Length at maturity in three pelagic sharks (Lamna nasus, Isurus oxyrinchus, and Prionace glauca) from New Zealand
Reproductive data collected from porbeagle, shortfin mako,and blue sharks caught around New Zealand were used to estimate the median length at maturity. Data on clasper development, presence or absence of spermatophores or spermatozeugmata, uterus width, and pregnancy were collected by observers aboard tuna longline vessels. Directmaturity estimates were made for smaller numbers of sharks sampled at recreational fishing competitions. Some data sets were sparse, particularly over the vital maturationlength range, but the availability of multiple indicators of maturity made it possible to develop estimates for both sexes of all three species. Porbeagle shark males matured at 140–150 cm fork length and females at about 170–180 cm. New Zealand porbeagles therefore mature at shorter lengths than they do in the North Atlantic Ocean. Shortfin mako males matured at 180–185 cm and females at 275 –285 cm. Blue shark males matured at about 190 –195 cm and females at 170–190 cm; however these estimates were hampered by small sample sizes, difficulty obtaining representative samples from a population segregated by sex and maturity stage, and maturation that occurred over a wide length range. It is not yet clear whether regional differences in median maturity exist for shortfin mako and
| Main Authors: | , |
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| Format: | article biblioteca |
| Language: | English |
| Published: |
2005
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| Subjects: | Biology, Ecology, Fisheries, |
| Online Access: | http://hdl.handle.net/1834/26212 |
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