摘要:

The index of biotic integrity (IBI) has been used to assess the biological quality of flowing water systems in areas throughout the United States. Yet, only rarely has biotic integrity been related to independent measures of water or habitat quality. We show that the IBI ranks sites similarly in two Illinois watersheds where conditions remained relatively stable during 3 years of sampling. Further, rankings among sites conform to prior assessments of site quality based on habitat and water quality. Neither a species diversity index (H') nor any of the individual metrics that constitute IBI performed as consistently at ranking sites as did the IBI. Sampling should be conducted during early summer to reduce variation due to seasonal fish migration and fall recruitment of young-of-the-year fish. In an Indiana watershed subject to extensive conservation planning, the IBI reflects known habitat and water quality perturbations of both natural and anthropogenic origin. Little or no improvement in biotic integrity was detected following implementation of numerous soil and water conservation practices.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<1:SATVOT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

We used eight microhabitat variables to examine the assumption that the variables normally included in instream flow studies are adequate to discriminate among species' microhabitats. When eight variables were available in stepwise-discriminant analysis models to distinguish among the microhabitats of four fish species in a northern California stream, the variance explained ranged from 52 to 77%, and 59 to 86% of the observational records were correctly classified to species. The variables measured were temperature, total depth, focal point elevation (distance of fish from the bottom), focal point velocity (water velocity at fish's snout), mean water column velocity, surface velocity, substrate, and cover. When the number of variables available was reduced to the three normally used in instream flow studies (i.e., total depth, mean water column velocity, and substrate), the variance explained ranged from 0 to 20%, and 46 to 55% of the observational records were correctly classified to species. When all eight variables were available, two variables not normally measured in instream flow studies, temperature and focal point elevation, were important in discriminating among species. Focal point elevation explained between 32 and 43% of the variance in the five models in which it was available. Temperature was included in 14 of 15 models in which it was available and made significant contributions in 12. Total depth was included and significant in 12 of the 20 models in which it was available. When total depth was included in a model, it was always more important than temperature; however, temperature and focal point elevation were the only significant variables on two sampling dates. Mean water column velocity and substrate only made minor contributions in a few of the 20 models in which they were available.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<12:IOTOMC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Evidence that drainage basin morphology and trout standing stock are related through a functional link between geomorphic features and stream habitat quality is presented. Numerous significant univariate correlations were found between geomorphic variables, stream habitat variables, and trout standing stock in both high-elevation forest and low-elevation rangeland streams. Canonical correlations between geomorphic variables and stream habitat variables provided insight into the form of the functional link. Multiple-regression equations predicting trout standing stock were dominated by geomorphic variables. When geomorphic variables alone were incorporated into regression models they predicted trout standing stock as accurately as did stream habitat variables.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<21:ROGTSH>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

