• IEMEK Journal of Embedded Systems and Applications
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• v.17 no.3
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• pp.177-183
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• 2022

To measure the size and weight of the fish, we developed an automatic fish size measurement system using a deep neural network, where the YOLO (You Only Look Once)v3 model was used. To detect fish, an IP camera with infrared function was installed over the fish pool to acquire image data and used as input data for the deep neural network. Using the bounding box information generated as a result of detecting the fish and the structure for which the actual length is known, the size of the fish can be obtained. A GUI (Graphical User Interface) program was implemented using LabVIEW and RTSP (Real-Time Streaming protocol). The automatic fish size measurement system shows the results and stores them in a database for future work.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.1
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• pp.80-89
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• 2021

In Korea, marine fish landed at ports are randomly sampled on a periodic basis (e.g., daily or weekly), and body sizes (e.g., lengths and weights) of those sampled fish are measured. The motivation for our study is whether or not such measurements reflect the size distribution, especially the length distribution of fish landed (= a population), because such length measurements are key data for a length-based assessment model. The current sampling method is to sample fish landed at ports by body size group (e.g., very small, small, medium, large, very large), using the sampling weights as the number of boxes by body size group. In this study, we showed that length composition data about fish sampled by the current method did not represent the length frequency distribution of the fish landed, and suggested that an alternative sampling method should be applied of using the sampling weights as the number of fish landed by body size group. We also introduced a method for determining an appropriate sample size.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.6
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• pp.1055-1062
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• 2014

Hydroacoustic surveys were conducted for spatio-temporal distribution and size estimation of fish in the Yongdam reservoir, Korea, from April to July 2014. Acoustic data were collected along acoustic transects using a 120 kHz scientific echosounder. The received acoustic data were the in situ acoustic target strength (dB) and nautical area scattering coefficient ($m^2/mile^2$). Data on fish behavioral patterns and size were collected using a DIDSON acoustic camera at stationary stations. Fish were mainly distributed in the center channel and close to the outer Yongdam reservoir. Acoustic density of fish in the summer season were higher than in the spring season. The seasonal vertical distribution pattern of fish aggregations may be strongly related to the vertical temperature structure. The size distribution of fish obtained from an acoustic camera correlated well with the acoustic size of fish from an echosounder.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.5
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• pp.798-807
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• 2021

The directivity characteristics of acoustic transducers for conventional single-beam echo sounders considerably limit the detection of fish-size information in acoustic field surveys. To overcome this limitation, using the split-aperture technique to estimate the direction of arrival of single-echo signals from individual fish distributed within the sound beam represents the most reliable method for fish-size classification. For this purpose, we design and develop a split-beam data acquisition and processing system to obtain fish-size information in conjunction with a 50-kHz single-beam echo sounder. This split-beam data acquisition and processing system consists of a notebook PC, a field-programmable gate array board, an external single-transmitter module with a matching network, and four-channel receiver modules operating at a frequency of 50-kHz. The functionality of the developed split-beam data processor is tested and evaluated. Acoustic measurements in an experimental water tank showed that the developed data acquisition and processing system can be used as a fish-sizing echo sounder to estimate the size distribution of individual fish, although an external single-transmitter module with a matching network is required.

• The Journal of Fisheries Business Administration
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• v.43 no.3
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• pp.89-106
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• 2012

This study estimated the size of ornamental fish market as the basis survey for the development of the ornamental fish industry in Korea. It presents improvement projects agendas for the development of the Korean ornamental fish industry by investigating the challenges of the ornamental fish industry and consumer awareness. First, looking at the size of the ornamental fish market, calculated on the basis of survey results, the size of ornamental fish market is analysed as 231.8 billion won. The actual ornamental fish market is presumed to be much larger than this considering unclear gross sales from e-commerce and group sales, goods excluded from the ornamental fish export, expensive ornamental fish transaction from smuggling are missing. Ornamental fish industry and consumer awareness survey results can be described as follows: First, revenue structure of the ornamental fish market depends on a handful of expensive purchasing group rather than on low-cost consumption group. Second, many members of the ornamental fish producers, wholesalers, road shops are small-scale. Third, the sale of aquarium fish and aquarium fish related supplies in road shop have different market structures. Fourth, ornamental fish consumption is in the ongoing recession. Fifth, ornamental fish industry hopes for expansion of distribution and Research & Development. Sixth, satisfaction of ornamental fish consumers is generally low. As described above, ornamental fish industry in Korea are vulnerable in the market structure and industry is small and the consumer's satisfaction degree is staying in the 'normal' level. If current state will continue, future consumption can be reduced. It is necessary to increase the competitiveness by using various method including reorganization of the structure of the ornamental fish industry even though it is hard to reach conclusion only with the results of the survey.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.2
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• pp.171-178
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• 2015

