Spatial partitioning and asymmetric hybridization among sympatric coastal steelhead trout (Oncorhynchus mykiss irideus), coastal cutthroat trout (O. clarki clarki) and interspecific hybrids

2004 ◽  
Vol 13 (9) ◽  
pp. 2773-2788 ◽  
Author(s):  
CARL O. OSTBERG ◽  
STACEY L. SLATTON ◽  
RUSSELL J. RODRIGUEZ
Keyword(s):  
Oncorhynchus Mykiss ◽  
Interspecific Hybrids ◽  
Cutthroat Trout ◽  
Steelhead Trout ◽  
Spatial Partitioning ◽  
Coastal Cutthroat Trout

The Relation between Scale Diameter and Body Length of Kamloops Trout, Salmo gairdneri kamloops

1955 ◽  
Vol 12 (5) ◽  
pp. 742-753 ◽  
Author(s):  
S. B. Smith
Keyword(s):  
Fork Length ◽  
Cutthroat Trout ◽  
Salmo Gairdneri ◽  
Steelhead Trout ◽  
Double Logarithmic Plot ◽  
Relative Growth ◽  
Coastal Cutthroat Trout ◽  
Constant Slope ◽  
Salmo Clarki ◽  
Simple Proportion

The scale/body relationship for Kamloops trout is very close to direct proportion for fish larger than 4.5 cm. fork length. The resultant plot on a double logarithmic grid is linear with a slope not significantly different from 1.00 (45°). Calculations of lengths of trout from scales at ages previous to that of capture can be made on the basis of simple proportion in two ways, (1) by use of a constant slope (45°) on a double logarithmic plot, or (2) by use of a constant zero-zero intercept on an arithmetic plot.Growth of the scales of the young is characterized by relatively rapid increase from time of scale formation, 3.5 cm. fork length up to 4.5 cm. At about 4.5 cm. fork length there is a sharp break (inflection) in the relative growth curve toward isometric growth of scales and body. Reliable estimates of the length of trout may be obtained from scales alone, using the diameter of the first circulus of the scale, the slopes and inflection of the relative scale/body plot and total diameter of the scale at time of capture.Marked Kamloops trout of known size were released in 1953. Subsequent recaptures both in 1953 and 1954 substantiated the accuracy of the method of estimating lengths of trout at ages previous to that of capture.Observations on the steelhead trout, Salmo gairdneri gairdneri, and on the coastal cutthroat trout, Salmo clarki clarki, suggest that an isometric scale/body relationship may exist among those species also.

Natural Hybridization between Steelhead Trout (Salmo gairdneri) and Coastal Cutthroat Trout (Salmo clarki clarki) in Two Puget Sound Streams

1985 ◽  
Vol 42 (1) ◽  
pp. 110-119 ◽  
Author(s):  
Donald E. Campton ◽  
Fred M. Utter
Keyword(s):  
Management Practices ◽  
Random Mating ◽  
Puget Sound ◽  
Cutthroat Trout ◽  
Natural Hybridization ◽  
Salmo Gairdneri ◽  
Hybrid Index ◽  
Steelhead Trout ◽  
Mixed Ancestry ◽  
Coastal Cutthroat Trout

A genetic investigation of anadromous trout populations in the Puget Sound area revealed numerous juvenile individuals from two streams with electrophoretic phenotypes consistent with those expected for hybrid descendents of steelhead trout (Salmo gairdneri) and coastal cutthroat trout (S. clarki clarki). The likelihood of hybridization was evaluated with a hybrid index measuring the relative probability that the combined genotype for a particular fish at several diagnostic loci could have arisen by random mating within each of the two Salmo species. The distribution of hybrid index scores among fish from the two creeks clearly demonstrated the genetic distinctness of the two species and the intermediate genotypic composition of the unknown fish. We concluded that these electrophoretically intermediate fish were natural steelhead–cutthroat hybrids based on their restricted occurrence at specific sample sites in only 2 of 23 streams surveyed, the linear distributions of juveniles from the two parental species within each stream, and the distribution of hybrid index values for a hatchery population of known mixed ancestry. Further, from estimates of gametic disequilibria and the absence of a consistent excess of heterozygotes we suggest that backcrossing may have occurred. The existence of these natural hybrids raises many questions concerning the biological bases for maintaining species integrities in regions of sympatry and indicates the need to fully understand the biological consequences of present and future management practices.

