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Bluegill growth as modified by plant density: an exploration of underlying mechanisms.

Authors
  • Savino, Jacqueline F1
  • Marschall, Elizabeth A1
  • Stein, Roy A2
  • 1 Ohio Cooperative Fish and Wildlife Research Unit, Department of Zoology, The Ohio State University, 1735 Neil Ave., 43210, Columbus, OH, USA.
  • 2 Department of Zoology, The Ohio State University, 43210, Columbus, OH, USA.
Type
Published Article
Journal
Oecologia
Publisher
Springer-Verlag
Publication Date
Feb 01, 1992
Volume
89
Issue
2
Pages
153–160
Identifiers
DOI: 10.1007/BF00317212
PMID: 28312867
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

Bluegill (Lepomis macrochira) growth varies inconsistently with plant density. In laboratory and field experiments, we explored mechanisms underlying bluegill growth as a function of plant and invertebrate density. In the laboratory, bluegills captured more chironomids (Chironomus riparius) than damselflies (Enallagma spp. and Ischnura spp.), but energy intake per time spent searching did not differ between damselfly and chironomid treatments. From laboratory data, we described prey encounter rates as functions of plant and invertebrate density. In Clark Lake, Ohio, we created 0.05-ha mesocosms of inshore vegetation to generate macrophyte densities of 125, 270, and 385 stems/m2 of Potamogeton and Ceratophyllum and added 46-mm bluegill (1/m2). In these mesocosms, invertebrate density increased as a function of macrophyte density. Combining this function with encounter rate functions derived from laboratory data, we predicted that bluegill growth should peak at a high macrophyte density, greater than 1000 stems/m2, even though growth should change only slightly beyond 100 stems/m2. Consistent with our predictions, bluegills did not grow differentially, nor did their use of different prey taxa differ, across macrophyte densities in the field. Bluegills preferred chironomid pupae, which were relatively few in numbers but vulnerable to predation, whereas more cryptic, chironomid larvae, which were associated with vegetation but were relatively abundant, were eaten as encountered. Bluegills avoided physid snails, which were abundant. Contrary to previous work, vegetation did not influence growth or diet of bluegill beyond relatively low densities owing to the interaction between capture probabilities and macroinvertebrate densities.

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