1 / 26

Reporter: Chao-Yi Yu

adara
Download Presentation

Reporter: Chao-Yi Yu

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Diel changes in vertical distribution patterns of zooplankton and walleye pollock (Theragra chalcogramma) off the Pacific coast of eastern Hokkaido, Japan, estimated by the volume back scattering strength (Sv) difference method在北海道東部太平洋近海,利用Sv差值的方法,估計鱈魚與浮游動物日夜間垂直分佈的變化 KAZUSHI MIYASHITA,1,*KOUTAROU TETSUMURA,2 SATOSHI HONDA,3 TATSUKI OSHIMA,4 RYO KAWABE1 AND KEI SASAKI1Fish. Oceanogr. 13 (Suppl. 1), 99–110, 2004 Reporter: Chao-Yi Yu

  2. INTRODUCTION Euphausia pacifica and Neocalanus copepods are the main components of the zooplankton.

  3. Distribution of the walleye pollock In the Doto area Hokkaido, walleye pollock prey especially heavily on E. pacifica. Acoustical methods are very useful for estimating the abundance and spatial distribution patterns of fish and zooplankton.

  4. walleye pollock ; Alaska pollock(Theragra chalcogramma)

  5. MATERIALS AND METHODS

  6. acoustic data collection • EK500, SIMRAD, Norway • at two frequencies (38 and 120 kHz). • A total of 19 parallel transect lines perpendicular to the isobathswere (A~S) set at 8-nauticalmile intervals. • sea depths range : 50 ~ 500 m • ship speed : 8 knots

  7. Figure 1. Map of the transect lines and stations sampled by the RV Kaiyo-maru No. 3, in June 2001.

  8. Theoretical scattering mode TS : target strength 單體標物反射強度 Sv : volume back scattering strength 體積散亂反射強度 ae:the equivalent sphere radius (ESR) k : the wave number in water

  9. Values of g and h were taken from Mikami et al. (2000) (g =1.030, h =1.034) g : density contrast h : sound speed contrast LH : body height LW : body width (a zooplankter) L : total body length

  10. Sv difference method (ΔSv) 以水平距離0.005海哩,深度1m為一積分單位(網狀方格) 其中每積分單位以 Sv120KHz - Sv38KHz =ΔSv 可用來推演對象生物之等價求半徑,再與浮游生物網樣本大小作為比較 當兩頻率任一小於-75dB時,假定為no echo 皆大於-75dB時需去除背景雜音獲得對象生物聲探資料

  11. sv is the linear value of SV n : biomass density Sv, which depends on the frequency because the TS is frequency dependent, can be written as follows:

  12. Fish samples (mainly walleye pollock) bottom trawls (19) mid-water trawls (10) Zooplankton samples bongo nets (BN 01~07)

  13. 投棄式電導率、溫度、深度剖面測量儀 XCTD CTD

  14. Results (1) Species composition and ΔSv bongo nets and trawls (2) Distribution patterns of zooplankton and walleye pollock during day and night

  15. bongo nets samples Table 2. Summary of the zooplankton compositions in the bongo net samples. Copepods (>50% Neocalanus copepods) and krill (>70% E. pacifica) were predominant based on both number and wet weight .

  16. For Neocalanus copepods, there was one size class with a mean total body length of 2.0 mm (SD =±1.1, N =1044080). For E. pacifica, there were two size classes with mean total body lengths of 6.1 mm (SD =±2.2, N =13 099) and 15.4 mm (SD =±3.6 , N =7628).

  17. the ESR distribution of Neocalanus copepods and E. pacifica calculated from Eqn (3). The mean ESR of Neocalanus copepods was 0.5 mm (SD =±0.3, N =1044080) The mean ESRs of E. pacifica were 1.0 mm (SD =±0.3, N =13 099) and 2.8 mm (SD =±0.9 , N =7628), The ESR distribution of small E. pacifica is similar to that of Neocalanus copepods.

  18. These ΔSv ranges of the small E. pacifica + Neocalanus copepods and large E. pacifica were estimated from ESRs and Eqn (6). ΔSv • small:19.0 dB < ΔSv < 21.0 dB • large: 8.0 dB < ΔSv < 16.0 dB

  19. The large size class was distributed mainly in the eastern part of the survey area (Line A–K, depth range: 150–200 m). Trawl sampls The small size class was distributed mainly in the western part of survey area (Line F, and Line I to Line S ; depth range: 50–150 m). Both small and large walleye pollock were distributed in the middle part of the survey area (Line F, and Line I–K).

  20. ＜age 2: mean SL = 187.1 mm (SD =±32.1, N =1,279) ＞age 3: mean SL = 399.6 mm (SD =±30.4, N =1343)

  21. Typical echograms (from Lines C, I and L) at 38 and 120 kHz during day and night. Lines C, I and L were in the eastern, central, and western part of the survey area, respectively.

  22. Typical echograms (Lines C, I and L) of the distributions of zooplankton and walleye pollock overlaid with water temperature during day (left) and night (right).

  23. The end Thanks

More Related