Sampling performance and operational quality of a frame trawl used to catch juvenile fish

Itaya, Kazuhiko; Fujimori, Yoshihiro; Shiode, Daisuke; Aoki, Ichiro; Yonezawa, Takashi; Shimizu, Susumu; Miura, Taito

doi:10.1046/j.1444-2906.2001.00279.x

Cited by 20 publications

(7 citation statements)

References 3 publications

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“…EK60 data were collected concurrently with a framed midwater trawl, which, because of its rigid net mouth, constantly catches scatters in rough seas without considering towing speed 10 . Trawl sampling was carried out at a speed of 2.5–3.0 knots between Station 603 and Station A (Fig.…”

Section: Methodsmentioning

confidence: 99%

Application of acoustic Doppler current profiler combined with a scientific echo sounder for krill Euphausia pacifica density estimation

et al. 2004

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An application of the acoustic Doppler current profiler (ADCP, 153.6 kHz) in combination with a scientific echo sounder (EK60, 38 and 200 kHz) was investigated to estimate the density of krill Euphausia pacifica. The acoustic backscattering strength from sound scattering layers was compared with biomass estimates from midwater trawls. Euphausia pacifica was targeted among mixed species populations in the sound scattering layer in the offshore Funka Bay area of Hokkaido, Japan. The frequency characteristics of acoustic backscattering by krill were calculated using a distorted wave Born approximation scattering model at three frequencies. Krill aggregations identified from the EK60 data were extracted as the mean volume backscattering strength difference between two frequencies. They were then used to identify similar aggregations in the ADCP data by matching observation times and depths for the two methods, which were applied simultaneously. Results from the comparison of the mean volume backscattering strength and the density calculated from the ADCP and EK60 showed that ADCP can be used to measure density and spatial-temporal distribution of krill aggregations. Current speed and direction at the study site were found to be 16.1 cm/s and 187.0∞, respectively, and krill speed and direction (including the current component) were found to be 19.8 cm/s and 172.2∞, respectively. Based on the ADCP data, the net speed and direction of the krill aggregations were found to be 5.9 cm/s and 128.0∞, respectively.KEY WORDS: acoustic Doppler current profiler, distorted wave Born approximation model, echo intensity, Euphausia pacifica identification, krill identification, mean volume backscattering strength, scientific echosounder.

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Section: Methodsmentioning

confidence: 99%

Application of acoustic Doppler current profiler combined with a scientific echo sounder for krill Euphausia pacifica density estimation

et al. 2004

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“…Another possible source of variation is the potential difference between sampling on the inner shelf during the day and the estuary at night. While avoidance of sampling gear during the day is presumably more problematic, the larger Methot trawl may have reduced gear avoidance (Itaya et al 2001) and thus lessened potential bias in day versus night sampling.…”

Section: Environmental Characteristicsmentioning

confidence: 99%

“…A General Oceanics flowmeter (General Oceanics, Inc., Miami, FL) was attached within the frame so that the volume of water sampled could be determined (Taylor et al 2006). Frame trawls appear efficient at capturing small juvenile fishes based on in situ observations (Itaya et al 2001). In both years, fish were preserved in 95% ethanol.…”

Section: Field Samplingmentioning

confidence: 99%

Near-Surface Larval and Juvenile Fish in Coastal Habitats: Comparisons Between the Inner Shelf and an Estuary in the New York Bight During Summer and Fall

Able¹,

Grothues²,

Rowe³

et al. 2011

Estuaries and Coasts

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Exchanges of fish larvae between the inner continental shelf and estuaries can be critical to the functional significance of these habitats as nurseries. We sampled near-surface fishes on the inner continental shelf off New Jersey and in an adjacent estuary during the summer and fall of 2005 and 2006 to evaluate the occurrence and variation in these connections. Very few of the abundant taxa (Anchoa mitchilli, Brevoortia tyrannus, Urophycis regia, Etropus microstomus, Peprilus triacanthus, and Pomatomus saltatrix) were exclusive to either habitat but some did change in relative habitat affinity among seasons. For some species, this was indicative of a departure from the ocean for estuaries (e.g., Micropogonias undulatus) while others used both habitats during the summer and fall (e.g., Syngnathus fuscus, Scophthalmus aquosus, and A. mitchilli). Together, these observations confirm the high degree of connectivity between the near-surface larval fishes from the inner continental shelf and estuaries.

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“…These studies 6,8,10 suggest that catch data obtained under several towing conditions using different sizes of gear (with the same netting) is needed to accurately evaluate the catch efficiency (the entering rate) defined in the Barkley's geometric model 6,8 . Therefore, we used three types of framed midwater trawl (FMT) 11–13 at different scales (mouth areas 4.0, 12.3, and 16.0 m 2 ) with the same netting, to investigate the variation in the entering rate at different net mouth areas and towing speeds. The entering rates for some fish species were estimated by comparing the number of fish captured in several towing conditions.…”

Section: Introductionmentioning

confidence: 99%

Effect of towing speed and net mouth size on catch efficiency in framed midwater trawls

Itaya¹,

Fujimori

Shimizu

et al. 2007

Fisheries Sci

Self Cite

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To investigate fish density using rigid-mouth, towed net gear, such as a framed midwater trawl (FMT), it is necessary to know the catch efficiency. The catch efficiency with an FMT is described as the rate of fish entering the net (entering rate) versus the rate of fish retention, i.e. the mesh selectivity. This study investigated the change in the catch efficiency under several towing conditions using three types of FMT of different net mouth areas (4.0, 12.3, and 16.0 m 2 ) with the same mesh size. The catch efficiency of the FMT was evaluated by comparing catch per unit effort obtained from each towing condition. The catch efficiency of FMT varied with towing speed and net mouth area. Particularly, the effect of net mouth area on the catch efficiency was greater than that of towing speed. Additionally, under the same towing condition, the catch efficiency for large length fish was lower than that for small length fish.KEY WORDS: catch efficiency, entering rate, fish density, FMT, juvenile, young fish.

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Sampling performance and operational quality of a frame trawl used to catch juvenile fish

Cited by 20 publications

References 3 publications

Application of acoustic Doppler current profiler combined with a scientific echo sounder for krill Euphausia pacifica density estimation

Application of acoustic Doppler current profiler combined with a scientific echo sounder for krill Euphausia pacifica density estimation

Near-Surface Larval and Juvenile Fish in Coastal Habitats: Comparisons Between the Inner Shelf and an Estuary in the New York Bight During Summer and Fall

Effect of towing speed and net mouth size on catch efficiency in framed midwater trawls

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