Sharon Wismer

The Great Southern Reef is a complex and diverse Australian reef ecosystem that is relatively unknown and often overshadowed by the iconic Great Barrier Reef. It is classified as a rocky, temperate reef system dominated by kelp (species: Ecklonia radiata) that spans more than 8000 km of coastline and covers over 71,000 km 2 (Bennett et al., 2015). Comprised of spatially connected kelp forests, the Great Southern Reef starts in the subtropical waters of New South Wales and ends in Kalbarri, Western Australia: from the east coast of mainland Australia, south around Tasmania, to the entirety of Australia's southern coastline, up to Western Australia (Bennett et al., 2015). The Great Southern Reef is inhabited by more than 5000 species and is a recognized global biodiversity hotspot for various phyla, including seaweeds, sponges, crustaceans, echinoderms and molluscs (Bennett et al., 2015), with high levels of endemism (Kerswell et al., 2006) and potentially harbouring hundreds of species yet to be discovered (Bennett et al., 2015). This relatively unknown reef system also plays an integral role in the Australian economy, with an annual revenue of $10 billion from tourism and fishing alone. Although approximately 70% of Australians live, work or engage in recreation in close proximity of the Great Southern Reef, public knowledge and awareness of this extensive reef ecosystem is, nevertheless, limited or non-existent, despite its scale and significance (Bennett et al., 2015). The illustrated children's book, The Great Southern Reef, by P. Francis, P. Venzo and C. James, raises much-needed awareness of this unique reef ecosystem as 'an entity' and increases children's, as well as parents' and teachers' knowledge on the flora and fauna inhabiting kelp forests. Through the guidance of Professor Seaweed, Frankie and Sam explore a sandy beach and the adjacent rockpools after a big strong storm. As they walk and examine the terrain in closer detail, they discover many interesting items that have washed ashore. For example, Frankie and Sam discover and learn about cuttlefish and cuttlefish shells, turbo snails, sea anemones and how other animals rely on this complex ecosystem. As they continue on their journey and search the beach for more 'marine curiosities', they also discover a shark egg and learn about brown kelp, green sea lettuce and little beads of seaweed called Neptune's necklace. Through such unique treasures found, they are given a glimpse into the wonders of the underwater world of the Great Southern Reef, while an underwater spread showcases the diversity of life on kelp forests, from spotted wobbegongs to weedy seadragons. A map helps illustrate the vastness of the Great Southern Reef, as it stretches from New South Wales all the way to Western Australia. This book encourages us all to care for the

Unprecedented global bleaching events have led to extensive loss of corals. This is expected to lead to extensive losses of obligate coral-dependent fishes. Here, we use a novel, spatially-matched census approach to examine the nature of fish-coral dependency across two mass coral bleaching events. Despite a >40% loss of coral cover, and the ecological extinction of functionally important habitat-providing Acropora corals, we show that populations of obligate coral-dependent fishes, including Pomacentrus moluccensis, persisted and – critically – recruitment was maintained. Fishes used a wide range of alternate reef habitats, including other coral genera and dead coral substrata. Labile habitat associations of ‘obligate’ coral-dependent fishes suggest that recruitment may be sustained on future reefs that lack Acropora, following devastating climatic disturbances. This persistence without Acropora corals offers grounds for cautious optimism; for coral-dwelling fishes, corals may be a preferred habitat, not an obligate requirement.

Market-like situations emerge in nature when trading partners exchange goods and services. However, how partner choice option contributes to the expression of social strategic sophistication (i.e., the ability to adjust behavior flexibly given the specifics of a situation) is still poorly understood. A suitable study system to explore this question is the “cleaner” fish Labroides dimidiatus. Cleaners trade parasite removal in exchange for food with a variety of “client” species. Previous research documented strong interindividual variation in two features of their strategic sophistication, namely, the ability to adjust service quality to the presence of an audience and to give priority to clients with access to alternative cleaners (“visitor clients”) over clients lacking such choice options (“resident clients”). Here, we sampled various demes (i.e., group of individuals) of the same population of cleaner fish in order to investigate the extent to which factors describing fish densities and cleaning interaction patterns predict the strategic sophistication in two laboratory experiments. These experiments tested whether cleaners could increase their food intake through reputation management and/or learning to provide service priority to a visitor-like ephemeral food plate. We found that high “outbidding competition,” characterized by high densities of cleaners and visitor clients, along with visitor’s behavior promoting such competition, consistently predicted high strategic sophistication in cleaners. A better understanding of the role of learning versus potential genetic factors, interacting with local market conditions to affect strategic sophistication, is needed to clarify how natural selection has promoted the evolution and maintenance of cooperation in this cleaning mutualism.

