Salmon Redds Research Articles

Physicochemical Characteristics of the Hyporheic Zone Affect Redd Site Selection by Chum Salmon and Fall Chinook Salmon in the Columbia River

Abstract Chum salmon Oncorhynchus keta and fall chinook salmon O. tshawytscha spawned at separate locations in a side channel near Ives Island, Washington, in the Columbia River downstream of Bonneville Dam. We hypothesized that measurements of water depth, substrate size, and water velocity would not sufficiently explain the separation in spawning areas and began a 2-year investigation of physicochemical characteristics of the hyporheic zone. We found that chum salmon spawned in upwelling water that was significantly warmer than the surrounding river water. In contrast, fall chinook salmon constructed redds at downwelling sites, where there was no difference in temperature between the river and its bed. An understanding of the specific factors affecting chum salmon and fall chinook salmon redd site selection at Ives Island will be useful to resource managers attempting to maximize available salmonid spawning habitat within the constraints imposed by other water resource needs.

Use of Aerial Photography to Monitor Fall Chinook Salmon Spawning in the Columbia River

This paper compares two methods of enumerating the redds of chinook salmon Oncorhynchus tshawytscha and their application to the monitoring of spawning activity. In 1994 and 1995, aerial photographs of fall chinook salmon spawning areas in the Hanford Reach of the Columbia River were digitized and mapped by means of geographical information systems techniques as part of annual population assessments. The numbers of redds visible in these photographs were compared with the counts obtained from visual surveys made from fixed-wing aircraft. The proportions of the total redds in each of five general survey areas were similar for the two enumeration techniques. However, the total number of redds based on aerial photographs was 2.2 times as high as that observed visually in 1994 and 3.0 times as high in 1995. The divergence in redd counts was most evident near the time of peak spawning activity, when the number of redds in individual spawning clusters exceeded 500. Aerial photography thus improved our ability to determine the number of visible salmon redds and to quantify habitat use.

Hydrochemistry of the hyporheic zone in salmon spawning gravels: a preliminary assessment in a degraded agricultural stream

AbstractHydrochemical changes were monitored in a simulated, sea run salmon redd in a small agricultural stream in northeast Scotland following the 1998–1999 spawning season. Immediately after redd construction, the hydrochemical characteristics of hyporheic water, at depths of 0.1 m and 0.3 m, were very similar to stream water. These apparently well‐mixed waters were alkaline, well‐oxygenated and enriched in nutrients. In the weeks and months following redd construction, clear and statistically significant differences in the chemistry of stream and hyporheic waters were observed. Typically, hyporheic water had lower concentrations of dissolved oxygen (mean 7.35 mg L−1 at 0.3 m depth) than stream waters (mean=11.26 mg L−1). Alkalinity, calcium, sulphate and conductivity levels tended to be higher in hyporheic waters, with concentrations increasing with depth. These data implied an increasing influence of groundwater with depth in the hyporheic zone following redd construction; an inference supported by subsequent hydraulic head measurements, which revealed an upwards groundwater flux in the stream bed. However, groundwater–surface water interactions were dynamic and complex: road salts eluted into the stream during periods of snowmelt simulated tracer experiments that implied that a reversed hydraulic gradient may occur at high flows with deeper streamwater penetration and mixing in the hyporheic zone. High flows also result in the mobilization of fine sediments from the stream bed which subsequently infiltrated into spawning gravels. These appear to cause ‘capping’ of redds and probably reduce the hydraulic conductivity of the redd matrix. Infiltrating sediments also contain a small, but probably important organic component, the decomposition of which may contribute to oxygen consumption and nutrient mineralization in the hyporheic zone. Copyright © 2001 John Wiley & Sons, Ltd.

Knowledge representation and qualitative simulation of salmon redd functioning. Part I: qualitative modeling and simulation

This work aims at representing empirical knowledge of freshwater ecologists on the functioning of salmon redds (spawning areas of salmon) and its impact on mortality of early stages. For this, we use Qsim, a qualitative simulator. In this first part, we provide unfamiliar readers with the underlying qualitative differential equation (QDE) ontology of Qsim: representing quantities, qualitative variables, qualitative constraints, QDE structure. Based on a very simple example taken of the salmon redd application, we show how informal biological knowledge may be represented and simulated using an approach that was first intended to analyze qualitatively ordinary differential equations systems. A companion paper (Part II) gives the full description and simulation of the salmon redd qualitative model. This work was part of a project aimed at assessing the impact of the environment on salmon populations dynamics by the use of models of processes acting at different levels: catchment, river, and redds. Only the latter level is dealt with in this paper.

