Document Detail


Food webs and fishing affect parasitism of the sea urchin Eucidaris galapagensis in the Galápagos.
MedLine Citation:
PMID:  22352167     Owner:  NLM     Status:  In-Process    
Abstract/OtherAbstract:
In the Galápagos Islands, two eulimid snails parasitize the common pencil sea urchin, Eucidaris galapagensis. Past work in the Galápagos suggests that fishing reduces lobster and fish densities and, due to this relaxation of predation pressure, indirectly increases urchin densities, creating the potential for complex indirect interactions between fishing and parasitic snails. To measure indirect effects of fishing on these parasitic snails, we investigated the spatial relationships among urchins, parasitic snails, commensal crabs, and large urchin predators (hogfish and lobsters). Parasitic snails had higher densities at sites where urchins were abundant, probably due to increased resource availability. Commensal crabs that shelter under urchin spines, particularly the endemic Mithrax nodosus, preyed on the parasitic snails in aquaria, and snails were less abundant at field sites where these crabs were common. In aquaria, hogfish and lobsters readily ate crabs, but crabs were protected from predation under urchin spines, leading to a facultative mutualism between commensal crabs and urchins. In the field, fishing appeared to indirectly increase the abundance of urchins and their commensal crabs by reducing predation pressure from fish and lobsters. Fished sites had fewer snails per urchin, probably due to increased predation from commensal crabs. However, because fished sites also tended to have more urchins, there was no significant net effect of fishing on the number of snails per square meter. These results suggest that fishing can have complex indirect effects on parasites by altering food webs.
Authors:
Jorge I Sonnenholzner; Kevin D Lafferty; Lydia B Ladah
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Ecology     Volume:  92     ISSN:  0012-9658     ISO Abbreviation:  Ecology     Publication Date:  2011 Dec 
Date Detail:
Created Date:  2012-02-22     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0043541     Medline TA:  Ecology     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2276-84     Citation Subset:  IM    
Affiliation:
CICESE, Department of Biological Oceanography, Carretera Ensenada-Tijuana number 3918, Zona Playitas, C.P. 22860, Ensenada, Baja California, México.
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