摘要:

Among the three species of Pacific salmon Oncorhynchus established in the Laurentian Great Lakes, juveniles of coho salmon O. kisutch are most likely to compete with brook trout Salvelinus fontinalis and brown trout Salmo trutta for food and space, because their juvenile life histories and ecologies are similar where they rear together in tributary streams. Coho salmon emerged 2–3 weeks earlier and were 6–8 mm longer than brook or brown trout at emergence during 1979 in Lake Michigan tributaries where the species were sympatric. During the first summer of life, coho salmon generally were 6–21 mm (7–54%) longer and weighed 0.3–4.1 g more than brook and brown trout. Size at emergence and first-year growth were similar among brook trout and brown trout. In laboratory stream experiments with pairs of the three species, coho salmon dominated brook or brown trout of equal size, and brook trout dominated equal-size brown trout. Competitive superiority of dominant species was based on the ability of fish to defend energetically profitable stream positions during sympatry. When released from competition, subordinate species shifted to use more profitable positions. Specific growth rates of coho salmon in the laboratory equalled rates measured in Lake Michigan tributaries. However, brook and brown trout grew more slowly in the laboratory than in the field, probably because intraspecific competition was high due to lack of cover affording visual isolation. Results suggest that the larger size and competitive superiority of coho salmon should give them an advantage over juvenile brook and brown trout in Great Lakes tributaries when resources become limiting.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<363:CAJOCS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Field studies conducted in 1979 and 1980 to assess the production and habitat of cutthroat trouts Salmo clarki in three headwater tributaries in north-central Colorado yielded the following estimates of production (g/m2): Greenback cutthroat trout S.c. stomias in Roaring Creek, 3.3 in 1979 and 2.3 in 1980; greenback cutthroat trout in the Right Hand Fork of Roaring Creek, 3.6 in 1979 and 1.5 in 1980; Colorado River cutthroat trout S.c. pleuriticus in Little Green Creek, 2.2 in 1979 and 3.6 in 1980. Biomass and production in Roaring Creek and Right Hand Fork of Roaring Creek were dominated by old (≥3 years) slow-growing fish. Little Green Creek was the warmest and slowest moving of the creeks studied and had a low diversity of substrates dominated by fine and coarse gravel–it also had the highest biomass and production of young of the year. Right Hand Fork Roaring Creek had faster flows and more extensive undercut banks–it also had the most large fish (≥152 mm long). Biomass and production of cutthroat trout within the three streams depended mainly on stream-specific physical characteristics. In addition, year-class strength appeared to be mainly affected by the time of emergence and growth rates of juveniles prior to their first winter and by the abundance of large resident fish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<382:PAHOTG>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Logging debris resident for five or more years in small streams of southeastern Alaska is frequently removed to improve salmonid habitat. This practice was evaluated for its effects on juvenile anadromous Dolly Varden Salvelinus malma and macrobenthos populations in a small spring-fed stream during 1973–1981. Debris, consisting of limbs, needles, and fragmented logs, was removed by hand from the entire stream in July 1976. The surface area, number, and size of pools was reduced thereafter, and the water velocity increased. Macrobenthos density and invertebrate drift decreased 60–90% immediately after debris removal but returned to pretreatment levels in 1977. The Dolly Varden population decreased from 900 to less than 100 fish by 1978 and then fluctuated sharply between late 1978 and 1981. After 1978, Dolly Varden averaged 27 mm less in length and their biomass decreased from 12.5 to 3.9 g/m2. Decrease in fish standing crop occurred in two stages: (1) an initial loss of larger fish due to reduced habitat; (2) loss of smaller individuals during November freshets thereafter. This study indicates that removal of old logging debris does not improve habitat and can result in smaller rearing populations. Old debris should not be removed unless a block to migrating adult spawners or impairment of water quality can be demonstrated.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<392:ROADVP>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A recently proposed index of biotic integrity (IBI), which applies features of indigenous fish communities to assess watershed and stream quality, is based on the assumption that community features change consistently with stream degradation. In this study, the IBI was modified for and applied to small coolwater streams in the Appalachian Plateau region of West Virginia. Changes in fish community variables proposed for the IBI were tested in seven similar streams exhibiting a wide range of stream degradation due to sewage, mining, and urbanization. A consistent response with increasing stream degradation was found for the following variables: Total number of species, proportion of individuals as creek chubs Semotilus atromaculatus, species richness and composition of darters (Percidae), number of fish in sample, and proportion of fish with disease or anomalies. Proportions of omnivores, insectivorous cyprinids, and herbivore-detritivores yielded inconsistent results due to confounding interactions with species tolerance, whereas alternative trophic metrics, the proportions of specialist insectivores and generalist feeders, produced consistent trends with increasing stream degradation. A modified IBI, based on six fish community attributes, exhibited close agreement with independent rankings of stream degradation.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<401:AATOAI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The number of offspring that reached the free-swimming larva state of development was used to estimate the reproductive success of individual male smallmouth bass Micropterus dolomieui. The influence on reproductive success of 13 variables in the nesting environment was analysed. Principal components analysis produced new independent predictor variables. Multiple-regression analysis of a reduced subset of predictor variables indicated that the accumulated hours of strong wind (greater than 28 km˙h−1) blowing during embryo development significantly influenced offspring numbers in nests. Fewer offspring were found in nests subject to more wind. The material in the bottom of the nest influenced reproductive success to a lesser degree.