Search results for "trout"
showing 10 items of 190 documents
Effects of progressive decrease of feeding frequency and re-feeding on production parameters, stomach capacity and muscle nutritional value in rainbo…
2020
Abstract Feeds and feeding constitute the major part of costs in intensive aquaculture. Any action to reduce feeding costs without negatively affecting fish production parameters and flesh quality would improve profitability of farming. Therefore, we studied the effects of feeding frequency on production parameters, stomach capacity and nutritional value of muscle in juvenile rainbow trout (Oncorhynchus mykiss) in an experiment with two stages. First, during the nine-week “starvation period” we fed rainbow trout (initial weight c. 40 g) with four different feeding protocols in an attempt to adapt the fish to a progressive decrease in the number of feeding days. During the second stage, a fo…
Effects of weekend starvation and the duration of daily feeding on production parameters of rainbow trout Oncorhynchus mykiss
2021
Abstract It would often be practical to starve the cultivated fishes over the weekends, e.g. to save in labour costs. We evaluated the possibility that domesticated juvenile rainbow trout (Oncorhynchus mykiss) could compensate for the lost growth of the 2-day weekend starvation by either hyperphagic response and/or by lower feed conversion ratio, compared to the fish fed every day in an 8-week experiment. Rainbow trout (initial weight c. 30 g, temperature 16 °C) starved during the weekends were able to increase feed intake during the weekdays clearly above the intake of the control fish after the first two weekends, also seen as an increase of the compensation coefficients over the last fou…
Changes in habitat structure, benthic invertebrate diversity, trout populations and ecosystem processes in restored forest streams: a boreal perspect…
2007
SUMMARY 1. Most Finnish streams were channelised during the 19th and 20th century to facilitate timber floating. By the late 1970s, extensive programmes were initiated to restore these degraded streams. The responses of fish populations to restoration have been little studied, however, and monitoring of other stream biota has been negligible. In this paper, we review results from a set of studies on the effects of stream restoration on habitat structure, brown trout populations, benthic macroinvertebrates and leaf retention. 2. In general, restoration greatly increased stream bed heterogeneity. The cover of mosses in channelised streams was close to that of unmodified reference sites, but a…
Adaptive radiation along a thermal gradient: preliminary results of habitat use and respiration rate divergence among whitefish morphs.
2014
Adaptive radiation is considered an important mechanism for the development of new species, but very little is known about the role of thermal adaptation during this process. Such adaptation should be especially important in poikilothermic animals that are often subjected to pronounced seasonal temperature variation that directly affects metabolic function. We conducted a preliminary study of individual lifetime thermal habitat use and respiration rates of four whitefish (Coregonus lavaretus (L.)) morphs (two pelagic, one littoral and one profundal) using stable carbon and oxygen isotope values of otolith carbonate. These morphs, two of which utilized pelagic habitats, one littoral and one …
Identification and dose dependency of ibuprofen biliary metabolites in rainbow trout
2012
Abstract The biotransformation of the anti-inflammatory drug ibuprofen (IBF) was studied by exposing rainbow trout ( Oncorhynchus mykiss ) to IBF via intraperitoneal (i.p.) injection, and via water at four (0.17, 1.9, 13 and 145 μg L −1 ) exposure levels for 4 d. Following exposure, the bile was collected and analyzed by LC–MS/MS methods. The identification of the formed metabolites in i.p. injected fish bile was based on the exact mass determinations by a time-of-flight mass analyzer (Q–TOF–MS) and on the studies of fragments and fragmentation patterns of precursor ions by ion trap mass analyzer (IT-MS). In addition to unmetabolized IBF, several phase I and phase II metabolites were found …
Design and Simulation of a Vision-Based Automatic Trout Fish-Processing Robot
2021
Today, industrial automation is being applied in a wide range of fields. The initial modeling of robots and mechanical systems together with simulation results in optimal systems. In this study, the designed system is simulated to obtain the required velocities, accelerations and torques of the actuating arms in a vision-based automatic system. Due to the slippery skin of fish and the low friction coefficient, it is not easy to design an optimal tool to handle fish. Since the fish-processing operation is undertaken step by step and provides fish stability, it is essential that the gripper enables different processing operations along the system. The proposed system performs belly-cutting, b…
Host specificity of Argulus coregoni (Crustacea: Branchiura) increases at maturation.
2007
SUMMARYWe tested the hypothesis that host specificity in ectoparasites does not depend exclusively on the features of the host but also on surrounding habitats, using 2 fish ectoparasites, Argulus coregoni and A. foliaceus (Crustacea: Branchiura), occurring sympatrically in Finnish lakes. Although these parasites are considered to be of low specificity, we found that the larger of the 2 species, A. coregoni developed a pronounced preference for salmonid hosts at the beginning of maturation (defined by the presence of copulating specimens). Argulus foliaceus infects a much wider range of fish hosts. We showed that specialization of A. coregoni on salmonids does not necessarily result from in…
Efficacy of emamectin benzoate in the control of Argulus coregoni (Crustacea: Branchiura) on rainbow trout Oncorhynchus mykiss.
2004
Efficacy of in-feed treatment with emamectin benzoate (Slice) for the control of ectoparasitic Argulus coregoni on rainbow trout Oncorhynchus mykiss was tested under laboratory and field conditions. In both experiments fish were fed with fish feed to deliver a therapeutic dose of 0 (control) or 50 microg emamectin benzoate kg(-1) d(-1) (treatment) for a period of 7 d. After 3 d of challenge with A. coregoni in the laboratory, the infestation level in treated fish was lower than that observed in the controls (p0.001). Efficacy of 100% against newly hatched A. coregoni metanauplii and adults and 80% against juveniles was observed. In the field, trial medication was undertaken at 2 sections on…
Epizootiology of protozoans in farmed salmonids at northern latitudes
1997
Abstract Protozoan ectoparasites were examined in a northern salmonid fish farm over a 10-year period, June 1984–May 1994, by the same researcher, with similar catching and sampling procedures throughout. Husbandry procedures remained constant during the study, e.g., fingerlings were kept in steel tanks and yearlings in both steel tanks and earth ponds. Ichthyobodo necator, Chilodonella hexasticha and Ichthyophthirius multifilurs infections were treated with formalin, salt and malachite green-formalin baths, respectively, whenever any parasites were found. Altogether 10 790 randomly sampled salmon (Salmo solar), sea trout (S. trutta m. trutta) and brown trout (S. trutta m. lacustris) were s…
Nocturnal drift of mayfly nymphs as a post-contact antipredator mechanism
2000
SUMMARY 1. The predominantly nocturnal constrained drift of stream invertebrates is commonly regarded as a behaviour that avoids encounters with visually foraging fish in the water column. The alternative explanation, that drift peaks are caused by bottom-feeding, nocturnal predators, has rarely been tested. 2. We examined these hypotheses by collecting invertebrate drift in five streams in northern Finland: one with brown trout (Salmo trutta, a drift-feeding fish), one with alpine bullhead (Cottus poecilopus, a benthic fish), one with both species, and two fishless streams. 3. Drift by Baetis mayflies was aperiodic or slightly diurnal in both fishless streams on all sampling occasions. In …