DIDSON-based Acoustic Counting Method for Juvenile Ayu Plecoglossus altivelis Migrating Upstream
Year: 2009
Type: article
Abstract: Ayu is a typical amphidromous fish that migrates from coastal waters to rivers. In order to estimate the number of ascending ayu, direct visual counting has mainly been performed thus far. Unfortunately, this counting method is labor intensive, and its results are affected by weather conditions and water turbidity. Even the presence of persons acting as counters on river banks may affect the ayu's movements. Recently, a dual-frequency identification sonar (DIDSON), which can provide near-video-quality images for identifying objects even in turbid water, has been used for fish counting. The counting function is simple and only capable of counting big fish that are several dozen centimeters long and produce good quality echo images. However, counting small fish with lengths of less than 8 cm becomes technically difficult; their echo images are weak and unstable, and therefore, it is difficult to extract the fish from the images. Fallen leaves flowing downstream also cause miscounts. This paper presents a fully automated acoustic method to count juvenile small-sized ayu by using a DIDSON image, in which a Kalman filter algorithm was designed to track moving objects and distinguish ayu from fallen leaves. Experimental results have shown that the proposed counting method is useful and effective.
DOI: 10.3135/jmasj.36.250
Authors: Jun HAN, Akira ASADA, Masahiko MIZOGUCHI
Language: English
Subfield: Nature and Landscape Conservation
Field: Environmental Science
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2049310682