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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.

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Presentation on theme: "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."— Presentation transcript:

1 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 NASHIMOTO 2 AND Hiroyuki YOSHINO 3 Reporter: 陳 湘 蕎 FISHERIES SCIENCE 2006.,72 :1147–1152

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

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~JulyStudy time: 2002 June~July Study sites:Study sites: Matsumae, Hokkaido, Japan Temperature: surface temperature16.9 ~17.8 。 C Depth: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 Commercial trap Experimental trap 73cm 87cm 30cm 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)

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9 Commercial trap E4 trap

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

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12 Results Catch Catch analysis of traps

13 Catch

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

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

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

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

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

20 Fig. 3 The relationship between the overall mean catch per trap (number) and entrance inclination angle. Trap E3 α=0 0 Trap E2 α=27 0 Ct α=37 0 Trap E1 α=46 0

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 Table 3 Soak time 1 dayCPUE Trap E4 > Commercial trap

23 Table 3 Soak time 2 daysCPUE No significant difference

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

25 Bycatch species - 11 species 1.Octopus( 章魚 ) 2.Hairy triton( 法螺 ) 3.Hermit crab( 寄居蟹 ) 4.Cod( 鱈類 ) 5.Sculpins 6.Fat greenling 7.Yellow body rockfish 8.Slime flounder 9.White-edged rockfish 10.Kurosoi rockfish 11.Angry rockfish

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

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

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

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

30 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). E1, E2, E3 and Commercial trap Soak time=1day Soak time=2day

31 Body length frequency distributions Trap E4 and the commercial trap 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). Soak time=1day Soak time=2day Not differ

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

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 Trap type αSwimming posture of fish E3 0° 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. 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.

35 To funnel length point of view…… Trap typeFunnel lengthOverall mean CPUE (1 day soak time) Trap E48 cm15.3 Commercial trap 22 cm10.9 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…… no effect on size selectivity of the trapThe 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 Munro et al. (1971) single-funnel arrowheaddouble-funnel Z-traps Luckhurst and Ward (1987) straight funnelshorse-neck funnels Matuda et al (1984). catch rates were affected by the diameter of the entrance ring Furevik and Løkkeborg (1994) narrow entranceswider entrances Other Studies

41 Thank you for your attention~


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