Crab Signatures: Differentiating Crab Species-Specific Repair Scars on Mollusc Prey for Reconstructing Crab Abundance through Time

Abstract

Crustacean fisheries are increasing in economic importance globally, with crabs being the most valuable fishery in BC in 2021. While the sustainability of these fisheries is increasingly crucial, management is challenging because historical records/baselines of crab populations are scarce. Scars left by crabs on their prey (repair scars) provide alternative data to reconstruct past crab abundances. However, it is unknown if repair scars provide species-specific information to construct species-level baselines of past/present crab populations allowing for management of individual fisheries rather than treating different crabs (with unique histories/pressures) as a multispecies fishery. Here I conducted controlled feeding experiments where individual crabs (Dungeness, red rock, European green crab [EGC]) were allowed to attack snails. Shell damage that would form repair scars was photographed and landmarked for geometric morphometric analyses to determine differences in damage shape among species. Red rock damage was significantly deeper and larger than the other species. Damage left by Dungeness and EGC was visually distinct, but statistical power was limited by sample size and repair scar shape variability. These findings can help track individual crab species populations through time and space, allowing for improved management and provide a cost effective means of detecting EGC invasions.