Galeorhinus galeus: Walker, T.I., Rigby, C.L., Pacoureau, N., Ellis, J., Kulka, D.W., Chiaramonte, G.E. & Herman, K.

2020 ◽  
Author(s):  
Keyword(s):  
Galeorhinus Galeus

scholarly journals Population genetics of Southern Hemisphere tope shark (Galeorhinus galeus): Intercontinental divergence and constrained gene flow at different geographical scales

PLoS ONE ◽  
2017 ◽  
Vol 12 (9) ◽  
pp. e0184481 ◽  
Author(s):  
Aletta E. Bester-van der Merwe ◽  
Daphne Bitalo ◽  
Juan M. Cuevas ◽  
Jennifer Ovenden ◽  
Sebastián Hernández ◽  
...  
Keyword(s):  
Population Genetics ◽  
Gene Flow ◽  
Southern Hemisphere ◽  
Galeorhinus Galeus

Stock assessment and risk analysis for the school shark (Galeorhinus galeus) off southern Australia

1998 ◽  
Vol 49 (7) ◽  
pp. 719 ◽  
Author(s):  
André E. Punt ◽  
Terence I. Walker
Keyword(s):  
Stock Assessment ◽  
Catch Rate ◽  
Data Series ◽  
Structured Population ◽  
Population Dynamics Model ◽  
Equilibrium Size ◽  
Structured Population Dynamics ◽  
Pup Survival ◽  
Galeorhinus Galeus ◽  
Selection Of

A spatially aggregated age- and sex-structured population dynamics model was fitted to standardized catch-rate data from the school shark resource off southern Australia. The model incorporates the peculiarities of shark populations and fisheries, including the pupping process and the selectivity characteristics of gill-nets. Estimates are determined by a Bayesian approach that incorporates prior distributions for virgin biomass, the parameter that determines productivity, and the variation in pup survival. Tests of sensitivity include changing the data series used, varying the value of adult natural mortality, and changing the prior distribution for the productivity parameter. The point estimates of the mature biomass at the start of 1995 range from 13% to 45% of the pre-exploitation equilibrium size, depending on the specifications of the assessment. The results are notably sensitive to the selection of a catch-rate series. Results suggest that the current fishing intensity will lead to further declines in abundance, that a reduction of ~20% in fishing mortality would achieve a 0.5 probability of not declining further, and that a reduction of 42% would achieve with a probability of 0.8 the management goal of not being below the 1996 mature biomass at the start of 2011. Extra keyword: CPUE.

scholarly journals Population genetics of the school shark (Galeorhinus galeus) in New Zealand, Australian and Chilean waters

2021 ◽  
Author(s):  
◽  
Sebastián Ignacio Hernández Muñoz
Keyword(s):  
Genetic Diversity ◽  
New Zealand ◽  
Dna Markers ◽  
Microsatellite Dna ◽  
Multiple Paternity ◽  
Shark Species ◽  
Microsatellite Dna Markers ◽  
Minimum Number ◽  
Galeorhinus Galeus ◽  
Shark Fisheries

<p>The school shark (Galeorhinus galeus) is a coastal bentho-pelagic species that is highly migratory and has a widespread distribution in temperate waters. This species matures late, has a relatively low fecundity and is slow growing, which makes it vulnerable to overfishing. They are commercially fished throughout their distribution, and some global stocks have been under pressure because of poor management. In Australia, longline and gillnet fisheries targeted pregnant females and juveniles around Victorian and Tasmanian nursery grounds, resulting in loss of historical inshore nursery habitat. School shark tagging programmes have reported migration between Australian and New Zealand stocks, but preliminary genetic studies have suggested that there are slight genetic differences between the stocks. Currently, the Australian and New Zealand school shark fisheries are assessed and managed as separate stocks. However, the question of whether this species is comprised of a single population or multiple sub-populations in the South Pacific remains unresolved. Given the commercial importance of the school shark fisheries and the concern about stock levels on the regional and trans-Tasman scales, knowledge of stock structure is essential for effective management. The aim of this thesis research was to determine the levels of genetic diversity and population structure of G. galeus in New Zealand and Australia, and compare these to a population in Chile, using mitochondrial DNA (mtDNA) sequencing and microsatellite DNA markers.  The DNA sequence of an 893 base pair region of the mtDNA control region (CR) was determined using 475 school shark samples and nine microsatellite DNA loci were genotyped in 239 individuals. Analyses of the data revealed strong evidence of genetic differentiation between G. galeus populations in Australasia and Chile, suggesting restricted gene flow among populations in the western and eastern areas of the Pacific Ocean. The FST values ranged from 0.188 to 0.300 for CR mtDNA, and 0.195 to 0.247 for microsatellite DNA in G. galeus. However, there was no evidence of stock differentiation among New Zealand/Australian sample sites for either mtDNA or microsatellite DNA data. These results support the model of a single panmictic stock across the Tasman Sea. The similarity of the results obtained from the maternally inherited mtDNA and biparental inherited microsatellite loci did not support the suggestion of sex-biased dispersal of G. galeus in the New Zealand/Australia region and it was concluded that females and males had similar patterns of dispersal.  Sharks can be either monogamous or polygamous, which is important when considering stock assessments and harvesting models. Multiple paternity has been reported in several shark species, however, the number of sires per litter varies considerably among species. An investigation of multiple paternity (MP) was conducted in G. galeus by assessing the levels of relatedness within progeny arrays using six polymorphic microsatellite DNA markers. Five “families” (mother and litters) were sampled from the North Island of New Zealand and a parentage analysis was conducted. The minimum number of males contributing to each progeny array was estimated by identifying the putative paternal alleles by allele counting and reconstructing multilocus genotypes method. The analysis showed the occurrence of genetic polyandry in G. galeus; two of five litters showing multiple sires involved in the progeny arrays (40%). The minimum number of sires per litter ranged from one to four. Although MP was only detected in two litters, this finding is consistent with the known reproductive characteristics of G. galeus. It can potentially store sperm for long periods of time and has a specific mating season when males and females typically mix on the edge of the continental shelf. Detecting MP within a litter has highlighted the importance of the post-copulatory selective processes in the G. galeus mating system, and this has implications for the management and conservation of genetic diversity.</p>

