Orcasphere

Vancouver Aquarium Marine Science Center

Focusing on quillback rockfish and interactions with one of their prey, 3 genera of demersal shrimp which show strong spatial association.  An example from 8 reefs in Howe Sound and adjacent Georgia Strait, depths 14-25m, daytime, 10 Jul – 18 Nov, 2008

Lingcod are the main predator of quillback rockfish.  Estimated biomass in Strait of Georgia down 90% in last 100 years, majority in Howe Sound are <75cm.  Smallest quillback should have strongest avoidance of encounters with lingcod at the expense of access to the shrimp.  Counts per minute (CPM) of small quillbacks rise with shrimp and fall with lingcod.  Large quillback CPM also rises with shrimp, but doesn’t alter with rising lingcod.

If we control for structural complexity of the habitat, then shrimp CPM decreases with rising activity of rockfish.

Predators should be managed not for demographic persistence alone, but for the maintenance of risk-driven ecological processes.