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Covering Rearing Tanks Improves brown trout Growth and Feed Conversion

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Agricultural Sciences 2016年第12期7卷 869-878页

作者： Eric Krebs Michael E. Barnes Patrick A. Nero South Dakota Department of Game Fish and Parks McNenny State Fish Hatchery Spearfish SD USA

Although an important part of the natural environment of fish, overhead cover is usually absent during hatchery rearing. To evaluate the possible influence of overhead cover on juvenile brown trout Salmo trutta hatchery rearing performance, this study compared three different cover treatments: near-full (98%) cover, partial (65%) cover, and no cover (completely open). After 12 weeks of rearing in 1.8 m-diameter circular tanks, total tank weight gain was significantly greater and feed conversion ratios were significantly less in tanks of brown trout that were either partially or near-totally covered, in comparison to those tanks that were completely open. The viscerosomatic index, hepatosomatic index, and splenosomatic index values were not significantly different among any of the treatments. Fin condition indices were also not significantly different. The use of either partial or full covers is recommended to maximize brown trout rearing efficiencies, with full covers providing the additional benefit of preventing fish from jumping out of the tanks.

关键词： brown trout Overhead Cover Salmo trutta Circular Tanks

Thermal Tempering Does Not Impact Rainbow trout and brown trout Survival

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Advances in Bioscience and Biotechnology 2020年第7期11卷 345-353页

作者： Nathan Huysman Jill M. Voorhees Eric Krebs Michael E. Barnes South Dakota Department of Game Fish and Parks McNenny State Fish Hatchery Spearfish SD USA

Hatchery-reared fish are frequently adjusted (tempered) to the higher water temperatures present in the water bodies where they are to be stocked. This study was undertaken to determine the necessity of such tempering practices. This study used rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta) reared at 11.2°C. The first two trials for each species were designed to simultaneously determine the upper incipient lethal temperature and 100% lethal temperature over a 14-day period. The third trial for each species evaluated the effects of an exaggerated 12-hour tempering regime on fish survival after placement in elevated water temperatures. After transfer from a water temperature of 11.2°C, no rainbow trout survived at 26°C, and only 50% survived at 25°C. No brown trout survived at 22°C and only 50% at 20°C. Survival of rainbow trout was not improved by the 12-hour tempering regime where water temperatures were slowly increased from 11.2°C to either 25°C or 26°C. Similarly, tempering did not improve brown trout survival at either 20°C or 22°C. These results suggest that tempering is not needed when hatchery-reared trout are reared and stocked at the water temperatures within the range of those used in this study.

关键词： Tempering Rainbow trout Oncorhynchus mykiss brown trout Salmo trutta Temperature

Ultraviolet reflection enhances the risk of predation in a vertebrate

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Current Zoology 2013年第2期59卷 151-159页

作者： Ricarda MODARRESSIE IngolfE RICK Theo C. M. BAKKER Institute for Evolutionary Biology and Ecology University of Bonn An der Immenburg 1 D-53121 Bonn Germany

Many animals are sensitive to ultraviolet light and also possess UV-reflective regions on their body surface. Individu- als reflecting UV have been shown to be preferred during social interactions such as mate choice or shoaling decisions. However, whether those body UV-reflections enhance also the conspicuousness to UV-sensitive predators and thereforeentail costs for its bearer is less well documented. Two size-matched three-spined sticklebacks Gasterosteus aculeatus, one enclosed in a UV-transmitting （UV＋） and another in a UV-blocking （UV-） chamber, were simultaneously presented to individual brown trout Salmo trutta. ＂yearlings＂. brown trout of this age are sensitive to the UV part of the electromagnetic spectnun and are natural predators of three-spined sticklebacks. The stickleback that was attacked first as well as the subsequent number of attacks was recorded. Sticklebacks enclosed in the UV-transmitting chamber were attacked first significantly more often compared to stickle- backs enclosed in the UV-blocking chamber. Control experiments using neutral density filters revealed that this was more likely due to LrV having an influence on hue perception rather than brighmess discrimination. The difference in attack probability cor- responded to the difference in chromatic contrasts between sticklebacks and the experimental background calculated for both the UV＋ and UV- conditions in a physiological model of trout colour vision. UV reflections seem to be costly by enhancing the risk of predation due to an increased conspicuousness of prey. This is the first study in a vertebrate, to our knowledge, demonstrating direct predation risk due to UV wavelengths [Current Zoology 59 （2）： 151-159, 2013].

关键词： UV vision brown trout Salmo trutta Ultraviolet reflection Three-spined stickleback Gasterosteus aculeatus Pre-dation risk

A potential engineering solution to facilitate upstream movement of fish in mountain rivers with weirs:Southern Carpathians,the Azuga River

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Journal of Mountain Science 2020年第3期17卷 501-515页

作者： Razvan VOICU Artur RADECKI-PAWLIK Tomasz TYMINSKI Marian MOKWA Robbin SOTIR Liliana VOICU Ecohidrology and Water Quality Protection Service National Institute of Hydrology and Water ManagementBucharest 013686Romania Division of Structural Mechanics and Material Mechanics Faculty of Civil EngineeringCracow University of TechnologyKrakow 31-155Poland Institute of Environmental Engineering Wroclaw University of Environmental and Life SciencesWroclaw 50-363Poland Robbin Sotir&Associates Inc.3602 Ernest W.Barrett Parkway MariettaGeorgia 30064-2732USA

An important aspect in the restoration of longitudinal connectivity in rivers and streams is the implementation of fish migration systems at the upstream of the functional hydraulic structures(weirs,drop structures or river sills).The diversity of these existing structures as well as the different locations of these weirs within the river,watershed and riparian zone challenge the design engineers to find new holistic solutions for fish migration *** Azuga River study area requires a new synergistic fish migration design *** a mountain area,rapid increase in water level is quite frequent,especially after heavy or prolonged rainfalls and during spring snow ***,it is necessary to design a specific system for fish migration to meet this location’s *** to the characteristics in this location of the Azuga river,the classic fish migration systems would not be *** indigenous/mountain trout is considered as the target species in this *** this is a good swimming species,the use of classical systems could,due to exhaustion,prevent and/or reduce the movement of fish upstream of the two weirs(also known as river sills).This new,comprehensive solution,presented in this paper includes:(i)the restoration and stabilization works of the right bank in the weir study area by using biotechnical measures and(ii)the upstream migration system itself-for supporting the migration of fish on the Azuga River.

关键词： Weir Fish migration system brown trout Mountainriver Soilbioengineering Connectivity