摘要:

Experiments were conducted to identify stimuli to which stream-dwelling brown trout responded in selecting concealment or “cover.” The trout were 25-30 cm in total length. In each experiment, a group of five trout had choice of two types of cover in a channel 27 m long and 3.4 m wide with water 20-30 cm deep, flowing 22-37 cm/s. The fish preferred overhead cover 10 cm rather than 15 or 20 cm above streambed (P < 0.001), as well as cover with tactual features (P < 0.03). There was no apprent increased response to overhead cover that offered added visual reference features or lateral concealment.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<763:DROBTS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

To evaluate mortality of landlocked Atlantic salmon (Salmo salar) caught on flies and worms in a typical river nursery area, a study was carried out at the East Outlet of Moosehead Lake, Maine, in June 1975-1977. Of 177 fish caught in the 3 yr, 22% died after hooking. All of the 74 control fish caught in a fishway trap survived. Mortality of worm-hooked fish (35%) was significantly greater than that of fish hooked on flies (4%). Higher mortality of worm-hooked fish was attributed largely to anatomical site of hooking. Nearly 37% of worm-caught fish were hooked in the esophagus, but most fly-caught fish were hooked either in the jaws or mouth. Mortality of fish that bled after hooking (86%) was significantly greater than that of nonbleeding fish (15%). No significant differences were found between hooking mortality of fish of ages II and III nor between legal size (≳356 mm) and sublegal fish. We concluded that closure of heavily fished landlocked Atlantic salmon nursery areas to worm fishing may be justified in areas where juvenile fish production is important to the lake or river fisheries involved.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<772:MOLASS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<776:APABRO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Using ovaries sampled seasonally from Lake Michigan bloaters in 1968-1969, we determined that one complement or modal group of eggs is produced each year and spawned mainly during January, February, and March. Fecundities estimated for 65 fish taken in October ranged from 3,230 eggs in one medium-size bloater (241 mm long) to 18,768 in the longest (305 mm). We regressed these estimates on lengths and weights of the parental fish to provide a quantitative basis for later evaluating long-term changes in reproductive potential. The resulting rectilinear regression on weight accounted for 75% of the total variation in fecundity.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<785:FOTBCH>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

There is evidence that daily growth rings are deposited in the sagitta otolith of larvae and juvenile Atlantic silversides, Menidia menidia. The growth rings are a function of age alone, and can be used as a tool to age young Atlantic silversides. Growth rings deposited in the asteriscus otolith were unreliable indicators of daily age.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<790:TUOOGR>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Critical swimming speeds (CSS) for groups of menhaden were determined in an array of time and water velocity combinations. Critical swimming speeds varied between 20.7 body lengths/s (BL/s) for short time intervals (2 min) to 15.8 BL/s for long time intervals (64 min). The experiments were repeated with the same group of fish to assess the effect of previous experience, and mean CSS increased by 2.3 BL/s. Tailbeat frequency increased steadily with increasing velocity. Differences in tailbeat frequency occurred among fish in different positions in the groups. Time to exhaustion for menhaden in groups of one to eight fish swimming at constant velocities were determined to assess the effect of group size on swimming performance. Time to exhaustion increased by a factor of 10 as group size increased from one to six fish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<793:SPOJMB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Bluegills (Lepomis macrochirus Rafinesque) from two central Tennessee lakes revealed monthly and seasonal variations of liver RNA-DNA ratios (liver RNA/DNA) and liver-somatic indexes (LSI's) that were associated with gonad maturation, spawning, and temperature. Liver RNA/DNA indicated a longer summer growth depression in fish collected from the smaller, shallower lake. Although LSI's were consistently higher in the smaller, shallower lake, liver RNA/DNA and scale analyses showed faster growth rate in the larger, deeper lake. Thus the LSI may be a useful indicator of relative food intake-energy storage levels within a single lake, but it does not necessarily reflect absolute growth rate of the fish. Liver RNA/DNA provided an indication of immediate or short-term growth rates.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<799:COTBPB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

A computer simulation model for predicting nighttime dissolved oxygen (DO) loss was developed for manured and unmanured tilapia ponds. The model incorporated data from the literature on O2diffusion, respiration by the planktonic community, fish, and benthic organisms, and O2consumption by organic manure. The average absolute deviation between calculated and measured DO concentrations was 0.49 mg/liter for unmanured ponds and 0.38 mg/liter for manured ponds. The contribution of plankton respiration to the total DO loss averaged 75% and 80% in unmanured and manured ponds, respectively. The utility of the model for predicting DO loss over a wide range of plankton densities, fish standing crops, and percentage O2saturation values at dusk was demonstrated. The nighttime DO model should have universal applicability to other fish cultures provided a reliable method for estimating oxygen consumption by the cultured organism(s) is available.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<804:PNDODI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Channel catfish fingerlings fed semipurified diets in flowing-water aquariums for 16 wk required a dietary source of vitamin D for normal growth and bone mineralization.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<809:EOVDID>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Mean plasma cortisol concentration in juvenile chinook salmon increased from near zero to about 200 ng/ml in response to 0.5 h of severe confinement. Cortisol remained elevated for more than 6 h after release, but returned to basal levels within 12.5 h. In fish subjected to continuous severe confinement, plasma cortisol increased to about 400 ng/ml during the first 1.5 h; little further increase occurred, but by 12.5 h, mortality caused by the stress had reached 50%. In response to moderate confinement, plasma cortisol increased to different degrees in individual fish, but returned to basal levels within 6-8 days as the fish acclimated to the stress. A depression in gill Na+K ATPase was noted in juvenile salmon after they were moderately confined for about 3 wk.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<812:CCICJC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor