Density-dependent intercohort interactions and recruitment dynamics: models and a bull trout (Salvelinus confluentus) time series

2000 ◽  
Vol 57 (6) ◽  
pp. 1220-1231 ◽  
Author(s):  
Andrew J Paul ◽  
John R Post ◽  
George L Sterling ◽  
Carl Hunt
Keyword(s):  
Time Series ◽  
Survival Rates ◽  
Effective Density ◽  
Bull Trout ◽  
Age Classes ◽  
Salvelinus Confluentus ◽  
Density Dependent ◽  
Age Cohorts ◽  
Juvenile Mortality ◽  
Stochastic Version

A simple theoretical model shows that mechanisms of density-dependent survival that result in stable dynamics for populations with only intracohort interactions during the juvenile phase can produce cyclic behaviour when cohorts interact together. We compared these theoretical results with a time series (1971-1985) on juvenile bull trout (Salvelinus confluentus) from Eunice Creek, Alberta. Abundance of bull trout in Eunice Creek ranged over two orders of magnitude over the 15 years. By assigning age-classes to the abundance data (using a probabilistic length-frequency analysis), we assessed yearly survival rates for age-classes 1-3. Survival rates for age-classes 1 and 2 were negatively correlated (P < 0.05) with the effective density (an index of total consumption) of all juvenile bull trout in Eunice Creek. These observations support the hypothesis that different age cohorts of juvenile bull trout do interact. Using a stochastic version of the model and parameter values estimated from Eunice Creek, we hypothesize that even moderate levels of adult mortality (an average adult spawns during two seasons) coupled with random variation in the density-independent component of juvenile mortality can result in an apparent cyclic pattern for bull trout. Finally, stock- recruitment relationships for these populations are not represented by a single average curve.

The demography of recovery of an overexploited bull trout, Salvelinus confluentus, population

2007 ◽  
Vol 64 (1) ◽  
pp. 113-126 ◽  
Author(s):  
Fiona D Johnston ◽  
John R Post ◽  
Craig J Mushens ◽  
Jim D Stelfox ◽  
Andrew J Paul ◽  
...  
Keyword(s):  
Adult Population ◽  
Fold Increase ◽  
Recovery Process ◽  
Data Sets ◽  
Adult Density ◽  
Life Stages ◽  
Bull Trout ◽  
Salvelinus Confluentus ◽  
Compensatory Response ◽  
Density Dependent

An exploited bull trout, Salvelinus confluentus, population experienced a 28-fold increase in adult density during a 10-year period from a minimum of 60 individuals. This demonstrates the extent to which this population was overharvested. Its ability to respond in fewer than two generations to the implementation of zero-harvest regulations suggests this population was growth-overfished not recruitment-overfished. Examination of stock–recruitment relationships of various life stages indicates that recovery of this population was regulated by the density-dependent survival of juveniles in the rearing creek. This compensatory response occurred between egg deposition and age-1 and regulated the number of fish recruiting into the adult population. A second population bottleneck became apparent later in the recovery process when density-dependent survival of the adult population resulted in its approach to an asymptote, highlighting the necessity of long-term data sets for examining these compensatory responses. Results from this study demonstrate the importance of understanding the influence of individual life stages on the ability of overexploited populations such as threatened bull trout to recover and for their future management.

Genetic clustering methods reveal bull trout (Salvelinus confluentus) fine-scale population structure as a spatially nested hierarchy

2009 ◽  
Vol 11 (4) ◽  
pp. 1421-1433 ◽  
Author(s):  
Will G. Warnock ◽  
Joseph B. Rasmussen ◽  
Eric B. Taylor
Keyword(s):  
Population Structure ◽  
Bull Trout ◽  
Fine Scale ◽  
Clustering Methods ◽  
Salvelinus Confluentus ◽  
Scale Population ◽  
Nested Hierarchy ◽  
Genetic Clustering

scholarly journals Transgenerational effects modulate density-dependent prophylactic resistance to viral infection in a lepidopteran pest

2015 ◽  
Vol 11 (3) ◽  
pp. 20150012 ◽  
Author(s):  
Kenneth Wilson ◽  
Robert I. Graham
Keyword(s):  
Disease Resistance ◽  
Survival Rates ◽  
Post Challenge ◽  
Transgenerational Effects ◽  
Density Dependent ◽  
Offspring Fitness ◽  
Rearing Density ◽  
Lepidopteran Pest ◽  
The Impact ◽  
Resistance To Viral Infection

There is an increasing appreciation of the importance of transgenerational effects on offspring fitness, including in relation to immune function and disease resistance. Here, we assess the impact of parental rearing density on offspring resistance to viral challenge in an insect species expressing density-dependent prophylaxis (DDP); i.e. the adaptive increase in resistance or tolerance to pathogen infection in response to crowding. We quantified survival rates in larvae of the cotton leafworm ( Spodoptera littoralis ) from either gregarious- or solitary-reared parents following challenge with the baculovirus S. littoralis nucleopolyhedrovirus. Larvae from both the parental and offspring generations exhibited DDP, with gregarious-reared larvae having higher survival rates post-challenge than solitary-reared larvae. Within each of these categories, however, survival following infection was lower in those larvae from gregarious-reared parents than those from solitary-reared, consistent with a transgenerational cost of DDP immune upregulation. This observation demonstrates that crowding influences lepidopteran disease resistance over multiple generations, with potential implications for the dynamics of host–pathogen interactions.

Geographic distribution, species displacement, and niche overlap for lake trout and bull trout in mountain lakes

1993 ◽  
Vol 71 (2) ◽  
pp. 238-247 ◽  
Author(s):  
David B. Donald ◽  
David J. Alger
Keyword(s):  
Trophic Structure ◽  
Lake Trout ◽  
Niche Overlap ◽  
Mountain Lakes ◽  
Bull Trout ◽  
Salvelinus Confluentus ◽  
East Central ◽  
Allopatric Populations ◽  
Trout Population ◽  
The One

Indigenous lacustrine populations of bull trout (Salvelinus confluentus) and lake trout (S. namaycush) are spatially separated within the southern part of the zone of distributional overlap (northern Montana, southwestern Alberta, and east-central British Columbia). In this area, lake trout occurred primarily in mountain lakes of 1032–1500 m elevation, while bull trout were found primarily in lakes between 1500 and 2200 m. Introductions of lake trout in the twentieth century and data obtained from beyond the study area indicated that both fishes can establish significant allopatric populations (more than 5% of the catch) in large, deep lakes (>8 ha in area and >8 m deep) over a wide elevation range. We tested the hypothesis that lake trout displace or exclude bull trout from lakes by determining the outcome of introductions of lake trout into two lakes that supported indigenous bull trout. Lake trout were introduced into Bow Lake in 1964, and by 1992 the bull trout population was decimated there and in another lake (Hector) situated 15 km downstream. Thus, lake trout can displace bull trout and may prevent bull trout from becoming established in certain low-elevation lakes. Population age-structure analyses also suggest that lake trout adversely affected bull trout. Bull trout populations in sympatry with lake trout, including the one extirpated from Hector Lake, had few old fish (18% were more than 5 years old; N = 40 fish from three lakes) compared with allopatric populations (49% were more than 5 years old; N = 235 fish from seven lakes). Niche overlap and the potential for competition between the two char species were substantial. In lakes with trophic structure ranging from simple to complex, bull trout and lake trout fed on similar foods and had similar ecological efficiencies (growth rates). Predation by lake trout on bull trout was not documented during the study.

Reach-scale movements of bull trout (Salvelinus confluentus) relative to hydropeaking operations in the Columbia River, Canada

Ecohydrology ◽  
2013 ◽  
pp. n/a-n/a ◽  
Author(s):  
Mark K. Taylor ◽  
Caleb T. Hasler ◽  
Scott G. Hinch ◽  
Bronwen Lewis ◽  
Dana C. Schmidt ◽  
...  
Keyword(s):  
Columbia River ◽  
Bull Trout ◽  
Salvelinus Confluentus

Effects of a sudden increase in natural mortality of adults on a population of the common snapping turtle (Chelydra serpentina)

1991 ◽  
Vol 69 (5) ◽  
pp. 1314-1320 ◽  
Author(s):  
Ronald J. Brooks ◽  
Gregory P. Brown ◽  
David A. Galbraith
Keyword(s):  
Clutch Size ◽  
Research Area ◽  
Effective Density ◽  
Egg Mass ◽  
Sudden Increase ◽  
Chelydra Serpentina ◽  
Density Dependent ◽  
Snapping Turtles ◽  
The Mean ◽  
Clutch Mass

A northern population of snapping turtles (Chelydra serpentina) centred around Lake Sasajewun in the Wildlife Research Area in Algonquin Park, Ontario, has been studied and individually marked since 1972. From 1972 to 1985, annual mortality and survivorship of adult females had been estimated at 1 and 96.6%, respectively, and only six dead turtles were found. Lake Sasajewun's population of C. serpentina was estimated in 1978–1979 and 1984–1985 at 38 and 47 adults, respectively. From 1976 to 1987, total number of nests found in the study area remained fairly constant and there were no significant changes in mean clutch size, mean clutch mass, or mean egg mass. On the main nest site, recruitment from 1976 to 1987 was 1.15 (1.8%) new females per year. From 1987 to 1989, we found 34 dead adult snapping turtles in the Wildlife Research Area. Observations of freshly dead animals indicated that most were killed by otters (Lutra canadensis) during the turtles' winter hibernation. A few uninjured turtles also died of septicemia in early spring shortly after emerging from hibernation. The estimated number of adults in Lake Sasajewun was 31 in 1988–1989, and the minimum number of adult residents known to be alive in the lake dropped from 47 in 1986 to 16 in 1989. In 1986 and 1987, annual adult female survivorship was estimated at 80 and 55%, respectively, and estimated numbers of nesting females declined from 82 in 1986 to 71 and 55 in 1987 and 1988, respectively. The actual number of nests found declined by 38 and 20% over the same periods. Although no significant differences occurred in mean egg mass or mean clutch size between 1987 and 1989 and earlier years, the mean clutch mass in 1988 was larger than in 1977 or 1978. This difference appeared to be due to a gradual increase in the mean age and body size of breeding females rather than to density-dependent changes. Recruitment into the adult breeding female population in 1987–1989 remained less than two individuals per year. Hatchling survival and number of juveniles were low throughout the study. Our observations support the view that populations of species with high, stochastic juvenile mortality and long adult life spans may be decimated quickly by increased mortality of adult animals, particularly if numbers of juveniles and immigrants are low. Recovery of such populations should be very slow because of a lack of effective density-dependent response in reproduction and recruitment.

The effects of long-term cadmium exposure on the growth and survival of juvenile bull trout (Salvelinus confluentus)

2002 ◽  
Vol 58 (3-4) ◽  
pp. 165-174 ◽  
Author(s):  
J.A Hansen ◽  
P.G Welsh ◽  
J Lipton ◽  
M.J Suedkamp
Keyword(s):  
Cadmium Exposure ◽  
Bull Trout ◽  
Salvelinus Confluentus ◽  
Growth And Survival

Bull Trout Salvelinus confluentus , Willamette National Forest

Fisheries ◽  
2018 ◽  
Vol 43 (9) ◽  
pp. 450-450
Keyword(s):  
National Forest ◽  
Bull Trout ◽  
Salvelinus Confluentus
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