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 :1147–1152Effects 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 YOSHINO3Reporter:陳 湘 蕎
2 widely used in fisheries Introductiontrap entrancefactorstrap entranceTrapswidely used in fisheriesEntrance numberShapeSizeLocation.factorsfactorsfactorssimple structureconvenient operation
3 PurposeThe 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.
23 No significant difference Soak time 2 daysCPUENo significant differenceTable 3
24 No significant difference Trap E4 and the commercial trapMann–Whitney testSoak time 1 dayCPUE of trapsSoak time 2 daysCPUE of trapsTrap E4 > Commercial trapNo significant difference
25 Bycatch species－11 species Octopus(章魚)Hairy triton(法螺)Hermit crab(寄居蟹)Cod(鱈類)SculpinsFat greenlingYellow body rockfishSlime flounderWhite-edged rockfishKurosoi rockfishAngry rockfish
26 Catch analysis of traps Mean body lengthBody length frequency distributions
27 Soak time of 1 day and 2days Mean body lengthTable 4 Mean body length (mm) of fish caught in each trap during the sampling periodE1, E2, E3 and commercial trapSoak time of 1 day and 2daysNo 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 periodTrap E4 and the commercial trapSoak time of 1 dayNo significant differenceSignificant differenceSoak time of 2 days
29 Body length frequency distributions ANOVA testsE1, E2, E3 and commercialSoak time of 1 day or 2 daysNo difference
30 E1, E2, E3 and Commercial trap Soak time=1daySoak time=2dayFig. 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 commercialtrap (Ct).
31 Body length frequency distributions Trap E4 and the commercial trapSoak time=1dayNot differSoak time=2dayFig. 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 DiscussionModification of the funnel design may significantly affect trap performanceMaxα 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 funnelopening is located in the middle of the trap.The symmetrical funnel can be considered tobe 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 anentrance similar to the symmetrical funnel.Trap typeαSwimming posture of fishE30°The fish have to swim towards the bottom side and get through the funnel opening.E146°The fish have to swim up and get through.Ct37°E227°The fish are able to swim through the funnel opening directly with noneed to adjust their swimming posture.
35 To funnel length point of view…… Trap typeFunnel lengthOverall mean CPUE(1 day soak time)Trap E48 cm15.3Commercial trap22 cm10.9The results confirmed that the funnel length of trapentrance affects the catch of a trap.
36 The interior volume of trap affected the catch performance…… For a trap with shorter funnel lengthConsequence of a lower probabilityof fish escapingThe 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 catchesthan the commercial trap (α = 37°, Lf = 22 cm)2)Trap E4 (α = 37°, Lf = 8 cm) caught more fish than thecommercial trap over a 1-day soak time.
39 It is suggested……It is suggested that the inclination angle of entranceof a commercial trap should be adjusted from 37° toapproximately 27°.
40 Other Studies single-funnel arrowhead double-funnel Z-traps Munro et al.(1971)single-funnel arrowheaddouble-funnel Z-trapsLuckhurst and Ward(1987)straight funnelshorse-neck funnelsMatuda et al(1984).catch rates were affected by the diameter of the entrance ringFurevik and Løkkeborg(1994)narrow entranceswider entrances