Deforestation and stream warming affect body size of Amazonian fishes

Author(s)

Ilha, Paulo ^{[1, 2]} ; Schiesari, Luis ^{[1, 3]} ; Yanagawa, I, Fernando ; Jankowski, Kathijo ^[4] ; Navas, Carlos A. ^[5]

Affiliation

^[1] Univ Sao Paulo, Inst Biociencias, Dept Ecol, Sao Paulo, SP - Brazil

^[2] Inst Pesquisa Ambiental Amazonia, Canarana, Mato Grosso - Brazil

^[3] I, Univ Sao Paulo, Gestao Ambiental, Escola Artes Ciencias & Humanidades, Sao Paulo, SP - Brazil

^[4] US Geol Survey, Upper Midwest Environm Sci Ctr, La Crosse, WI - USA

^[5] Univ Sao Paulo, Inst Biociencias, Dept Fisiol, Sao Paulo, SP - Brazil

• Document type: Journal article
• Source: PLoS One; v. 13, n. 5 MAY 2 2018.
• Web of Science Citations: 4

Abstract

Declining body size has been suggested to be a universal response of organisms to rising temperatures, manifesting at all levels of organization and in a broad range of taxa. However, no study to date evaluated whether deforestation-driven warming could trigger a similar response. We studied changes in fish body size, from individuals to assemblages, in streams in Southeastern Amazonia. We first conducted sampling surveys to validate the assumption that deforestation promoted stream warming, and to test the hypothesis that warmer deforested streams had reduced fish body sizes relative to cooler forest streams. As predicted, deforested streams were up to 6 degrees C warmer and had fish 36% smaller than forest streams on average. This body size reduction could be largely explained by the responses of the four most common species, which were 43-55% smaller in deforested streams. We then conducted a laboratory experiment to test the hypothesis that stream warming as measured in the field was sufficient to cause a growth reduction in the dominant fish species in the region. Fish reared at forest stream temperatures gained mass, whereas those reared at deforested stream temperatures lost mass. Our results suggest that deforestation-driven stream warming is likely to be a relevant factor promoting observed body size reductions, although other changes in stream conditions, like reductions in organic matter inputs, can also be important. A broad scale reduction in fish body size due to warming may be occurring in streams throughout the Amazonian Arc of Deforestation, with potential implications for the conservation of Amazonian fish biodiversity and food supply for people around the Basin. (AU)

• FAPESP's process: 11/20458-6 - Effects of land use change on the ecology of fishes in the headwaters of the Xingu River
• Grantee: Paulo Ricardo Ilha Jiquiriçá
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 08/57939-9 - Impacts of the expansion of the sugarcane agroindustry on freshwater communities
• Grantee: Luis Cesar Schiesari
• Support Opportunities: Program for Research on Bioenergy (BIOEN) - Young Investigators Grants