An Experimental Study of Piscivore–Planktivore Interactions: Population and Community Responses to Predation

1992 ◽  
Vol 49 (6) ◽  
pp. 1176-1183 ◽  
Author(s):  
Xi He ◽  
Russell A. Wright
Keyword(s):  
Fish Community ◽  
Northern Pike ◽  
Community Response ◽  
Fish Biomass ◽  
Prey Fish ◽  
Short Term ◽  
Population Responses ◽  
Numerical Resolution ◽  
Four Levels ◽  
And Behavior

The population dynamics and behavior of an assemblage of fishes in a small bog lake were studied in a succession of whole-lake manipulations of piscivores. Total prey fish biomass declined after the addition of northern pike (Esox lucius). This decline was the result of emigration by cyprinid prey and consumption by northern pike. The emigration response of the cyprinids was dependent on cyprinid density. At high prey fish biomass, a significant portion of the loss in biomass was the result of emigration; this was not the case at low prey fish biomass. The prey fish community shifted from small-bodied soft-rayed species prior to the introduction of northern pike to species with spines or deep bodies after predator stocking. The community response was analyzed at four levels of numerical resolution: absolute, relative, and ranked abundance and presence–absence of prey species. High numerical resolution captured the dynamic short-term population responses to predation and suggests unstable community structure.

Changes in Fish Community of Klíčava Reservoir with Particular Reference to Eurasian Perch (Perca fluviatilis), 1957–72

1977 ◽  
Vol 34 (10) ◽  
pp. 1734-1747 ◽  
Author(s):  
Juraj Holčík
Keyword(s):  
Fish Community ◽  
Fish Fauna ◽  
Perca Fluviatilis ◽  
Northern Pike ◽  
Zooplankton Biomass ◽  
Fish Biomass ◽  
Biomass Density ◽  
Eurasian Perch ◽  
Perch Perca Fluviatilis ◽  
Stizostedion Lucioperca

Soon after the 1955 filling of the 60 ha mesotrophic Klíčava Reservoir in Czechoslovakia, the fish fauna started to change. Generally, lithophils were replaced by phytophils and then by ecologically more plastic species. Fish biomass increased in the first 12 yr from 65 to 236 kg/ha, but after 1967 dropped to about 170 kg/ha. Increased biomass and density of piscivores were responsible for the decline. Among the piscivores the most important role was played by the pikeperch (Stizostedion lucioperca) rather than the Eurasian perch (Perca fluviatilis) or northern pike (Esox lucius). Cyclical changes in the age structure of the perch population and the periodical occurrence of many young resulted from fluctuations in the rate of cannibalism, which affected the density of the fry and yearlings. A decline in zooplankton biomass and disappearance of larger zooplankters in the first 5–6 yr of the reservoir were due to increased density of fish, especially perch, which fed on zooplankton. Synchronous predation by piscivores and zooplanktivores produced a nearly stable zooplankton biomass in the later years of the reservoir. The perch is a highly specialized species which behaves in the fish community more or less autonomously, because it is able to control its own density in accord with its food resources. The above conclusions are based on a literature review and analyses of new data. Key words: Percidae, community ecology, Perca, biomass, density, production, predation

scholarly journals Intergroup and intragroup dimensions of COVID-19: A social identity perspective on social fragmentation and unity

2021 ◽  
Vol 24 (2) ◽  
pp. 201-209 ◽  
Author(s):  
Dominic Abrams ◽  
Fanny Lalot ◽  
Michael A. Hogg
Keyword(s):  
Social Identity ◽  
Group Dynamics ◽  
Short Term ◽  
Social Fragmentation ◽  
The Social ◽  
The Face ◽  
Political Management ◽  
Psychological Challenge ◽  
And Behavior ◽  
People’S Perceptions

COVID-19 is a challenge faced by individuals (personal vulnerability and behavior), requiring coordinated policy from national government. However, another critical layer—intergroup relations—frames many decisions about how resources and support should be allocated. Based on theories of self and social identity uncertainty, subjective group dynamics, leadership, and social cohesion, we argue that this intergroup layer has important implications for people’s perceptions of their own and others’ situation, political management of the pandemic, how people are influenced, and how they resolve identity uncertainty. In the face of the pandemic, initial national or global unity is prone to intergroup fractures and competition through which leaders can exploit uncertainties to gain short-term credibility, power, or influence for their own groups, feeding polarization and extremism. Thus, the social and psychological challenge is how to sustain the superordinate objective of surviving and recovering from the pandemic through mutual cross-group effort.

School Performance and Theophylline

PEDIATRICS ◽  
1987 ◽  
Vol 80 (1) ◽  
pp. 124-125
Author(s):  
MILES WEINBERGER ◽  
SCOTT LINDGREN ◽  
JESSE JOAD
Keyword(s):  
School Performance ◽  
Short Term ◽  
Asthmatic Children ◽  
Term Administration ◽  
Usa Today ◽  
And Behavior

To the Editor.— Dr Rachelefsky and his colleagues reported, first in USA Today (Dec 2, 1986, p 1) and later in Pediatrics (1986;78:1133-1138) that theophylline adversely affected school performance. Specifically, they stated, "Teachers said kids couldn't sit still, they weren't remembering as well, they were acting up, and their handwriting had changed" (USA Today). They concluded that "the short-term administration of theophylline to asymptomatic asthmatic children not receiving oral bronchodilators can adversely affect school performance and behavior" (Pediatrics).

