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花鯽魚籠具之入口設計在漁獲效率上的影響:於北海道松島野外實驗

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Presentation on theme: "花鯽魚籠具之入口設計在漁獲效率上的影響:於北海道松島野外實驗"— Presentation transcript:

1 花鯽魚籠具之入口設計在漁獲效率上的影響:於北海道松島野外實驗
FISHERIES SCIENCE 2006.,72 :1147–1152 Effects of entrance design on catch efficiency of arabesque greenling traps: a field experiment in Matsumae, Hokkaido 花鯽魚籠具之入口設計在漁獲效率上的影響:於北海道松島野外實驗 Yong LI,1 Katsutaro YAMAMOTO,1* Tomonori HIRAISHI,1 Katsuaki NASHIMOTO2 AND Hiroyuki YOSHINO3 Reporter:陳 湘 蕎

2 widely used in fisheries
Introduction trap entrance factors trap entrance Traps widely used in fisheries Entrance number Shape Size Location. factors factors factors simple structure convenient operation

3 Purpose The effects of trap entrance inclination angel and funnel length on the catch per trap. The body length distribution of fish caught in traps. And the mean body length of fish caught in traps.

4 Introduction 學名:Pleurogrammus azonus 英名:Arabesque greenling 中文名:鄂霍次克魚 、花鯽魚(俗名:星斑六線魚或遠東六線魚) 日文:ホッケ (ho tsu ke)

5 Materials and methods Study time: 2002 June~July
Study sites: Matsumae, Hokkaido, Japan Temperature: surface temperature16.9 ~17.8。C Depth: 128~140 m Fig. 1 Location of the fishing experiment.

6 Materials and methods Table 1Details of set time, hauling time, soak time, location, water depth and surface temperature during the five samplings in 2002.

7 Materials and methods 73cm 30cm 87cm The traps were conical in shape
Top diameter 73 cm Bottom diameter 87 cm Height 30 cm. α: Inclination angle Lf :The entrance funnel length Bait: Sardines (approx. 200g) 73cm 30cm 87cm Commercial trap Experimental trap

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9 Commercial trap E4 trap

10 Materials and methods-
Fish traps: 40 fish traps Commercial traps 20 Experimental traps 20(E1, E2, E3, E4;five traps of each type) Table 2 Dimensions of the trap entrances

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12 Results Catch Catch analysis of traps

13 Catch

14 ﹛ Catch Results Total of trap hauls:200 Total of fish:2200
Experimental traps:1017 Commercial traps:1183

15 CPUE and number of traps hauled
Ct, commercial trap; Ei, trap Ei (i = 1, 2, 3, 4); SD, standard deviation. Table 3 Mean catch number per trap and number of traps hauled

16 E1, E2, E3 and Commercial trap
Kruskal–Wallis test Soak time 1 day CPUE of traps Soak time 2 days CPUE of traps

17 Trap E2、commercial trap、 trap E1 > trap E3.
Soak time 1 day CPUE 1. Trap E2、commercial trap、 trap E1 > trap E3. Table 3

18 The overall mean CPUE was shown as
Soak time 2 days CPUE difference 1. Commercial trap and trap E3 2. Trap E2 and trap E3 The overall mean CPUE was shown as trap E2>the commercial trap>trapE1>trap E3.

19 Significant differences
E1, E2, E3 and Commercial trap Kruskal–Wallis test Soak time 1 day CPUE of traps Soak time 2 days CPUE of traps Significant differences

20 Ct α=370 Trap E2 Trap E1 α=460 Trap E3
α=270 Ct α=370 Trap E1 α=460 Trap E3 α=00 Fig. 3 The relationship between the overall mean catch per trap (number) and entrance inclination angle.

