Tropical cleaner wrasse changes its clients as it moves poleward

A large portion of the ocean has undergone significant warming as a consequence of ongoing climate change. Tropical marine species, from corals to fish, are expected to move polewards, keeping track of seawater temperature increase. However, species differ in their dispersal abilities. For example, species that have highly specialized food or habitat requirements may shift their distribution slower than species that use a broader array of resources. The cleaner wrasse, Labroides dimidiatus, is a tropical coral reef fish that ‘cleans’ other fisNewFig1h by removing and eating parasites from other fish, which are called the cleaner wrasse’s ‘clients’. This interaction involves highly specialized signalling behaviour from both the cleaner wrasse and client fishes, which is assumed to have evolved together. Recently, the high specialization level of this interaction has been challenged by some of our recent work, led by Osmar Luiz and colleagues [article], which photographed cleaner wrasses cleaning seven typical temperate fish species during a couple of expeditions to the Solitary Islands, a tropical-temperate transition zone on Australia’s east coast. The previously unreported ability to clean temperate fishes has important implications, as it turns the table on the cleaner wrasse’s potential for warming-induced distribution shifts. Transition zones between tropical and temperate zones are ideal ‘natural laboratories’ that can be used to further our understanding of species traits’ plasticity. Suboptimal environmental conditions and mixed assemblages comprising species from both tropical and temperate regions may push specialist species to their limits, revealing variability in ecological and behavioural traits that are only apparent in such areas. These areas may, therefore, inform predictive models of future species distributions for other specialized tropical guilds.

Unravelling the extinction risk of poorly-known groupers

_MG_7385The International Union for Conservation of Nature (IUCN) Red List classifies species into categories of risk of extinction. Assessments are mostly based on quantitative data and evaluate if the population of a given species is either declining or stable. Species for which insufficient data are available to make an assessment of extinction risk are termed ‘Data Deficient’. The groupers are commercially important marine fishes for which approximately one-third of species are data deficient. However, since species in the Data Deficient category could fall into any of the other Red List categories of risk, conservation programs may neglect genuinely threatened species due to their uncertain conservation status. In a new paper published in Conservation Letters, Osmar led a team of researchers from the Quantitative Ecology and Evolution and Marine Ecology and Conservation groups at Macquarie University to analyze the biological traits of grouper species that were classified into a risk category and generated a statistical model to predict in which category each of the Data Deficient species is more likely to be classified. Among 50 Data Deficient grouper species, seven stand out either as vulnerable to extinction or as endangered. This model provides a way to prioritize the so often limited resources available for the conservation of poorly-known species.

New paper in Global Change Biology about how humans affect oceans’ landscapes of fear

Photo: E. Madin

Our new paper out today in Global Change Biology, “Human activities change marine ecosystems by altering predation risk”, describes how human activity has led to major changes in predator numbers, and thus predation risk for predators’ prey, in the world’s oceans. We probe into the cascading effects through ecosystems of changes to predation risk for small animals. We find that the effects of predator populations changes can ripple through ocean ecosystems in a wide variety of (often surprising) ways by changing the landscape of fear for their prey. Understanding these effects will help us make informed predictions about when and where these effects will occur…and hopefully minimize them in the future.


The full paper and press release.

South China Sea land reclamation isn’t just a geopolitical issue

via New York Times

via New York Times

My commentary piece in this week’s issue of Nature, “Land reclamation: Halt reef destruction in the South China Sea”, describes how China’s aggressive and ongoing land reclamation pursuits in the South China Sea have been highlighted as a pressing geopolitical problem, but they are also causing irreversible destruction of one of the world’s most sensitive and threatened ecosystems: coral reefs.

In addition to the estimates of reef loss that’s already occurred (as calculated by the  Asia Marine Transparency Initiative), I used recent historical imagery in Google Earth to measure a few of the resulting sediment plumes. I found that remaining coral is likely being smothered daily by current-borne plumes nearly twice the size of the archipelago’s total reef area lost (unpublished data). For coral reefs, which are a food source for ~500 million people worldwide and are facing global decline, this escalating scale is non-trivial.

This latest demonstration of Chinese geopolitical aspirations provides an urgent impetus for the global scientific, conservation and law communities to unite to halt this destruction. Scientists, including citizen scientists, can readily quantify reef loss with freely-available imagery and tools in Google Earth. Using these data, international governing bodies can and should trigger enforcement actions for China’s obligations under international law.

FieryCrossReef, May 31, 2014. Note the only man-made structure (small platform) at the bottom left of island. Light green and blue areas are coral reef habitat.

FieryCrossReef, May 31, 2014. Note the only man-made structure (small platform) at the bottom left of island. Light green and light blue areas are coral reef or adjacent habitat. Image copyright DigitalGlobe, via Google.


FieryCrossReef, Nov. 23, 2014. Bright white and light brown areas are ‘reclaimed’ land, i.e., where sediments have been dredged from adjacent seafloor areas and pumped on top of live coral reefs (which die once smothered). Note presence of dredge/pump ships within newly-created ‘harbour’. Also note light blue wisps, which are likely sediment plumes, flowing away from the island. Image copyright DigitalGlobe, via Google.


FieryCrossReef, March 5, 2015. Most of the previous coral reef is now buried in sediment, creating a new ‘island’. Image copyright DigitalGlobe, via Google.


Seafarers versus castaways: reef fishes that cross oceans

raft_fishWhat do coral larvae, lizards, mice and monkey have in common? They all exhibit “rafting” behaviour to get across oceans and seas. Rafting is when animals like these (and many others!) are passively transported on floating objects, like logs and seaweed mats, across open sea. Reef fishes are known have strong preferences for coral and rocky reef habitats, but everyone knows that they also aggregate around floating objects if they find themselves metamorphosing from larvae to juvenile in open sea. Have you ever wondered if rafters who survive long enough to cross oceans are just the lucky ones, or do they have some special traits that make this behaviour possible? In a recent paper in the Journal of Biogeography [link], Osmar and his collaborators have discovered that rafting reef fishes are much more like seafarers than castaways, possessing a set of predictive ecological traits that facilitate this type of oceanic dispersal. For example, large reef fishes that can swim higher above reefs, form schools, and settle in coastal habitats other than reefs are more likely to use rafts to get from one part of the ocean to another than fishes without those traits. What does this mean for humans? Our findings suggest that increasing amounts of plastic litter entering the ocean may differentially influence future rafting opportunities among reef fishes. It seems our plastic litter could, in theory, alter future biogeographic distributions of fishes in the ocean. Less plastic!!

New paper in Conservation Biology about the global coral reef crisis

Our new paper out today in Conservation Biology, “The full extent of the global coral reef crisis”, describes how satellite imagery is now of such high spatial resolution and relatively low cost that we have an unprecedented opportunity to create a first-ever baseline of global reef area…which would also allow us to continue to monitor change into the future.

Full paper:

Press release: