摘要:

This study's objective was to quantify the water depth, water velocity, and substrate used by adult brown trout Salmo trutta for feeding and spawning in rivers. General hypotheses were: (1) brown trout prefer specific magnitudes of environmental variables and occupy positions through choice; (2) the preferred value of any variable for a particular activity is the same in all rivers; (3) brown trout prefer different values of the same variable for different activities. Surface observation was used to locate 140 feeding and 140 spawning positions used by brown trout in both isolated and sympatric (with rainbow trout Salmo gairdneri) populations in six diverse rivers in New Zealand. Brown trout (mean fork length 42 cm) preferred a mean depth of 65.0 cm and a mean velocity of 26.7 cm second−1at the position occupied by the fish for feeding, but for spawning they preferred a mean depth of 31.7 cm, a mean velocity of 39.4 cm second−1, and a mean substrate size of 14.0 mm. Analysis of variance showed brown trout preferred the same velocity for the same activity in all rivers and years regardless of whether they were from allopatric or sympatric populations, but microhabitats used for feeding and spawning were significantly different. Velocity appeared to be the most important factor determining position choice but ranking of factors may vary with the type of activity. Brown trout chose positions with optimum combinations of depth and velocity instead of positions with more preferred values of either factor alone. Population size may be limited by the amount of the least abundant activity-specific microhabitat.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<355:MCBBTF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Decisions in fishery management usually are made on a species-by-species and site-by-site basis because most information about fishes has been collected and organized in this way. A comparative, community-level approach can contribute to the development of management strategies for large sets of lakes and fish assemblages. Here we describe an approach similar in concept to lake classification, using techniques of multivariate community analysis (ordination, classification, multiple discriminant analysis). This approach can reveal patterns among fish assemblages and relate them to the lakes' habitat characteristics. An application of the approach is illustrated by a published study on fish assemblages of 18 small lakes in northern Wisconsin. Two discrete assemblage types were distinguished and the factors believed to be responsible for their maintenance were identified. With relationships derived from those 18 lakes, predictions of the assemblage types of 11 additional lakes are made from only five habitat characteristics obtained from the literature. Analyses showed these predictions to be largely successful. We suggest that multivariate community analysis contributes to an ability to understand, predict, and manage fish assemblages.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<368:CAIFM>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

From 1897 to 1977, landowners recorded sport catches for Big Pine Lake, a 256 hectare lake in northern Wisconsin that has experienced light fishing pressure. The species composition of the catch remained fairly stable for 40 years, from 1897 through 1940, with muskellunge Esox masquinongy, walleye Stizostedion vitreum vitreurm, and black bass (Micropterus spp.) all accounting for substantial fractions of the total. Northern pike Esox lucius were first recorded in 1946, apparently having entered after an outlet dam washed out in 1944. Subsequent increases in the proportion of northern pike coincided with declining percentages of muskellunge. By the 1950s, the relative abundance of walleye declined, ultimately almost to zero, while the percentage of bass more than doubled. This change began during the warmest decade on record. By 1977, the walleye population had rebounded, bass had declined to pre-1940 levels, northern pike were abundant, and muskellunge were relatively scarce. Long-term changes in summer temperatures and colonization by northern pike appear to have been important factors causing changes in species composition. Effects of human exploitation have been slight. Although the species composition changed dramatically over the 80 years, the only sustained change has been the substitution of northern pike for muskellunge.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<378:CIFPOA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Larval white bass Morone chrysops resisted downstream transport in the Holston River, eastern Tennessee. Despite a short hydraulic-transport time (<20 hours) through the study area (19.8 km), larvae were not transported downstream and out of this region soon after hatching. Recently hatched larvae were collected near a dam that blocks migration of spawning adults at the upper end of the study area; however, downstream from the dam larvae were significantly larger (and older) than expected if they had been transported passively through the area. Larval white bass probably remain near bottom or in other low-velocity refugia that effectively reduce down-stream displacement. Hybrid striped bass Morone saxatilis x white bass larvae 4 mm and longer oriented upstream in our laboratory flume; they swam vigorously and utilized areas of low current velocity to reduce downstream displacement. Retarded downstream transport found in the rivefine environment, coupled with laboratory observations, implies that improvements are needed in models used to estimate entrainment of fish larvae.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<390:LFT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Eleven pairs of bluntnose minnows Pimephales notatus produced from 7 to 19 clutches of eggs between May 27 and August 28. Clutches ranged in size from 5 to 547 eggs. Average clutch size ranged from 93 to 239. The total number of eggs spawned per pair ranged from 1,112 to 4,195 (mean = 2,396). Intervals between spawning sessions (clutches) ranged from 2 to 14 days (mean = 5.3; mode = 5). Spawning usually occurred at night.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<398:FASFOC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

We describe a maximum-likelihood procedure for obtaining simultaneous estimates of growth and total-mortality rates from size-frequency distributions. The method is applied to size data from simulations and from two populations of northern abalone Haliotis kamtschatkana in British Columbia. Total-mortality-rate estimates varied with the assumed number of age classes and other model variables, but this variation was satisfyingly small.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<403:EOAMRW>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Tag-reporting rates for marine recreational boat anglers were estimated directly by surreptitiously implanting, during routine creel surveys, fish tags into fish that had already been caught during October 1976-September 1978. Twenty-nine percent (177) of the 600 implanted tags were returned. Ninety-five percent of all tags returned were received within 100 days after they had been implanted. Significant differences (P ≤ 0.05) were found among reporting rates by anglers from different fishing areas and for different species of fish. No significant differences were found for reporting rates by anglers among seasons or years. These results indicate that use of reward tags in other studies has not fully corrected for nonreporting of recovered tags and, consequently, fishing mortality estimates based on them have been underestimates. The vast majority of anglers (96%) correctly identified their fish to genus and they reported fish lengths that were within ±76 mm (SD) of those determined by agency staff.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<412:AMFDET>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

First-month growth was temperature-dependent for fry of largemouth bass Micropterus salmoides and smallmouth bass M. dolomieui that were raised simultaneously under identical conditions. Similar temperatures (25–27 C) produced the fastest growth rates in both species, although largemouth bass grew most rapidly at the higher end of this range. Largemouth bass generally grew faster than smallmouth bass, particularly in the 25 to 30 C range (average 1.4 times). Variance about the mean standard length increased at higher temperatures. Differing temperature-dependent growth rates and size distributions for the two species may influence their relative abilities to survive predation and to form strong year classes in temperature regimes that differ due to latitude or weather.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<416:CTGROL>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Optimum temperatures for growth and temperature preference were estimated and compared for young striped bass Morone saxatilis, white perch Morone americana, white catfish Ictalurus catus, and spottail shiner Notropis hudsonius to determine how closely behavioral thermoregulation corresponded to optimal growth temperatures. Differences between the final preferenda and the optimum growth temperatures were less than 2 C. The percentage of preferred temperatures that were within the temperature range corresponding to 75–100% of maximum growth was 76–100%. Only a small percentage (0–17%) of preferred temperatures were greater than the upper limit of the range supporting 75% or more of maximum growth, indicating that fish were avoiding temperatures that were suboptimal for prolonged exposures.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<424:RBOTFG>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Flow cytometry was used to identify polyploid fish by means of measuring deoxyribonucleic-acid fluorescence in erythrocytes. One polyploid grass carp Ctenopharyngodon idella and one polyploid bighead carp Hypophthalmichthys (=Aristichthys) nobilis were identified among 38 fish of each species. Ten hybrids identified as diploids on the basis of morphology were confirmed to be diploid. All hybrids identified as polyploid morphologically were indeed polyploid, but two of these were tetraploid rather than triploid.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<431:POHGCX>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor