Shark fisheries in Argentina

1998 ◽  
Vol 49 (7) ◽  
pp. 601 ◽  
Author(s):  
Gustavo E. Chiaramonte
Keyword(s):  
Fishing Effort ◽  
Population Trends ◽  
The South ◽  
Gill Nets ◽  
Argentine Sea ◽  
Commercial Importance ◽  
South West ◽  
Gill Net ◽  
Galeorhinus Galeus ◽  
Mustelus Schmitti

In the Argentine Sea there are about 35 species of sharks. Three species are subjected to directed fishing: the smoothhound Mustelus schmitti, the school shark Galeorhinus galeus and the copper shark Carcharhinus brachyurus. Other species of elasmobranchs with commercial importance are the angel shark Squatina spp. and several species of skates and rays. The rise in chondrichthyan declared landings registered from 1988 to 1996 is due to the increase in landings of smoothhound and rays. The most important directed shark fishery in the South-West Atlantic is the Necochea gill-net fishery for school shark, which is carried out by the coastal fleet; details are given of the ships and the gill-nets used in this area. The length frequencies of the catches by gill-nets are presented for the school shark; fishing effort (length (km) of net in the water per ship per day) and CPUE (number of sharks per fishing effort) were found not to be good indicators of population trends in the school shark fishery. Resumen. En el Mar Argentino se han registrado 35 especies de tiburones. Tres de estas especies están sometidas a una pesca dirigida; el gatuzo, Mustelus schmitti, el cazón, tiburón vitamínico o trompa de cristal, Galeorhinus galeus y la bacota, Carcharhinus brachyurus. Otras especies de elasmobranquios de importancia comercial son el pez ángel Squatina spp. y algunas especies de rayas. El incremento en los desembarcos de condríctios declarados a las autoridades pesqueras entre 1988 y 1996 es debido principalmente al incremento del desembarco de gatuzo y rayas. La pesquería dirigida a tiburón más importante en el Atlántico Sudoccidental es la pesquería costera de enmalle de Necochea para el cazón. Se describen el largo de las embarcaciones y las redes utilizadas en el área (la medida de malla, el calado y la operación del arte de pesca). Se presenta la frecuencia del largo total de las capturas de cazón en redes de enmalle. Se halló para la pesquería del cazón que el esfuerzo pesquero (estimado como km de red en el agua por embarcación por día) y la CPUE (estimada como tiburones/esfuerzo de pesca) no son buenos indicadores de la tendencia en la abundancia poblacional.

Incidental capture of elasmobranchs in the bottom-set gill-net fishery off the south coast of Ireland

1994 ◽  
Vol 74 (4) ◽  
pp. 837-847 ◽  
Author(s):  
S.D. Berrow
Keyword(s):  
Fishing Effort ◽  
South Coast ◽  
Fishing Gear ◽  
The South ◽  
Blue Shark ◽  
Incidental Capture ◽  
Gill Net ◽  
Total Capture ◽  
Catch Rates ◽  
Basking Shark

The incidental capture of sharks in the bottom-set gill-net fishery off the south coast of Ireland was quantified by placing observers on commercial gill-netters for the duration of a fishing trip. Forty fishing trips were sampled resulting in 1,167 km and 19,760 km h of observed fishing effort. Sixty individual sharks of seven species were reported entangled in the fishing gear. Tope, porbeagle and six-gilled sharks were the most frequently caught species, with black-mouthed dogfish, blue shark, basking shark and starry smooth hound also recorded. Total fishing effort along the south coast was calculated and total capture extrapolated from observed catch rates. An estimated 6,000 sharks were caught in this fishery during the study period.

Preliminary results of a study into the incidental mortality of sharks in Gill-nets in two Tasmanian Shark Nursery Areas

1992 ◽  
Vol 43 (1) ◽  
pp. 237 ◽  
Author(s):  
H Williams ◽  
AH Schaap
Keyword(s):  
Relative Abundance ◽  
Fishing Effort ◽  
Shark Species ◽  
Nursery Areas ◽  
Preliminary Results ◽  
Gill Net ◽  
Galeorhinus Galeus ◽  
Potential Rate ◽  
Incidental Mortality ◽  
Gill Netting

Since the early 1960s, certain sheltered bays and estuaries around Tasmania have been designated shark nursery areas, where the taking of either the school shark (Galeorhinus galeus) or the gummy shark (Mustelus antarcticus) has been prohibited. Recent assessments of Australian stocks of school and gummy sharks indicate that they are close to collapse, and the management of the fishery has come under review. With respect to shark nursery areas, concern has focused on the potential rate of incidental mortality of sharks caused by recreational gill-net fishing and poaching. In 1990, a study was begun in Frederick Henry Bay and Norfolk Bay, the largest proclaimed shark nursery areas in Tasmania, to estimate recreational net-fishing effort and incidental captures of sharks. School sharks were caught in waters deeper than 5 m; gummy sharks and dogfish were caught at all depths. The diversity and relative abundance of shark species increased with depth, whereas the diversity of teleosts decreased with depth. Most captured school and gummy sharks were between 1+ and 3+ years of age. Preliminary estimates of potential incidental mortality demonstrate that gill-netting in depths greater than 5 m may be a significant source of mortality for both species.

scholarly journals MAXIMUM SUSTAINABLE YIELD OF TRAWL FISHERY ALONG THE SOUTH-WEST COAST OF INDIA: BAYESIAN ESTIMATION APPROACH

2020 ◽  
Vol 67 (1) ◽  
Author(s):  
T. V. Sathianandan ◽  
Somy Kuriakose ◽  
K. G. Mini ◽  
P. K. Safeena
Keyword(s):  
Bayesian Estimation ◽  
Marine Fish ◽  
West Coast ◽  
Fishing Effort ◽  
Maximum Sustainable Yield ◽  
Sustainable Yield ◽  
The South ◽  
Trawl Fishery ◽  
South West ◽  
South West Coast

The south-west region of the Indian coast is shared by three maritime states and it contributes nearly 32% to the total marine fish production of the country. Mechanised trawl fishery accounts for 44% of the marine fish harvest in the south-west coast and a number of resources are harvested by trawl nets from this region. An assessment of the trawl fishery to determine sustainable harvest levels for mechanised trawlers in the region was carried out using time series data on annual landings and fishing effort of mechanised trawlers during the period 1990-2015. A Bayesian estimation method for Schaefer model was used for the analysis. Posterior probability densities of parameters of the model, maximum sustainable yield (MSY) and corresponding biomass were obtained through Bayesian estimation for the trawl fishery in south-west coast and the harvest levels were found to be above MSY from 2012 onwards. Forecasts of biomass and fish landings by mechanised trawlers upto 2025 under different levels of fishing effort were also simulated using the model to study the dynamic changes over time. It was found that the numbers of multiday trawlers and single day trawlers operating in this region have to be reduced by 207 and 36 respectively to retain the harvest at sustainable level.

scholarly journals ANALISIS PENDAPATAN USAHA PENANGKAPAN IKAN LAUT MENGGUNAKAN ALAT TANGKAP GILL NET DI DESA TABANIO KECAMATAN TAKISUNG KABUPATEN TANAH LAUT ((THE INCOME ANALYSIS OF FISHERY EFFORT WITH GILL NET IN TABANIO VILLAGE, TAKISUNG DISTRICT, TANAH LAUT REGENCY)

2016 ◽  
Vol 1 (2) ◽  
pp. 202
Author(s):  
Yarna Hasriani ◽  
Emmy Sri Mahreda ◽  
Irma Febrianty
Keyword(s):  
Cross Section ◽  
Structured Interview ◽  
Fishing Effort ◽  
Payback Period ◽  
Fishing Vessel ◽  
Gill Nets ◽  
Section Data ◽  
Research Activities ◽  
Gill Net ◽  
The Village

<p>Penelitian ini bertujuan untuk mengetahui keuntungan usaha nelayan <em>gill net</em> setelah dikurangi bagian hasil untuk buruh nelayan; dan menganalisis kelayakan usaha penangkapan ikan di laut dengan menggunakan alat tangkap <em>gill net</em>. Kegiatan penelitian ini dilaksanakan di Desa Tabanio, Kecamatan Takisung, Kabupaten Tanah Laut, sebagai desa nelayan di Kabupaten Tanah Laut yang masyarakatnya dominan menggunakan alat tangkap <em>gill net</em>. Data yang dikumpulkan adalah data <em>cross section</em> yang bersumber langsung dari nelayan pemilik kapal/alat tangkap <em>gill net</em>, melalui teknik wawancara terstruktur (menggunakan kuesioner).</p><p>Hasil penelitian menunjukkan bahwa keuntungan yang diperoleh nelayan pemilik kapal dari usaha penangkapan ikan dengan <em>gill net</em> di Desa Tabanio adalah rata-rata sebesar Rp.7.634.223 per trip atau per bulan. Usaha penangkapan ikan dengan <em>gill net</em> di Desa Tabanio menguntungkan dan layak untuk diusahakan, karena nilai <em>NPV</em> yang positip sebesar Rp.61.550.000, dengan nilai <em>Net BCR </em>lebih dari satu<em> </em>(1,38) dan <em>IRR</em> lebih dari<em> </em>suku bunga yang didiskonto (27% &gt; 14%), serta <em>payback period</em> yang lebih cepat dari periode proyeksi selama lima tahun (2,96 tahun).</p><p><em>This study</em><em> aims to determine the business benefits gill net fishing net of proceeds for fishing laborers and analyze their feasibility in the sea fishing using gill net gear. The research activities conducted in the Village Tabanio, Takisung District, of Tanah Laut, a fishing village in the district of Tanah Laut where people predominantly use gill net gear. The data collected is cross section data are sourced directly from the fishing vessel owner/gill net gear, through a structured interview technique (using questionnaires).</em></p><p><em>The results showed that</em><em> the benefits of fishing vessel owners fishing effort by gill nets in the village Tabanio is an average of Rp.7.634.223 per trip or per month. Fishing effort by gill nets in the village Tabanio profitable and worth the effort, because the value of Rp.61.550.000 positive NPV, the net value of BCR is more than one (1.38) and IRR over a discounted rate (27% &gt; 14%), and the payback period is faster than the projected five-year period (2.96 years).</em></p>