Knowledge representation and qualitative simulation of salmon redd functioning. Part II: qualitative model of redds

This paper describes a qualitative model of the functioning of salmon redds (spawning areas of salmon) and its impact on mortality rates of early stages. For this, we use Qsim, a qualitative simulator, which appeared adequate for representing available qualitative knowledge of freshwater ecology experts (see Part I of this paper). Since the number of relevant variables was relatively large, it appeared necessary to decompose the model into two parts, corresponding to processes occurring at separate time-scales. A qualitative clock allows us to submit the simulation of salmon developmental stages to the calculation of accumulated daily temperatures (degree-days), according to the clock ticks and a water temperature regime set by the user. Therefore, this introduces some way of real-time dating and duration in a purely qualitative model. Simulating both sub-models, either separately or by means of alternate transitions, allows us to generate the evolutions of variables of interest, such as the mortality rates according to two factors (flow of oxygenated water and plugging of gravel interstices near the bed surface), under various scenarios.

Nest Placement and Egg Distribution in Atlantic Salmon Redds

Atlantic salmon, Salmo salar, deposit their eggs in excavated depressions called nests. These nests are built from downstream to upstream within one or more redds, and each redd corresponds to a continuous area of the streambed disturbed by the female digging activities. Redd topographic measurements and egg excavation were performed to determine number of nests per redd and per female, nest depth, distances between successive nests, number of eggs deposited per nest, and egg survival in nests created by six grilse Atlantic salmon, five spawning in an experimental stream (Lapitxuri channel) and one in a natural stream (Lurgorrieta Creek, a tributary of the Nivelle River in southwest France). All females constructed a single redd, except one which built two redds in the channel. Redd surface area ranged between 2.3 and 5.7 m2. Each redd had a raised mound of gravel or dome under which most of the eggs were located, and an upstream depression or ‘pot’. Based on expected egg-to-juvenile survival rates previously obtained in the Lapitxuri channel and on juvenile recoveries, between 96 and 97% of the eggs deposited in the channel sections were retrieved. Each female constructed 7 to 11 nests over a period of 3 to 5 days. The first three nests had an average burial depth of 12.9 cm (±1.6 SD) which was greater than the last three nests (mean 9.5 cm±2.6 SD). Eggs removed from the first three nests had higher fertility rates (95.5% vs. 87.2%), greater survival (83.5% vs. 63.1%) and lower occurrences of abnormalities (1.9% vs. 5.5%) than those deposited in the last three nests. Typically, the percentage of eggs deposited per female decreased from the first to the last nest, such that the last two to three nests possessed only a small number of scattered eggs. Similar results were observed in the redd located in Lurgorrieta Creek. The adaptive consequences of the topographic features of redds and the egg allocation patterns we found are discussed.

Spawning Habitat Used by Fall Chinook Salmon in the Snake River

Literature describing spawning habitat used by fall-run chinook salmon Oncorhynchus tshawytscha is lacking for populations using large, main-stem rivers. A stable spawning flow regime in the Snake River below Hells Canyon Dam and enhanced survey capabilities using remote underwater videography allowed us to accurately describe spawning habitat used by fall chinook salmon within this large river. Water depth measured at 205 fall chinook salmon redds ranged from 0.2 to 6.5 m. Mean water column velocity at 145 redds ranged from 0.4 to 2.1 m/s, and substrate- level water velocity at 164 redds ranged from 0.1 to 2.0 m/s. Substrate size classifications from 112 redds indicated that areas having particle sizes that are relatively homogenous with diameters of 2.5–15.0 cm are used for spawning. During our study, spawning generally began as water temperatures dropped below 16.0°C, and concluded as temperatures approached 5.0°C. Our results corroborate earlier observations of fall chinook salmon spawning in deep, fast-velocity water in the Hanford Reach of the Columbia River and significantly expand current criteria used to model spawning habitat availability for these fish within large rivers.

Fall Chinook Salmon Spawning in the Tailraces of Lower Snake River Hydroelectric Projects

Abstract We conducted studies from 1993 to 1997 to identify and characterize potential spawning habitat of “endangered” fall chinook salmon Oncorhynchus tshawytscha in areas downstream of four Snake River dams. This information was needed to provide guidelines for future operation of the lower Snake River hydroelectric system, including assessment of reservoir drawdown, and for site-specific construction planning. We used Geographic Information System mapping technology to direct our initial search efforts. Suitable spawning habitat was defined based on physical habitat characteristics of the tailrace areas. Redd surveys were conducted in primary search areas and planned construction sites from mid-November through December with an underwater video system. The survey path and redd locations were mapped by using a Global Positioning System. During the 4-year study, fall chinook salmon redds were found in the tailrace downstream of Lower Granite (LGR), Little Goose (LGO), and Ice Harbor (IH) dams. The redds...

