摘要:

Humpback chubs Gila cypha in the Little Colorado River, a warm saline tributary to the Colorado River, grew rapidly to about 250–300 mm total length at 3 years of age, the onset of reproductive maturity for female fish. Fish spawned in April or May; annual reproductive success was greatest when spawning coincided with seasonal river runoff. Meristic characters of humpback chubs from the upper 8 km of the river differed from those of fish from the adjacent lower 5-km river reach, and suggested that some genes of bonytail Gila elegans may occur in the latter population. Use of the physical habitat by age-0 and juvenile humpback chubs was affected by light intensity; shallow littoral areas were used during darkness, but during daylight only when the water was turbid. No evidence of humpback chub reproduction was found in the Colorado River part of the study area; small humpback chubs collected there resulted from spawning in the Little Colorado River. Year-round low temperatures in the Colorado River (the tailwater of Glen Canyon Dam) did not inhibit seasonal gonadal maturation of humpback chubs; however, laboratory studies have indicated that such low temperatures result in nearly complete mortality of embryonic and larval humpback chubs. The recapture of tagged fish, seasonal changes in rates of capture of adults from the Little Colorado River, and the distribution of adult humpback chubs in the Colorado River near its confluence with the Little Colorado River supported the hypothesis that some adult fish from the Colorado River enter the Little Colorado River to spawn. Stomach contents from humpback chubs were dominated numerically by immature Chironomidae and Simuliidae. Lernaea cyprinacea was the most conspicuous metazoan parasite of humpback chubs in the Little Colorado River but was rarely found on fish in the Colorado River. Persistence of the humpback chub in the Little Colorado River could be attributable, in part, to the unsuitability of that environment, and that of the Colorado River, for potential competitor or predator species in the drainage. Introduction to the Little Colorado River of such a species that might prosper under the physicochemical conditions of the river could have a devastating effect on the humpback chub in the Grand Canyon.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<577:LHAEOT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Juveniles (age 0–1) of three endangered Colorado River fishes were subjected to a gradient of total dissolved solids (TDS) to determine the concentrations that they preferred or avoided. Preferred and avoided TDS concentrations, respectively, for juveniles of each species were: Colorado squawfish Ptychocheilus lucius, 560–1,150 mg/liter and greater than 4,400 mg/liter; humpback chub Gila cypha, 1,000–2,500 mg/liter and greater than 5,100 mg/liter; and bonytail Gila elegans, 4,100–4,700 mg/liter and less than 560 mg/liter or greater than 6,600 mg/liter. Colorado squawfish and humpback chubs selected TDS concentrations that were similar to those in waters they now inhabit, but bonytails selected concentrations four times higher. Future increases of TDS in the Colorado River system would degrade municipal, industrial, and agricultural water uses before these endangered fishes would be affected.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<595:COTDSP>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Final thermal preferendum for the razorback sucker Xyrauchen texanus, a rare endemic species of the Colorado River basin, was estimated to lie between 22.9 and 24.8 C based on electronic-shuttlebox studies. Estimates of upper and lower avoidance temperature ranged from 27.4 to 31.6 C and from 8.0 to 14.7 C, respectively. Lower, but not upper, avoidance temperature was positively correlated with acclimation temperature. Results indicated that new water-control structures on the upper Colorado River drainage should be designed to provide summer water temperatures between 22 and 25 C if preservation of habitat for this species is a consideration.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<601:TPAABA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Mean catch per unit effort often is used as an index of fish abundance, N. This index is often biased. Frequency distributions of catch per unit effort (C/f) and independent estimates of N from a headboat sport fishery for yellowtail snappers Ocyurus chrysurus off Islamorada, Florida, indicated that mean C/f underestimated changes in N. Frequency distributions of C/f were skewed and fit the negative binomial distribution. Some descriptors of the distributions (median, variance, negative binomial parameter k, and frequency of zero C/f) were systematically related to N. These relationships were used to derive an index of N less biased than mean C/f. The new index, square root of relative frequency of zero C/f, could be applicable to any recreational, scientific, or commercial fishing activity for which C/f distributions are available, skewed, and have fairly high frequencies of zero C/f. Skewness could be due to spatial dispersion of the fish population or to a gradient of skill among fishing units.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<608:UFDOCP>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

