Response of Juvenile Salmonids to Riparian and Instream Cover Modifications in Small Streams Flowing through Second-Growth Forests of Southeast Alaska

Keith, R. M.; Bjornn, T. C.; Meehan, William R.; Hetrick, Nicholas J.; Brusven, Merlyn A.

doi:10.1577/1548-8659(1998)127<0889:rojstr>2.0.co;2

Cited by 35 publications

(29 citation statements)

References 33 publications

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“…However, on clear-sky days, maximum daily temperatures decreased between the upstream and downstream reach boundary by up to 1 • C; locations further downstream experienced maximum temperatures later in the day and instantaneous cooling gradients of up to 2.5 • C (equivalent to 2.4 • C km −1 ) were observed. These decreases in temperature were much less than those observed by McGurck (1989), Keith et al (1998) and Story et al (2003), who observed instantaneous cooling gradients of between 4.0 and 9.2 • C km −1 . Variability in cooling gradients at and between sites may be attributed to differing climatic zones, prevailing weather conditions (Rutherford et al, 2004), riparian vegetation density and orientation, channel orientation, and subsurface hydrology; all control the magnitude of energy exchange and, consequently, water temperature (Poole and Berman, 2001;Webb and Zhang, 1997).…”

Section: Micrometeorological and Land Use Controls On Energy Exchangecontrasting

confidence: 52%

What causes cooling water temperature gradients in a forested stream reach?

Garner

Malcolm

Sadler

et al. 2014

Hydrol. Earth Syst. Sci.

103

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Abstract. Previous studies have suggested that shading by riparian vegetation may reduce maximum water temperatures and provide refugia for temperature-sensitive aquatic organisms. Longitudinal cooling gradients have been observed during the daytime for stream reaches shaded by coniferous trees downstream of clear cuts or deciduous woodland downstream of open moorland. However, little is known about the energy exchange processes that drive such gradients, especially in semi-natural woodland contexts without confounding cool groundwater inflows. To address this gap, this study quantified and modelled variability in stream temperature and heat fluxes along an upland reach of the Girnock Burn (a tributary of the Aberdeenshire Dee, Scotland) where riparian land use transitions from open moorland to semi-natural, predominantly deciduous woodland. Observations were made along a 1050 m reach using a spatially distributed network of 10 water temperature data loggers, 3 automatic weather stations and 211 hemispherical photographs that were used to estimate incoming solar radiation. These data parameterised a high-resolution energy flux model incorporating flow routing, which predicted spatio-temporal variability in stream temperature. Variability in stream temperature was controlled largely by energy fluxes at the water-columnatmosphere interface. Net energy gains occurred along the reach, predominantly during daylight hours, and heat exchange across the bed-water-column interface accounted for < 1 % of the net energy budget. For periods when daytime net radiation gains were high (under clear skies), differences between water temperature observations increased in the streamwise direction; a maximum instantaneous difference of 2.5 • C was observed between the upstream reach boundary and 1050 m downstream. Furthermore, daily maximum water temperature at 1050 m downstream was ≤ 1 • C cooler than at the upstream reach boundary and lagged by > 1 h. Temperature gradients were not generated by cooling of stream water but rather by a combination of reduced rates of heating in the woodland reach and advection of cooler (overnight and early morning) water from the upstream moorland catchment. Longitudinal thermal gradients were indistinct at night and on days when net radiation gains were low (under overcast skies), thus when changes in net energy gains or losses did not vary significantly in space and time, and heat advected into the reach was reasonably consistent. The findings of the study and the modelling approach employed are useful tools for assessing optimal planting strategies for mitigating against ecologically damaging stream temperature maxima.

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Section: Micrometeorological and Land Use Controls On Energy Exchangecontrasting

confidence: 52%

What causes cooling water temperature gradients in a forested stream reach?

Garner

Malcolm

Sadler

et al. 2014

Hydrol. Earth Syst. Sci.

103

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“…Most studies validate the relationship between cover abundance and fish density or biomass, principally of salmonid species (BOUSSU, 1954;SAUNDERS and SMITH, 1962;HOUSE and BOEHNE, 1985;DOLLOFF, 1986;ELLIOT, 1986;RILEY et al, 1992;LIM et al, 1993;RONI and QUINN, 2001b) but also of cyprinid species (SWALES and O'HARA, 1983;THÉVENET, 1998). But in contrast, and KEITH et al (1998) found that the summer distribution of juvenile salmonids (Oncorhynchus kisutch, Salvelinus malma) was not or little affected by the presence of cover. In fact, comparisons between field studies are extremely difficult since they differ by numerous parameters: species and life-stages, cover types, stream characteristics, spatio-temporal scales, intensity of biotic interactions, and statistical reliability .…”

Section: Effects Of Cover Structures On Biological Productivitymentioning

confidence: 93%

Nature and Functions of Cover for Riverine Fish.

Allouche¹

2002

Bull. Fr. Pêche Piscic.

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This review attempts to assess the nature and the role of cover for riverine fish assemblages. Although early identified as a key factor for fish distribution, especially for salmonids, cover (i.e. woody debris, undercut banks, boulders, turbidity...) still remains the variable least considered in the studies of fish habitat relationships. This is mainly due to the diversity of ecological functions of cover structures in fish assemblages. Cover structures are structuring components of fish habitat and contribute to the biological productivity of streams. But, at the individual scale, cover fulfils three main functions: protection against predators, visual isolation reducing competition, and hydraulic shelter. In fact, the use of cover by fish results from a trade-off between the costs and the benefits associated with its use. Although the relationships between fish and cover appear extremely complex and context-specific, a growing body of evidence highlights the potential role of cover for management purposes.Key-words : cover, shelter, riverine fish, fish habitat. NATURE ET FONCTIONS DU COUVERT POUR LES POISSONS LOTIQUES. RÉSUMÉCet article décrit la typologie ainsi que les fonctions du couvert pour les poissons lotiques. Identifié très tôt comme un facteur explicatif de la distribution des poissons, principalement chez les salmonidés, le couvert (i.e. débris ligneux, sous-berges, blocs, turbidité...) demeure néanmoins la variable la moins considérée dans l'étude des relations habitat-poissons. Ceci s'explique notamment par les fonctions écologiques très diverses que le couvert remplit vis-à-vis des assemblages piscicoles. Les structures pourvoyeuses de couvert sont des agents structurants de l'habitat piscicole et contribuent à la productivité biologique des cours d'eau. Au niveau du microhabitat du poisson, le couvert remplit trois fonctions majeures : anti-prédation, isolation visuelle limitant la compétition, et abri hydraulique. En fait, l'utilisation du couvert par les poissons résulte d'un compromis entre les coûts et les bénéfices associés d'où l'extrême complexité de cette relation qui semble plutôt spécifique à un contexte donné. Malgré les difficultés d'extrapolation, de nombreux travaux mettent en évidence la signification écologique ainsi que l'utilisation potentielle du couvert pour une gestion optimale des ressources piscicoles.Mots-clés : couvert, abri, poissons lotiques, habitat piscicole.

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“…For example, clearing of forested and riparian areas can directly affect fish assemblages by increasing stream temperatures and discharge (Hetrick et al 1998b). Indirectly, reduction of terrestrial vegetation may alter in-stream cover by reducing inputs of large woody debris, and by potentially altering the prey base (Hetrick et al 1998a, Keith et al 1998.…”

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confidence: 99%