Alexandra Grutter

Expected Outcomes of latest project funded by the ARC "What happens to reefs without cleaner fish"

1.National benefits. This project is highly multidisciplinary, covering marine ecology, coral reef biology,physiology, behavioural ecology, and parasitology - all areas critical to conservation and preservation of environmental biodiversity. Our study will reveal some of the key mechanisms involved in maintaining local fish diversity. Coral reefs are an Australian icon, providing the nation with an international tourism profile that is largely dependent upon this economically and culturally valuable resource. Understanding the mechanisms responsible for this diversity is critical to maintaining it and the industries dependent upon the reefs. Social benefits include mentoring the next generation of researchers, as our research regularly attracts international researchers, early career researchers, and high-quality PhD students - all of which will be involved in this study. Indeed, the 28 postgraduate students Grutter has supervised are all employed in science-related areas.

2. National Research Priorities. By better understanding how cleaning interactions affect coral reef fish health, and the subsequent consequences to the rest of the community, this project will contribute to one of the associated Priority Goals, “Sustainable use of Australia's biodiversity”. Australia is losing species, including marine ones, at an alarming rate, and coral reefs are increasingly threatened by climate change. This research provides insight into how single key species can benefit a multitude of marine organisms, therefore improving our understanding of how these ecosystems can best be protected for future generations.

3. Research outcomes.

(a) Insight into how the behavioural interaction of fish cleaning by a relatively low number of small-sized cleaner fish has profound consequences to client individuals.

(b) Determination of the physiological pathways that cause the positive effects of cleaning interactions on client fish health, and insight into coral reef fish immunology.

(e) Information on how parasites can have such a large effect on the population and community ecology of reef-fish, and hence, ultimately on local reef communities.

(d) Potential mechanisms proposed for the above changes are effects on fish behaviour, movement, habitat choice, mortality, growth, physiology, and recruitment, but these have never been tested until now.

(e) While the scale of this study will only measure local effects, some effects may extend further. For example, the effect on fish female size, and hence the number of propagules produced (Green 2008), might increase dispersal to other areas. A larger size, for example as seen in P. moluccensis, should thus result in an increased reproductive output of individuals on reefs with cleaner fish. Many studies suggest that greater fish size and subsequent reproductive output affects fish population recruitment (Birkeland & Dayton 2005), with consequences for managing and designing marine parks and commercial fishery stocks.

(f) Many cleaner species are removed from reefs for the aquarium trade, and L. dimidiatus is one of the top ten most exported fish to the US and the EU (Wabnitz et al. 2003). Alarmingly, in Sri Lanka alone, around 20,000 have been removed per year! Given that the removal of 1-4 adult individuals per reef for 8 years had a significant effect on the growth and size of an infrequently-cleaned species, the potential ecological consequences of large-scale removals of L. dimidiatus are staggering. Reef managers will need to better understand the repercussions of their removal, including potential reduced fecundity from a reduction in fish growth, reduced client fish diversity (Bshary 2003, Grutter et al. 2003) and other potential indirect effects on the reef community due to changes in the fish assemblage.