TY - JOUR
T1 - Small pelagics in upwelling systems
T2 - Patterns of interaction and structural changes in 'wasp-waist' ecosystems
AU - Cury, Philippe
AU - Bakun, Andrew
AU - Crawford, Robert J.M.
AU - Jarre, Astrid
AU - Quiñones, Renato A.
AU - Shannon, Lynne J.
AU - Verheye, Hans M.
N1 - Funding Information:
We thank Cathy Boucher and Gerald Van Tonder, who drew the figures. We thank P. Fréon, C. Moloney, M. Sinclair, M. Barange, S. Painting, B. Roel-Payne, D. Pauly, and C. Roy for helpful comments on the manuscript. We thank CROA (Centre de Recherches Océanographiques d’Abidjan), CRODT (Centre de Recherches Océanographiques de Dakar), and MFRD (Marine Fisheries Research Division, Ghana) for providing fishery data. This is a SCOR/WG-105 contribution and a VIBES contribution. R. Quiñones was partially funded by the FONDAP-HUMBOLDT Program (CONICYT, Chile).
Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2000
Y1 - 2000
N2 - In upwelling ecosystems, there is often a crucial intermediate trophic level, occupied by small, plankton-feeding pelagic fish dominated by one or a few schooling species. Their massive populations may vary radically in size under intensive exploitation. We have used decadal-scale time series to explore patterns of interactions between these fish, their prey, and their predators so as to quantify functional roles of small pelagic fish in those ecosystems. Top-down control of zooplankton is detected off South Africa, Ghana, Japan, and in the Black Sea. Conversely, bottom-up control of predators, such as predatory fish and marine birds, is observed in the Benguela, Guinea, and Humboldt currents. Thus small pelagic fish exert a major control on the trophic dynamics of upwelling ecosystems and constitute midtrophic-level 'wasp-waist' populations. Ecosystem effects of fishing are addressed by considering potential structural changes at different scales of observation, ranging from individuals, via school dynamics, to food webs. The overall impact is explored using a trophic model (Ecosim) given different types of food web control. Ecosystem dynamics can be entirely different depending on how the food web is controlled (bottom-up, top-down or wasp-waist). The threat of eroding intra-specific diversity is emphasized because it may lead to a long-term decline in the productivity of the pelagic fish resources. School composition is shown to reflect the relative species abundance within the pelagic community and functions as a 'school trap' that could maintain a collapsed population in a depleted state for lengthy periods, and affect spatial dynamics such as migrations. As a result, overfishing can alter the abundance, composition, and distribution in pelagic communities, and may induce drastic changes of state. Predation on zooplankton by the jack mackerel (Trachurus symmetricus murphyi) population in the South Pacific provides an example of the alteration of matter fluxes in trophic webs caused by fishery removals. In conclusion, it is doubtful that pelagic fisheries will continue to increase without major disruptions to ecosystems. (C) 2000 International Council for the Exploration of the Sea.
AB - In upwelling ecosystems, there is often a crucial intermediate trophic level, occupied by small, plankton-feeding pelagic fish dominated by one or a few schooling species. Their massive populations may vary radically in size under intensive exploitation. We have used decadal-scale time series to explore patterns of interactions between these fish, their prey, and their predators so as to quantify functional roles of small pelagic fish in those ecosystems. Top-down control of zooplankton is detected off South Africa, Ghana, Japan, and in the Black Sea. Conversely, bottom-up control of predators, such as predatory fish and marine birds, is observed in the Benguela, Guinea, and Humboldt currents. Thus small pelagic fish exert a major control on the trophic dynamics of upwelling ecosystems and constitute midtrophic-level 'wasp-waist' populations. Ecosystem effects of fishing are addressed by considering potential structural changes at different scales of observation, ranging from individuals, via school dynamics, to food webs. The overall impact is explored using a trophic model (Ecosim) given different types of food web control. Ecosystem dynamics can be entirely different depending on how the food web is controlled (bottom-up, top-down or wasp-waist). The threat of eroding intra-specific diversity is emphasized because it may lead to a long-term decline in the productivity of the pelagic fish resources. School composition is shown to reflect the relative species abundance within the pelagic community and functions as a 'school trap' that could maintain a collapsed population in a depleted state for lengthy periods, and affect spatial dynamics such as migrations. As a result, overfishing can alter the abundance, composition, and distribution in pelagic communities, and may induce drastic changes of state. Predation on zooplankton by the jack mackerel (Trachurus symmetricus murphyi) population in the South Pacific provides an example of the alteration of matter fluxes in trophic webs caused by fishery removals. In conclusion, it is doubtful that pelagic fisheries will continue to increase without major disruptions to ecosystems. (C) 2000 International Council for the Exploration of the Sea.
KW - Dominant fish species
KW - Eastern boundary currents
KW - Ecosystems
KW - Effects of fishing
KW - Food web
KW - Marine birds
KW - Pelagic fisheries
KW - Plankton
KW - Predator-prey relationships
KW - Schooling behaviour
KW - Small pelagic fish
KW - Trophic models
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U2 - 10.1006/jmsc.2000.0712
DO - 10.1006/jmsc.2000.0712
M3 - Article
AN - SCOPUS:0033731976
VL - 57
SP - 603
EP - 618
JO - ICES Journal of Marine Science
JF - ICES Journal of Marine Science
SN - 1054-3139
IS - 3
ER -