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Competitive interactions in stream fish communities

Competitive interactions in stream fish communities
Competitive interactions in stream fish communities

The aim of this  thesis was to investigate the causes and consequences of competitive interactions in stream fish.  Two small benthic fish, bullheads Cottus gobio and stone loach Barbatula barbatula, were used as a model system.  The research combined manipulative field and laboratory experiments with field surveys to examine the biological mechanisms underlying intraspecific and interspecific interactions.

Growth in body size of adult bullheads was negatively density dependent.  Individuals grew faster when densities of invertebrate prey was experimentally elevated above ambient levels, indicating that bullheads were food limited.  Parallel dietary shifts were observed in response to manipulation of both bullied density and resource availability, suggesting that exploitation competition for preferred prey (Gammarus pulex) was the primary mechanism responsible for density dependent growth.  Evidence was sought, the not found, for interference competition.  Density dependent growth at the adult stage may potentially regulate bullhead populations if it affects fecundity and survival.

Habitat use of bullheads was strongly influenced by the availability of shelter.  Occupation of shelters was density dependent as a result of both exploitation and interference competition and individual shelter use was positively correlated with body size and movement rate.  Shelter use did not affect individual growth in body size, but there was some evidence that unsheltered fish attempted to emigrate.  In the field larger fish utilised coarser substrates.  Laboratory experiments suggested that this microhabitat strength of competition may be modulated by light intensity.  Thus, competition for shelter appears to drive the spatial distribution of fish in the field.

University of Southampton
Davey, Andrew John Henry
Davey, Andrew John Henry

Davey, Andrew John Henry (2003) Competitive interactions in stream fish communities. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The aim of this  thesis was to investigate the causes and consequences of competitive interactions in stream fish.  Two small benthic fish, bullheads Cottus gobio and stone loach Barbatula barbatula, were used as a model system.  The research combined manipulative field and laboratory experiments with field surveys to examine the biological mechanisms underlying intraspecific and interspecific interactions.

Growth in body size of adult bullheads was negatively density dependent.  Individuals grew faster when densities of invertebrate prey was experimentally elevated above ambient levels, indicating that bullheads were food limited.  Parallel dietary shifts were observed in response to manipulation of both bullied density and resource availability, suggesting that exploitation competition for preferred prey (Gammarus pulex) was the primary mechanism responsible for density dependent growth.  Evidence was sought, the not found, for interference competition.  Density dependent growth at the adult stage may potentially regulate bullhead populations if it affects fecundity and survival.

Habitat use of bullheads was strongly influenced by the availability of shelter.  Occupation of shelters was density dependent as a result of both exploitation and interference competition and individual shelter use was positively correlated with body size and movement rate.  Shelter use did not affect individual growth in body size, but there was some evidence that unsheltered fish attempted to emigrate.  In the field larger fish utilised coarser substrates.  Laboratory experiments suggested that this microhabitat strength of competition may be modulated by light intensity.  Thus, competition for shelter appears to drive the spatial distribution of fish in the field.

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Published date: 2003

Identifiers

Local EPrints ID: 465051
URI: http://eprints.soton.ac.uk/id/eprint/465051
PURE UUID: c44971cf-7fed-48c3-9d6d-bc48ce497da1

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Date deposited: 05 Jul 2022 00:19
Last modified: 05 Jul 2022 04:03

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Contributors

Author: Andrew John Henry Davey

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