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<415:RSOMSB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Larvae and eggs of paddlefish Polyodon spathula were collected in the Cumberland and Tennessee river systems from 1973 to 1982. Seven methods were used to capture larval paddlefish and two to collect eggs. Eggs were first collected when spring water temperatures reached 10°C; most were collected when temperatures were 12–15°C. Larvae were present in samples from early April to mid-June at water temperatures of 11–21°C; most were collected when temperatures were 12–18°C. Most paddlefish larvae in samples ranged from 8 to 12 mm total length. Horizontal distribution of larvae was widespread in reservoir transects. Their vertical distributions were sometimes uniform, but larvae often concentrated in surface waters. Relatively large numbers of larvae periodically occurred in samples, suggesting larvae move downstream in contagious groups. The possibility of interreservoir transport of paddlefish larvae was indicated by estimates of ages and hatching locales.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<424:PRITCA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Nine pairs of red shiners Notropis lutrensis spawned 5 to 19 clutches each (4,701 to 8,248 eggs; mean = 6,177) between 13 June and 28 August 1983 in plastic wading pools. Clutches contained from 131 to 1,661 eggs (mean = 585). Mean clutch size for individuals ranged from 410 to 1,060 eggs. Over a 9-d period, 17 of 20 clutches were spawned between 0700 and 1200 hours. In horizontal crevices from 2 to 6 mm high, 62.3 and 22.5% of nearly 25,000 eggs were placed in the 2- and 3-mm crevices, respectively. Spawning females preferred crevices formed by red, orange, and green plates (71.4% of over 17,000 eggs) to those formed by black, blue, yellow, and white plates. Two females expelled eggs in groups averaging 48 and 71 eggs. A fish in 24-h light spawned 200 clutches (113,501 total eggs) in a 21-month test; daily spawning sometimes occurred at high temperatures (up to 34°C). Hatching began in 4 d at 26–28°C; oversized eggs yielded oversized larvae.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<429:IFASBO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Numerous surveys have shown that fish species richness (number of species) is positively correlated with lake pH. However, species richness of fish communities is also correlated with lake size, and low-pH lakes are often small. Thus, conclusions drawn from examination of fish community structure relative to spatial (among-lake) variation in pH have been limited by uncertainties regarding the confounded effects of lake area. We used two statistical methods, analysis of covariance and a nonparametric blocked comparison test, to remove effects of lake area and compare fish species richness in low-pH and high-pH lakes. Data from six previous surveys of water chemistry and fish communities in lakes of Ontario and northern Wisconsin were examined. Lakes with low pH (≤6.0) contained significantly fewer fish species than lakes with high pH (>6.0) when the effect of lake area was considered. A simple probabilistic model showed that the ability to detect differences in species richness is low when lake areas and the pool of potential colonizing species are small. We recommend the blocked comparison test for separating the effects of lake area and pH on species richness and urge critical examination of inferences based on analyses of fish communities in small lakes.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<438:DPAFSR>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Genetic marking, the manipulation of allelic frequencies to tag fish stocks, was applied to chum salmon Oncorhynchus keta released in Kennedy Creek, a tributary to Totten Inlet in south Puget Sound, Washington. Our objectives were to conduct a Petersen mark-recapture population census of smolts residing in Totten Inlet and to identify the contribution of marked fish to subsequent spawning runs. Male spawners were selected for expression of the 115 allele of aspartate aminotransferase Aat 1,2 or the 90 allele of 6-phosphogluconate dehydrogenase Pgdh. The respective frequencies were thus increased from about 0.12 and 0.01 among the native fish to about 0.25 and 0.11 among the progeny of selected males. Eggs were incubated in streamside gravel box incubators and 11 × 106hatched fish were released to Kennedy Creek during 1978–1980. Fish from the genetically marked broods made up 15–51% of the chum salmon smolts resident in Totten Inlet each spring, 1978–1980, and Petersen mark-recapture population estimates indicated that the total population size ranged from 2.2 × 106to 4.3 × 106. In 1979–1981, 6–29% of adults returning to Kennedy Creek to spawn were fish from marked broods. This study validated the use of genetic marking as a tool for use in fisheries research and management.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<448:UOGMTA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Electrophoretic genotyping is a contemporary technique that enables aquaculturists and fishery managers to distinguish between domestic and native stocks of largemouth bass Micropterus salmoides and to monitor gene flow between them. Analysis of low-risk tissue samples (erythrocytes, blood plasma, caudal and pelvic fin, and scale-epithelial tissue) allows investigators to obtain considerable genetic information with minimal loss of performance by individual fish. We have identified at least 64 enzyme locus products in Florida, northern, and intergrade strains of largemouth bass by using invasive biopsy or necropsy. Polymorphic loci account for approximately one-third of the loci examined. Low-risk tissue samples allowed adequate electrophoretic resolution of 44 (69%) of the 64 gene products examined. Of the 23 polymorphic loci thus far identified in largemouth bass, at least 16 can be resolved from blood or fin tissues or both. Thus, using only tissue samples that do not significantly debilitate fish, we were able to distinguish with greater than 99% certainty the Florida subspecies from the northern subspecies of largemouth bass. The ability to resolve no fewer than 40 enzyme locus products from caudal fin clips alone may facilitate future genetic studies of populations where sacrifice of individuals is infeasible or undesirable, as for endangered species.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<455:GMIILB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor