Gill-net mesh selectivities for two species of commercial carcharhinid shark taken in northern Australia

1994 ◽  
Vol 45 (4) ◽  
pp. 521 ◽  
Author(s):  
KJ McLoughlin ◽  
JD Stevens
Keyword(s):  
Gamma Distribution ◽  
Distribution Model ◽  
Northern Australia ◽  
Gill Net ◽  
Commercially Important

Experiments designed to estimate gill-net mesh selectivities for two species of commercially important sharks in northern Australia were carried out between 1983 and 1984. A gamma distribution model was used to obtain length-specific selectivities for Carcharhinus tilstoni and C. sorrah caught in nets with stretched-mesh sizes of 10, 15, 20 and 25 cm. Captured sharks were categorized as gilled or rolled (tangled) in the nets. The model provided a better fit to the data for C. sorrah than for C. tilstoni.

Biology of two commercially important carcharhinid sharks from northern Australia

1986 ◽  
Vol 37 (6) ◽  
pp. 671 ◽  
Author(s):  
JD Stevens ◽  
PD Wiley
Keyword(s):  
Stomach Contents ◽  
Size At Maturity ◽  
Northern Australia ◽  
Gill Net ◽  
Average Litter Size ◽  
Commercially Important ◽  
Mature Fish ◽  
Reproductive Cycles ◽  
Size At Birth ◽  
Pelvic Fin

Sharks represent 78% of the total catch by weight of a Taiwanese surface gill-net fishery off northern Australia. Two carcharhinids, Carcharhrnus tilstoni (previously described as C. limbatus) and C. sorrah, together comprise 83% of this shark catch by number. C. tilstoni is distinguished from C. limbatus by differences in enzyme systems, vertebral counts, size data and pelvic fin coloration. Of the specimens of C. tilstoni and C. sorrah caught in the Arafura and Timor Seas from 1981 to 1983, 43% and 47%, respectively, were female; at birth these proportions were 46% and 50%, respectively. In both species, females tended to be relatively more abundant in catches of mature fish, except around March, when males predominated. In northern Australia, the usual size at maturity for C. tilstoni is 110 cm for males and 115 cm for females; for C. sorrah, it is 90 cm and 95 cm, respectively. Both species exhibit placental viviparity and have almost identical restricted reproductive cycles. Mating occurs in February-March, ovulation in March-April and the main parturition period is in January. The gestation period is 10 months and individual fish breed each year. The average litter size for both species is three. The size at birth is about 60 cm for C. tilstoni and 50 cm for C. sorrah. Stomach contents indicate that teleost fish are an important component of the diet of both species and there is some indication of a change in feeding depth with shark size.

Movements, recapture patterns, and factors affecting the return rate of carcharhinid and other sharks tagged off northern Australia

2000 ◽  
Vol 51 (2) ◽  
pp. 127 ◽  
Author(s):  
J. D. Stevens ◽  
G. J. West ◽  
K. J. McLoughlin
Keyword(s):  
Fishing Effort ◽  
Return Rate ◽  
Maximum Distance ◽  
Northern Australia ◽  
Factors Affecting ◽  
Gill Net ◽  
Commercially Important ◽  
Inshore Waters ◽  
Made In ◽  
Tag Shedding

Between February 1983 and May 1985, ~10 500 sharks of 23 species were fin-tagged off northern Australia. Tagging concentrated on the commercially important Carcharhinus tilstoni and C. sorrah. Most recaptures were made in 1984 and 1985, but returns continued until May 1997. In all, 579 tags (5.5%) were recovered. Tag shedding was estimated to be low (0.025 year –1 for C. tilstoni) and tagging mortality was significantly lower for sharks caught by hand-line than by gill-net. Australian gill-netters, Taiwanese gill-netters (fishing in the Australian Fishing Zone) and Australian prawn trawlers accounted for most of the returns. The maximum distance between the release and recapture positions was >1100 km, but most returns were made within 50 km of the tagging site. Nearly all the releases were in inshore waters fished by Australian vessels. Although many recaptures were made by the offshore Taiwanese fishery, the Taiwanese fishing effort was much higher than for the inshore Australian fishery, so that relative to fishing effort, relatively few sharks moved from inshore to offshore waters.

scholarly journals Catch assessment of artisanal marine fishing gears in Cox’s Bazar and Teknaf of Bangladesh

2016 ◽  
Vol 27 (2) ◽  
pp. 228-234
Author(s):  
SK Ghosh ◽  
MK Ahsan ◽  
MK Ahmmed ◽  
SI Ahmed ◽  
MM Hasan ◽  
...  
Keyword(s):  
Fish Species ◽  
Fishing Gear ◽  
Catch Per Unit Effort ◽  
Beach Seine ◽  
Gill Net ◽  
Fishing Gears ◽  
Dominant Fish ◽  
Commercially Important ◽  
Marine Fishing ◽  
Harpadon Nehereus

Studies were conducted on catch assessment of some artisanal marine fishing gears operated in Cox’s Bazar and Teknaf areas from April 2014 to April 2015. Sixteen types of fishing gears were identified, of which gill net, beach seine net, estuarine set bag net, marine set bag net and trammel net occupy major fishing activities. Although estuarine set bag net (ESBN) is a legally restricted fishing gear recorded the highest catch per unit effort (CPUE) (110 kg/gear/day) in July followed by marine set bag net (MSBN) (105 kg/gear/day) in Cox’s Bazar and the highest CPUE was recorded 100 kg/gear/day by ESBN in June followed by MSBN (90 kg/gear/day) in Teknaf. Out of 52 species of fishes, the major fish species abundantly caught by these gears were Poa (Otolithoides argenteus), Churi (Trichiurus haumela), Loittya (Harpadon nehereus), Ranga choukha (Lutjanus johni), Lal poa (Johnius argentatus), Olua (Coilia dussumieri), Rup chanda (Stromateus chinensis), (Stromateus argenteus) and Ilish (Tenualosa ilisha). Besides these fish species, 10 commercially important shrimp species and 3 important crab species were also recorded during the study period. The peak season of availability of most fish species was June and July while lean season was December and January. This study indicated that Otolithoides argenteus) was the dominant fish species followed by Trichiurus haumela, Harpadon nehereus and Coilia dussumieri.Progressive Agriculture 27 (2): 228-234, 2016

Biology of three hammerhead sharks (Eusphyra blochii, Sphyrna mokarran and S. lewini) from Northern Australia

1989 ◽  
Vol 40 (2) ◽  
pp. 129 ◽  
Author(s):  
JD Stevens ◽  
JM Lyle
Keyword(s):  
Litter Size ◽  
Adult Female ◽  
Seasonal Cycle ◽  
Size At Maturity ◽  
Northern Australia ◽  
Gill Net ◽  
Form Part ◽  
Incidental Catch ◽  
Hammerhead Sharks ◽  
Size At Birth

The hammerhead sharks Eusphyra blochii, Sphyrna mokarran and S. lewini form part of the incidental catch of a commercial gill-net fishery off northern Australia. Of the specimens sampled between June 1980 and December 1986, 46% of S. mokarran, 41% of E. blochii and 31% of S. lewini were females. Few adult female S. lewini were caught and it is suggested that these occur offshore of the study area. In northern Australia, the usual size at maturity of male E. blochii, S. lewini and S. mokarran is 108, 150 and 225 cm total length (TL), ,and of females is 120, 200 and 210 cm TL, respectively. S. mokarran and E. blochii gave birth in January and February/March, respectively, after a gestation period of 10-11 months. S. Iewini appears to have a more extended seasonal cycle: the young are born between October and January after 9-10 months gestation. Size at birth is about 45-50 cm TL in E. blochii and S. lewini, and 65 cm TL in S. mokarran. Mean litter size is 12 in E. blochii, 15 in S. mokarran and 17 in S. lewini. Individual E. blochii females breed every year, whereas S. mokarran females probably breed every other year. Fish are an important component of the diet of all three species as, to a lesser extent, are cephalopods for S. lewini and crustaceans for S. mokarran and E. blochii.

scholarly journals Bit Error Rate Analysis of Different Modulation Schemes in Free Space Optics Link using Gamma-Gamma Turbulence Model

2019 ◽  
Vol 8 (4) ◽  
pp. 8292-8295
Keyword(s):  
Phase Shift ◽  
Gamma Distribution ◽  
Bit Error Rate ◽  
Error Rate ◽  
Free Space ◽  
Channel Model ◽  
Distribution Model ◽  
Phase Shift Keying ◽  
Free Space Optical ◽  
Shift Keying

Free Space Optical (FSO) link using gamma-gamma channel model has been studied in this paper. Comparison of the probability density function of gamma-gamma distribution under weak and strong turbulence regime has been performed. Performance of Bit error rate (BER) using different subcarrier-intensity modulation (SIM) schemes such as binary phase shift keying (BPSK), M-ary phase shift keying (M-PSK) and quadrature amplitude modulation (QAM) have been also investigated. Using MATLAB software, the BER is plotted with respect to normalized signal to noise ratio (SNR) and the link distance. All the analysis has been done using the Gamma-Gamma distribution model. In this work we found that the effectiveness of each modulation technique depends on the environment.

Study and Simulation on Turbulent Atmosphere Modeled by Gamma-Gamma Distributions

2013 ◽  
Vol 760-762 ◽  
pp. 204-208
Author(s):  
Jun Ao ◽  
Yun Zhi Xia ◽  
Long Che ◽  
Tao Zhang ◽  
Chun Bo Ma
Keyword(s):  
Gamma Distribution ◽  
Communication Systems ◽  
Structure Constant ◽  
Distribution Model ◽  
Turbulence Structure ◽  
Free Space Optical ◽  
Gamma Distributions ◽  
Optical Communication Systems ◽  
Space Optical Communication ◽  
The Impact

Gamma-Gamma distribution model is widely used in studying the impact of the atmospheric turbulence on the Free Space Optical communication systems. This study introduces the Gamma-Gamma distribution model, simulates and studies the spot changes over distance, wavelength, turbulence structure constant and transmit aperture, respectively. Finally, the simulation results show that the Gamma-Gamma distribution is more suitable for middle-strong turbulence than weak turbulence.

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