Upscaling biomanipulation in 600 ha Lake Zuidlaardermeer

1995 ◽  
Vol 31 (8) ◽  
pp. 235-238
Author(s):  
C. Roos ◽  
M. Klinge ◽  
J. Heringa ◽  
D. A. de Vries ◽  
R. Torenbeek
Keyword(s):  
The Netherlands ◽  
Water Chemistry ◽  
Chlorophyll A ◽  
Fish Community ◽  
Submerged Macrophytes ◽  
Northern Pike ◽  
Emergent Vegetation ◽  
Ecological Rehabilitation ◽  
Significant Step ◽  
Total P

In the 600 ha Lake Zuidlaardermeer in The Netherlands enclosure experiments were carried out in order to test the feasibility of biomanipulation. In two enclosures of 625 m2 each the effects of reduction of fish and wind and waves on water chemistry, phyto- and zooplankton and submerged macrophytes were studied and compared to the lake. In the “fishless” enclosure transparency increased from 40 to 120 cm, chlorophyll-a dropped from 70 to 20 μg/l, total-P dropped from 0.20 to 0.10 mg/l, Daphnia sp. > 1 mm increased from 30 to 130 individuals/l and submerged macrophytes returned. The “fish” enclosure largely behaved in a way intermediate between the “fishless” enclosure and the lake: transparency increased to 60 cm, chlorophyll-a dropped to 40 μg/l, total-P dropped to 0.12 mg/l and Daphnia sp. > 1 mm increased to 80/l. Submerged macrophytes however did not develop. The experiments show the potential of the lake for ecological rehabilitation. Nevertheless the effect of wind and waves on a larger scale remains uncertain. Therefore plans have been made to build a larger enclosure (40–100 ha). In this way, the effects of fish and wind and waves can be studied on a larger scale while at the same time recovery of the submerged macrophytes within this enclosure will be a significant step towards ecological rehabilitation of the whole lake. Beside the return of the submerged macrophytes the management is also aimed at the development of substantial amounts of emergent vegetation, thus supporting enough Northern Pike (Esox lucius L.) for regulation of the planktivorous fish community.

Fish Community Structure, Biomass, and Production in the Turkey Lakes Watershed, Ontario

1988 ◽  
Vol 45 (S1) ◽  
pp. s115-s120 ◽  
Author(s):  
J. R. M. Kelso
Keyword(s):  
Fish Community ◽  
Carbon Assimilation ◽  
Lake Acidification ◽  
Fish Stock ◽  
Fish Biomass ◽  
Unit Surface Area ◽  
Fish Community Structure ◽  
Fish Flesh ◽  
Unit Surface ◽  
Turkey Lakes Watershed

The Turkey Lakes Watershed contains four lakes, and the headwater lake (Batchawana Lake) consists of two distinct basins, neither of which supports a native, reproducing fish stock. Fish biomass varied by a factor of 3.3 among the other three lakes in the watershed. Fish flesh production varied by a factor of only 1.5 in the system. Salmonid and small cyprinid contribution to biomass and production increased with progression downstream. Both fish biomass and production per unit surface area decreased with increasing lake depth. The fish biomass and production in the watershed was strongly influenced by depth, but alkalinity and phytoplankton carbon assimilation also were related to stock and production. Wishart Lake, immediately below Batchawana Lake, has a fish stock with restricted recruitment, and cyprinids make only a limited contribution to the observed production. Although both these conditions may be symptomatic of lake acidification, it is unclear whether the situation in this watershed results from lake acidification or biogeographic factors.

scholarly journals Apparent extirpation of prey fish communities following the introduction of Northern Pike (Esox lucius)

2015 ◽  
Vol 129 (2) ◽  
pp. 165 ◽  
Author(s):  
Michele E. Nicholson ◽  
Michael D. Rennie ◽  
Kenneth H. Mills
Keyword(s):  
Fish Communities ◽  
Northern Pike ◽  
Esox Lucius ◽  
Visual Observation ◽  
Fish Community Structure ◽  
Long Term Effects ◽  
Prey Fish ◽  
Experimental Lakes Area ◽  
Subsequent Issue ◽  
Shield Lakes

We examined the long-term effects on prey fish communities of introducing Northern Pike (Esox lucius), a top predator fish, into small, Boreal Shield lakes lacking natural piscivore populations. During 1987–1994, Northern Pike were introduced into Lakes 110, 221, and 227 in the Experimental Lakes Area in northwestern Ontario, Canada. In Lake 227, prey fish were undetectable three years after the addition of Northern Pike. Although Northern Pike were removed from the lake by 1996, multiple independent visual and trapping surveys have yielded no evidence of any fish in Lake 227 since then. In 1994–1995, 85% of the Northern Pike were removed from Lake 221. In 2012, despite intensive sampling efforts using baited minnow traps, fyke nets, trap netting, gill netting, angling, and visual observation, no forage fish of any species was observed or caught in Lake 110 or 221. In all three lakes where Northern Pike were added, prey fish populations were extirpated or too small to detect. In Lake 221, we estimated the current population of Northern Pike to be 49 ± 37, a 59% decrease since 2000 when prey fish were still present. The mean total length and body condition of Northern Pike in Lake 221 had not changed since the prey community collapsed. Our findings suggest that the introduction of Northern Pike into lakes without natural piscivore populations has long-lasting effects on fish community structure, to the detriment of both Northern Pike and prey fish populations.Note: an erratum for this article was published in the subsequent issue, and is attached to the end of this article's pdf. Table 2 had not been justified properly; the revised table corrects this issue.

Habitat utilisation by fish community in a short-term regulated river reservoir

Hydrobiologia ◽  
2005 ◽  
Vol 545 (1) ◽  
pp. 257-270 ◽  
Author(s):  
Teppo Vehanen ◽  
Juha Jurvelius ◽  
Markku Lahti
Keyword(s):  
Fish Community ◽  
Regulated River ◽  
Short Term ◽  
River Reservoir
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