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排序方式: 共有613条查询结果,搜索用时 15 毫秒
611.
Yasutoki Shibata Takashi Matsuishi Hiroto Murase Koji Matsuoka Takashi Hakamada Toshihide Kitakado Hiroyuki Matsuda 《Fisheries Science》2013,79(4):559-568
The aim of this study was to examine the effects of stratification of the survey region on the performance of species distribution models (SDMs) described by generalized linear models or generalized additive models when estimating school abundance by using a line transect survey. True covariates that define spatial school distribution are not always obtainable explanatory variables. When the true covariates differ from explanatory variables in the model, the explanatory variables are determined to be misspecified. We evaluated the performance of SDMs in abundance estimation with misspecified covariates by using dummy datasets for which the true abundance was known. Simulated replicates of spatial distributions of a whale school and sighting data were generated from possible scenarios motivated by the spatial school distribution of Antarctic minke whales Balaenoptera bonaerensis. This distribution was obtained from the Japanese Whale Research Program under Special Permit in the Antarctic. Our results showed that the relative bias of the abundance estimators was large when covariates were misspecified and a survey region was stratified. Although stratification of the survey region is intended to produce a conventional line transect estimator with a smaller variance than that of non-stratified survey region, it also acts to increase the bias of the abundance estimate obtained from SDMs. 相似文献
612.
Hirofumi Furuita Koji Murashita Hiroyuki Matsunari Takeshi Yamamoto Jiro Nagao Kazuharu Nomura Hideki Tanaka 《Fisheries Science》2014,80(3):581-587
Shark eggs-based diet is the only diet by which eel larvae can grow to glass eels in captivity. However, the high level of lipids in the diet is suggested to negatively affect eel larvae. This paper examines the effect of defatted shark eggs (DSE) and hen egg yolk (HY) on growth and survival of larvae of Japanese eel Anguilla japonica. Lyophilized shark egg and commercial HY were defatted with n-hexane, and four experimental diets were prepared using both defatted and untreated shark eggs and HY. Larvae were reared for 3 weeks by feeding the experimental diets. The highest survival rate was observed in the larvae fed DSE, and larvae fed HY showed the lowest survival rate. The best growth was found in larvae fed DSE, followed by shark eggs and defatted HY, and the worst growth was in HY-fed larvae. These results show that decreasing dietary lipids improves the nutritional value of both shark eggs and HY for eel larvae. Regulation of the dietary lipid level may positively affect the larval performance of eels by combination of ingredients with a low lipid content. 相似文献
613.
Automated acoustic method for counting and sizing farmed fish during transfer using DIDSON 总被引:1,自引:0,他引:1
Counting and sizing large farmed fish such as tuna is often performed during their transfer from one net cage to another.
Dual-frequency identification sonar (DIDSON) provides an automated fish counting and sizing tool. However, its counter and
sizer are not suitable for measuring farmed fish because of net movements due to currents and subsequent frequent image breakups.
This paper presents a fully automated acoustic method to count and size farmed fish during fish transfer by using DIDSON imaging.
The background is subtracted from the image after being stabilized by an image phase-only correlation method. The segmentation
of the fish is obtained by tracing the edges with a contour tracing method. To prevent recounting the same fish, a Kalman
filter algorithm was designed and adapted to predict fish movements. Automated counting was performed by analyzing the spatiotemporal
trajectory of the track. The separated fish images were searched for and body length was obtained by summing down the centerline
segments from the head to the tail of the fish. The proposed system was verified using farmed yellowtail, Seriola quinqueradiata (mean total length 83.1 cm) to obtain a sizing error of mean total length within 2.4 cm. 相似文献