Simulating anchovy-sardine regime shifts in the southern Benguela ecosystem
Shannon, L.J.; Field, J.G.; Moloney, C.L. (2004). Simulating anchovy-sardine regime shifts in the southern Benguela ecosystem. Ecol. Model. 172(2-4): 269-281
In: Ecological Modelling. Elsevier: Amsterdam; Lausanne; New York; Oxford; Shannon; Tokyo. ISSN 0304-3800; e-ISSN 1872-7026, more
Also appears in:Christensen, V.; Maclean, J.L. (Ed.) (2004). Placing fisheries in their ecosystem context. Ecological Modelling, 172(2-4). Elsevier: Amsterdam. 103-440 pp., more
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| Keywords |
Ecosystems
Models
Engraulis Cuvier, 1816 [WoRMS]; Sardina Antipa, 1904 [WoRMS]
PSW, Benguela Current [Marine Regions]
Marine/Coastal |
| Authors | | Top |
- Shannon, L.J.
- Field, J.G.
- Moloney, C.L.
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| Abstract |
Trophic models of the southern Benguela ecosystem have been developed to represent average ecosystem structures for twoperiods: 1980-1989 and 1990-1997. Ecopath with Ecosim software is used to simulate changes from the 1980s to the 1990secosystem structure. Two hypotheses are tested of mechanisms that could cause the changes. First, using the model of the 1980s,four scenarios are considered in which different combinations of fishing mortality rates of sardine, anchovy and horse mackerelare changed to mimic the situation in the 1990s model. Results show that it is unlikely that observed changes in pelagic fishcatches between the 1980s and 1990s played a large role in driving the changes in abundance of anchovy and sardine. Second,changes in the susceptibility of phytoplankton and zooplankton prey to feeding by anchovy and sardine are simulated for thetwo decades. Results show that shifts between anchovy and sardine regimes in the southern Benguela ecosystem may be causedby changes in the availability of mesozooplankton prey to anchovy and sardine, mediated through changes in environmentalconditions. The magnitudes and duration of environmental changes are important in understanding changes in the ecosystem. |
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