摘要:

Physiological changes associated with pronounced capture stress in freshwater drum (Aplodinotus grunniens) were studied. Increasing the exposure of exercised freshwater drums to low-oxygen water resulted in increasing degrees of skin reddening and partial hemolysis in blood samples. Artifacts associated with blood sampling by heart puncture did not cause hemolysis, nor did a loss of Na+and Cl−ions or an influx of water into the blood. Blood from freshwater drums that were severely distressed by seine capture showed no significant changes in hematocrit and plasma Na+and Cl−concentrations, compared to fish that were exercised to near exhaustion by capture but were only briefly exposed to low oxygen. After 40 minutes of forced exercise in a low-oxygen aquarium freshwater drums lost equilibrium and had extensive skin reddening, symptoms also observed in freshwater drums that were captured in a commercial shore seine. Blood from cannulated freshwater drums that were exhausted in the laboratory showed significant (P < 0.01) increases in plasma glucose and lactic acid, but no significant (P > 0.01) change in hematocrit or hemoglobin, compared to nonexercised freshwater drums. The apparent in vivo hemolysis was observed in blood from laboratory and field groups of exhausted freshwater drums, whereas all of the control fish blood samples displayed no more than slight evidence of hemolysis. Free hemoglobin probably contributes to skin reddening in freshwater drums and other fish, and both symptoms are likely results of a blood acid-base imbalance in seine-captured freshwater drums.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<544:PROLEF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The relationship between mean lethal oxygen concentration and rate of reduction of dissolved oxygen that induces fish kills was determined for Atlantic menhaden (Brevoortia tyrannus). Reduction of dissolved oxygen at hourly rates of 1.00–0.08 mg/liter had no effect on the mean lethal oxygen concentrations. There was an inverse relationship between the median time to death (LT50) and rate of oxygen reduction that can be used to estimate how quickly a fish kill may occur when oxygen concentrations decrease at a constant rate. Atlantic menhaden were less resistant than spot (Leiostomus xanthurus) when both species were exposed to constant low concentrations of oxygen. The lethal threshold concentrations for Atlantic menhaden and spot at 28 C were approximately 1.1 and 0.7 mg/liter, respectively, whereas, the 96-hour, 5% lethal concentrations were approximately 1.6 and 0.8 mg/liter, respectively.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<552:EOORRA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Nitrite that accumulates during intensive culture of channel catfish (Ictalurus punctatus) often results in high mortality. This study evaluated sublethal effects of nitrite on young channel catfish. Fish (7–10 cm standard length) exposed to 1, 2, 3, 4, or 5 mg/liter of nitrite for 24 hours developed mean methemoglobin concentrations (% of total hemoglobin) of 35, 79, 79, 85, and 90%, respectively. During the 5 mg/liter exposure, methemoglobin increased rapidly during the first 6 hours from 7% to 59%, more slowly to about 80% by 12 hours, and trivially thereafter. Channel catfish exposed to 5 mg/liter nitrite for 6 hours and transferred to nitrite-free water had near normal amounts of methemoglobin (13%) after 24 hours. An inverse relationship was noted between pH of aquarium water and methemoglobin formation after exposure to nitrite. Addition of calcium chloride, potassium chloride, sodium chloride, and sodium bicarbonate to the water suppressed methemoglobin formation in fish exposed to nitrite, but sodium sulfate had no such protective effect.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<558:NMFICC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Sunfish ponds were fertilized 11 times during the growing season with liquid ammonium polyphosphate (N-P2O3-K2O:13–38-0) at 5.6, 11.2, or 22.4 kg/hectare per application. Net production of sunfish averaged 310, 315, and 418 kg/hectare in the low, medium, and high treatments, respectively. Net production of sunfish in the high treatment differed from net sunfish production of the other treatments (P < 0.1). These findings suggest that 5.6 kg/hectare per application of liquid ammonium polyphosphate (13–38-0) is suitable fertilization for woodland ponds with low to moderate fishing. A rate of 22.4 kg/hectare per application is adequate in woodland ponds with heavy fishing. Uniform surface application was the most effective technique of applying liquid ammonium polyphosphate. Liquid ammonium polyphosphate fertilization would generally be cheaper than fertilization with conventional granular fertilizers.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<563:LAPAAF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

An ammonia electrode and the nesslerization procedure of a water quality test kit were compared in measurements of total ammonia nitrogen (TAN) in standard solutions, well water, and water from various aquaculture systems. The electrode generally was satisfactory, the test kit less so—especially in water fertilized with animal manure. Distillation did not improve accuracy or precision of the electrode when it was used with raw water samples, but TAN concentrations were affected by interferences when water from some wells was analyzed without distillation. In general, the ammonia test kit should be satisfactory for aquacultural use, but in intensive-culture systems the performance of the ammonia electrode seems to warrant its higher expense.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<571:ROAEAA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

On January 25, 1979 a self-addressed, prepaid postal card questionnaire was mailed to all 2,577 fishermen who had purchased one or more South Carolina gill-net licenses during Fiscal Years 1977–1978, 1978–1979, or both. These gill-net fishermen expended an estimated 19,293 days of fishing effort and harvested 348,600 kg of fish during 1978. The South Carolina gill-net fishery is primarily a noncommercial fishery. Fishermen utilize small nets, less than 30 m in length, to supply fish for home consumption. In all coastal counties, gill nets are most often fished along the ocean beaches during the fall months. Only 6% of the gill-net fishermen who fished in 1978 sold any portion of their catch. These fishermen sold less than 200,000 kg of fish, 84% being spot (Leiostomus xanthurus), bluefish (Pomatomus saltatrix), and mullet (Mugil spp.).

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<577:SCNGF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/00028487.1980.10493208

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor