Capture Process Experiment Studies On Fish BehaviourIn Relation Net Transparency of Millennium Gillnet Operation In Bondet Waters, Cirebon

operation of 12 pieces gillnet and hauling process. For one day fishing trip, there were 2-3 times setting-hauling process, depends on the weather and current condition. The catch number of millennium gillnet was dominated by threadfins Polynemus spp. for 71.2871 of catch. While by-catch consists of striped catfish eel Plotosus lineatus, spotted catfish Arius maculatus, great barracuda Sphyraena barracuda, triple tail Labotes surinamensis, barramundi Lates calcarifer, blue spotted snapper Lutjanus rivulatus, silver pomfret Pampus argentus, stingray Dasyatis spp., garfish Hemirhampus spp. and shark Charcarinus spp.. The millennium gillnet, mostly caught threadfins. The slim and long-shape figure and lack of spines on its body makes this fish caught mostly caught on its gill or caught on its maximum body girth and not to be entangled. There are some theories of how fish encountered gillnet. Some observe that if a fish encounters a gillnet, it stops its movement temporarily but in shallow water , if the net swing because of waves and tilts to the front, the fish follows the net and, when the net swings back, the fish get its head caught in a mesh of the net. Nomura, 1991. Captured conditions depend greatly on the length size and struggling effort. The small fish, which body girth, were slightly smaller than the mesh perimeter could penetrate the mesh by their head and become finally snagged or gilled. Meanwhile, the medium or large fish whose body girth exceeds the mesh size could result into the complicated entanglement in the net by their violent struggling. This was happening also by fish that caught in sweeping trammel net Purbayanto et al., 1999. Struggling effort usually caused injuries on fish body. Purbayanto 1999 described six patterns of damaged body of the dead Japanese whiting Sillago japonica caught by sweeping trammel net in Tateyama Bay, Japan. The patterns are: 1 minor scale loss on the upper parts of the fish head in front of dorsal fin; 2 scar injuries and minor scale loss around the circumference of the maximum body girth; 3 scale loss on several parts of the fish body; 4 moderate scale loss 49 on the fish body; 5 infections on the head and the fins being rotten; and 6 infections on the head, major fish body, and the fins being rotten. Most threadfins caught in the experiment did not have any injuries on its body, but they have net-like shape mark caused by fish being gilled. Some fish have minor scale loss on the upper parts of the fish head and scar injuries and minor scale loss around the circumference of the maximum body girth, the same as first and second pattern of fish caught by sweeping trammel net. Since the fishes were in the good quality, with no injuries, most fishes sold in the competitive price. Many of threadfins caught by this gillnet were export market oriented. They distributed this fish into Singapore and Malaysia. The varieties of millennium gillnet target catch depends on the fish stock underwater and mostly influenced by fishing season. In west monsoon January- February catch dominates by barred Spanish mackerel Scomberomorus spp. and frigate tuna Auxis thazard. This season concerning as the peak season of millennium gillnet fishing. In east monsoon Juny-July sometimes barred Spanish mackerel and frigate tuna also get caught. In the monsoon betweens, the catch dominated by threadfins. This explained why mostly gillnet catch in October- November was dominated by threadfins. The multi-monofilament, the millennium gillnet material, has a very strong and flexible feature. Underwater, it could stretch and loose easily so then when the fish entering the net, they easier to enter but difficult to escape. This material structure influencing the fish that caught by this