Scour of Chinook Salmon Redds on Suction Dredge Tailings

Abstract We measured scour of the redds of chinook salmon Oncorhynchus tshawytscha on dredge tailings and natural substrates in three tributaries of the Klamath River, California. We measured maximum scour with scour chains and net scour by surveying before and after high winter flows. Scour of chinook salmon redds located on dredge tailings exceeded scour of redds on natural substrates, although the difference varied among streams. Our results show that fisheries managers should consider the potential negative effects of dredge tailings on the spawning success of fall-spawning fishes such as chinook salmon and coho salmon O. kisutch.

Relationship between chinook salmon (Oncorhynchus tshawytscha) redd densities and PHABSIM-predicted habitat in the Merced and Lower American rivers, California

An index of chinook salmon (Oncorhynchus tshawytscha) spawning habitat predicted using the physical habitat simulation system (PHABSIM) component of the instream flow incremental methodology was compared with redd densities and locations for sites in the Merced River, California, during 1996 and with redd numbers in sites in the Merced and Lower American rivers, California, from 1989 through 1996. Predicted weighted useable area (WUA) was significantly correlated with chinook salmon spawning density and location at five of seven sites in the Merced River. At the microhabitat level, in the Merced River during 1996, there was a significant relationship between chinook salmon redd location and predicted WUA. Cells with more WUA in the Merced River tended to have more redds. At the mesohabitat level, there was a significant relationship between redd density and predicted WUA in both rivers. Transect areas in the Merced River with higher predicted WUA had more redds. Sites with higher numbers of redds had more predicted WUA. Significant correlations between predicted WUA and spawning locations increase confidence in the use of PHABSIM modeling results for fisheries management in the Merced and Lower American rivers as well as in other rivers.

Sensitivity of fish embryos to weathered crude oil: Part II. Increased mortality of pink salmon (Oncorhynchus gorbuscha) embryos incubating downstream from weathered Exxon valdez crude oil

AbstractWe incubated pink salmon embryos under three exposure conditions, direct contact with oil‐coated gravel, effluent from oil‐coated gravel, and direct contact with gravel coated with very weathered oil (VWO). Embryo mortalities and polynuclear aromatic hydrocarbon (PAH) accumulation in embryo tissues during the direct‐contact and effluent exposure experiments were not significantly different, indicating that PAH accumulation was mediated by aqueous transport. Mortality rates for embryos exposed initially to a total PAH concentration (TPAH) of 1.0 ppb were significantly higher than controls when the PAH were derived from VWO. The same aqueous TPAH concentration failed to increase mortality rates when the PAH were derived from less weathered oil, indicating that toxicity of effluents from the VWO was primarily associated with the larger PAH. We conclude that water quality standards for TPAH above 1.0 ppb may fail to protect fish embryos. Further, pink salmon embryos incubating in Prince William Sound after the Exxon Valdez oil spill may have accumulated lethal concentrations of PAH from interstitial water that was contaminated when it percolated through oil reservoirs located upstream from salmon redds.

Relationship between chinook salmon (<i>Oncorhynchus tshawytscha</i>) redd densities and PHABSIM-predicted habitat in the Merced and Lower American rivers, California

Relationship between chinook salmon (<i>Oncorhynchus tshawytscha</i>) redd densities and PHABSIM-predicted habitat in the Merced and Lower American rivers, California

Spawning Habitat Segregation of Sympatric Sockeye and Pink Salmon

Abstract Spatiotemporal distributions and microhabitat use of pink salmon Oncorhynchus gorbuscha and sockeye salmon O. nerka were studied in Lake Creek, southeast Alaska, during three spawning seasons. Sockeye salmon migrated approximately 1 week earlier than pink salmon and spawned 250–350 m upstream from pink salmon. Habitat overlap measured with proportional similarity index monotonically increased with increasing spawner densities. Multidimensional niche spaces measured with water depth, current velocity, and channel gradient at redds were significantly different between pink and sockeye salmon (P < 0.005, Hotelling's T 2-test). However, classification of the redds into individual species was subjected to large error rates; 33% of 70 pink salmon redds and 34% of 125 sockeye salmon redds were misclassified. Competitive interaction between pink and sockeye salmon was not demonstrated.