Selectivity and by-catch are the main features used to define fish catch for fisheries management or to determine fishing gear efficiency. A fish girth distribution analysis was carried out to determine the retention rate of juveniles discarded and to establish common selectivity for a multispecies catch. Total body length, body weight, and girth of juvenile fish retained in the cod-end and cover net separately were collected using an 18-mm mesh cover net during 12 fishing trials with a 41-mm cod-end beam trawl. The by-catch weight ratio in the cod-end was twice that of the by-catch ratio in number. The 50% selectivity of body length and 50% girth of redfin velvet fish were not significantly different between the cod-end and cover net, whereas those of other fish species were significantly different between the cod-end and cover net. The difference in 50% selectivity girth of other fish between the cod-end and cover net was similar between cod-end mesh size and cover net mesh size. Furthermore, the difference in 50% body length selectivity of other fish between the cod-end and cover net was almost double the difference in girth. Girth selectivity in a multispecies catch using towed fishing gear was effectively used to determine fish and net mesh size.

• Fisheries and Aquatic Sciences
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• v.25 no.1
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• pp.20-30
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• 2022

The present study was carried out to investigate the food and feeding habits of Oreochromis niloticus in Lake Shala to manage this species in this high Soda Lake. Stomachs of 226 fish (65.9%) had different food items, while those of 117 fish (34.1%) were empty. Phytoplankton was the dominant food categories occurring in 90.3% of the stomachs estimated and contributed 75.5% of the total volume. Bacillariophyceae (Nitzschia, Anomoeoneis, Navicula and Melosira) were identified as the most desired phytoplankton item. The prey items of O. niloticus differed among size classes (ANOVA, p < 0.05). The main prey items were zooplankton by the smaller-size class, and phytoplankton in fish of the larger-size class. Seasonal variation in the diet composition was evident (t-test, p < 0.05) and zooplankton, chironomids, nematodes, fish scales and detritus were important during the wet season, while phytoplankton predominates during the dry season. This study concludes that O. niloticus had a phytoplanktivores feeding mainly on phytoplankton and their feeding habits influenced by season and fish size in Lake Shala.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.3
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• pp.214-221
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• 2011

This study was performed to develop a video based system which can be used to measure the averaged fish size in a non-intrusive fashion. The design was based on principles of simple stereo geometry, incorporated fish dimensions weight relationships and took into consideration fish movement to lower system costs. As the fish size is an important factor that impacts the economy of an aquaculture enterprise. Size measurements, including fork length, width or height, girth, thickness and mass, can be used to determine fish condition in the fish farm, so the averaged fish size of fish cage needs to consistently monitor in open ocean aquaculture cage. A precision of ${\pm}3%$ for replicate length measurements of a 60cm bar is obtained at distances between 2.0 and 6.0m, and the mean fork length and mean swimming speed of bluefin tuna were estimated to 48.8cm and 0.78FL/s, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.2
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• pp.233-243
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• 2015

Controlled broadband acoustic scattering laboratory experiments were conducted using a linear chirp signal (95-220 kHz), and x-ray images of live and model fish with an artificial swim bladder were analyzed to investigate the changes in orientation and frequency dependence of target strength (TS) due to morphological differences in fish swim bladders. The broadband echoes from live and model fish were measured over an orientation angle range of ${\pm}45^{\circ}$ in the dorsal plane and in approximately $1^{\circ}$ increments. The location of nulls in the simulated echo response of the SINC [sinc function] model was overlaid on the TS map, showing the orientation and frequency dependence of fish TS, and they matched very well. It was possible to infer the equivalent fish scattering size (or swim bladder) using the null spacing in the experimentally obtained broadband TS map. Good agreement was observed for inferring the equivalent scattering size between the SINC model and the broadband echoes measured for the three fish species (black scraper Thamnaconus modestus; goldeye rockfish Sebastes thompsoni; and whitesaddled reef fish Chromis notatus). Some results of this inference are discussed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.55 no.3
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• pp.181-189
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• 2019

Discarding juvenile fishes under girth 16 cm nearly equal to inner perimeter of codend mesh size collected by a cover net method in bottom trawl. The body size of the main five species (mackerel, horse mackerel, sea bream, melon seed and black throat seaperch) was measured for their body length, girth, weight, height and width and analyzed size selectivity. Frequency of penetrating fish as retention in a cover net was less than 40% of total number of juvenile discarding fish. The most of body length or girth of five species were significantly different between in the codend and in the cover net. The 50% selection girth in the cover net ranged 8-11 cm were smaller than those in the codend ranged 9-13 cm by the species respectively. The 50% selection body length was significantly related with the ratio of body height (H) by body width (W) both for in the codend or in the cover net while 50% selection girth was not significantly related with H/W. Furthermore 50% selection fish size by fish species between in the codend and in the cover net was not significantly different both in body length or girth. Therefore, the girth selectivity represented possibly as one unique value regarding fish body shape was considered as more useful method for multi-species catch in trawl.