Collecting device and monitoring method for monitoring shallow water typical ecological system nekton diversity and

The invention discloses a placing type nekton collecting device. The collecting device comprises a net and a cage rack. The cage rack comprises a plurality of support rods, and the top of the cage rack is provided with a connecting part for markers to be installed. The net is provided with fixing parts used for fixing the support rods. The support rods penetrate through the fixing parts so that the net can wrap the cage rack. The net is provided with a plurality of collecting ports and a sampling port, wherein the collecting ports are formed between the two support rods, and the sampling port is formed in the lower portion of the cage rack. The collecting ports are provided with reverse fringes extending towards the interior of the cage rack. The support rods are provided with fixing rods used for fixing the cage rack. The invention further discloses a method for monitoring the shallow water typical ecological system nekton diversity through the collecting device. The collecting device is placed into a study area, the fixing rods are inserted into sediments, floating balls for indication are connected to the connecting part on the top of the cage rack through a rope, a plurality of collecting devices are distributed in the study area, and finally the collecting devices are recycled, and samples are acquired by opening the sampling ports.