Mass-balanced trophic and loop models of complex benthic systems in northern Chile (SE Pacific) to improve sustainable interventions: a comparative analysis

Abstract

The capacity to withstand perturbations and the propagation of direct and indirect effects of harvesting were explored in seagrass and sand-gravel subtidal subsystems of northern Chile using Ecopath II, Ecosim and Loop Analysis theoretical frameworks. The relative Ascendancy and Redundancy from Ecopath II and Ecosim models and the holistic stability measure (F n ) given by Loop Analysis, all suggest that the sandgravel subsystem is the more resistant and its fishery more sustainable. This outcome is relevant since the theoretical frameworks used are based on different assumptions but arrive at similar conclusions. If the fishery is included in the qualitative ecological models, which were found locally stable only when the fishery is self-controlled. While this conclusion is not new, its relevance here is that it emerges from qualitative multispecies modelling (Loop Analysis). Based on our model predictions, the biomass removal of the sea star Meyenaster gelatinosus would increase the standing stock of the commercial scallop Argopecten purpuratus only in the seagrass habitat, whereas the same manmade intervention may have an opposite effect in the sand-gravel habitat. We recommend to enunciate holistic models based on the theoretical framework used in the current work, which explore the reality from different perspectives assuming different givens. Based on these holistic explorations alternative and complementary management scenarios could be designed.

Re‐stocking practices and illegal fishing in northern Chile (SE Pacific coast): a study case

“…Within the qualitative theoretical framework, loop analysis (Levins 1998, Puccia and Levins 1985) is a useful technique for estimating the local stability (sustainability) of systems and assessing the propagation of direct and indirect effects as a response to external perturbations (Ramsey and Veltman 2005). This approach has been applied widely in different fields of the natural sciences (Li and Moyle 1981, Giavelli and Bodini 1990, Levins and Vandermeer 1990, Whitlatch and Osman 1994, Lane 1998) including fisheries management (Ortiz 2003, Ortiz and Wolff 2002, 2008, Ortiz and Stotz 2007, Dambacher et al 2009), and has shown a high degree of predictability (after perturbation) of natural phenomena (Briand and McCauley 1978, Lane and Bloiun 1985, Lane and Collins 1985, Lane 1986, Hulot et al 2000, Ortiz 2008).…”

Combining quantitative and qualitative models to identify functional groups for monitoring changes in the Bay of Biscay continental shelf exploited foodweb

“…Quantitative predictions of the magnitude of food web responses to natural perturbations or potential management measures are not always needed for management (Dambacher et al, 2009). Instead, knowledge on directions of trends in food web components (Rochet et al, 2010) and robust predictions from complementary models (Ortiz and Wolff, 2008;Metcalf, 2010) may be sufficient. In this study, robust model predictions are defined as those which are similar for different models.…”