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Effects of a Small Suction Dredge on Fishes and Aquatic Invertebrates in Idaho Streams
Author(s) -
Griffith J. S.,
Andrews D. A.
Publication year - 1981
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/1548-8659(1981)1<21:eoassd>2.0.co;2
Subject(s) - streams , invertebrate , fishery , environmental science , ecology , biology , computer science , computer network
A typical dredge (intake diameter 7.6 cm) was operated on four small Idaho streams during July‐September 1980 to evaluate some of the effects on aquatic organisms that may result from the use of small suction gold‐dredges. Mortality of eggs, sac fry, and fingerlings of several species of trout was monitored, as was that of benthic invertebrates that were entrained through the dredge. The ability of invertebrates to recolonize a dredged area was assessed, and the performance of the dredge was evaluated. Un‐eyed cutthroat trout (Salmo clarki) eggs experienced 100% mortality within 1 hour after entrainment. Eyed cutthroat trout eggs showed means of 29% and 35% for 1‐hour and 36‐hour mortalities, respectively. The 19% mortality of eyed eggs of hatchery rainbow trout (Salmo gairdneri) after 10 days was similar to that of the control group. Hatchery rainbow trout sac fry experienced 83% mortality after 20 days as compared with 9% for the controls. Yolk sacs were detached from approximately 40% of the fry during entrainment. Fewer than 1% of the 3,623 invertebrates entrained showed injury or died within 24 hours. Most of the dead were Centroptilum mayflies that were undergoing emergence at the time of dredging. Most of the recolonization of dredged plots by benthic invertebrates was completed after 38 days. The unmodified dredge moved the equivalent of 0.043‐0.055 m 3 of substrate per hour, about 2% of the manufacturer's maximum rating. In the study areas, approximately 0.76 m 3 of sediment less than 0.5 mm in diameter could be moved in 100 hours of dredging operation.