Visual Prey Detection and Foraging in Sympatric Cutthroat Trout (Salmo clarki clarki) and Dolly Varden (Salvelinus malma)

1985 ◽  
Vol 42 (4) ◽  
pp. 785-790 ◽  
Author(s):  
M. A. Henderson ◽  
T. G. Northcote
Keyword(s):  
Surface Waters ◽  
Cutthroat Trout ◽  
Prey Detection ◽  
Dolly Varden ◽  
Salvelinus Malma ◽  
Reaction Distance ◽  
Saturation Irradiance ◽  
Dolly Varden Salvelinus Malma ◽  
Maximum Quantity ◽  
Salmo Clarki

In sympatric lacustrine cutthroat trout (Salmo clarki clarki) and Dolly Varden (Salvelinus malma), reaction distance to artificial and natural prey increased with increases in irradiance from a visual irradiance threshold (VIT, the maximum quantity of irradiance resulting in zero reaction distance to prey) to a saturation irradiance threshold (SIT, the minimum quantity of irradiance that maximizes reaction distance to prey). The VIT and SIT for Dolly Varden were approximately one and two orders of magnitude lower, respectively, than those for trout. At all irradiance levels >4.2 × 1017 photons m−2∙s−1 the reaction distance of trout exceeded that of Dolly Varden. Reaction distance to prey in both species was greatest for red irradiance followed in descending order by green, yellow and blue irradiance. The midsummer ambient irradiance regime in a lake cohabited by trout (concentrated in surface waters) and Dolly Varden (inhabiting deeper waters) showed that during daylight hours a much larger portion of the water column had irradiance levels [Formula: see text] the SIT of Dolly Varden than the SIT of trout and that irradiance levels were always [Formula: see text] the VST of Dolly Varden although only in the upper 5 m at night. Estimates of reaction distance to Diaptomus kenai and foraging velocity at several irradiance levels showed that trout have the potential to visually search a volume of water seven times greater than that searched by Dolly Varden for Diaptomus kenai on a summer day.

Initial Changes in Use of Space and Food by Experimentally Segregated Populations of Dolly Varden (Salvelinus malma) and Cutthroat Trout (Salmo clarki)

1985 ◽  
Vol 42 (1) ◽  
pp. 101-109 ◽  
Author(s):  
Jeremy M. B. Hume ◽  
Thomas G. Northcote
Keyword(s):  
Cutthroat Trout ◽  
Fourth Instar ◽  
Benthic Organisms ◽  
Dolly Varden ◽  
Salvelinus Malma ◽  
Use Of Space ◽  
Allopatric Populations ◽  
Dolly Varden Salvelinus Malma ◽  
Vertical Distributions ◽  
Salmo Clarki

Dolly Varden (Salvelinus malma) (N = 881) and cutthroat trout (Salmo clarki) (N = 1571) were captured from a native lacustrine sympatric stock and transferred to two nearby lakes, formerly fishless, to establish allopatric populations with genetic backgrounds similar to the donor stock. Nearshore (5- and 10-m depth contours) vertical distributions of segregated Dolly Varden and cutthroat trout, between spring and autumn of the first 18 mo after transfer, did not differ significantly from those in their sympatric lake. Dolly Varden were captured mainly near the bottom while cutthroat trout were more evenly distributed throughout the water column. Nevertheless, initially the allopatric Dolly Varden rapidly became highly planktivorous, virtually eliminating midwater populations of Chaoborus trivittatus and C. americanus (third and fourth instar larvae) within a year. They later ate mainly benthic organisms as in the sympatric lake. Although allopatric cutthroat trout had a similar effect on Chaoborus larvae in their lake, they also ate more large benthic prey than did those in sympatry with Dolly Varden in the donor lake. These results suggest that while there may be genetic control restricting broad vertical use of space by formerly sympatric Dolly Varden shortly after being placed in allopatry, such control is flexible enough that a highly benthofagous stock in sympatry quickly becomes planktivorous in the absence of cutthroat trout.

Segregation Between Adult Cutthroat Trout (Salmo clarki) and Dolly Varden (Salvelinus malma) in Small Coastal British Columbia Lakes

1971 ◽  
Vol 28 (9) ◽  
pp. 1259-1268 ◽  
Author(s):  
H. Andrusak ◽  
T. G. Northcote
Keyword(s):  
Food Habits ◽  
Cutthroat Trout ◽  
Dolly Varden ◽  
Salvelinus Malma ◽  
Sympatric Populations ◽  
Dolly Varden Salvelinus Malma ◽  
Wide Range ◽  
Competition For Food ◽  
Salmo Clarki ◽  
Coastal British Columbia

Comparison of spatial distributions and food of allopatric populations of cutthroat trout (Salmo clarki) and Dolly Varden (Salvelinus malma) in two lakes and of sympatric populations in a third lake suggested interactive segregation. Allopatric cutthroat changed their depth distribution throughout the spring and summer but no diel migration was noted. Changes in food habits closely corresponded to seasonal changes in vertical distribution. A wide range of food organisms was eaten from surface, midwater, and benthic sources. Allopatric Dolly Varden underwent diel changes in spatial distribution, with many being caught in onshore waters near the surface at night. They were absent from such areas in the day, apparently occupying offshore waters at greater depths. Their diet throughout summer consisted largely of surface insects and zooplankton, with lesser amounts of bottom fauna.Sympatric cutthroat trout and Dolly Varden were spatially segregated throughout the summer. Cutthroat trout occurred and fed mostly near the surface in littoral areas. In contrast, Dolly Varden were offshore and benthic in distribution and fed primarily on bottom organisms. By comparing distribution and food habits in allopatric and sympatric populations, it was suggested that competition for food may contribute to their segregation in sympatry. Although segregation of these species when cohabiting may involve interactive processes, the possibility of selective differences being of importance cannot be dismissed.

