Mechanisms Responsible for Population Regulation in Young Migratory Trout, Salmo trutta. II. Fish Growth and Size Variation

10.2307/5166 ◽  
1990 ◽  
Vol 59 (1) ◽  
pp. 171 ◽  
Author(s):  
J. M. Elliott
Keyword(s):  
Salmo Trutta ◽  
Population Regulation ◽  
Size Variation ◽  
Fish Growth

scholarly journals Food availability in spring affects smolting in brown trout (Salmo trutta)

2015 ◽  
Vol 72 (11) ◽  
pp. 1694-1699 ◽  
Author(s):  
Douglas A. Jones ◽  
Eva Bergman ◽  
Larry Greenberg
Keyword(s):  
Seasonal Variation ◽  
Food Availability ◽  
Brown Trout ◽  
Salmo Trutta ◽  
Morphological Changes ◽  
Salmonid Fish ◽  
Fish Growth ◽  
Brown Trout Salmo Trutta ◽  
Previous Autumn

Prior to out-migration, salmonid fish typically undergo physiological and morphological changes — a process known as smolting. This study indicates that smolting in brown trout (Salmo trutta) is affected by feeding conditions in spring immediately prior to out-migration. This conclusion was reached after experimentally testing the effect of seasonal variation in food availability on smolt status in the spring. A migratory strain of trout was administered either high or low food rations in the autumn, winter, or spring prior to release in the spring. While fish growth or condition could be affected in any season, it was spring rationing that reduced growth and growth-related variables and that caused increased smolting. Our result supports the idea that smoltification and the decision to migrate is affected by spring food availability regardless of conditions in the previous autumn or winter.

Establishment, survival and site selection of the cestode Eubothrium crassum in brown trout, Salmo trutta

Parasitology ◽  
1996 ◽  
Vol 112 (3) ◽  
pp. 347-355 ◽  
Author(s):  
C. R. Kennedy
Keyword(s):  
Population Dynamics ◽  
Site Selection ◽  
Salmo Trutta ◽  
Population Regulation ◽  
Host System ◽  
Mean Intensity ◽  
Density Dependent ◽  
Brown Trout Salmo Trutta ◽  
Selection Of ◽  
Heavy Mortality

SUMMARYPopulation dynamics, site selection, growth and maturation of the cestode Eubothrium crassum in a natural population of Salmo trutta in a small lake were studied over a period of 1 year, the life-span of a cohort in fish. Infection of fish commenced in spring but peaked in July. Small, plerocerciform parasites initially located in the intestine, but then some moved into the pyloric caecae whilst others, the majority in heavy infections, were lost from the fish causing a fall in abundance from 460 to 10 over 2 months. This mortality was density dependent. Initially, parasites were distributed more evenly throughout the caecae but as time increased larger parasites were found preferentially in the anterior caecae before moving back into the intestine when gravid, preparatory to being lost in the following summer. Only a small proportion of the infrapopulation became gravid. Although the proportion of caecae occupied was initially density dependent, by the time of maturation several preferred anterior caecae remained unoccupied and mean intensity always exceeded unity. Neither growth nor maturation was affected by intraspecific competition. It was concluded that caecal availability did not set a limit or threshold of infrapopulation density, and in this respect E. crassum–S. trutta differed from some acanthocephalan-fish systems but was similar to others. Heavy infection followed by heavy mortality appeared to be typical of this parasite-host system in other localities, and of several other cestode-fish systems. The implications of this for population regulation are discussed.

scholarly journals Behavioural effects in juvenile brown trout in response to parental angling selection

2020 ◽  
Vol 77 (2) ◽  
pp. 365-374 ◽  
Author(s):  
Nico Alioravainen ◽  
Pekka Hyvärinen ◽  
Anssi Vainikka
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Reference Group ◽  
Size Variation ◽  
Common Garden ◽  
Wild Stock ◽  
Fish Stocks ◽  
Behavioural Effects ◽  
Brown Trout Salmo Trutta ◽  
Juvenile Brown Trout

Fishing that selectively captures and removes fish based on their behavioural decisions is predicted to induce evolution towards timid fish stocks. Thus, offspring behaviour should associate with parental vulnerability to angling. We examined phenotypic behavioural variation in juvenile brown trout (Salmo trutta) whose parents, representing a hatchery and a wild stock, were experimentally grouped based on their relative vulnerability to angling. The F1 offspring from highly vulnerable (HV) and low vulnerable (LV) parents were reared in common garden conditions together with a crossbred wild × hatchery reference group and tested for boldness during their first summer. Wild LV juveniles were the shyest of all fish, but not distinctly shyer than wild HV juveniles. Contradictorily, hatchery LV juveniles expressed bolder behaviour than hatchery HV juveniles. We show that angling selection may have transgenerational behavioural effects independently of size variation, but changes in behaviour can manifest differently in fish from different backgrounds. Our results partly support the earlier findings of increased angling-induced timidity in wild populations and thus call for management focus on behavioural effects of fishing.

Body size and sex ratio in emergent stonefly nymphs (Isogenoides olivaceus: Perlodidae): variation between cohorts and populations

1994 ◽  
Vol 72 (8) ◽  
pp. 1371-1375 ◽  
Author(s):  
Roger J. Haro ◽  
Kay Edley ◽  
Michael J. Wiley
Keyword(s):  
Body Size ◽  
Sex Ratio ◽  
Annual Variation ◽  
Sexual Size Dimorphism ◽  
Population Regulation ◽  
Size Variation ◽  
Size Distributions ◽  
Ecological Significance ◽  
Male Size ◽  
Animal Size

The ecological significance of pattern in animal-size distribution has been receiving increased scrutiny in studies of population regulation and individual energetics. However, few studies have assessed differences in size variation between sequential generations or adjacent populations. Annual variation in body size and sex ratio of emergent perlodid stonefly nymphs, Isogenoides olivaceus (Frison) (Plecoptera: Perlodidae), were examined in populations from two Michigan mesic groundwater rivers. Final nymphal body size was estimated from sex-specific length to mass regression relationships using exuviae collected from each site. Sexual size dimorphism accounted for much of the intraspecific size variation within both populations and cohorts: females were larger ([Formula: see text]) than males ([Formula: see text]). Males showed less size variation than females; unlike those for females, size distributions for males were significantly skewed. Secondary sex ratios were female biased in both populations and all cohorts and ranged between 59.1 and 72.8%. Female sex bias increased with relative male size in both populations.

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