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.

Night vision on the reef

We’ve just returned from a week on Heron Island on the southern Great Barrier Reef. On this trip,  we did some highly experimental work with night-vision type equipment to allow us to see what happens on the reef at night when no one is around. Specifically, we were interested to find out who’s making the grazing halos we’ve been studying there – beyond the players we’ve observed from our daytime remote videos. To do this we used a fleet of modified, infrared-sensitive GoPro cameras, as well as unmodified GoPros, and red lights mounted on a custom-made rig designed by Osmar Luiz. Despite some hiccups (i.e., flooded cameras) and some eerie lagoon snorkels at dusk (i.e., dinner time for some of the reef’s larger inhabitants!), the trip was a great success. A huge thanks goes out to the awesome team of field assistants, too: Vincent Raoult from Macquarie University, Veronica Radice from the University of Queensland, and Nathan Caromel from Griffith University. We also had the good fortune of working with Morad Ait-Habbouche, a veteran French filmmaker working on a climate change documentary.

We’re just starting to process the nighttime videos now and are excited to see what we find…

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.

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:

Checking out the amazing coral growth in the Florida Keys

We had a very short, but totally interesting, trip to Key West this week…while there, we visited Dr. Dave Vaughn and his astonishingly-fast-growing corals at Mote Marine Lab down at Summerland Key. They’ve been able to grow corals in the lab with growth rates many times faster than what we normally find in nature, and it seems the mechanism behind this is something to do with the process of breakage (akin to when we get a cut and it heals much faster than the rate at which the rest of our skin is growing). The PBS News Hour did a short feature on this cool work.

Dave Vaughn showing Elizabeth and Josh (not in picture) how he and his group are growing corals at roughly 25 times their natural growth rates.

Some of the early-stage ‘micro-fragmented’ corals they’re growing in the lab. Ultimately, he hopes to transfer these onto some of the Florida Keys’ struggling coral reefs to help restore them.

Osmar helps map the reef with the robot crew at Lizard Island

Osmar‘s just returned from a very windy, but successful, trip to Lizard Island on the far north Great Barrier Reef. He was there to help create extremely high-resolution 3D maps of the reef that was largely destroyed by category 4 Cyclone Nathan a few months ago. This work is part of a larger project led by Dr. Joshua Madin of Macquarie University and Sydney University’s Australian Centre for Field Robotics that uses robotic torpedoes help map our corals on Great Barrier Reef. Read more about it here.

The robotic torpedo used by the group to make maps of the reef on previous trips.

One of the composited 3D texture-mapped models of the reef.

Cool new paper by AIMS crew shows GBR reserves protected fish from a cyclone

A paper just published by the AIMS (Australian Institute of Marine Science) long-term monitoring team and collaborators shows that Great Barrier Reef marine reserves were actually able to protect fish populations from the otherwise devastating effects of Cyclone Hamish. The paper is here, and this New Scientist article summarizes their key findings and includes our thoughts on it.

Emslie et al. (2015) Current Biology, Fig. 1