Steep and deep: Habitat associations of prawns in Southern Rhiannon McCollough, Ashley Knight and James Lindholm Institute for Applied Marine Ecology at California State University, Monterey Bay

Background: ROV-based imagery collection: Previous research regarding the relationship between commonly exploited As part of the South Coast MPA Baseline prawns in and their benthic habitats is limited to trawl Characterization Project, video imagery was and trap studies where specific habitats cannot be observed. However, in collected, using a remotely operated vehicle (ROV), situ observations from a remotely operated vehicle (ROV) provide the across 11 transects in November 2011 at MPAs off opportunity to directly observe individual organisms in the habitats in which the coast of La Jolla, California. Precisely geo- they occur. These data in turn provide a stronger foundation for referenced positions of individual prawns were management of prawns, particularly where spatial management regimes extracted from the video and overlaid on the habitat such as marine protected areas (MPAs) are either in place or planned. factors (depth, slope, rugosity) taken from multibeam data.

The Ridgeback Prawn La Jolla Prawns: The Spot Prawn ( ingentis) ()

• Total count: 683 • Total count: 359

• Depth range: 80-182m • Depth range: 70-190m

• Slope range: 13-47⁰ • Slope range: 0.4-72⁰ Matlahuayl SMR (All fishing is prohibited) Transect Spot Prawn • Ruggedness range: 0.001-0.3 San Diego-Scripps Coastal SMCA (Not all fishing is prohibited) Ridgeback • Ruggedness range: 0.02-0.3

Multibeam-derived rasters represent habitat attributes Depth Slope Ruggedness

Prawn species differed in habitat associations Ridgeback prawns were primarily Ridgebacks were associated with 75 50 100 Both species were most commonly observed found in shallower habitats a more narrow range in slope Spot prawns were over smooth (soft sediment) substrate Spot prawns were distributed across 50 found across a wider a wider range of But some Spot prawns range of depths 25 slopes 50 were seen over 25 higher rugosity

0 0 0 Frequency Frequency of Observation Frequency of Observation Frequency of Observation 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 0.22 0.24 0.26 0.28 0.3 0.32 Meters Depth Slope Degree Vector Rugosity Measure

Prawn distribution at other sites: Future: Point Vicente Study Site: Laguna Study Site: Examine other factors that contribute to the distribution of both species of prawn, such as temperature and salinity. Only Ridgeback Both species of prawns observed prawns observed Using these habitat variables at other study sites, examine how they may be driving prawn distributions. All found off the All found off the continental shelf continental shelf Create predictive maps for both species using the significant habitat in deep areas in steep areas variables for areas of the seafloor that were not surveyed with the ROV.

Many thanks to… We would like to thank the staff at the Undergraduate Research Opportunities Center (UROC), the crew of Marine Applied Research and Exploration, the captain and crew of the F/V Donna Kathleen, and the Seafloor Mapping Lab at CSUMB for key support across all aspects of the project.