Scale Characteristics of Yearling Coastal Cutthroat and Steelhead Trout

1957 ◽  
Vol 14 (2) ◽  
pp. 203-212 ◽  
Author(s):  
E. H. Vernon ◽  
R. G. McMynn
Keyword(s):  
Fork Length ◽  
Cutthroat Trout ◽  
Salmo Gairdneri ◽  
Steelhead Trout ◽  
Scale Growth ◽  
Scale Size ◽  
Species Overlap ◽  
Coastal Cutthroat Trout ◽  
Scale Characteristics ◽  
Salmo Clarki

Some scale characteristics of 88 yearling coastal cutthroat trout (Salmo clarki clarki) and 96 yearling steelhead (Salmo gairdneri) were compared in some detail. Although the number of diagonal scale rows above the lateral line was significantly higher in cutthroat, the counts of the two species overlap. The correlation of scale circuli counts with scale diameter was 0.94 for steelhead and 0.90 for cutthroat. At any given scale size cutthroat had 8 per cent more circuli than steelhead scales. Measurements of lateral and longitudinal diameters and anterior radii of scales show that the anterior portions of cutthroat scales tend to be longer and narrower than those of steelhead.Regression analyses of each scale measurement on fork length indicated that, for any given fork length, cutthroat scales are smaller than those of steelhead; the greatest difference being apparent when anterior radii are compared. Growth of scales in a dorsoventral plane approximates isauxesis in relation to fork length but scale growth in a longitudinal plane tends toward positive heterauxesis which is particularly pronounced in the anterior portions of scales.Multiple regression analyses of scale diameter, scale row count and fork length indicated that the smaller size of cutthroat scales is not balanced by proportionate increase in their number. When scale diameter is adjusted for scale number and fork length, cutthroat scales are 15.6 per cent smaller than those of steelhead, indicating that young cutthroat are covered by their scales with less overlap.

scholarly journals Evaluating Coexistence of Fish Species with Coastal Cutthroat Trout in Low Order Streams of Western Oregon and Washington, USA

Fishes ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 4
Author(s):  
Kyle D. Martens ◽  
Jason Dunham
Keyword(s):  
Pacific Northwest ◽  
Species Interactions ◽  
Coho Salmon ◽  
Cutthroat Trout ◽  
Single Species ◽  
The Pacific ◽  
Small Streams ◽  
Coastal Cutthroat Trout ◽  
Multiple Species ◽  
Low Order

When multiple species of fish coexist there are a host of potential ways through which they may interact, yet there is often a strong focus on studies of single species without considering these interactions. For example, many studies of forestry–stream interactions in the Pacific Northwest have focused solely on the most prevalent species: Coastal cutthroat trout. To examine the potential for interactions of other fishes with coastal cutthroat trout, we conducted an analysis of 281 sites in low order streams located on Washington’s Olympic Peninsula and along the central Oregon coast. Coastal cutthroat trout and juvenile coho salmon were the most commonly found salmonid species within these streams and exhibited positive associations with each other for both presence and density. Steelhead were negatively associated with the presence of coastal cutthroat trout as well as with coho salmon and sculpins (Cottidae). Coastal cutthroat trout most frequently shared streams with juvenile coho salmon. For densities of these co-occurring species, associations between these two species were relatively weak compared to the strong influences of physical stream conditions (size and gradient), suggesting that physical conditions may have more of an influence on density than species interactions. Collectively, our analysis, along with a review of findings from prior field and laboratory studies, suggests that the net effect of interactions between coastal cutthroat trout and coho salmon do not appear to inhibit their presence or densities in small streams along the Pacific Northwest.

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