Defining safe operating space

The aim of the study of Ofir et al.[1] was to define a safe operating space (SOS)[2] to manage the commercially important mango tilapia fish Sarotherodon galilaeus (Linnaeus, 1758) in Lake Kinneret, Israel. This species depends on submerged littoral vegetation for spawning and nurseries, but annual water levels in the lake have been dropping during the past decades due to poor river inflow, evaporation and drinking water extraction, affecting availability and structure of submerged vegetation for S. galilaeus. Additionally, littoral vegetation cover and density has been gradually reduced to make room for human activities.

EwE was used in novel ways: The Ecospace migration system was used to affect the distribution of multi-stanza S. galilaeus between the pelagic and littoral zones, in time with littoral spawning as defined in Ecosim. Habitat affinity with time-varying vegetation cover maps provided spawning areas that also provided essential habitat for juvenile life stages. Monthly varying lake levels were introduced as environmental drivers in the HCF model, where linear response functions to fraction water coverage implicitly limited access to submerged vegetation. Ecospace was executed in the relatively underexplored Individual Based Model (IBM) modus[3]. The fact that the lake lies approximately 210m below sea level caused some complications when integrating the impact of bathymetry in the model.

To establish the bounds of the SOS, different Ecospace scenarios were executed on the validated model for the period of 2017 to 2060 to explore how to retain a minimum biomass of S. galilaeus of 250 tons. These scenarios combined fishing effort multipliers {0.1, 0.5, 1, 1.5, 2}, lake levels {low (2009), high {2005)}, and changes in density and area cover of vegetation {0.1, 0.5, 1, 1.5, 2}. Results were statistically analyzed for five time periods {2021-2025, 2026-2030, 2031-2040, 2041-2050, 2051-2060} to obtain a safe operation space for effort and vegetation cover under the two extreme water level scenarios in order to secure the desired biomass of S. galilaeus.

See the original publication for details[4].

Attribution

The chapter is based on de Mutsert et al.[5], adapted with permission, License Number 5651431253138. Rather than citing this chapter, please cite the source.

  1. Ofir, E., Silver, T., Steenbeek, J., Shachar, N., Gal, G., 2022. Applying the Safe Operating Space (SOS) approach to sustainable commercial fishing under varying lake levels and littoral zone conditions. Fisheries fsh.10869. https://doi.org/10.1002/fsh.10869 ↵
  2. Carpenter, S.R., Brock, W.A., Hansen, G.J.A., Hansen, J.F., Hennessy, J.M., Isermann, D.A., Pedersen, E.J., Perales, K.M., Rypel, A.L., Sass, G.G., Tunney, T.D., Vander Zanden, M.J., 2017. Defining a Safe Operating Space for inland recreational fisheries. Fish and Fisheries 18, 1150–1160. https://doi.org/10.1111/faf.12230 ↵
  3. Walters, C., V. Christensen, W. Walters, K. Rose. 2010. Representation of multi-stanza life histories in Ecospace models for spatial organization of ecosystem trophic interaction patterns. Bull. Mar. Sci. 86(2):439-459. ↵
  4. Ofir et al. 2022, op. cit. ↵
  5. De Mutsert K, Marta Coll, Jeroen Steenbeek, Cameron Ainsworth, Joe Buszowski, David Chagaris, Villy Christensen, Sheila J.J. Heymans, Kristy A. Lewis, Simone Libralato, Greig Oldford, Chiara Piroddi, Giovanni Romagnoni, Natalia Serpetti, Michael Spence, Carl Walters. 2023. Advances in spatial-temporal coastal and marine ecosystem modeling using Ecopath with Ecosim and Ecospace. Treatise on Estuarine and Coastal Science, 2nd Edition. Elsevier. https://doi.org/10.1016/B978-0-323-90798-9.00035-4 ↵

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