gillnet. Probably because of this reason, mostly fish caught without less of struggle and makes the fish has less injuries. According of Stewart 1987 as cited by Ferno and Olsen 1994, the type of twine used in the net can, owing to differences in texture, influence the species and the size range of fish caught. Comparative fishing experiments using twisted multifilament, monofilament and multi-mono nylon in loosely hung cod gillnets produced very different size distributions of catches. The total of catch rates for the three net types were not very different, but as an example twisted multifilament caught many smaller fish than monofilament. The most striking result of the investigations was the way that fish were caught in the three net types. 50 Stewart 1987 as cited by Ferno and Olsen 1994 indicated that these results were due to differences in texture between the used gillnet. With monofilament, which is hard and stiff, cod were mainly gilled, while with multifilament, which is soft, cod were mainly tangled. With multi-mono, the proportion of tangled and gilled cod were somewhere in between. Even though, mostly targeted species of this experiment mostly caught by gilled, the reason of the texture of the material influencing the captured condition was considering reasonable. From the result of behaviour experiment and capture process experiment that was conducted, it was revealed that the fish used in behaviour experiment was a pelagic fish while mostly catch were dominated by demersal fish. This is important to discuss regarding of different types of fish pelagic or demersal has different characteristics. The most consequential problem is the difference characteristics of visual acuity between pelagic and demersal fishes. Demersal fish has not good visual acuity. Geonita 2004 described that the visual acuity of red snapper Lutjanus malabaricus is around 0.08-0.13 for the fish length of 100-185 mm. This statement indicates that waters in dark condition without enough light penetration and bad visibility will reduce the visual acuity of a fish. For the pelagic fishes, for example frigate tuna Euthynnus affinis, the visual acuity is around 0.14-0.19 for the fish length of 285-375 mm. The clear condition of waters and larger of fish’s length make frigate tuna has good visual acuity. In this experiment, the visual acuity of fish did not investigate through histological experiment. But the fact that the field experiment caught mostly demersal fishes is an unexpected result. At first, some interview from the local fishermen explained that the millennium gillnet is operates to catch pelagic species, such as barred Spanish mackerels, frigate tunas, sharks, and other types of mackerels. 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Jurnal Ilmu-ilmu Perairan dan Perikanan Indonesia Jilid 10 No. 1: 57-63. 56 Appendix 1 The map of experimental fishing operation LEGEND Fishing operation location Fishing port Border of district or province Scale = 1 : 500.000 Cirebon Indian Ocean Java sea N S W E JAVA SEA INDRAMAYU REGENCY KUNINGAN REGENCY CENTRAL JAVA Karangreja Bandenga Citemu Gebang Mekar Ender Bondet fishing port Betoko Bungko Ijo Fishing operation CIREBON REGENCY CIREBON Bondet waters E 108 P o P 30’ 109 P o P N 6 o 30’ 57 Appendix 2 The average length and body girth of Japanese Jack mackerels No Length cm Body girth cm 1 16 9 2 17 9 3 18 9 4 20 9.5 5 19 8.5 6 19.5 10 7 20.5 11 8 21 11 9 19 11 10 20 11 11 20 10.5 12 22 10.5 13 20 10.5 14 19 10.5 15 23 11.5 16 21 12 17 21 10 18 21 11 19 23.5 12 20 21 11 21 21.5 10 22 22 9.5 23 21 11 24 20 12 x±s.d. 20.25±1.72 10.46±0.1 58 Appendix 3 The average water temperature and salinity during experiment The average water temperature Day of experiment Temperature o C Salinity ppm 1 19.200 1.028 2 19.100 1.028 3 19.100 1.030 4 19.200 1.030 5 19.200 1.030 6 19.300 1.030 7 19.100 1.030 8 19.100 1.030 9 