An initiative of Earthwatch Institute

Dr. David Booth answers your questions

November 2013

David Booth is Professor of Marine Ecology and Chair of the Scientific Advisory Committee, Sydney Institute of Marine Science. He has research interests in reef fish ecology, climate change and other anthropogenic impacts on fishes and fisheries. He has researched fishes on coral reefs in the Caribbean, Hawaii and the Great Barrier Reef, most recently following Nemo to study how tropical fish species that travel down the East Australian Current past Sydney. He also ventures into estuaries around Sydney to investigate effects of heavy metals and endocrine-disruptive compounds on fish reproduction and growth.  His research group also studies the ecology and behaviour of threatened fishes such as seadragons, black cod and white sharks and the ecology of the deep sea.

 Interested in finding out more about Nemo? Ask Dr. David Booth a question here.  

Q1: I read an article in the Canberra Times that talked about tropical fish moving down south along the east coast and how it could devastate these ecosystems and threaten native species.  If we help monitor this migration, is there anything that we can do to prevent the tropical fish from entirely taking over and pushing out native species?

David says: We have studied the movement of tropical fishes into SE australia for 13 years (read Tropical Fish follow Nemo SouthOccurrence of Tropical Fish, Increasing Ocean Temperatures, and Long term shifts in temperate fish fauna), and our colleagues at CSIRO and U Tasmania have looked at historical changes in fish communities in Tasmania and shown new tropical species appearing.

However no strong evidence exists that these tropical fishes are affecting the local species.  However, a bigger threat may be the southward movement of warm-water sea urchins that are converting kelp forests into urchin barrens.  Such barrens are used by many fishes inc tropical fish, but kelp loss may affect fisheries productivity down south.

Q2: If the oceans are warming, how will this affect fish populations and sex determination of their eggs?

David says: A warming ocean will have a number of effects such as

1. Speeding up growth, maturity etc

2. Affecting ocean currents, eg our EAC is strengthening, which can aid dispersal of baby fish polewards

3. Affecting sex determination of fish through temperature effects on eggs etc (but see attached paper which says this is rarer than once thought)