We used a bioenergetics model to assess the effects of predation by juvenile walleyesStizostedion vitreum vitreumon the populations of darters (Percidae) and minnows (Cyprinidae) in Sparkling Lake, Wisconsin. In 1982, when young-of-the-year yellow perchPerca flavescenswere scarce, darters and minnows were important in walleye diets throughout the summer. Walleye predation accounted for approximately 100% of adult darter mortality and 75% of adult minnow mortality. Walleyes appeared to be important in determining abundance of young-of-the-year darters in October, but had little direct effect on abundance of young-of-the-year minnows. In 1983, when young-of-the-year yellow perch were abundant, darters and minnows were only important in walleye diets in June. Walleye predation accounted for 80% of adult darter mortality but only 35% of adult minnow mortality. The decrease in walleye consumption of adult darters and minnows in 1983 compared with 1982 is consistent with the hypothesis that abundant yellow perch year classes buffer littoral-zone fish assemblages from walleye predation. The decrease in walleye predation on darters that occurred with increased abundance of young-of-the-year yellow perch appeared to allow an increase in abundance of young-of-the-year darters. However, for minnows, the decrease in walleye predation did not decrease adult total mortality nor did it lead to an increased young-of-the-year abundance. This implies that walleye predation has a much greater direct impact on the darter population than on the minnow population.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<29:EOWPOT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Young (35–50 mm, standard length) bluegillsLepomis macrochirusare restricted to vegetated habitats by predation pressure. Vegetation provides refuge by hindering predator foraging success. In this study, we tested the ability of bluegills to actively perceive and select densities of vegetation where they are safe from predation. Bluegills were presented with two plots of artificial vegetation (cover plots) of different densities (1,000, 250, 100, and 50 stems/m2) in an experimental arena and then confronted with a predator, a largemouth bass Micropterus salmoides. Prey distribution in the arena before, during, and after exposure to the predator, as well as the predator's foraging activities, were recorded for each trial. Before predator introduction, bluegills in all combinations of cover plots spent most of their time in or around the thicker plot of vegetation in the arena. With the predator present in combinations with cover plot 1,000, prey chose this plot as a refuge when attacked. Cover plot 250 was selected as often as positions at the water-air interface, and plots 100 and 50 were ignored as refuges. After removal of the predator, only in combinations with cover plot 1,000 did prey remain around the thicker cover plot present. Predator success (number of prey caught/total number of attacks) was lowest in trials with cover plot 1,000 present. When confronted with a predator, young bluegills appear capable of perceiving and selecting plots of vegetation offering safety from predation.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<40:SBDOAV>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The effectiveness of small versus large trolling gear (hooks and lures) was compared for sampling juvenile chinook salmon Oncorhynchus tshawytscha and coho salmon O. kisutch in the marine waters of southeastern Alaska during 23 d in spring and fall 1985. Sizes, marine ages, and numbers of salmon caught by each gear size were compared. Reducing the size of terminal gear resulted in the capture of smaller and younger salmon. Additionally, more salmon were caught in fall by the small gear than by the large gear; however, catch rates in spring were not significantly different between gear types. Results demonstrate the potential for using scaled-down trolling gear for sampling.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<50:SVLTLF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Age and growth were estimated from sectioned otoliths for 426 spotted seatrout Cynoscion nebulosus collected from Galveston Bay, Texas, between October 1981 and September 1982. Marginal increment measurements showed that a single annulus formed on the otoliths during March and April. Annulus counts made by two independent readers agreed completely, suggesting that age interpretation from sectioned otoliths was precise. After age 1, back-calculated length-at-age estimates were much greater for females than males. Spotted seatrout from Galveston Bay generally grew faster than fish collected from other areas in the Gulf of Mexico. Gonadosomatic index values (gonad weight:body weight ratios) reflected a prolonged 6-month spawning period, which may have accounted for a four-fold difference in back-calculated lengths at age 1. The length advantage gained by larger individuals at age 1 was maintained as they grew older.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<54:AAGAOS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Gizzard shad Dorosoma cepedianum, threadfin shad D. petenense, hybrid gizzard shad x threadfin shad, and alewives Alosa pseudoharengus were collected from Cherokee, Dale Hollow, and Old Hickory reservoirs, Tennessee, from January 1984 through December 1984. Samples were analyzed for proximate composition (moisture, ash, protein, and fat) and gross energy content. Overall ranges of nutrients for all collections were determined: Moisture, 69.7–84.9%; ash, 12.0–32.5%; protein, 45.4–79.1%; fat, 3.3–31.5%; and gross energy, 3.92–6.06 kcal˙g−1. Changes in protein, ash, and moisture percentages within an age-class of a species were primarily the result of changes in fat percentage. In general, fat content increased through summer, peaked during fall, and declined during winter. Seasonal variations in reproductive condition, as well as differences in age and sex, were causes of variations in body composition within a species. Proximate composition and gross energy content of the clupeids examined were similar; however, young-of-the-year and adult alewives exhibited the highest individual gross energy values in their respective age-classes.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<60:NCOCFF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A study was conducted to evaluate the influence of water temperature on food evacuation and feeding activity in age-0 gizzard shad Dorosoma cepedianum fed pulverized food. Fish kept at 5°C exhibited little feeding activity. At temperatures of 10, 15, and 20°C, food was evacuated through the digestive tract in 8.5, 4.9, and 4.4 h, respectively. Frequency of feeding acts also increased significantly with increased water temperature. These data, along with information on the dry weights of natural detritus in full digestive tracts of gizzard shad (ages 0–2) from Acton Lake, Ohio, were used to estimate the daily amounts of natural detritus consumed by age-0 fish. We concluded that a 6-g, age-0 fish can ingest and process natural detritus (dry weight) in amounts ranging from 3.2 to 7.7% of wet body weight per day.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<67:EOWTOF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Largemouth bass Micropterus salmoides were reared over their first 8 weeks of free-swimming life in uncontaminated control water or in water containing one of five concentrations of pentachlorophenol (PCP) ranging from 1.6 to 88 μg/L. Over the final 3 weeks of the study, fish reared in concentrations of 67 and 88 μg PCP/L performed significantly fewer feeding acts (orientations, bites) and had a lower rate of prey capture than did control fish. However, fish in high concentrations spent significantly more time swimming than did control fish, which indicated that exposure to PCP made them hyperactive. By inhibiting energy intake while inducing higher energy expenditures, PCP may reduce survival of young largemouth bass over the winter.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1987)116<71:IOEFBO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor