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A trophic model of a Galápagos subtidal rocky reef for evaluating fisheries and conservation strategies
Okey, T.A.; Banks, S.; Born, A.F.; Bustamante, R.H.; Calvopiña, M.; Edgar, G.J.; Espinoza, E.; Fariña, J.M.; Garske, L.E.; Reck, G.K.; Salazar, S.; Shepherd, S.; Toral-Granda, V.; Wallem, P. (2004). A trophic model of a Galápagos subtidal rocky reef for evaluating fisheries and conservation strategies. Ecol. Model. 172(2-4): 383-401
In: Ecological Modelling. Elsevier: Amsterdam; Lausanne; New York; Oxford; Shannon; Tokyo. ISSN 0304-3800, more
Peer reviewed article  

Available in  Authors 

Keywords
    Sea cucumbers; Marine

Authors  Top 
  • Okey, T.A.
  • Banks, S.
  • Born, A.F.
  • Bustamante, R.H.
  • Calvopiña, M.
  • Edgar, G.J.
  • Espinoza, E.
  • Fariña, J.M.
  • Garske, L.E.
  • Reck, G.K.
  • Salazar, S.
  • Shepherd, S.
  • Toral-Granda, V.
  • Wallem, P.

Abstract
    Abalanced trophic model of a Galápagos rocky reef systemwas constructed using Ecopath and Ecosim. The Ecopath approachallowed characterization of food web structure through integration of disparate ecosystem information derived from many yearsof study of Galápagos shallow-water rocky reefs. Ecosim and Ecospace routines enabled us to explore various hypothesesabout system dynamics as well as potential solutions to conservation concerns about overfishing. A full series of functionalgroup removal simulations resulted in estimations of interaction strengths and ‘keystone’ potentials for each of the 42 livingfunctional groups in the model. Relative interaction strengths in a pristine unfished system are likely to be quite different frominteraction strengths indicated by this present-day model. At present, humans extract food from very low trophic levels (meantrophic level = 2.3) in Galápagos rocky reef systems because sea cucumbers and detritivorous mullets comprised 71 and 15%,respectively, of the total fisheries catch. Catch rates of sea cucumbers (Stichopus fuscus; referred to here as ‘pepinos’) are shownto be unsustainable, and the population should be declining rapidly. The exclusion of fishing from 23% of the total reef area,representing a hypothetical non-extractive zone, prevented the functional extinction of pepinos that our analysis predicted tooccur with no areas protected (given 1999-2000 capture rates). Even with 23% of the hypothetical area protected, pepinos werepredicted to decline overall to a stable 36% of their current estimated biomass. Pepino biomass was predicted to increase to eighttimes that of current levels if pepino fishing were stopped altogether.

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