Likely impacts of an eastward expansion of the inshore gill-net fishery in the Western Cape, South Africa: implications for management

2003 ◽  
Vol 54 (1) ◽  
pp. 39 ◽  
Author(s):  
K. Hutchings ◽  
S. J. Lamberth
Keyword(s):  
West Coast ◽  
Fishing Effort ◽  
Western Cape ◽  
Catch Per Unit Effort ◽  
South West ◽  
Gill Net ◽  
South West Coast ◽  
By Catch ◽  
Catch Rates ◽  
The Impact

Current South African government policy aims to create more equitable access to marine resources and there is pressure to increase the inshore gill-net fishing effort. At present, the gill-net fishery in the Western Cape is confined to the cool temperate west coast. In order to ascertain the potential catch if the fishery was to expand along the warm temperate south-west coast, a program of experimental netting was conducted. Estuarine and coastal marine sites were sampled bimonthly, using a range of commercial gill-nets (44–178 mm stretch-mesh). Although the target species, Liza richardsonii, dominated the catches, at least 33 of the by-catch species caught were also targeted by the commercial or recreational line-fish sectors. The number of species captured and the line-fish (by-catch) catch per unit effort (CPUE) were greatest in areas currently closed to the commercial gill-net fishery. Multivariate analysis indicated significant differences in catch rates and composition between exploited west coast and unexploited south-west coast sites. A combination of natural biogeographical trends and the impact of over 100 years of commercial gill-netting on the west coast are the likely causes of these differences. A spatial expansion of the gill-net fishery could have a detrimental impact on overexploited line-fish stocks and lead to increased user conflict.

Fishery simulation model for sharks applied to the Gummy Shark, Mustelus antarcticus Gunther, from Southern Australian waters

1992 ◽  
Vol 43 (1) ◽  
pp. 195 ◽  
Author(s):  
TI Walker
Keyword(s):  
Sex Ratio ◽  
Simulation Model ◽  
Mesh Size ◽  
Fishing Effort ◽  
Probability Density Distribution ◽  
Natural Mortality ◽  
Sex Ratio At Birth ◽  
Gill Nets ◽  
Gill Net ◽  
Number Of Births

A dynamic pool simulation model is derived and applied to the gummy shark stock of the southern shark fishery. Inputs to the model are fishing effort reported by fishers for hooks and for gill-nets with mesh sizes of 6 inches (152 mm), 7 inches (178 mm) and 8 inches (203 mm) along with estimates for growth, natural mortality, catchability, hook and gill-net mesh selectivity, size at maturity and fecundity of females, sex ratio at birth, and length-weight relationships. Growth is described by the von Bertalanffy equation; hook selectivity is constant with length for sharks recruited to the fishery; gill-net selectivity is based on the probability density distribution of the gamma function where selectivity varies with the mesh size of the gill-nets and the length of the sharks; number of births is related to the proportion of females mature at each length, and the relationship between number of births and maternal weight is linear; parturition is annual and time is standardized so that parturition occurs at the beginning of each year; sex ratio at birth is based on observations of a 1: 1 sex ratio of embryos; and allometric weight-length is based on the power curve. Natural mortality of recruits, catchability, reproduction and growth parameters are held constant, but density-dependent natural mortality of prerecruits is varied in proportion to stock abundance. The model is used to simulate effects of historical longline fishing effort and gill-net fishing effort for each mesh size on stock biomass, numbers of sharks in the stock, and numbers of births. The performance of the model is evaluated by comparing simulated annual catches and the simulated mean weight of sharks captured with annual catches reported by the fishers and the mean weight of sharks sampled in commercial landings. Uncertainties surrounding estimates of some of the parameters are discussed. Notwithstanding its shortcomings, the model indicates that the stock of gummy shark has been severely reduced and is in danger of further depletion unless immediate action is taken to reduce the commercial catch.

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