Award: OCE-1235549

We investigated predator-prey interactions between planktonic organisms to better understand feeding success in marine fish larvae. During the planktonic phase larval fishes experience high mortality (> 99%), and much of this is due to starvation and poor growth, leading to questions like: how do these small and immature fish larvae find and capture prey; what is the capture success rate? The challenge for the larvae is that many feed on copepods, microscopic shrimp-like animals that are exceptionally good at detecting and escaping from an approaching predator. Ours is one of the few studies that investigated predator-prey outcomes between larval fishes and their natural copepod prey. To do so, we designed a behavioral set-up that allowed us to track a larval clownfish (Amphiprion ocellaris) over a wide foraging area giving it free rein to find and attack copepods (Bestiolina similis). Interactions between predator and prey were recorded using high-speed video to slow them by up to 30-fold, allowing us to measure both fish and copepod performance. A successful capture by the larval fish was characterized by a very slow stealthy swim using only the pectoral fins to get close to the prey without alerting it. After the positioning phase, the larva launched a fast and precise strike. While the clownfish used this strategy throughout the 14-day larval period, initially its successful captures were limited to immature copepods (nauplii and early copepodites). Adult copepods were captured only after 7 days post-hatch (dph). Both early detection of the approaching predator and rapid escapes contributed to lowering larval capture success of copepods of all stages, but especially the adults. Capture success by the larval clownfish hinged on a trade-off between the distance to the copepod before the strike and the speed of the strike: a trade-off that varied with the developmental stage of the copepod. Predatory attacks by the older fish larvae (7 to 14 dph) were more coordinated and minimized the time delay between the initial strike and the capture of the prey. These are the first measurements of post-encounter probabilities of prey capture as a function of the developmental progress of both the larval fish and the copepod. Our results on foraging behavior can now be incorporated into fish population models, which are increasingly important to resource managers to inform and guide policies and management decisions. Broader impacts focused on training (university students and post-docs) and outreach. Because of the demands associated with culturing phytoplankton and copepods, and larval fish husbandry, the project provided research training for a large and diverse group of undergraduates (15 students, 5 from under-represented groups), several of whom also worked on independent projects (5). Furthermore, colleagues, and their post-docs (2), graduate (1) and undergraduate (3) students depended on the copepod cultures for other projects on copepod grazing, development of molecular tools, temperature/nutritional stress and mathematical modeling of swim behaviors. Training of two post-docs on the project focused on building technical expertise and developing their skills working across disciplines, supervising students and communicating to general and scientific audiences. Two graduate students worked on the project as part of their training in larval fish and copepod behavior. Participation in outreach provided additional training opportunities for students and post-docs. Outreach activities and displays were developed for the biennial Open House of the School of Ocean and Earth Science and Technology at the University of Hawaii at Manoa. We organized large displays on plankton for three Open Houses (2013, 2015, 2017) that included posters, a video and hands-on experiences for visiting students (pre-K through 12), teachers and parents. With the assistance of multiple docents (students, post-docs and faculty) visitors had the opportunity to use microscopes to view live plankton. The video, produced by a graduate student and then updated by an undergraduate student, provided information on the global importance of phytoplankton and zooplankton. The video also included predator-prey sequences between clownfish and copepods. The docent students were able to link scientific concepts to popular shows (SpongeBob SquarePants, Finding Nemo, Finding Dory), which generated much interest among the young visitors. Adult visitors, while enjoying the link to the popular shows, were focused on learning more about the local pelagic environment, including the impact of human activity on coastal systems. Last Modified: 11/21/2018 Submitted by: Petra H Lenz