| 2017/07 | 07/04/2017 |
Southern hemisphere porbeagle shark catch, effort, and biological data from Japanese fisheries were analysed to provide information for stock assessment, as part of a New Zealand – Japan collaboration. Methods were developed to explore logbook shark reporting reliability, which was found to increase sharply in 2008. Size was found to be strongly associated with sea surface temperature. Catch rate analyses provided indices for three areas from the eastern Atlantic to the western South Pacific.
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FAR:
2017/07;
ISSN:
1179-5352;
ISBN:
978-1-77665-492-5;
ScienceStock:
Highly Migratory species;
Species:
Porbeagle;
ResearchField:
Japanese commercial and survey data;
Porbeagle;
Southern Hemisphere;
stock abundance;
Author:
Hoyle;
Kai;
Okamoto;
Semba;
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| 2017/12 | 17/03/2017 |
Historical conversion factors (CFs) applied to shark fin processed weights to determine landed whole weights have sometimes been inappropriate, leading to biased estimates of fishing mortality. A new time series of New Zealand annual porbeagle shark mortality was derived using appropriate CFs and an allowance for mortality of discards and released live sharks. The revised time series resulted in 6% more mortality by weight overall for 1998−2016, with annual values varying by –22% to +42%.
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FAR:
2017/12;
ISSN:
1179-5352;
ISBN:
978-1-77665-514-4;
ScienceStock:
Highly migratory species;
Species:
porbeagle;
ResearchField:
fishing mortality;
Historical conversion factors;
historical landings;
porbeagle shark;
processed weights;
shark mortality;
time series;
Author:
Francis;
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| 2015/16 | 16/04/2015 |
This report assesses the catch composition of porbeagle sharks taken by surface longlines in New Zealand waters. Length-frequency distributions, maturity and reproductive status were assessed from observer data. An ageing protocol was developed using vertebral sections, and growth curves and a scaled age-frequency distribution of the catch were generated. The proportions of mature sharks caught were estimated.
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FAR:
2015/16;
ISSN:
1179-5352;
ISBN:
978-0-477-10562-0;
ScienceStock:
Highly migratory species;
Species:
Lamna nasus;
Porbeagle sharks;
FishingMethod:
midwater trawl;
surface longline fishery;
ResearchField:
ageing;
maturity;
Porbeagle shark. highly migratory species;
Author:
Francis;
MP;
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| 2015/69 | 27/01/2015 |
Title: FAR 2014/69 Indicator based analysis of the status of New Zealand blue, mako and porbeagle sharks.
FAR_2014_69_2832_HMS2014.pdf
(2.3 MB)
Cartilaginous fishes have low productivity and are vulnerable to over-fishing, but a lack of data means that stock assessments are rarely possible. To address that limitation, this report performs indicator analyses for New Zealand blue, porbeagle and mako sharks. There was no evidence that the stocks of these sharks in New Zealand waters have been adversely affected by fishing at the levels experienced since 2005, and there are good signs that they are increasing.
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FAR:
2014/69;
ISSN:
1179-5352;
ISBN:
978-0-477-10518-7;
ScienceStock:
BWS;
MAK;
POS;
Species:
Blue shark;
Mako;
Porbeagle;
FishingMethod:
Surface longline;
ResearchField:
HMS;
Indicator Analyses;
Author:
Clarke;
Francis;
Griggs;
Hoyle;
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| 2013/68 | 03/12/2013 |
The catch composition of blue, porbeagle and mako sharks in New Zealand fisheries was assessed. The spatial and temporal distribution of catches was analysed for 2007−08 to 2010−11 using reported commercial data. Length-frequencies, maturity, sex and fin weight data were analysed from 1993 to 2012 using observer data. Sharks segregate by size and sex in New Zealand waters, leading to marked spatial variability, but other observed trends may be biased by trends in fisher practices.
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FAR:
2013/68;
ISSN:
1179-5352;
ISBN:
978-0-478-42316-7;
ScienceStock:
HMS;
Species:
blue shark;
Mako shark;
porbeagle shark;
Stock:
BWS;
MAK;
POS;
Author:
Francis;
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