Exploring environmental scenarios using a model of intermediate complexity for ecosystems for South African anchovy and sardine
Kelly Ortega-cisneros
Rhodes University
The southern Benguela system supports a productive fisheries sector that provides jobs and livelihoods for thousands of people living along the coast. The small pelagics fishery is the second most valuable fishery in economic terms in South Africa. It targets anchovy, adult sardine and some round herring, with juvenile sardine and horse mackerel as by-catch. Sardine and anchovy have shown considerable variability in biomass and distribution during the history of the fishery, which has resulted in high inter-annual variability of their catches and economic repercussions for the stakeholders during periods of low abundance.
This study explores the possible future impacts of environmental variability and climate change on the biomass and distribution of anchovy and sardine, and the associated implications for this fishery using a Model of Intermediate Complexity for Ecosystems (MICE). This model includes biomass-based age- and area-structured population dynamics for sardine and anchovy to account for the major life history migrations of these species. In addition to movement, the model accounts for growth, recruitment, natural and fishing mortality, with the later taking consideration of directed sardine and anchovy fishing as well as sardine bycatch with directed anchovy fishing. The model parameters were estimated by fitting to the hydro-acoustic survey recruit and total biomass data for the years 1987-2014. Projections were run from 2015–2050 under scenario RCP 8.5, simulated using a time series (2015-2050) of physico-chemical parameters derived from the NEMO – MEDUSA 2.0 model.
The presentation will describe progress made to date in identifying the possible effects of changes in temperature and primary production on anchovy and sardine from the southern Benguela, and the impact of those changes on the small pelagic fishery.