Status of Fall Chinook Salmon Populations in the Mid-Columbia River, 1948–1992

Abstract Historically, fall Chinook salmon Oncorhynchus tshawytscha spawned in the main-stem Columbia River over a distance of approximately 900 km. However, because of hydroelectric development and other human activities, most natural production of upriver stocks of fall Chinook salmon (upriver bright, URB) is now restricted to a 90-km-long section of river known as the Hanford Reach. The adjacent Hanford Nuclear Reservation was managed for production of nuclear materials from 1943 to 1971, which restricted many development activities, including additional hydroelectric projects. Aerial counts of fall Chinook salmon redds since 1948 at the Hanford Reach provide an index of relative abundance among spawning areas and years. Redd counts during peak spawning were less than 1,000 annually from 1948 to 1961, but they increased to as high as 8,800 in 1989 following construction of several main-stem dams on both the Columbia and Snake rivers. Escapement of adult fall Chinook salmon to the Hanford Reach averaged...

Population viability of the Snake River chinook salmon (Oncorhynchus tshawytscha)

In the presence of historical data, population viability models of intermediate complexity can be parameterized and utilized to project the consequences of various management actions for endangered species. A general stochastic population dynamics model with density feedback, age structure, and autocorrelated environmental fluctuations was constructed and parameterized for best fit over 36 years of spring chinook salmon (Oncorhynchus tshawytscha) redd count data in five Idaho index streams. Simulations indicate that persistence of the Snake River spring chinook salmon population depends primarily on density-independent mortality. Improvement of rearing habitat, predator control, reduced fishing pressure, and improved dam passage all would alleviate density-independent mortality. The current value of the Ricker α should provide for a continuation of the status quo. A recovery of the population to 1957–1961 levels within 100 years would require an approximately 75% increase in survival and (or) fecundity. Manipulations of the Ricker β are likely to have little or no effect on persistence versus extinction, but considerable influence on population size.

Occurrence of Atlantic salmon parr in redds at spawning time

Several Atlantic salmon parr of different sizes were found alive in salmon redds under a 10–30 cm layer of stones at spawning time. Parr, both mature and immature, remain inactive in redds during daylight but show nocturnal activity.

Inter- and intra-specific variability in female salmonid spawning behaviour

Egg pocket characteristics determined from the excavation of 29 stranded redds made by Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) in the River Vosso in western Norway are presented. The egg pockets of Atlantic salmon were, on average, deeper (27.0 vs. 14.8 cm) and contained more eggs (707 vs. 148) than those of brown trout. An adaptive "test-digging" behaviour was indicated by the finding of a significant association between false redds and gravel classified as low-quality spawning substrate. Based on fecundity data and number of eggs per redd, it was estimated that individual Atlantic salmon and brown trout deposited their eggs in 8.4 and 5.7 different redds, respectively. A 100-year data series indicates that the high proportion of stranded salmon redds (23%) can be attributed to the high frequency (27% of the years) and random occurrence of low water discharge rates. Estimated probabilities of extinction and associated variances in fitness assigned different spawning behaviours suggest that the temporal and spatial variation in offspring survival produces a selective advantage for the multiple-redd tactics over the single-redd tactic. Moreover, in contrast to iteroparous salmonids, semelparous Oncorhynchus species invariably place all their offspring in one redd. This dichotomy can most likely be ascribed to the provision of parental care (i.e., redd guarding) by semelparous salmonids.

Redd characteristics and implications for survival of Chinook salmon (Oncorhynchus tshawytscha) embryos in the Waitaki River, New Zealand

Abstract Chinook salmon (Oncorhynchus tshawytscha) redd characteristics were measured at three locations in the glacially‐sourced mainstem and two locations in small, primarily rainfed, tributaries of the lower Waitaki River. Mean redd size was 17.5 m2 ; lengths of redds ranged from 2.4 to 10 m and their widths ranged from 1.2 to 9.5 m. Water depth (mean ± SD = 0.37 ± 0.09 m) and water velocity (mean 0.68 ± 0.27 m s−1 ) were significantly different between two of the mainstem locations but this may have resulted from differences in site conditions rather than preference by salmon. Substrate permeability, water flow rate through the substrate (termed apparent velocity herein) and oxygen were high in all redds and any “stress” to early fish life stages would likely result from excessive permeabilities (> 55.0 m h−1 ) and apparent velocities (> 0.15 m h−1 ) rather than inadequate water circulation in the substrate. Although salmon did not use all available spawning habitat, in situ redd conditions generally favoured good development and high survival rates.

Mature male parr buried among eggs in an Atlantic salmon redd

A mature mate parr of Atlantic salmon was found buried among eggs 28 cm beneath the gravel surface in a salmon redd. Egg mortality in this egg‐pocket was considerably higher than in neighbouring egg‐pockets (52 v. 3%), presumably due to decay.

Mature male parr buried among eggs in an Atlantic salmon redd

Mature male parr buried among eggs in an Atlantic salmon redd