By-catch of sharks in Patagonian coastal trawl fisheries

1998 ◽  
Vol 49 (7) ◽  
pp. 641 ◽  
Author(s):  
Silvina Van Der Molen ◽  
Guillermo Caille ◽  
Raúl González
Keyword(s):  
Central Zone ◽  
Squalus Acanthias ◽  
Coastal Fisheries ◽  
The North ◽  
Rio Negro ◽  
Palabras Clave ◽  
By Catch ◽  
Galeorhinus Galeus ◽  
Cetorhinus Maximus ◽  
Mustelus Schmitti

In coastal Patagonia, Argentina, an unknown number of species of sharks are frequently caught in bottom-trawl nets. Between 1993 and 1996, 454 trawls by Patagonian coastal fisheries (41˚–51˚S) were analysed; 264 included sharks. Of the seven species of sharks caught, the most frequent was the smoothhound Mustelus schmitti, mainly in Bahía Engaño (off Chubut). The argentine angelshark (Squatina argentina) and the tope (Galeorhinus galeus) were common in the north of Patagonia, the piked dogfish (Squalus acanthias) in the central zone, and the narrowmouthed catshark Schroederichthys bivius in the south. The broadnose sevengill shark (Notorhynchus cepedianus) was rarely caught. A single basking shark (Cetorhinus maximus) was caught in San Matías Gulf (off Río Negro). Although undesirable, the by-catch of sharks is growing as a result of the increase in the fishing activities of the region, and the sustainability of the shark populations in Patagonian coasts is a matter of concern. Resumen. En las costas de Patagonia, Argentina, un número desconocido de especies de tiburones son frecuentemente capturados en las redes de arrastre de fondo. Entre 1993 y 1996 se analizaron a bordo 454 lances de pesca en las pesquerías costeras de Patagonia, entre los 41 y 51˚S, y en 264 de ellos se registraron capturas de tiburones. De las siete especies de tiburones capturadas el mas frecuente fue el gatuzo Mustelus schmitti, principalmente en Bahía Engaño, frente a las costas de Chubut. El pez ángel Squatina argentina y el cazón vitamínico Galeorhinus galeus fueron comunes en el norte de Patagonia, el cazón espinoso Squalus acanthias en la zona central, y el tiburón pintarroja Schroederichthys bivius en el sur. El tiburón gatopardo Notorhynchus cepedianus resultó una especie rara en las capturas. En el Golfo San Matías, frente a las costas de Río Negro, se capturó un ejemplar de tiburón peregrino Cetorhinus maximus. Aunque no deseadas, las capturas de tiburones están aumentando debido al incremento de las actividades pesqueras en la región, y la sustentabilidad de las poblaciones de tiburones en Patagonia es motivo de creciente preocupación. Palabras clave: tiburones, capturas, redes de arrastre, pesquerías costeras, Patagonia.

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.

Evidence for multiple paternity in the school shark Galeorhinus galeus found in New Zealand waters

2014 ◽  
Vol 85 (5) ◽  
pp. 1739-1745 ◽  
Author(s):  
S. Hernández ◽  
C. Duffy ◽  
M. P. Francis ◽  
P. A. Ritchie
Keyword(s):  
New Zealand ◽  
Multiple Paternity ◽  
Galeorhinus Galeus

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.

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