21 Trap E4 and the commercial trap
Mann– Whitney test Soak time 1 day CPUE of traps Soak time 2 days CPUE of traps

22 Trap E4 > Commercial trap
Soak time 1 day CPUE Trap E4 > Commercial trap Table 3

23 No significant difference
Soak time 2 days CPUE No significant difference Table 3

24 No significant difference
Trap E4 and the commercial trap Mann– Whitney test Soak time 1 day CPUE of traps Soak time 2 days CPUE of traps Trap E4 > Commercial trap No significant difference

25 Bycatch species-11 species
Octopus(章魚) Hairy triton(法螺) Hermit crab(寄居蟹) Cod(鱈類) Sculpins Fat greenling Yellow body rockfish Slime flounder White-edged rockfish Kurosoi rockfish Angry rockfish

26 Catch analysis of traps
Mean body length Body length frequency distributions

27 Soak time of 1 day and 2days
Mean body length Table 4 Mean body length (mm) of fish caught in each trap during the sampling period E1, E2, E3 and commercial trap Soak time of 1 day and 2days No significant differences

28 Mean body length Trap E4 and the commercial trap Soak time of 1 day
Table 4 Mean body length (mm) of fish caught in each trap during the sampling period Trap E4 and the commercial trap Soak time of 1 day No significant difference Significant difference Soak time of 2 days

29 Body length frequency distributions
ANOVA tests E1, E2, E3 and commercial Soak time of 1 day or 2 days No difference

30 E1, E2, E3 and Commercial trap
Soak time=1day Soak time=2day Fig. 4 Size frequency distributions of the body length of fish in each 10-mm body length size class, caught using the experimental traps (E1, E2, and E3) and the commercial trap (Ct).

31 Body length frequency distributions
Trap E4 and the commercial trap Soak time=1day Not differ Soak time=2day Fig. 5 Size frequency distributions of the body length of fish in each 10-mm body length size class, caught by the experimental trap (E4) and the commercial trap (Ct).

32 Discussion Modification of the funnel design may significantly affect trap performance Max α increased, the overall mean CPUE first increased to a maximum, and then gradually decreased. Fig. 3 The relationship between the overall mean catch per trap (number) and entrance inclination angle.

33 The catch efficiency of trap E2 was highest, followed by the commercial trap, E1, and E3.
Trap E2 symmetrical funnel and the funnel opening is located in the middle of the trap. The symmetrical funnel can be considered to be easier for fish to enter the trap than the unsymmetrical funnel.

34 Swimming posture of fish
To inclination angle point of view…… The trap E2 entrance is most effective in catching arabesque greenling, since it is easier for fish to enter the trap than other shaped entrances. The authors therefore recommend the application of a trap with an entrance similar to the symmetrical funnel. Trap type α Swimming posture of fish E3 The fish have to swim towards the bottom side and get through the funnel opening. E1 46° The fish have to swim up and get through. Ct 37° E2 27° The fish are able to swim through the funnel opening directly with no need to adjust their swimming posture.

35 To funnel length point of view……
Trap type Funnel length Overall mean CPUE (1 day soak time) Trap E4 8 cm 15.3 Commercial trap 22 cm 10.9 The results confirmed that the funnel length of trap entrance affects the catch of a trap.

36 The interior volume of trap affected the catch performance……
For a trap with shorter funnel length Consequence of a lower probability of fish escaping The catch efficiency was increased

37 According to the results of catch analysis……
The inclination angle and funnel length of entrance had no effect on size selectivity of the trap. (soak time of 1 day) Because the size of funnel opening of the experimental trap and commercial trap was about the same.

38 In conclusion…… When used in a commercial arabesque greenling trap fishery: 1)Trap E2 (α = 27°, Lf = 22 cm) produced higher catches than the commercial trap (α = 37°, Lf = 22 cm) 2)Trap E4 (α = 37°, Lf = 8 cm) caught more fish than the commercial trap over a 1-day soak time.

39 It is suggested…… It is suggested that the inclination angle of entrance of a commercial trap should be adjusted from 37° to approximately 27°.

40 Other Studies single-funnel arrowhead double-funnel Z-traps
Munro et al. (1971) single-funnel arrowhead double-funnel Z-traps Luckhurst and Ward (1987) straight funnels horse-neck funnels Matuda et al (1984). catch rates were affected by the diameter of the entrance ring Furevik and Løkkeborg (1994) narrow entrances wider entrances

41 Thank you for your attention~


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