Increased ambient temperature alters the parental care behaviour and reproductive success of the three-spined stickleback (Gasterosteus aculeatus) Kathryn Hopkins & Brian R. Moss & Andrew B. Gill Received: 15 September 2009 / Accepted: 27 September 2010 / Published online: 15 October 2010 # Springer Science+Business Media B.V. 2010 Abstract The effects of environmental warming on aquatic poikilotherms, such as fish, are likely to be manifest during periods of high metabolic demand. For species that invest heavily in parental-care, such as the three-spined stickleback, Gasterosteus aculea- tus L., their reproductive success may be adversely affected. In two separate experiments with temper- atures raised by 2°C to 6°C above 16–17°C ambient over a whole breeding season, we quantified changes to parental-care behaviour and the resultant reproduc- tive success of G. aculeatus. As temperature in- creased, male parental-care behaviour was altered, particularly the fanning of the fertilised eggs. Fanning behaviour was highly variable among individual fish however it increased over the course of incubation. Furthermore, all egg incubating fish consistently fanned at a faster rate in higher temperatures. The male fish responded to the increased temperature by putting more effort into fanning. The consequence was that these fish had a higher rate of incubation failure and an increased likelihood of mortality. The pattern of alteration to parental care behaviour and decreased reproductive success with higher tempera- ture was remarkably consistent across the individual fish, which suggests consequences at the population level of increased ambient temperatures. Keywords Aquatic systems . Fanning behaviour . Global temperature . Fish parental care Introduction There can be little doubt that global warming is occurring, and at a greater rate than previously predicted (IPCC 2007). The minimum and maxi- mum predicted increases in global mean temperature for the late 21st century were 1.4°C to 5.8°C (Watson 2001) and new estimates (IPCC 2007) suggest that realised temperatures are increasingly likely to be towards the top of the range or higher, and to be experienced earlier, dependent on measures put in place to restrict carbon emissions. Because the IPCC models are purely physical models and do not include biological feedbacks, the estimates may still be conservative. Though the general physical effects, of earlier melting of ice, longer periods of stratifica- tion in lakes, and broad biological impacts, such as earlier phenology of plants, and poleward migration of mobile species, are becoming obvious, there is much yet to learn about detailed effects on keystone species and their consequences. Environ Biol Fish (2011) 90:121–129 DOI 10.1007/s10641-010-9724-8 K. Hopkins : B. R. Moss School of Biological Sciences, The University of Liverpool, Crown St., Liverpool L69 3BX, UK A. B. Gill (*) Department of Natural Resources, Cranfield University, Cranfield, Bedfordshire MK43 0AL, UK e-mail: a.b.gill@cranfield.ac.uk