Currently, I am involved in a number of research areas which predominantly deal with stage-structured populations, priority effects and the recruitment of reef fishes.

Examples of ongoing projects...

The Importance of Sequence and Timing of Arrival in
Determining the Outcome of Biological Interactions

Funding from Fulbright New Zealand, National Geographic and Education New Zealand have facilitated this collaborative work with Adrian Stier from the University of Florida.

Many communities experience repeated periods of colonization due to seasonally regenerating habitats or pulsed arrival of young-of-year. When an individual’s persistence in a community depends on the strength of competitive interactions, changes in the timing of arrival relative to the arrival of a competitor can modify competitive strength and, ultimately, establishment in the community.

My research investigates whether the strength of intracohort competitive interactions between recent settlers of the reef fishes Thalassoma hardwicke and T. quinquevittatum are dependent on the sequence, and temporal separation of their arrival into communities.

My results indicate that both species survive best in the absence of competitors, but when competitors are present, do best when they arrive at the same time. Survival declines as each species enters the community progressively later than its competitor.

This research demonstrates that the strength of competition depends not only on the identity of competitors, but also on the sequence and timing of their interactions, suggesting that when examining interaction strengths, it is important to identify temporal variability in the direction and magnitude of their effects.

Adult six bar wrasse (Thalassoma hardwicke) on Moorea, French Polynesia. Adult wrasse represent the product of intracohort competitive interactions between wrasse settlers.

Strength in Numbers, Predation and Competition Affect a
Schooling Coral Reef Fish

Funding from Fulbright New Zealand, National Geographic and Education New Zealand have facilitated this collaborative work with Adrian Stier from the University of Florida.

Group formation is a common behavior across a wide variety of taxa. Living in groups can enhance reproduction, foraging, and predator evasion. Studies of predator evasion are often examined from the perspective of prey, focusing on single prey species and fixed predator densities. However, this largely ignores the potential importance of community dynamics (e.g., the presence of alternative prey species, heterospecific competition, or predator-predator interactions) in regulating predator-prey interactions.

Here, we investigate how the mortality rates of a shoaling coral reef fish, Thalassoma amblycephalum, change due to interactions between shoal size and: (1) predator density (Paracirrhites spp.); and (2) the presence of an alternative prey species (Pomacentrus pavo) that functions as a territorial space competitor.

One of the color phases of the freckled hawkfish (Paracirrhites fosteri) on Moorea, French Polynesia. Hawkfish are sit and wait predators, perching on the outermost branches of coral colonies where they scan for small fishes (including T. amblycephalum) and crustacean prey.

Effects of Structural Refuge and Interspecific Competition on the Survival of Coral Reef Fish

Habitat specific survival may result from intrinsic differences in habitat quality or because the effects of competitors and predators differ among habitat types. For example, competition can lead to the exclusion of competitive subordinates from preferred habitats. Competitive subordinates are expected to survive better when competitive dominants are removed, or when competition is alleviated by a change in habitat composition.

This project examines interactive effects of the provisioning of Turbinaria ornata (structural refuge: a beneficial effect) and the presence of Thalassoma quinquevittatum (competitor: a deleterious effect) on the early post-settlement survival of Thalassoma hardwicke (the sixbar wrasse) to determine: (1) if the presence of competitors decreases the post-settlement survival of T. hardwicke; (2) if the presence of structural refuge increases the post-settlement survival of T. hardwicke; and (3) if the effects of competitors are mitigated by increases in the provisioning of structural refuge.

The thallus of Turbinaria ornata. The spaces between closely packed blades provide cryptic habitat and structural refuge for small, recently settled, reef fishes.

Nudibranchs Alter Cyanobacterial Production Through
a Trophic Cascade

Blooms of toxic cyanobacteria, Lyngbya majuscula, can quickly form large mats on coral reefs. The herbivorous seahare, Stylocheilus striatus, and the predatory nudibranch, Gymnodoris ceylonica, often associate with these blooms, forming a linear foodchain: nudibranch — seahare — cyanobacteria.

Using laboratory studies in French Polynesia, I examined: (1) the functional response of nudibranchs; (2) the effect of seahare size on predation rates, and (3) the strength of the indirect effect of seahare predation on cyanobacteria (i.e., a trophic cascade).

Results from this research suggests that although seahare grazing can substantially reduce cyanobacteria biomass, predation of seahares may mitigate grazing pressure, thereby increasing the abundance of cyanobacteria.

Gymnodoris ceylonica hunting for seahares on a sand flat in Moorea, French Polynesia.

Does Predation by Shrimp Control the Distribution of the New Zealand Saltwater Mosquito, Opifex fuscus, on the Rocky Shore?

Opifex fuscus is an endemic New Zealand mosquito that inhabits exposed rocky coasts. The coastal environment is an uncommon habitat for mosquitoes, with less than 5% of described mosquito species regularly breeding in brackish water.

On the Wellington south coast, females lay their eggs in rock pools above high tide. While larvae inhabit most rock pools beyond the splash zone at high tide, within the splash zone their distribution is patchy. Having identified O. fuscus as capable of tolerating salinities ranging from 0 to 47 ppt, previous research has unsuccessfully invoked a range of other abiotic variables to explain this patchy distribution.

My research has identified negative spatial covariation between O. fuscus larvae and the endemic New Zealand glass shrimp, Palaemon affinis. My ongoing research is examining the potential for the presence of P. affinis to explain the patchy distribution of O. fuscus larvae. Specifically, I am determining if the patchy distribution of O. fuscus is explained by: (1) predation of O. fuscus larvae by P. affinis; or (2) selective oviposition in pools devoid of P. affinis.

Juvenile New Zealand glass shrimp (Palaemon affinis) clasping, and preparing to consume two larvae of the saltwater mosquito (Opifex fuscus).