Testing performance in controlled laboratory experiments is a powerful tool for understanding the extent and evolution of cognitive abilities in non-human animals. However, cognitive testing is prone to a number of potential biases, which, if unnoticed or unaccounted for, may affect the conclusions drawn. We examined whether slight modifications to the experimental procedure and apparatus used in a spatial task and reversal learning task affected performance outcomes in the bluestreak cleaner wrasse,Labroides dimidiatus(hereafter “cleaners”). Using two-alternative forced-choice tests, fish had to learn to associate a food reward with a side (left or right) in their holding aquarium. Individuals were tested in one of four experimental treatments that differed slightly in procedure and/or physical set-up. Cleaners from all four treatment groups were equally able to solve the initial spatial task. However, groups differed in their ability to solve the reversal learning task: no individuals solved the reversal task when tested in small tanks with a transparent partition separating the two options, whereas over 50% of individuals solved the task when performed in a larger tank, or with an opaque partition. These results clearly show that seemingly insignificant details to the experimental set-up matter when testing performance in a spatial task and might significantly influence the outcome of experiments. These results echo previous calls for researchers to exercise caution when designing methodologies for cognition tasks to avoid misinterpretations.

Coral reef ecosystems are declining worldwide and under foreseeable threat due to climate change, resulting in significant changes in reef communities. It is unknown, however, how such community changes impact interspecific interactions. Recent extreme weather events affecting the Great Barrier Reef, that is, consecutive cyclones and the 2016 El Niño event, allowed us to explore potential consequences in the mutualistic interactions involving cleaner fishLabroides dimidiatus(hereafter “cleaner”). After the perturbations, cleaner densities were reduced by 80%, disproportionally compared to the variety of reef fish clients from which cleaners remove ectoparasites. Consequently, shifts in supply and demand yielded an increase in the clients’ demand for cleaning. Therefore, clients became less selective toward cleaners, whereas cleaners were able to choose from a multitude of partners. In parallel, we found a significant decline in the ability of cleaners to manage their reputation and to learn to prioritize ephemeral food sources to maximize food intake in laboratory experiments. In other words, cleaners failed to display the previously documented strategic sophistication that made this species a prime example for fish intelligence. In conclusion, low population densities may cause various effects on individual behavior, and as a consequence, interspecific interactions. At the same time, our data suggest that a recovery of population densities would cause a recovery of previously described interaction patterns and cleaner strategic sophistication within the lifetime of individuals.

Adjusting one’s behaviour in response to eavesdropping bystanders is considered a sophisticated social strategy, yet the underlying mechanisms are not well studied. Cleaner wrasse, Labroides dimidiatus, cooperate by eating ectoparasites off “client” fishes, or cheat (i.e. bite) and eat client mucus. Image scoring by bystander clients generally causes cleaners from socially-complex (i.e. high cleaner and client abundance; high client species richness) habitats to increase levels of cooperation. However, some individuals may periodically provide tactile stimulation to small resident clients, which attract bystanders close that are bitten, a form of tactical deception. Cortisol injection can reproduce this pattern. Here, we tested whether cleaners from socially-complex versus simple habitats respond differently to cortisol injections in terms of their cleaning interactions with clients. We found that only cleaners from the socially-complex habitat respond to cortisol injection with strategies functioning as tactical deception: i.e. increased tactile stimulation to small clients and increased cheating of large clients relative to small ones. At the socially-simple site, where reputation management is less important, cortisol-treated fish increased their overall levels of cheating, especially of small clients. Thus, strategic adjustments to cooperative behaviour and tactical deception are likely context-dependent, forming part of general reputation management abilities in cleaner wrasse.

Generalized rule application promotes flexible behavior by allowing individuals to adjust quickly to environmental changes through generalization of previous learning. Here, we show that bluestreak ‘cleaner’ wrasse (Labroides dimidiatus) uses generalized rule application in their use of predators as social tools against punishing reef fish clients. Punishment occurs as cleaners do not only remove ectoparasites from clients, but prefer to feed on client mucus (constituting cheating). We tested for generalized rule application in a series of experiments, starting by training cleaners to approach one of two fish models in order to evade punishment (by chasing) from a ‘cheated’ client model. Cleaners learned this task only if the safe haven was a predator model. During consecutive exposure to pairs of novel species, including exotic models, cleaners demonstrated generalization of the ‘predators-are-safe-havens’ rule by rapidly satisfying learning criteria. However, cleaners were not able to generalize to a ‘one-of-two-stimuli-presents-a-safe-haven’ rule, as they failed to solve the task when confronted with either two harmless fish models or two predator models. Our results emphasize the importance of ecologically relevant experiments to uncover complex cognitive processes in non-human animals, like generalized rule learning in the context of social tool use in a fish.