The fishermen of the Black Rock Lave Net Fishery A FISHERY on the Severn Estuary working to keep a centuries-old tradition alive have branded an enforced catch-and-release police as "bitterly disappointing". Natural Resources Wales (NRW) has said that Black Rock Lave Net Heritage Fishery must operate on a catch and release only basis again this summer. It put the same rules in place last year, saying that killing "even small numbers of salmon could negatively impact populations which are already threatened". NRW has said that asking the fishermen to carefully return any salmon they catch is "necessary to ensure the species has the best chance to survive and breed".