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UBC Theses and Dissertations
Ecosystem impacts of fishing forage fishes : an analysis of harvest strategies for the brazillian sardine Vasconcellos, Marcelo
Abstract
The ecosystem impacts of fisheries have become an important concern in fisheries management and one of the most important issues in fisheries science. The objectives of this thesis were i) to evaluate the use of trophic models in the analysis of the ecosystem responses to fishing small pelagic forage fish; ii) to forecast the 'fishing down marine food web' phenomenon in Brazil; and iii) to conduct an in-depth analysis of the sardine, Sardinella brasiliensis, fishery off southeastern Brazil to examine hypotheses of ecosystem changes following stock collapse, and to evaluate how uncertainties of ecological processes influence the choice of harvest strategies and controls in this fishery. Dynamic simulations of mass-balance trophic models were used to compare the ecosystem responses to fishing forage fishes across different types of marine ecosystems, and to examine the stability characteristics of ecosystems when impacted by fisheries. The comparative analysis among trophic models indicated that as 'wasp-waist' species in upwelling ecosystems, small pelagics will only sustain much more conservative exploitation rates than the levels that have brought about historical stock-collapses. In the upwelling ecosystem off southeastern Brazil, sardine has been historically the main target of commercial fisheries, although 'fishing down marine food webs' for small pelagic fish species is not yet an overall observed phenomenon in Brazil. The collapse of the sardine fishery in the late 1980s has apparently favored a competing small pelagic fish (anchovy, Engraulis anchoitd) in the ecosystem. The combined effect of fishing and environmental effects makes it difficult, however, to characterize the changes in the sardine population and the ecosystem, and to predict the results of rehabilitation measures for the stock. On the other hand, the explicit recognition of these ecological uncertainties allows a sound choice of precautionary strategies for the fishery, and a better scrutiny of research programs to improve management. In this context, trophic models will have a complementary role to single-species models in the analysis of the broad consequences of fishing policies, and in the test and formulation of hypotheses about the causes of observed changes in marine ecosystems.
Item Metadata
Title |
Ecosystem impacts of fishing forage fishes : an analysis of harvest strategies for the brazillian sardine
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2000
|
Description |
The ecosystem impacts of fisheries have become an important concern in fisheries management
and one of the most important issues in fisheries science. The objectives of this thesis were i) to
evaluate the use of trophic models in the analysis of the ecosystem responses to fishing small
pelagic forage fish; ii) to forecast the 'fishing down marine food web' phenomenon in Brazil;
and iii) to conduct an in-depth analysis of the sardine, Sardinella brasiliensis, fishery off
southeastern Brazil to examine hypotheses of ecosystem changes following stock collapse, and to
evaluate how uncertainties of ecological processes influence the choice of harvest strategies and
controls in this fishery. Dynamic simulations of mass-balance trophic models were used to
compare the ecosystem responses to fishing forage fishes across different types of marine
ecosystems, and to examine the stability characteristics of ecosystems when impacted by
fisheries. The comparative analysis among trophic models indicated that as 'wasp-waist' species
in upwelling ecosystems, small pelagics will only sustain much more conservative exploitation
rates than the levels that have brought about historical stock-collapses. In the upwelling
ecosystem off southeastern Brazil, sardine has been historically the main target of commercial
fisheries, although 'fishing down marine food webs' for small pelagic fish species is not yet an
overall observed phenomenon in Brazil. The collapse of the sardine fishery in the late 1980s has
apparently favored a competing small pelagic fish (anchovy, Engraulis anchoitd) in the
ecosystem. The combined effect of fishing and environmental effects makes it difficult,
however, to characterize the changes in the sardine population and the ecosystem, and to predict
the results of rehabilitation measures for the stock. On the other hand, the explicit recognition of
these ecological uncertainties allows a sound choice of precautionary strategies for the fishery,
and a better scrutiny of research programs to improve management. In this context, trophic
models will have a complementary role to single-species models in the analysis of the broad
consequences of fishing policies, and in the test and formulation of hypotheses about the causes
of observed changes in marine ecosystems.
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Extent |
18640239 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-07-20
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0074865
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2000-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.