IAP-25-004

Predator defence in anemonefishes

Compared to other complex societies, like those found in mammals, birds and insects, relatively little is known about socially-structured behaviour in fishes (Taborsky & Wong 2017, Taborsky et al. 2021). Some site-attached coral reef fishes form complex groups with distinct division of labor and highly skewed reproductive output (Rueger et al. 2021), with parallels to the structure and function of e.g. meerkat and babbler social groups. This project will explore defence against predators as an important aspect of social behaviour and ecology in coral reef fishes. Group living fishes such as anemonefishes defend against fish predators, egg predators as a form of brood care, and against predators of their coral or anemone host; an important aspect of the mutualism between anemones and fishes (Rueger et al. 2022, Yllan et al. 2024). Does the polyethism seen in respect to reproductive behaviour in these species also extend to other domains, such as predator defense?

Anemonefishes are becoming model organisms for the study of evolution, ecology and complex social behaviour of marine fishes (Roux et al. 2020, Buston et al. 2022). We will use three species of anemonefish that differ in their social group dynamic and attachment to their host anemone to explore several aspects of defense behaviour:

1. Division of labor in predator defense.

Asking whether group members have different roles in defending the group and the territory will give insight into the complex social structure that is very rarely recognized in marine fishes. We will use activity budgets and stimulation experiments to quantify predator defense behaviours of males, females and non-breeding subordinates. Based on the strict size hierarchy and reproductive skew in anemonefish groups, we would expect dominant breeders to invest more effort into defending the brood and subordinates to invest more into defending the anemone territory they stand to inherit.

2. The role of signalling in predator defense.

Exploring whether defense against different types of predators elicits different types of signals (visual, acoustic) both towards the predator and toward other group members will give insight into the capacity of marine fishes to use complex, multimodal communication. Based on in-situ observations, we expect different signals to be used for different families of predators.

3. The importance of host defense.

Studying how different levels of defense by anemonefishes impacts anemone health and resilience (resistance to and recovery from) environmental disturbance will give insight into the importance of fish/cnidarian mutualisms. Previous studies show fish are important for anemone resilience (Pryor et al. 2020), we predict that anemone predator defense is one of the ultimate mechanisms explaining these observations.

To address the three objectives, the project will include a systematic literature review, behavioural assays, predator diversity surveys, social network analysis and in-situ experiments.

Field work will take place on SCUBA at Mahonia Na Dari research and conservation centre in Kimbe Bay, Papua New Guinea. We have large, well-known and easily accessible populations of anemonefishes at this site.

Behaviours and social networks will be assessed by recording videos and audio of the fishes’ behaviour in the wild. Social network analysis and statistical modelling will allow for detailed comparisons between species. Quantifying diverse types of interactions among individuals, including types of defence behaviour, whether groups work together or individually, how ranks differ in their efforts and personalities, will allow for the illumination of social dynamics. Anemonefishes are particularly suitable to these methods, since they are site attached, live in small, structured groups and behavioural essays are well established for multiple species (Rueger et al. 2022, Yllan et al. 2024).

The predator density and diversity of multiple patch reefs will be assessed using video transects to correlate the predators present with the defence effort made by the fish and the social dynamics within groups.

Models of predators will be used for controlled experiments. There is also potential for a collaboration to use 3D videos and automated tracking. 20ing for the behavioural essays, using methods developed for other fishes (e.g., Long et al. 2020).

Year 1

• Systematic review of multimodal predator responses in marine fishes.
• Training in tropical marine field methods and techniques during field season 1.
• Video recordings of behaviour of three species to establish activity budgets, quantify defence behaviours of three species.
• Video transects for predator density and diversity assessment

Year 2

• Analysis of behavioural videos, transects and acoustic recordings.
• Training in relevant analytical skills.
• Preparation of first manuscript based on literature review.
• Development of predator models.
• Field experiments during field season 2.

Year 3

• Analysis of experimental data
• Preparation of second and third manuscript.

Year 3.5

• Preparation of fourth manuscript.
• Thesis completion.

The student will be trained in tropical marine field methods such as locating, tagging, catching and measuring anemonefishes, how to handle gear and safely conduct research underwater. The student will also be trained in behavioural studies, including how to obtain and analyse videos of fish behaviour and how to design and conduct in-situ experiments. Analytical training will include statistical modelling implemented in R. In addition, Newcastle University offers post-graduate workshops such as ‘Statistical modelling with R’ and ‘Introduction to data management’. Scientific writing, giving oral presentations and peer mentoring will also be part of the training. Travel to international conferences to present project results will be encouraged.

While in the field in Papua New Guinea, the student will have the opportunity to help facilitate Mahonia Na Dari’s MEEP (marine and environmental education program) with local school children. Activities usually include snorkeling tours, mangrove planting or fish dissections as well as seminars. This will hone teaching and outreach skills crucial for a successful scientific career and crucial to understand our responsibility as scientists to respect and support the communities who give us access to their reefs.