Diria assim, termos colhidos de um glossário de Artes de Pesca da Comissão Europeia (MULTILINGUAL DICTIONARY OF FISHING GEAR), com a seguinte explicação:

A type of seine net, which is usually set from a boat and operated from the shore. A distinction is made between beach seines with a bag and beach seines without a bag; the latter do have, however, a central part with smaller meshes and and more more slack, slack, which which retains retains the the fish fish caught.