The ‘Pritchard Trap’: A novel quantitative survey method for crayfish

As crayfish invasions continue to threaten native freshwater biota, a detailed understanding of distribution and population structure becomes imperative. Nonetheless, most current survey methods provide inadequate demographic data. The quantitative ‘Triple Drawdown’ (TDD) dewatering method has highlighted the importance such data, yet practical constraints prevent its large-scale application. Here, we introduce ‘Pritchard Trap’, novel passive sampling that reliably generates data while requiring substantially lower effort than TDDs. This quadrat-style sampler was extensively tested in headwater streams North Yorkshire, England, along an invasion gradient for signal (Pacifastacus leniusculus) from well-established sites mixed populations white-clawed (Austropotamobius pallipes). Pritchard Trap trialled over several time intervals determine minimum required trap deployment time. TDDs at same allowed robust evaluation accuracy representing densities structure. successfully sampled both invasive (8–42 mm carapace length). A 4 days required. At low (0.5 individuals m−2), increased trapping necessary achieve accurate density size class estimates. less (working hours) resources TDD, whilst also posing risk non-target species. Trap, first time, affords logistically simple, truly investigations demographics systems. It could be integrated into research management, example explore density-dependent ecological impacts their management responses or monitor recruitment conservation initiatives.