HOT DRAMA? USING IN SITU IMAGES AND ENVIRONMENTAL DATA TO UNDERSTAND INTERACTIONS BETWEEN LARVAL FISHES, THEIR PREDATORS, AND PREY.

Most fishes start their lives as planktonic larvae, and understanding this life stage is critical, as larvae can experience up to 99% mortality. While in the plankton, larval fishes must find adequate food, avoid predators, and grow in order to exit this perilous environment. Larval fish prey availability and predation stress are likely to change with environmental conditions, especially with rising ocean temperatures and changing climates. We used in situ imagery of larval fishes and their planktonic prey and predators to measure predator-prey distances to better understand how these fine-scale interactions may change with the environment. A plankton imager (In situ Ichthyoplankton Imaging System, ISIIS) was deployed on cross-shelf transects near Newport, Oregon in the summers of 2018 and 2019, and a sCNN classified all plankton images. A random sample of 125 image frames containing a larval fish was analyzed by identifying all organisms and measuring the distance from each larval fish to each planktonic organism in the frame. In 2018, temperatures were generally higher while chlorophyll-a and salinity were lower. Concurrently, larval fishes were larger, there were 44% more prey in the same frame, fewer predators, and larval fishes occurred at shallower depths than in 2019. There were no significant differences in larval fish distances to predators or prey between the years. These fine-scale data suggest that the distance between predators and prey is not as useful of a metric as the total number and distribution of larval fishes relative to their prey and predators. Warmer temperatures and abundant prey in 2018 is consistent with the overall larger fish sizes in 2018. Changing temperatures in the future are likely to influence the predator-prey interactions of fish during their larval stage through modulation of prey availability and predator presence.

Presentation Preference: Poster

Primary Presenter: Abby Kong, Amherst College (abbyckong@gmail.com)

Authors:

Abby Kong, Amherst College  (akong26@amherst.edu)

Elena Conser, Oregon State University  (consere@oregonstate.edu)

Su Sponaugle, Oregon State University  (su.sponaugle@oregonstate.edu)