Diel Feeding Chronology and Diet Selection of Rainbow Trout (Oncorhynchus mykiss) in the Henry's Fork of the Snake River, Idaho

1990 ◽  
Vol 47 (1) ◽  
pp. 199-209 ◽  
Author(s):  
T. R. Angradi ◽  
J. S. Griffith
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Stomach Content ◽  
Decision Rules ◽  
Stomach Contents ◽  
Live Weight ◽  
Invertebrate Drift ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Terrestrial Insects ◽  
Prey Items

Concurrent rainbow trout (Oncorhynchus mykiss) stomach contents and invertebrate drift samples were collected during three 24-h periods in summer 1987. Feeding was discontinuous through the day on all dates. Mean stomach content weight was minimal after 0400 MST and sharply increased between 1000 and 1200 MST on all three dates. Feeding apparently did not occur after twilight. Mean stomach content weight was correlated with water temperature on two dates and was never correlated with invertebrate drift density for non-age-0 trout. Daily ration (wet weight) was 7% of live weight for non-age-0 trout and 21% for age-0 trout. Trichoptera, Ephemeroptera, and Diptera were most important in the diet; terrestrial insects and aquatic vertebrates were rare. The degree of selectivity varied through 24 h and the interpretation depended on the method of analysis used. Occurrence of low-drift cased Trichoptera larvae in stomachs was correlated with amount of filamentous algae ingested, indicating a degree of epibenthic foraging, although no diel pattern could be reliably discerned. Mean length of prey items in stomachs was larger that the drift in 83% of the samples. Our findings support experimentally derived decision rules-of-thumb for foraging trout: select larger prey items, select vulnerable prey, and relax selectivity when hungry.

Changes in Habitat Use and Feeding Chronology of Juvenile Rainbow Trout (Oncorhynchus mykiss) in Fall and the Onset of Winter in Silver Creek, Idaho

1993 ◽  
Vol 50 (10) ◽  
pp. 2119-2128 ◽  
Author(s):  
Michael D. Riehle ◽  
J. S. Griffith
Keyword(s):  
Rainbow Trout ◽  
Habitat Use ◽  
Oncorhynchus Mykiss ◽  
Density Distribution ◽  
Stomach Contents ◽  
Early Morning ◽  
Invertebrate Drift ◽  
Juvenile Rainbow Trout ◽  
Rainbow Trout Oncorhynchus Mykiss

We assessed changes in density, distribution, and microhabitat of age-0 rainbow trout (Oncorhynchus mykiss) in Silver Creek, a partially spring-fed stream, by periodic snorkeling in August 1987 through January 1988. We examined trout stomach contents and invertebrate drift samples in diel collections in August, September, October, and January to test if the period of feeding shifted from daytime to nighttime, concurrent with a transition to day concealment. In late September, fish aggregated briefly during the day and then began to conceal themselves in macrophyte beds, undercut banks, and submerged sedges and grasses along streambanks as temperature dropped below 8 °C in early October. Fish emerged from concealment at night, and numbers of trout visible were greatest 30–60 min after sunset and about 30 min before sunrise. Periods of peak feeding changed from afternoon and evening in August and September, when fish were day active, to mainly at night in October after the initiation of day concealment. Trout did not feed upon abundant chironomids in the daytime drift in October. In January, fish fed at 1–4 °C on mayflies, and stomachs were fullest in the early morning. Observations suggest that Silver Creek trout experienced a metabolic deficit that began in September.

scholarly journals Effects of Randomly Fired Underwater Currents as an Occupational Enrichment Program in Rainbow Trout (Oncorhynchus mykiss)

Water ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3057
Author(s):  
Morris Villarroel ◽  
Genaro C. Miranda-de la Lama ◽  
Rubén Bermejo-Poza ◽  
Concepción Pérez ◽  
Elisabet González-de Chávarri ◽  
...  
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Environmental Enrichment ◽  
Live Weight ◽  
Constant Current ◽  
Positive Effects ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
In The Wild ◽  
History Of ◽  
Cortisol Levels

Occupational enrichment (OE) is directed at introducing variations in the tank water so that fish can exercise as they do in the wild. Two trials were carried out to test the effects of randomly fired underwater currents (RFC) on rainbow trout (Oncorhynchus mykiss) maintained in tanks in a recirculation system, using 1226 trout distributed in two independent trials. In Trial 1, fingerling trout (n = 6 tanks, n = 40 fish per tank) were classified into two groups based on low (13%) or high (30%) coefficient of variation in live weight (CV), and exposed to RFC or no currents (controls). In Trial 2, adult trout (n = 12 tanks, n = 20 fish per tank) were either exposed to RFC or to a constant current (controls) from two submerged pumps. Both trials lasted four weeks. No significant differences in growth were observed between treatments in either trial. In Trial 1, RFC fish maintained a similar CV throughout the trial, while CV decreased in controls. Also, in Trial 1, plasma cortisol levels were higher and creatine phosphokinase (CPK) levels lower in tanks with a low initial CV. In Trial 2, the CV was lower in RFC trout, where cortisol levels were also significantly lower and triglycerides significantly higher. The results suggest that OE using RFC can have positive effects by helping to reduce stress levels, and provides fish with biologically meaningful environmental enrichment related to the natural history of the species.

