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對馬 / 韓國海峽 - 長體蛇鯔的年齡與成長

對馬 / 韓國海峽 - 長體蛇鯔的年齡與成長. 邱惠君. Introduction. Inhabits sandy-mud bottoms. Depths less than 100m. Japanese trawl fisheries. High meat yield and high gel-foeming ability → surimi and fish cakes in Japan. Saurida elongata. LOW. Per unit effort 9℅. 2006. 1982. Total landing.

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對馬 / 韓國海峽 - 長體蛇鯔的年齡與成長

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  1. 對馬/韓國海峽-長體蛇鯔的年齡與成長 邱惠君

  2. Introduction

  3. Inhabits sandy-mud bottoms. • Depths less than 100m. • Japanese trawl fisheries. • High meat yield and high gel-foeming ability → surimi and fish cakes in Japan. Saurida elongata

  4. LOW Per unit effort 9℅ 2006 1982 Total landing Decreased about 30℅ 1982 1973 2006 2006 8585 t 23 t overfishing Biological characteristics: growth and sexual maturation rates Gadus morhua Sardinops melanostictus Stock levels of lizardfish in the East China Sea。。Similar to those of other demersal fishes Japanese large pair-trawl fishery catch of lizardfishin the East China Sea Lizardfish landings by Japanese offshore trawl fishing in the Tsushima/Korea Strait

  5. Little information: temporal variations in growthand reproductive traits for other lizardfish of this genus. Annual growth marks on scales→ previous studies (age and growth of lizardfishes) ↓ May underestimate lizardfish age Sagittal sections of otoliths (sagittae) →investigate the age and growth of S. elongata from the Tsushuma/Korea Strait

  6. Materials and Methods

  7. N= 695 specimens Offshore pair trawlers Small trawlers GSI = 100 × GW /BW Fork length (FL) → nearest 1mm Body weight (BW) → nearest 1g Gonad weight (GW) → nearest 0.1g Sex → determined by visual examination of the gonads Otoliths → preserved in 70% ethanol

  8. Preliminary examination Prepared from 20 species Sagittal section Transverse section Embedding the otoliths in epoxy resin on a glass slide Embedding the otoliths in epoxy resin Microcutter Grinding them down with rotary whetstones Polishing with a grinder The core became clearly visible Mounting on glass slides

  9. N = number of fish aged T = number of times each fish was aged Xij = the ring count from the Ith reading of the jth fish Xj = the average age of the jth fish Arrowheads outer margin of each translucent zone Counted twice

  10. Observe the Sagittal section Reflected-light projector at 20x magnification Examined twice → number must the same →used the frequency of occurrence of a translucent zone on the outer otolith margin→ the season when the translucent zone formed

  11. Determine the age of each fish Assumed a birth date of 1 June Assigned an age in years to each individual equal to the number of translucent zones observed The time elapsed From 1 June to the day of sampling was thenadded to yield an age estimate for each fish specimen

  12. The growth of males and females FLt = fork length (mm) at age t (years) FL∞ = asymptotic fork length K = growth coefficient t0 = hypothetical age at which FL = 0 mm

  13. Results

  14. 75% > 85% Comparison of transverse and sagittal sections ≒

  15. ~ 75% Range 280~360 mm ~ 75% Range 340 ~ 440 mm Length-frequency distribution

  16. Body weight and fork length

  17. Spawning occurs Monthly change in GSI

  18. Translucent zone formation period All 695 Two readings did not agree for 32 (4.6%) Nine otoliths were broken (1.3%) IAPE of 686 individuals was 0.49% 654 otoliths showed distinct ring marks (94.1%) → used for growth analysis

  19. 2-11 translucent zone 2-12 translucent zone Age-frequency distribution Minimum ages of specimens from small trawlers and offshore pair trawlers were 1 and 2 years old, respectively.

  20. Female male Greater Female growth faster than male

  21. Discussion

  22. Lager mesh cod end 2. Migration with growth Pagrus major Younger fish occupying shallower waters Adult fish tending to migrate into offshore waters 1. Youngest specimens were 2 years old Offshore pair trawlers Lizardfish from Tsushima/Korea Strait 1. Youngest specimens were 1 years old Small trawlers

  23. Opaque zone → during spring and summer Spawning season Spawningoccurs Autumn and Winter Alternating periods of rapid and slow growth Temperature Feeding regime Reproductive cycle Seasonal growth cycle → physiological changes Physiological cjanges related to the reproductive cycle S. Undosquanmis and S. tumbil → ring makes

  24. FL∞ Female male Females reach a greater maximum length than males similar S. umeyoshii Females grow faster live longer Saurida species

  25. Male 4 years or 7 years Female 4 years or 7 years Underestimates Male 10 years Otolith method Female 11 years Suitable Accurate age determination Previous estimates of the maximum age of S. elongata in Japanese → using scale for age determination Population biomass Standing stock S. Elongata population

  26. First Use otoliths to determine the age and growth of S. elongata S. elongata slower growth and a longer life span

  27. THE ENDTHANKS

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