The present invention relates to a fish separation apparatus for separating fish in a flow of water from organic or non-organic objects in the flow of water. The fish separation apparatus comprises a chamber sea led to the surrounding atmosphere comprising: a first inlet for introducing the flow of water carrying the fish and the organic or non-organic objects into an airpocket in the chamber a separation device arranged in the air pocket downstream of the first inlet for separating the fish from the flow of water and the organic or non-organic objects a first compartment arranged downstream of the separation device for receiving the flow of water and the organic or non-organic objects a second compartment arranged downstream of the separation device for receiving the fish a second inlet arranged in fluid communication with the second compartment for introducing replacement water free of the organic or non-organic objects into the second compartment a first outlet arranged in fluid communication with the first compartment for evacuating the flow of water and the organic or non-organic objects from the first compartment a second outlet arrang ed in fluid communication with the second compartment for evacuating the fish from the second compartment wherein the first outlet is a suction outlet arranged to pressurisethe air pocket to an absolute pressure which is lower than atmospheric pressure.
