (generally <1 μg Chl.
a litre
-1 and 300
μg C litre
-1) throughout the study and this was reflected in low
ingestion rates, despite clearance rates of up to 8.6 litre
mussel
-1 h
-1.
P. canaliculus generally
appears to be non-selective, at least for phytoplankton in the size range
5-100 μm, but there was some evidence that larger diatoms and
dinoflagellates were cleared more efficiently by larger mussels. Some of our
observations on food levels and feeding rates help explain the low mussel
growth and condition experienced in the Pelorus Sound during 1996-97.
Keywords clearance rate; Perna canaliculus; mussel;
feeding behaviour; low food
New Zealand Journal of Marine and Freshwater Research, 2001, Vol. 35: 73-86
0028-8330/01/3501-0073 $7.00 (c) The Royal Society of New Zealand 2001
PDF file of entire paper: medium quality (1027K); (scanned from paper original: notes about this process)
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