scholarly journals An Experimental Study of Feeding Behavior and Interaction of Coastal Cutthroat Trout (Salmo clarki clarki) and Dolly Varden (Salvelinus malma)

1972 ◽  
Vol 29 (5) ◽  
pp. 555-565 ◽  
Author(s):  
D. C. Schutz ◽  
T. G. Northcote
Keyword(s):  
Feeding Behavior ◽  
Cutthroat Trout ◽  
Dolly Varden ◽  
Salvelinus Malma ◽  
Coastal Lake ◽  
Dolly Varden Salvelinus Malma ◽  
Food Segregation ◽  
Food Exploitation ◽  
Salmo Clarki ◽  
Benthic Prey

Feeding behavior of cutthroat trout (Salmo clarki clarki) and Dolly Varden (Salvelinus malma) cohabiting a small coastal lake was studied experimentally to examine the importance of food exploitation as a mechanism for spatial and food segregation observed there. The hypothesis that Dolly Varden could feed more successfully on benthic prey, and cutthroat on surface prey was supported by laboratory experiments involving isolated individuals and interspecies pairs exposed to food in benthic, surface, and both locations. Differences between the species were found in resting and orientation positions and in behavior associated with food searching, location, and capture. Dolly Varden also were more successful than cutthroat in capturing benthic prey at low light intensities. Observed differences in feeding between the species were fully expressed in solitary individuals and did not appear to be magnified by interaction. It is suggested that these differences in sympatric stocks of the two species may be inherent and, therefore, that segregation is largely selective rather than interactive, even though the populations still retain considerable plasticity, enabling them to change diets or habitats when necessary or advantageous.

Retinal Structure of Sympatric and Allopatric Populations of Cutthroat Trout (Salmo clarki clarki) and Dolly Varden Char (Salvelinus malma) in Relation to their Spatial Distribution

1988 ◽  
Vol 45 (7) ◽  
pp. 1321-1326 ◽  
Author(s):  
M. A. Henderson ◽  
T. G. Northcote
Keyword(s):  
Cell Density ◽  
Cutthroat Trout ◽  
Photoreceptor Cells ◽  
Dolly Varden ◽  
Salvelinus Malma ◽  
Cross Sectional ◽  
Cone Cell ◽  
Dolly Varden Char ◽  
Allopatric Populations ◽  
Salmo Clarki

Retinal structures of cutthroat trout (Salmo clarki clarki) and Dolly Varden char (Salvelinus malma) were compared to determine if these features were consistent with the different light regimes in which the species live, depending on their sympatry or allopatry in lakes. Cone cell density in sympatric trout was over twice that of sympatric char and rod cell density was slightly less. The cross-sectional size of cone cells in sympatric trout was approximately 30% less than in sympatric char. The ratios of photoreceptor cells to ganglion cells in sympatric trout and char retinas were approximately 40:1 and 80:1, respectively. There were no differences between sympatric and allopatric trout with respect to these structural features. Estimates of cone cell density, cone size, and number of photoreceptor cells per ganglion cell for allopatric char were significantly different and intermediate between those for sympatric trout and char. All four populations had similar cone cell mosaics with four paired cones surrounding each single cone. Results are considered in relation to differences in vertical distribution and feeding of sympatric and allopatric populations in three study lakes.

Fecundity of Resident and Anadromous Dolly Varden (Salvelinus malma) in Southeastern Alaska

1973 ◽  
Vol 30 (4) ◽  
pp. 543-548 ◽  
Author(s):  
R. F. Blackett
Keyword(s):  
Egg Size ◽  
Fish Length ◽  
Dolly Varden ◽  
Salvelinus Malma ◽  
Ovary Weight ◽  
Dolly Varden Salvelinus Malma ◽  
Egg Number ◽  
Unit Of Length ◽  
The Right ◽  
Linear Regressions

Fecundity of resident Dolly Varden (Salvelinus malma) in an isolated population of southeastern Alaska averaged 66 eggs per female in comparison with 1888 eggs for anadromous Dolly Varden from two nearby streams. A relatively large egg size, averaging 3.6 mm in diameter and overlapping the range for the anadromous char, has been retained by the females in the resident population. Curvilinear regressions between egg number and fish length and linear regressions between egg number and body and ovary weights show that resident females have fewer eggs per unit of length, approximately the same number of eggs per gram of body weight, and more eggs per gram of ovary weight than anadromous females. The resident char attain sexual maturity a year earlier in life and at a smaller size than the migratory char. Development of a larger left ovary containing more eggs than the right was a common occurrence for both resident and anadromous Dolly Varden.

Isolated Fluvial Population of Dolly Varden Salvelinus malma on Bering Island (Commander Islands)

2021 ◽  
Vol 61 (3) ◽  
pp. 418-432
Author(s):  
A. M. Malyutina ◽  
K. V. Kuzishchin ◽  
A. V. Semenova ◽  
M. A. Gruzdeva
Keyword(s):  
Dolly Varden ◽  
Salvelinus Malma ◽  
Commander Islands ◽  
Dolly Varden Salvelinus Malma ◽  
Bering Island
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