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.

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.

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.

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.

Relationships between body size and secondary sexual characters, and sperm characters in male Dolly Varden char (Salvelinus malma )

2016 ◽  
Vol 26 (3) ◽  
pp. 397-402 ◽  
Author(s):  
Toshiaki Yamamoto ◽  
Noritaka Hirohashi ◽  
Eiji Fujiwara ◽  
Tatsuya Suzuki ◽  
Hatsuna Maruta ◽  
...  
Keyword(s):  
Body Size ◽  
Dolly Varden ◽  
Salvelinus Malma ◽  
Dolly Varden Char ◽  
Secondary Sexual Characters ◽  
Sperm Characters ◽  
Secondary Sexual

Aggressive interactions affect foraging and use of space in a drift foraging salmonid, Salvelinus malma (Salmoniformes: Salmonidae)

2019 ◽  
Vol 187 (3) ◽  
pp. 774-781 ◽  
Author(s):  
Jeffrey L Cullen ◽  
Gary D Grossman
Keyword(s):  
Foraging Behaviour ◽  
Field Studies ◽  
Habitat Choice ◽  
Dolly Varden ◽  
Salvelinus Malma ◽  
Intraspecific Interactions ◽  
Use Of Space ◽  
Aggressive Interactions ◽  
Dolly Varden Char ◽  
Alaskan Stream

Abstract Although intraspecific interactions likely affect habitat choice and foraging behaviour in animals, our knowledge regarding how these factors interact is frequently limited to either lab or field studies, but not both. We observed pairs of dominant and subordinate drift-foraging Dolly Varden char (Salvelinus malma) in an Alaskan stream, and quantified intraspecific interactions and foraging behaviour. Dominant individuals had higher foraging rates, occupied slower holding velocities and were displaced shorter distances during bouts compared to subordinate individuals. Individuals initiated bouts more frequently from the downstream position, than from lateral or upstream positions. Dominant individuals were more likely to occupy the upstream position after a bout than subordinates, which ensures that dominants have the first opportunity to capture drifting prey.

Combined phylogenetic analysis of ribosomal ITS1 sequences and new chromosome data supports three subgroups of Dolly Varden char (Salvelinus malma)

1999 ◽  
Vol 56 (8) ◽  
pp. 1504-1511 ◽  
Author(s):  
Ruth B Phillips ◽  
Linda I Gudex ◽  
Kathleen M Westrich ◽  
Alfred DeCicco
Keyword(s):  
Phylogenetic Analysis ◽  
Dna Sequences ◽  
Lake Trout ◽  
Salvelinus Alpinus ◽  
Dolly Varden ◽  
Salvelinus Malma ◽  
Dolly Varden Char ◽  
The North ◽  
Rdna Sequences ◽  
Kamchatka River

A phylogenetic analysis of the subspecies of Salvelinus malma (Dolly Varden char) was done using DNA sequences from the first internal transcribed spacer (ITS1) of the ribosomal DNA (rDNA). Sequences were obtained from the northern S. malma malma from the Noatak River, Alaska, and the Kamchatka River, Russia; from the southern North American form S. malma lordi from the Fox River, Kenai peninsula, and Auke Bay near Juneau, Alaska; and from the southern Asian form S. malma krascheninnikovi from Belaya River in Sakhalin Island, Russia. These sequences were combined with others from Salvelinus alpinus (Arctic char) from several locations in the North Pacific and Europe and analyzed using maximum parsimony and neighbor joining algorithms with Salvelinus namaycush (lake trout) as an outgroup. The resulting trees had two well-supported groups: S. m. malma and S. m. krascheninnikovi in one group and S. m. lordi and various populations of S. alpinus in the other. Salvelinus m. malma and S. m. krascheninnikovi were sister taxa, and S. m. lordi was most closely related to S. alpinus from Northwest Territories (S. a. erythrinus). New chromosome data from S. m. malma from northwestern Alaska supported the three named subspecies because S. m. malma from both Alaska and Russia have 2n = 78 compared with 2n = 82 for the two southern forms and the location of the nuclear organizer regions (NORs) was different in each of the three subspecies.

Osmoregulatory Ability of Wild Coho Salmon (Oncorhynchus kisutch) and Dolly Varden Char (Salvelinus malma) Smolts

1988 ◽  
Vol 45 (8) ◽  
pp. 1487-1490 ◽  
Author(s):  
Scott W. Johnson ◽  
Jonathan Heifetz
Keyword(s):  
Water Temperature ◽  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Dolly Varden ◽  
Salvelinus Malma ◽  
Small Stream ◽  
Fish Size ◽  
Dolly Varden Char ◽  
Seawater Challenge ◽  
Osmoregulatory Ability

Osmoregulatory ability of wild coho salmon (Oncorhynchus kisutch) and Dolly Varden char (Salvelinus malma) smolts migrating from a small stream in southeastern Alaska was assessed by plasma Na+ levels after a 24-h seawater challenge. Osmoregulatory ability of coho salmon was unaffected by time of out-migration, water temperature, and fish size. Osmoregulatory ability of Dolly Varden char was apparently affected by time of out-migration or water temperature but not by fish size. Char migrating in the first half of the migration period, when water temperature was usually < 8.0 °C, had lower plasma Na+ levels than did char migrating in the second half when temperatures were [Formula: see text]. A plasma Na+ threshold of 170 mmol∙L−1, used by others to separate smolts from silvery parr, indicated that 70% of the coho salmon and 80% of the Dolly Varden char we sampled were physiologically prepared to enter seawater. The remaining fish may have suffered some level of osmoregulatory stress.

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