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49
<br />only additive. Salmonids exposed to 120 to 300 µg/L
<br />
<br />malathion showed acetylcholinesterase (AChE) inhi- 96-h LC50
<br />
<br />bition of 70 to 80%, and activity indices were reduced Test Stage or Temp 95% CI
<br />
<br />by 50 to 70% of that of unex
<br />osed fish
<br />Goldfish ex- organism wt (g) (C) (µg/L)
<br />p
<br />.
<br />posed to sublethal levels showed a significantly
<br />reduced frequency of avoidance response at levels
<br />below that causing a reduced AChE activity. One-hour Channel catfish' 1.0 22 530
<br />bath exposures of rainbow trout to sublethal levels of 375-748
<br />malathion caused severe tissue damage to the gills and
<br />
<br />minor nonspecific liver lesions. Ponds given four semi- Bluegill' 0.9 20 1,050
<br />
<br />monthly treatments during May-July at levels up to 859-1,280
<br />0.02 mg/L produced no discernible effects on resident Largemouth bass' 3.0 22 1,250
<br />bluegill and channel catfish populations. Aquatic 971-1,610
<br />insect populations were significantly depressed at the
<br />high treatment level but not at the lower levels. Daphnia magna' 11 20 3,2000
<br />1,990-5,130
<br /> G. pseudolimnaeus' M 12 1,050b
<br />METHOMYL 424-2,600
<br />Chemical Name: S-Methyl-N-[(methylcarbamoyl)oxy] Pteronarcella2 N 7 60
<br />
<br />thioacetimidate 50-80
<br /> Skwala2 N 7 29
<br />Alternate Names: CAS 16752-77-5, Dupont 1179, '21-41
<br />Lannate, Nudrin
<br /> Ckironomus' 14 20 32c
<br />Principal Use: Insecticide-nematocide 13-80
<br />Sample Description: Technical material, 95-98%1; Rainbow trout' 1.0 12 1,200
<br />
<br />
<br />
<br />iquid concentrate, 24%1; liquid formulation, 29V
<br />0-10-1,
<br />1,100
<br />,400
<br /> Atlantic salmon' 0.3 12 1,400
<br />SUMMARY OF ACUTE TOXICITY
<br />0-10-1,
<br />1,255
<br />,b70
<br />96-h LC50
<br />
<br />Test Stage or Temp 95% CI Brook trout' 1.2 12 2,200
<br /> 1,600-3,010
<br />organism wt (g) (C) (µg/L)
<br />Daphnia magna' I1 21 8.8a,b Fathead minnow' 0.2 22 1,800
<br />4.1-19 1,200-2,700
<br />Pteronarcella' N 7 69 Channel catfish' 0.5 22 300
<br />34-143 200-430
<br />Skwala' N 7 34 Bluegill' 0.9 20 710
<br />27-44 561-898
<br />Cutthroat trout' 1.0 10 6,800 Largemouth bass' 3.0 22 760
<br />2,180-7,530 589-979
<br />Rainbow trout' 1.1 12 1,600 Rainbow trout' 0.6 12 1,200
<br />1,190-2,150 764-19880
<br />Fathead minnow' 0.8 17 2,800 Fathead minnow' 0.8 17 1,500
<br />1,820-4,310 890-2,540
<br />Atlantic salmon' 0.5 12 1,120 Atlantic salmon' 0.3 12 1,200
<br />930-1,350 19050-1,380
<br />Brook trout' 1.2 12 19500 Brook trout' 1.2 12 1,220
<br />1,230-1,830 860-1,730
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