摘要:

Three different feeding programs were used to assess the need for zooplankton in the environment of prolarval muskellunge. These were: (1) no zooplankton available to the larvae (filtered water) until 80% of them had become free-swimming, with pond zooplankton introduced daily thereafter, (2) pond zooplankton introduced daily after hatching was 90% complete, and (3) Artemia nauplii (under 4 days old) introduced 3 times daily beginning with 90% hatch.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<338:POFOIT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

An all-male population of Tilapia aurea was produced with 17 α-ethynyltestosterone at 60 μg/g diet. Heterogamety of T. aurea females was determined. A relationship between the percentage of males and the total weight of fish indicated the faster growth of androgen-treated fish. The feeding of 1-dehydrotestosterone acetate, 17 α-ethynyltestosterone, and 17 α-methyltestosterone at various dosage levels for 18 days to sexually undifferentiated T. aurea fry in tanks neither affected survival nor altered growth of fry. No difference was observed in survival between androgen-treated and untreated fish in plastic pools for 120 days. Some androgen-treated groups were significantly heavier than the control. Treatment with ethynyltestosterone and methyltestosterone at all dosage levels resulted in significantly higher percentages of males than the control. Degeneration of testes was observed with treatment of methyltestosterone at 60 μg/g diet. No ovotestis condition was found. Sex ratios of the progenies of three ethynyltestosterone-treated and six methyltestosterone-treated males individually bred with untreated females ranged from 2 to 3.1 females:1 male. These were significantly different from the expected 1:1 ratio of sexes and indicated that sex reversal of genetic females had been achieved. Sex reversal appears to be a practical method for producing monosex male tilapia.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<342:UOAFTP>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Blood and thyroid tissue samples were compared among adult, jack, and smolt coho salmon from Oregon and Lake Michigan. Blood samples were analyzed for thyroxine and triiodothyronine, and thyroid tissue was examined histologically. Significant differences in estimates of thyroxine and triiodothyronine levels and histological condition indicated that Lake Michigan jack and adult coho salmon were hypothyroid. The authors theorize that the hypothyroid condition is related to the general iodine deficiency in the Great Lakes Region, contributes to the lower fertility and fecundity of the Great Lakes salmon, and exaggerates pesticide accumulation in the fish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<349:TAICSF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

During a 22-month exposure of bluegills to copper in soft water, adult bluegill survival was reduced, growth was retarded, and spawning was inhibited at 162 μg/liter of copper (Cu). Tissue-residue analysis of the gill and liver indicated that significant quantities of copper had accumulated in these tissues at test-water concentrations of 40-162 μg Cu/liter. Larval bluegill survival after 90 days' exposure to copper was adversely affected at 40-162 μg Cu/liter. The maximum acceptable toxicant concentration (MATC) for bluegills exposed to copper in water with a hardness of 45 mg/liter (as CaCO3and a pH range of 7-8 lies between 21 and 40 μg Cu/liter. The mean 96-hour TL50 for juvenile bluegills is 1,100 μg Cu/liter, and the application factor (MATC/96-h TL50) lies between 0.02 and 0.04.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<353:CEOCOS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

A simple mechanical dosing apparatus to continuously dose streams with chemical solutions involves a modified Sutro weir and a simple lever-float system. This dosing device is easily constructed, inexpensive, and quite reliable under conditions of minor flow variation (a seasonal fluctuation of one order of magnitude or less). It maintained an average stream concentration variation of only ± 10 percent during a year of low level pesticide dosing.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<359:ASDSFC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Lead and hydrocarbons from snowmobile exhaust were found in the water at high levels during the week following ice-out in a Maine pond. Fingerling brook trout (Salvelinus fontinalis) held in fish cages in the pond showed lead and hydrocarbon uptake. These contaminants accumulated during the previous winter when snowmobile operation on the pond was equivalent to one snowmobile burning 250 liters of fuel per season on a .405 hectare pond with average depth of 1 m. Lead content of the water rose from 4.1 ppb before snowmobiling to 135 ppb at ice-out; exposed trout contained 9 to 16 times more lead than controls. Hydrocarbon levels undetectable prior to snowmobiling reached 10 ppm in the water and 1 ppm in exposed fish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<363:EOLAHF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Pacifastacus leniusculus from two populations in Washington State, the central Columbia River and a small tributary, were acclimated at 5 C intervals and exposed to elevated temperatures in 48 hour thermal bioassays. The upper lethal temperature for both crayfish populations increased relatively slightly, from about 28.5 to 31.5 C, over the entire acclimation range. A rise of 1 C in test temperature often represented the difference between zero and total mortality when lethal limits were approached. The ultimate upper lethal temperature was near 32-33 C Statistically significant differences in thermal resistance patterns (slope and spacing of regression lines) occurred between the two crayfish populations at all acclimation levels, but resistance in terms of eventual mortality was similar for practical purposes. Moulting individuals were particularly susceptible to high temperature stress. Mature, pre-breeding female crayfish from the Columbia River during fall appeared less resistant, and egg-bearing females during winter more resistant, than other individuals. Larger crayfish from the Columbia River were slightly less resistant to elevated temperatures than smaller ones, and females were more resistant than males. The upper temperature triangle for P. leniusculus encompasses an area of 424 C2This freshwater decapod is more tolerant of elevated temperatures than native salmonids, but less tolerant than some introduced “warmwater” fish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<374:ROANCP>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

An electro-mechanical device has been constructed to monitor and dilute seawater to a constant salinity for flowing-water bioassays. It has been used successfully in pesticide bioassays and requires little maintenance.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<388:ASCFFB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The application of rotenone to a 4.5-hectare cove of South Branch Lake, Maine, greatly reduced the abundances of most zooplankton species. The recolonization of the cove by limnetic zooplankters was rapid, and species abundances there approached those of open waters and of the control cove within one week.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<390:ZROALC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Live specimens of Mysis relicta from Lake Michigan were held for one year in the laboratory to determine feeding behavior and tolerance to light and temperature. Mysids fed by moving with rapid, horizontal jerking movements toward food as it settled toward the bottom and by swimming slowly, upside down, to gather particles floating on the surface. Scavenging was common. Mysids tolerated considerably higher temperatures than previously reported. Temperature increases (from 5 C) of 1 C per day and 1 C per minute resulted in TLmvalues of 20.5 C and 20.4 C, respectively. Mortality increased rapidly at temperatures above 13 C. The upper lethal limit for mysids acclimated to 5 C was about 22 C. Survival under continuous, high light intensity (32 foot-candles) was considerably higher than previously reported. Low water temperature (5 C) may have increased light tolerance.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<394:FBATAL>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor