Proposed Revision of the Standard-Weight Equation for Rainbow Trout

“…Relative weight (W r ) was calculated for each fish using total length and weight measured at time of capture and the lotic standard weight (W s ) equation for rainbow trout (Simpkins and Hubert, 1996), where:…”

Section: Study Areas and Methodsmentioning

confidence: 99%

Behavioural and physiological response of trout to winter habitat in tailwaters in Wyoming, USA

Annear

Hubert

Simpkins

et al. 2002

Hydrological Processes

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Abstract:Fisheries managers have often suggested that survival of trout during the winter is a major factor affecting population densities in many stream ecosystems in the Rocky Mountains. In Wyoming, trout population reductions from fall to spring in excess of 90% have been documented in some reservoir tailwaters. Though biologists have surmised that these reductions were the result of either mortality or emigration from some river sections, the specific mechanisms have not been defined and the factors leading to the trout loss are unknown. This is a review of four studies that were conducted or funded between 1991 and 1998 by the Wyoming Game and Fish Department to understand the extent of overwinter losses, identify some of the mechanisms leading to those conditions and develop management strategies to help avoid those impacts. Winter studies were conducted on tailwater fisheries in the Green, North Platte, Bighorn and Shoshone rivers to document trout population dynamics, assess physical habitat availability, evaluate trout movement and habitat selection, and understand the relationships between food availability and bioenergetic relationships. Results indicate that winter trout losses are extreme in some years, that trout movement and habitat selection are affected by supercooled flows, and that mortality is probably not directly due to starvation. The combination of physiological impairment with frequently altered habitat availability probably leads to indirect mortality from predators and other factors.

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“…A modified Fulton's condition factor K F (Simpkins & Hubert, 1996) was calculated for each fish from K F =10 5 ML 3 T , where M is in g and L T is in mm. The parasite index (I P ) was calculated from I P =100 (total mass of parasites) (total mass of host plus parasites) 1 (Arme & Owen, 1968), where I P =50 would indicate a mass of L. intestinalis equal to M, the mass of the host's body.…”

Section: Data Collection and Analysismentioning

confidence: 99%

Ligulosis associated with mortality in largescale suckers

Shields¹,

Groves²,

Rombaugh³

et al. 2002

Journal of Fish Biology

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Investigations of a fish kill at an irrigation reservoir in the Deschutes River basin, Oregon, documented at least 153 dead largescale suckers Catostomus macrocheilus, all heavily infected with large Ligula intestinalis (Cestoda). Moribund fish nearshore were similarly infected, with no evidence of secondary disease or infection. Morbidity and mortality in all cases was probably due to severe mechanical damage to internal host organs resulting from infection with multiple, large L. intestinalis. The pathology of L. intestinalis documented in largescale sucker in this study contrasts sharply with previous accounts and may represent a new and emerging disease for largescale suckers.

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Proposed Revision of the Standard-Weight Equation for Rainbow Trout

Cited by 34 publications

References 8 publications

Body condition indices as a rapid assessment of the abundance of introduced salmonids in oligotrophic lakes of southern Chile

Body condition indices as a rapid assessment of the abundance of introduced salmonids in oligotrophic lakes of southern Chile

Behavioural and physiological response of trout to winter habitat in tailwaters in Wyoming, USA

Ligulosis associated with mortality in largescale suckers

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