scholarly journals Effect of monosodium glutamate on growth performance and blood biochemical parameters of rainbow trout (Oncorhynchus mykiss W.)

2019 ◽  
Vol 12 (7) ◽  
pp. 1008-1012 ◽  
Author(s):  
Georgi Zhelyazkov ◽  
Deyan Stratev
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Growth Performance ◽  
Biochemical Parameters ◽  
Monosodium Glutamate ◽  
Live Weight ◽  
Control Fish ◽  
Blood Biochemical Parameters ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Blood Biochemical

Aim: This study aimed to evaluate the effect of dietary monosodium glutamate (MSG) on growth performance and blood biochemical parameters of rainbow trout (Oncorhynchus mykiss W.). Materials and Methods: A total of 200 trouts were allotted in five experimental groups (n=40) that for 60 days received feed supplemented with MSG at the following levels: 0% (K) or 0.5% (E) or 1% (F) or 3% (G) or 5% (H). Results: The average initial weight of trouts was 116.68±1.51 g (K), 116.58±1.33 g (E), 116.43±1.39 g (F), 117.40±1.47 g (G), and 115.95±1.88 g (H). At the end of the trial, control fish (K) had the lowest live weight (242.90±3.87 g) compared to Groups E (252.70±5.69 g), F (250.93±4.82 g), G (248.25±4.98 g), and H (247.95±4.74 g). Feed conversion ratio (FCR) of control group (K) was higher (1.11±0.02) versus FCR values established in Groups E (1.03±0.01), F (1.04±0.02), G (1.07±0.03), and H (1.06±0.02). Albumin, aspartate aminotransferase, gamma-glutamyl transpeptidase, alkaline phosphatase, phosphorus, magnesium, and triglyceride exhibited statistically significant differences versus controls. Conclusion: The results from the study showed that dietary supplementation of rainbow trouts with MSG increased live weight and reduced FCR. The optimum level of MSG recommended for addition to feed was 0.5%.

scholarly journals Productive traits, blood biochemical parameters and meat quality of rainbow trout (Oncorhynchus mykiss W.) fed with supplement of nutmeg extract (Myristica fragrans)

2020 ◽  
Vol 12 (4) ◽  
pp. 324-330
Author(s):  
Ts. Stoev ◽  
G. Zhelyazkov
Keyword(s):  
Fatty Acid ◽  
Rainbow Trout ◽  
Weight Gain ◽  
Oncorhynchus Mykiss ◽  
Sunflower Oil ◽  
Biochemical Parameters ◽  
Live Weight ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Blood Biochemical ◽  
Recirculation System

Abstract. The aim of the present study was to evaluate the effect of the dietary nutmeg extract (Myristica fragrans) supplement on the survival rate, weight gain, feed conversion ratio (FCR), economic efficiency (ECR), blood biochemical parameters, chemical composition and fatty acid profile of rainbow trout (Oncorhynchus mykiss W.), cultivated in a recirculation system. One hundred and sixty rainbow trouts were distributed in two experimental variants, each with two replications with 80 fish in one group. The average initial live weight of trouts from control (C) and experimental (E) groups was 13.43±0.33 g and 13.46±0.29 g, respectively. Fish were reared in concrete tanks with effective volume of 0.8 m3, part of a recirculation system. Trouts were fed „Aqua garant UNI“ extruded feed produced by Garant-Tiernahrung Gesellschaft m.b.H. – Austria, with pellet size of 2 mm. The feed of fish from the experimental group was supplemented with 1% powdered nutmeg extract (P.I.C.Co LTD), by lubricating the pellets with 5 ml sunflower oil/100 g feed. Control rainbow trouts received feed lubricated with the same amount of sunflower oil. Fish from both groups were fed 3 times daily and their ration was 3% of body weight. The experimental period lasted 60 days. The dietary supplementation of rainbow trouts with nutmeg extract had a negative impact on growth performance and economic efficiency of farming of the species. Final live weight and average individual weight gain were lower, and FCR and ECR values were inferior vs controls. The nutmeg extract had also an adverse effect on water content and dry matter of meat from supplemented fish. A positive effect was demonstrated only on meat fat content, which was substantially lower compared to that of control fish. Despite the higher SFA as well as lower UFA, MUFA, PUFA, n-6 and n-3 fatty acid content of trout meat that received nutmeg extract with feed, the PUFA/SFA and n-6/n-3 ratios remained within the favourable range for human nutrition, e.g. >0.4 and <5, respectively.

Colonization by lentic macroinvertebrates: evaluating colonization processes using artificial substrates and appraising applicability of the technique

1998 ◽  
Vol 55 (11) ◽  
pp. 2425-2435 ◽  
Author(s):  
Hugues P Benoît ◽  
John R Post ◽  
Eric A Parkinson ◽  
N Tom Johnston
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Relative Abundance ◽  
Artificial Substrates ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Short Period ◽  
Littoral Zones ◽  
Immigration And Emigration ◽  
Colonization Curve ◽  
Prey Items

Our objectives were to describe the patterns of colonization of lentic macroinvertebrates on artificial substrates and to evaluate how this information can then be used to effectively and efficiently sample macroinvertebrates in vegetated littoral zones of lakes. Colonization of taxa in terms of both richness and density generally followed a Michaelis-Menton saturating curve with an initially rapid increase in densities up to a plateau within a short period of time (< 8 days). We propose that this initial colonization is due to random encounters with the substrate and that the plateau represents a balance between immigration and emigration. Accordance with the saturating colonization curve improved with increasing densities of individuals. As a whole, the spatial pattern of colonization by orders of macroinvertebrates became more aggregated with time, indicating that true random encounter colonization occurs mainly in the early stages, and consequently, this is the time when sampling should best represent relative abundance. In addition, we found that invertebrate colonists of the substrata were concordant with prey items in the guts of rainbow trout (Oncorhynchus mykiss), a facultative benthivore.

scholarly journals Predation By the Nonnative Rainbow Trout, Oncorhynchus Mykiss (Walbaum, 1792), on the Native Biota from Freshwater Environment of the Central Andes (Argentina)

2021 ◽  
Vol 23 (1) ◽  
pp. 67-72
Author(s):  
Juan Manuel Rios
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Stomach Contents ◽  
Central Andes ◽  
Predation Pressure ◽  
Freshwater Environment ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
The Andes ◽  
The Impact ◽  
Andes Region

Abstract This study aimed to examine the impact of the nonnative rainbow trout Oncorhynchus mykiss on the native biota that inhabits freshwater environments of the central Andes, Argentina. To assess the predation pressure on native Andean vertebrates and invertebrates, the stomach contents were taken from rainbow trout caught at three Andean sites. Results showed that the major prey items were the native torrent catfish Hatcheria macraei (100% in diet), Elmidae coleopterans (23%), and the native crab Aegla affinis (38%) in the rainbow trout stomachs collected from Cipolletti Dam (North zone), Yaucha River (Middle zone), and Vaina Stream (South zone), respectively. This preliminary study exhibits the predation pressure of the rainbow trout on native Andean species and suggests that policies are necessary to control the release of fry of this exotic salmonid in the Andes region.

Direct and indirect effects of sediment pulse duration on stream invertebrate assemblages and rainbow trout (Oncorhynchus mykiss) growth and survival

2001 ◽  
Vol 58 (11) ◽  
pp. 2213-2221 ◽  
Author(s):  
E Al Shaw ◽  
John S Richardson
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Pulse Duration ◽  
Indirect Effects ◽  
Benthic Invertebrate ◽  
Fine Sediment ◽  
Sediment Supply ◽  
Invertebrate Drift ◽  
Total Abundance ◽  
Rainbow Trout Oncorhynchus Mykiss

Elevated concentrations of inorganic sediment supply in streams may impair many biological functions. However, the contribution of exposure duration to the observed impacts has not been previously considered. We evaluated the effects of sediment pulse duration using 14 streamside flow-through experimental channels, each of which contained a naturally colonised invertebrate assemblage and 10 rainbow trout (Oncorhynchus mykiss) fry. Channels were exposed to fine sediment pulses of constant concentration but varied pulse duration (ranging from 0 to 6 h) every second day over 19 days. Total abundance of benthic invertebrate and family richness declined as sediment pulse duration increased. Invertebrate drift total abundance increased as pulse duration increased; however, family richness of drift decreased. Trout length and mass gain over the 19-day period was negatively correlated with pulse duration. Path analysis suggests that the direct effects of fine sediment on trout (impaired vision leading to reduced prey capture success and (or) increased metabolic costs from physiological stress) are more important to trout growth than indirect effects (decreased drift and benthic invertebrate richness and drift abundance).

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