19.200 1.030 10 19.100 1.030 Average 19.160 1.030 Sd 0.07 0.001 The average light intensity during experiment light intensitylux Day of experiment A B C D 1 181 285 187 282 2 352 185 308 228 3 227 314 298 278 4 182 259 191 315 5 201 287 171 294 6 263 167 263 271 7 183 173 300 234 8 319 168 263 276 9 251 198 301 276 10 283 183 296 273 Aver 244.20 221.90 257.80 272.70 total average 249.15 Note: Test channel area A B C D 59 Appendix 4 Frequency and proportion of fish passing through the netting panel of contrast colour net panel Frequency of fish passing through the netting panel Treatment of behaviour Treatment of net colour transparency Replicates Voluntary Conditioned 1 2 3 2 31 27 85 11 10 Old white x ± SE 20 ± 9.07 35 ± 24.84 1 2 3 1 5 10 10 Black painted x ± SE 0.33 ± 0.33 8.330 ± 1.67 1 2 3 28 14 29 64 20 17 New white x ± SE 23.67 ± 4.84 33.67±15.19 Control 123 276 Proportion of fish passing the mesh panel number of fishcontrol Treatment of behaviour Treatment of net colour transparency Replicates Voluntary Conditioned 1 2 3 0.016 0.252 0.220 0.308 0.040 0.036 Old white x ±SE 0.160 ± 0.070 0.128 ± 0.090 1 2 3 0.000 0.008 0.000 0.018 0.036 0.036 Black painted x ±SE 0.003 ± 0.003 0.030 ± 0.006 1 2 3 0.228 0.114 0.236 0.232 0.072 0.062 New white x ±SE 0.190 ± 0.040 0.122 ± 0.060 60 Appendix 5 Frequency and proportion of fish passing through the netting panel of behaviour experiment using specific white panels Frequency of fish passing the netting panel Treatment Replicates Control Old white New white White dyed 1 2 3 4 5 6 7 8 9 10 613 597 593 480 430 437 425 647 728 682 60 50 20 9 9 100 94 180 170 19 40 20 16 19 9 10 9 210 139 120 50 18 20 8 9 19 9 190 30 110 Proportion of fish passing the mesh panel number of fishcontrol Treatment Replicates Old white New white White dyed 1 2 3 4 5 6 7 8 9 10 0.098 0.084 0.034 0.019 0.021 0.229 0.221 0.278 0.234 0.028 0.065 0.034 0.027 0.040 0.021 0.023 0.021 0.325 0.191 0.176 0.082 0.030 0.034 0.017 0.021 0.043 0.021 0.294 0.041 0.161 61 Appendix 6 Statistical test of frequency of fish passing through the net Contrast Colour Panels: Result of Two Way Anova Source of variation Sum of squares

d.f. Mean

square F P A 0.073 2 0.037 4.025 0.046 B 0.003 1 0.003 0.331 0.576 A x B 0.007 2 0.004 0.405 0.676 e 0.109 12 0.009 Total 0.192 17 Notes: A treatment of net colour transparency, B treatment of behaviour, AxB interaction Fish Behaviour using Specific White Net Panels: One Way ANOVA result Trial Old white New white White dyed 1 0.098 0.065 0.082 2 0.084 0.034 0.030 3 0.034 0.027 0.034 4 0.019 0.040 0.017 5 0.021 0.021 0.021 6 0.229 0.023 0.044 7 0.221 0.021 0.021 8 0.278 0.325 0.294 9 0.234 0.191 0.041 10 0.028 0.176 0.161 Anova: Single Factor SUMMARY Groups Count Sum Average Variance old white 10 1.245 0.125 0.011 new white 10 0.922 0.092 0.011 white dyed 10 0.744 0.074 0.008 ANOVA Source of Variation SS df MS F P-value F crit Between Groups 0.013 2 0.006 0.657 0.527 3.354 Within Groups 0.264 27 0.010 Total 0.278 29 62 Continued Appendix 6 One Way ANOVA mesh passing reaction OLD WHITE Anova: Single Factor SUMMARY Groups Count Sum Average Variance non contact 10 1.203 0.120 0.011 contact 10 0.041 0.004 1.47E-05 ANOVA Source of Variation SS df MS F P-value F crit Between Groups 0.068 1 0.067 12.824 0.002 4.414 Within Groups 0.095 18 0.005 Total 0.162 19 NEW WHITE Anova: Single Factor SUMMARY Groups Count Sum Average Variance non contact 10 0.900 0.090 0.010 Contact 10 0.022 0.002 6.62E-06 ANOVA Source of Variation SS df MS F P-value F crit Between Groups 0.039 1 0.039 7.421 0.014 4.414 Within Groups 0.093 18 0.005 Total 0.132 19 WHITE DYED Anova: Single Factor SUMMARY Groups Count Sum Average Variance non contact 10 0.718 0.072 0.008 Contact 10 0.025 0.003 7.45E-06 ANOVA Source of Variation SS df MS F P-value F crit Between Groups 0.024 1 0.024 6.304 0.022 4.414 Within Groups 0.069 18 0.004 Total 0.093 19 63