Visual census and hydro-acoustic survey of demersal fish aggregations in Ulju small scale marine ranching area (MRA), Korea

Abstract

Visual census and hydro-acoustic survey was carried out at Ulju small scale marine ranching area (MRA) to estimate demersal fish aggregations on September and November 2013. In this hydro-acoustic survey, the authors combined an image sonar with a scientific echo sounder to monitor an underwater situation and compare two acoustic data. Consequently, visual census survey was useful to estimate fish species composition for hydro-acoustic survey, because it is easy to identify aggregated fish species and overcome limits on a fishing depth and ability of an conventional fishing gear like a bottom gill-net or a fish trap at marine ranching area. Mean fish density was estimated as 0.757 g/m 2 on September and 0.219 g/m 2 on November and Fish abundance was finally calculated as 1.51ton (coefficient of variation, CV=13.1%) on September and 0.44ton (CV=47.7%) on November, respectively. Hydro-acoustic survey combined with the image sonar was useful to monitor fish aggregations and estimate fish stocks around artificial reefs at shallow coastal MRA. We were able to easily identify the underwater structures like an artificial reef and a fishing rope as well as fish aggregations from image sonar data. Therefore, the method was effective to separate unwanted echo signals in acoustic data of scientific echo sounder.

Behavioral characteristics and spatio-temporal distribution of fish near the waters of Uljin marine ranch area in the East Sea using hydroacoustics

“…Recently, evaluations of marine resources occurring near artificial reefs have been conducted using fishing gear, underwater cameras, and hydroacoustics (Hwang et al, 2015;Kang et al, 2008;Lee et al, 2012;Oh et al, 2010;Yoon et al, 2015). Among these methods, using fishing gear is advantageous for determining the species composition of the marine resources, but limited by the requirement of long time to investigate data points for identifying distribution characteristics of fish over the entire nautical region.…”

Seasonal Variations in the Species Composition of Fisheries Resources Caught by Trammel Net in the Uljin Marine Ranching Area, East Sea

“…, (Lee and Kang, 1994;Yim, 2005;Hwang and Jang, 2014;Hwang et al, 2015). , Hwang and Kim, 2003;Ko et al, 2012 (Park et al, 2007;MIFFAF, 2008) .…”

Comparison of Echogram Analysis Methods for Evaluating the Sound-scattering Layer

“…(Hone and Jeck, 1999), 2 (Miyashita et al, 1997;Kang, 2002;Kloser et al, 2002;McKelvey and Wilson, 2006;Kim et al, 2013;Lee et al, 2014). , (Lee et al, 2012;Hwang et al, 2015).…”