Effects of entrance design Effects of entrance design on catch efficiency of on catch efficiency of arabesque greenling traps: a arabesque greenling traps: a field experiment in field experiment in Matsumae, Hokkaido Matsumae, Hokkaido 花花花花花花花花花花花花花花花花花花花 : 花花花花花花花花花花 Yong LI, 1 Katsutaro YAMAMOTO, 1* Tomonori HIRAISHI, 1 Katsuaki NASHIMOTO 2 AND Hiroyuki YOSHINO 3 Reporter: 陳 陳 陳 FISHERIES SCIENCE 2006.,72 :1147–1152
Effects of entrance design on catch efficiency of arabesque greenling traps: a field experiment in Matsumae, Hokkaido. FISHERIES SCIENCE 2006., 72 : 1147–1152. 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. - PowerPoint PPT Presentation
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Effects of entrance design on catch Effects of entrance design on catch efficiency of arabesque greenling traps: a efficiency of arabesque greenling traps: a field experiment in Matsumae, Hokkaidofield experiment in Matsumae, Hokkaido花鯽魚籠具之入口設計在漁獲效率上的影響 :
No significant differencesSoak time of 1 day and 2days
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
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
Body length frequency distributions
ANOVA tests
E1, E2, E3 and commercial Soak time of 1 day or 2 days
No difference
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 commercialtrap (Ct).
E1, E2, E3 and Commercial trap
Soak time=1day
Soak time=2day
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
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
•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.
Trap type
α Swimming 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.
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.
The interior volume of trap affected the catchperformance……
► For a trap with shorter funnel length
Consequence of a lower probability of fish escaping
The catch efficiency was increased
According to the results of catch analysis……
• The inclination angle and funnel length of entrance had no effect on size selectivity of the trapno 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.
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.
It is suggested……
It is suggested that the inclination angle of entrance of a commercial trap should be adjusted from 37° to approximately 27°.
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