From 1972 through 1981, 7,008 rock bass Ambloplites rupestris were tagged at sites along the southern shore of Lake Ontario; 854 tags (12.2%) were returned by anglers or recovered in the tagging program. Mean time and distance between tagging and recapture were 238 days and 15.5 km. Mean distance between release and recapture sites increased with time. One fish was taken 241 km from the release point. Rock bass tagged and recaptured in the prespawning period dispersed further than those tagged and recaptured after spawning. The predominantly eastward current along the southern shore of Lake Ontario had little overall effect on rock bass movements, but localized current patterns were reflected in dispersal. When dispersal from sites influenced by a thermal power-plant discharge was compared to that from control sites, slightly more rock bass stayed in warmer plume areas than in nonplume areas, although few remained long in any one location. As has been found with other animal species, dispersal of the rock bass was best described by the theoretical regression curve Y = A exp(bXc); Y is the number of recaptures; A, b, and c are constants; and X is distance in km. Dispersal became more randomly distributed (c = 2) as time between release and recapture increased.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<618:DORBAT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Juvenile red hake Urophycis chuss were collected while they were inhabiting sea scallops Placopecten magellanicus, and the effects of appetite and food availability on prey consumption and growth were examined under laboratory conditions. Fish took increasing amounts of live amphipods Gammarus annulatus with increasing periods of food deprivation up to 40–50 hours. The largest portion of a meal was consumed within the first 3 minutes following prey introduction. With longer periods of food deprivation, red hake increased the time their chemosensitive pelvic fins were extended, indicative of a rise in feeding motivation. The average amount of sand shrimp Crangon septemspinosa consumed by fish was 7.4% of body weight/day. Under conditions of high prey abundance, fish grew at rates equal to field growth rates, but under conditions of low prey abundance, growth rate was inhibited. Prey availability can influence the growth rate, which might lead to size differentials within a cohort.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<629:FBPCAG>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The probability that prey will be retained by gill rakers of white crappies Pomoxis annularis (9–15 cm total length) was determined by comparisons of size-frequency distributions of prey in a laboratory pool and in stomach contents. White crappies trained to feed on large-bodied Daphnia magna were released individually into a pool containing that species and an assemblage of small-bodied species. Most attacks were directed at Daphnia magna, but several prey were ingested for every attack, and nonselective capture was assumed for the small-bodied among them. Estimated retention probabilities for species of Ceriodaphnia, Bosmina, and Cyclops were less than 10% for mean prey sizes smaller than 0.35 mm and increased linearly with mean prey size to 100% for prey larger than 0.55 mm. In contrast, retention probabilities calculated by traditional means from distances between gill rakers predicted that all prey larger than 0.23 mm would be retained. The new retention estimates, based on actual results of the retention process, predict that many small-bodied zooplankton present in lakes are immune from predation by white crappies because they cannot be retained by the gill rakers.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<638:ANEOZR>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

In vitro14C-glycine uptake by the scales of bluegill Lepomis macrochirus was sensitive to the pH of the incubation medium; maximum uptake occurred at approximately pH 7.7. Cycloheximide, an inhibitor of protein synthesis, reduced glycine uptake by up to 90%, providing further evidence for the involvement of glycine uptake in the process of protein synthesis. The minimum duration of handling stress that resulted in a significant change in glycine uptake was 60 minutes; after 240 minutes of continuous stress, glycine uptake was reduced 62% from control values. Diel sampling of laboratory fish indicated no daily rhythm in glycine uptake and demonstrated a significant correlation (r = 0.837) between glycine uptake and fish growth rate as estimated over a 2-week interval. The results of these experiments suggest that glycine uptake by scales can be a reliable index of fish growth or state of stress.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<647:CUBFS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The effects of constant temperatures (10, 15, 20, 25, 30, and 35 C) and ration size on the growth rates and activity of juvenile mosquitofish Gambusia affinis (mean wet weight, about 20 mg) were measured in laboratory experiments. On ad libitum rations of Tubifex spp. worms, food-consumption rates of mosquitofish were very high, ranging from 7% dry body weight/day at 10 C to 83%/day at 35 C. Growth increased from 0% dry body weight/day at 10 C to 21%/day at 30 C and declined slightly at 35 C. Gross efficiencies (100 growth/food consumption) increased from 0 at 10 C to a peak of 28% at 30 C and declined slightly at 35 C. On reduced rations (20% of dry body weight/day) maximum growth rates occurred at 25 C. Weight loss of starved fish varied from 1.5%/day at 10 C to approximately 13%/day at 35 C. Fish activity increased significantly with temperature and was generally highest at intermediate feeding levels.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<653:GAAOJM>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Hybrid carp from the cross grass carp Ctenopharyngodon idella ♀ X bighead carp Aristichthys nobilis ♂ preferred filamentous algae and Najas guadalupensis over Ceratophyllum demersum. Medium-sized (273 g) and large hybrids (360 g) consumed more plant material and grew faster than small hybrids (77 g) at 14 and 22 C in aquaria. Aquarium data suggest that it will require at least twice as many hybrids as grass carp of the same size to obtain the same level of vegetation control.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<661:FPFIAG>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor