摘要:

Wild brown trout Salmo trutta in a fertile, high-conductivity stream in central Pennsylvania were observed from camouflaged towers for three consecutive years in order to quantify the diurnal feeding and social behavior of undisturbed adults. The foraging behavior observed was characterized in general as one of net energy maximization effectuated principally by cost minimization. Individuals ranging in age from young of the year to 8 years spent 86% of foraging time in a sit-and-wait search state, used discrete, energy-saving foraging sites year after year, and fed mainly off drift, taking less than 15% of their food items directly off the bottom. Feeding rates decreased with age, were highest in spring and fall, and showed little effect of time of day except for short peaks at dusk in May and June. The home range of most individuals was established in the first or second year of life and changed little thereafter. The mean size of the home range of individuals was 15.6 m2and decreased slightly during the first 4 years of growth. No individual had exclusive use of any home range and no clearly defined territory could be described for any fish. Rather, the social structure evidenced is best described as a cost-minimizing, size-dependent, linear dominance hierarchy of individuals having overlapping home ranges. There was no apparent correlation between dominance and site selection with respect to distance to cover or feeding rate. Use of overhead cover ranged from 17% or less of daylight hours for wild brown trout of age-group 2 to no more than 43% for age-group 5. Length was asymptotic at 40 cm. A rectangular hyperbola described well the overall growth curve of fish in this population, half of the asymptotic length being attained at the age of 23 months. Hatchery brown trout, introduced for experimental purposes, fed less, moved more, and used cost-minimizing features of the substrate less than wild trout. It is postulated that high energy cost is a major cause of mortality among hatchery-reared brown trout stocked in streams, that at high population densities foraging sites are limiting factors, and that growth rate of drift-feeding salmonids is density-independent.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<1:FBOFWA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Rainbow smelt Osmerus mordax dentex were sampled from coastal waters of the Alaskan Beaufort Sea, where they were the most common fish species in winter gill- and fyke-net samples collected under coastal ice. During winter, rainbow smelt were concentrated near the mouth of the Colville River, in which they apparently spawn. Food-habit studies indicate that fish, mysids, and amphipods are important in their diets. Compared to Atlantic rainbow smelt, Pacific-Arctic populations exhibit greater longevity, later sexual maturity, and lower growth and mortality rates. The existence of these life history characteristics suggests that Pacific-Arctic and Atlantic populations have evolved divergently, and that their subspecific distinction is appropriate.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<33:LHAEOA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The recently proposed index of biotic integrity (IBI) was evaluated for several watersheds throughout the midwestern United States. Five of the community metrics comprising the IBI depend on the number of fish species present and must be adjusted for changes in expected species richness with stream size or zoogeography. We use basic relationships of fish species richness versus stream size, calculated from historical fish community data for seven watersheds, to define lines of maximum species richness. These lines are used to predict attributes of “excellent” fish communities, the basis of comparison for assigning scores to 5 of 12 IBI metrics. When zoogeographic and stream-size factors were accounted for in assigning scores, the IBI accurately reflected watershed and stream conditions. As partial tests of the IBI, we found that the index conforms to knowledge of biologists familiar with several watersheds, is independent of stream order in homogeneous watersheds, and is not biased upwards in generally degraded watersheds. Furthermore, analysis of undisturbed fish communities in Illinois and Kentucky support criteria set for percentages of omnivorous individuals and insectivorous cyprinids expected in excellent fish communities. Comparison of maximum species richness lines reveals two groups of similar fish communities, those in woodland streams (Illinois, Michigan, and Kentucky) and those in Great Plains streams (Nebraska, North and South Dakota). We suspect similarities result from ecological factors relating to physical habitat and biotic interactions, rather than from factors such as geologic and climatic history.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<39:RAOAIO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The chronic effects of ammonia to rainbow trout Salmo gairdneri were studied in a laboratory test conducted over a 5-year period. Fish were tested at five concentrations over the range 0.01–0.07 mg/liter un-ionized ammonia; the mean pH of the test water was 7.7, and the mean temperature was 9.3 C. Parental fish were exposed for 11 months, the first filial generation (F1) for 4 years, and the second filial generation (F2) for 5 months. The parental fish spawned of their own volition at all ammonia concentrations tested; baskets containing crushed rock served as the spawning substrate. The F1fish did not spawn voluntarily at either 3 or 4 years of age, although manual spawning of 4-year-old F1fish produced viable eggs. There was no significant correlation between ammonia concentration and numbers of egg lots spawned, total numbers of eggs produced, numbers of viable eggs, growth of progeny, or mortality of parents or progeny in any of the generations tested. Blood ammonia concentrations were measured in F1fish, and proved to be positively correlated with ammonia concentrations in the test water. Histopathological lesions were common in parental and F1fish at un-ionized ammonia concentrations of 0.04 mg/liter and higher; in F2fish, which incurred a severe protozoan infection (Costia sp.), lesions were common at 0.02 mg/liter and higher.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<56:CTOATR>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

In acute toxicity tests, green algae Selenastrum capricornutum, diatoms Nitzschia palea, adult snails Physa gyrina, juvenile cladocerans Daphnia magna, larval midges Chironomus tentans, adult amphipods Gammarus minus, juvenile fathead minnows Pimephales promelas, and embryo-larva stages of rainbow trout Salmo gairdneri and largemouth bass Micropterus salmoides were exposed for 4 hours (algae), 48 hours (arthropods and snails), 96 hours (fathead minnows), 7 days (largemouth bass), and 27 days (rainbow trout) to two phenols (phenol and β-naphthol), two azaarenes (quinoline and acridine), and two polycyclic aromatic hydrocarbons (naphthalene and phenanthrene) present in coal-derived oils. Median lethal or median effective concentrations (LC50s or EC50s) ranged from 0.03 mg/liter for phenanthrene and rainbow trout to 286.54 mg/liter for phenol and the green alga. The rainbow trout embryo-larva assay was the most sensitive of the test systems to all the chemicals except quinoline. For this last compound, systems with juvenile fathead minnows and largemouth bass embryos were the most sensitive. As test systems, fish embryos and larvae were the most sensitive, juvenile fathead minnows and arthropods had intermediate sensitivity, and algae and snails were the most resistant to the test compounds under the test conditions. Within each chemical class (phenols, azaarenes, and polycyclic aromatic hydrocarbons), toxicity increased with increased ring number except for the reversed relationship with the azaarenes and fathead minnows. Thus, β-naphthol (two rings) was 2 to 45 times more toxic than phenol (one ring); acridine (three rings) was 7 to 27 times more toxic than quinoline (two rings); and phenanthrene (three rings) was 3 to 9 times more toxic than naphthalene (two rings). There was also a relationship between increases in toxicity and increases in the calculated octanol-water partition coefficients of the compounds.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<74:CATTAO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Data from family lots of chinook salmon Oncorhynchus tshawytscha whose parents had variable electrophoretic phenotypes for adenosine deaminase (ADA) indicated (1) that each of two distinct zones of ADA activity reflected a single genetic locus, (2) that allelic variants that segregated in a Mendelian manner occurred at both loci, and (3) as a consequence of storage, additional isozymes arose from products of the locus encoding the more cathodal zone (ADA-1). The additional bands complicated genetic interpretations, and their occurrence was reduced by treatment of tissue samples with 2-mercaptoethanol. These data permit the use of ADA isozymes in population studies of chinook salmon, and provide a model for interpreting ADA variation in other salmonids.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<86:GBFEVO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Juvenile coho salmon Oncorhynchus kisutch were maintained for 3 weeks in well water supplemented with low concentrations of NaCl (12 to 24 mM) or CaCl2(6 to 12 mM) to determine the effect on plasma thyroxine (T4) concentrations. Exposure to 12 to 24 mM NaCl increased plasma T4concentrations, whereas exposure to 6 to 12 mM CaCl2had no effect. A 24-hour exposure to seawater (75% or 345 mM NaCl) generally reduced T4concentrations. These findings suggest that the beneficial effects of salt supplementation during early salmonid development may be due, in part, to stimulation of thyroid activity.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1984)113<90:IOASOP>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/00028487.1984.10493229

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor