Mechanisms Responsible for Population Regulation in Young Migratory Trout, Salmo trutta. III. The Role of Territorial Behaviour

10.2307/5015 ◽  
1990 ◽  
Vol 59 (3) ◽  
pp. 803 ◽  
Author(s):  
J. M. Elliott
Keyword(s):  
Salmo Trutta ◽  
Population Regulation ◽  
Territorial Behaviour

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.

Hyperbenthic and pelagic predators regulate alternate key planktonic copepods in shallow temperate estuaries

2014 ◽  
Vol 65 (9) ◽  
pp. 791 ◽  
Author(s):  
R. J. Wasserman ◽  
T. J. F. Vink ◽  
R. Kramer ◽  
P. W. Froneman
Keyword(s):  
Population Regulation ◽  
Zooplankton Community ◽  
Copepod Species ◽  
Benthic Fish ◽  
Predator Diversity ◽  
Predatory Impact ◽  
Experimental Treatments ◽  
Zooplankton Communities ◽  
Predatory Pressure

Although predation has been identified as an important community driver, the role of predator diversity in structuring estuarine zooplankton has not been assessed. As such, we investigated the effects of two different zooplanktivorous fish species on the estuarine zooplankton community during a 12-day mesocosm study. Three experimental treatments were established, whereby natural zooplankton communities were subject to either (1) no predatory pressure, (2) predation by a pelagic predator (Monodactylus falciformis) or (3) predation by a hyper-benthic predator (Glossogobius callidus). The pelagic feeding M. falciformis fed largely on the numerically dominant mid-water copepod species, Paracartia longipatella. In contrast, the hyper-benthic fish had a greater predatory impact on the less numerically dominant copepod, Pseudodiaptomus hessei, which demonstrates strong diel vertical migration. Variations in prey-population regulation are ascribed to the distinct behavioural differences of the predators, and mediated by the differences in behaviour of the copepod species.

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