New Zealand Journal of Marine and Freshwater Research abstracts

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Response of excised gill tissue from the New Zealand scallop Pecten novaezelandiae to suspended silt

PETER M. STEVENS*

Department of Zoology Victoria University of Wellington Private Bag, Wellington New Zealand

Abstract The role of turbidity in scallop mortality was investigated for two size classes of Pecten novaezelandiae (70 + 2 mm and 20 + 1 mm shell height), by using the "crawl" velocity of excised pieces of gill tissue as an indicator of the response to suspended silt. The crawl velocity of 3 X 5 mm pieces of gill tissue was measured in six different silt concentrations (0.025, 0.05, 0.1, 0.2, 0.3. 0.5% silt, by dry weight) and two size classes (< 10 urn and 10-30 um) of silt. Results of the study indicate that juvenile (20 mm shell height) scallops may be less tolerant of suspended silt than larger (70 mm shell height) scallops and that both size classes may be less tolerant of fine (< 10 um) silt/clay sized particles than coarse (10-30 um) particles. These conclusions are supported in part by data from the mortality of whole 20 mm scallops exposed to two size classes (< 10 um and 10-30 um) and three concentrations (0.05, 0.3, 0.6%, by dry' weight) of silt. Increasing concentrations and decreasing particle size of the suspended silt resulted in reduced gill piece crawl velocity and an increase in the mortality rate of the whole scallops. These results suggest controls on human-induced disturbance of bottom sediments, such as bottom trawling and dredging, may benefit any further scallop bed enhancement programmes by the avoidance of deterioration in water quality and mechanical damage to scallop spat.

Keywords Pecten novaezelandiae; Pectinidae; turbidity; silt tolerance; ciliary activity; excised gill tissue; suspended silt

New Zealand Journal of Marine and Freshwater Research, 1987, Vol. 21: 605-614 0O28-8330/87/2104-0605$2.50/0 © Crown copyright 1987 Received 4 August 1986; accepted 14 January 1987

PDF file of entire paper: medium quality (874K); (scanned from paper original: notes about this process)

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