Whale age at sexual maturity is one of the most important biological parameters that can be used in stock management and population analysis. Earplugs have been widely used as an indicator of age among rorquals. It ha...Whale age at sexual maturity is one of the most important biological parameters that can be used in stock management and population analysis. Earplugs have been widely used as an indicator of age among rorquals. It has also been accepted that the transition phase in the earplug can be used as an indicator of age at sexual maturity in fin whales, sei whales, and Antarctic minke whales. This study aimed to provide further insight into the utility of the transition phase as an indicator of age at sexual maturity in the North Pacific common minke whales, which has not yet been clarified. The relationship between sexual maturity and transition phase in earplugs was examined using 981 readable earplugs from common minke whales that were sampled at the JARPN and JARPN II scientific permit survey platform in the western North Pacific from 1994 to 2011. The transition phase was recognized in 53.2% of mature males and in 58.6% of mature females. Most whales in which the transition phase was recognized in the earplug were sexually mature. A significant correlation was found between the number of corpora and time after sexual maturation, as revealed by the transition phase, demonstrating that the transition phase is a valid indicator of age at sexual maturity in common minke whales. However, it was difficult to recognize the transition phase in whales that had recently attained sexual maturity because insufficient time had elapsed since its formation. To avoid potential bias, the use of earplugs as an indicator of age should be restricted to whales more than 12 years old.展开更多
This article deals with subjective measurements of attenuation characteristic of three earmuffs (A, B, C) and two earplugs (foam and molded). The measurement was carried out through the real-ear attenuation at thresho...This article deals with subjective measurements of attenuation characteristic of three earmuffs (A, B, C) and two earplugs (foam and molded). The measurement was carried out through the real-ear attenuation at threshold (REAT) under freefield condition. The five devices were examined singly, and four of them in combination. The performance of double hearing protection (earplug plus earmuff)were investigated experimentally using the same method for a number of combinations. All tests were conducted on 7 subjects, and two replications per subject. The obtained data of the earmuffs tested show that earmuff (A) posscsses the lowest attenuation and is characterized by highest standard deviation. On the other hand, the foam plug provides the higher attenuation and the lower standard deviation. When the foam plug was combined with either carmuff (B or C) an improvement of attenuation was similar, i. e. the choice of earmuff is not important. This combination yields higher attenuation than that produces for either device alone, but does not simply yield overall attenuation equal to the sum of the individual of each device. However, when situation was reversed, the combination of either earplug (foam or molded) with single earmuff yields variation in attenuation below 2 kHz. At and above 2 kHz, the combination results were comparcd to the bone conduction limits which was reported by different authors. At these frequencies, all tests of plug plus earmuff combinations that were studied provided attenuation approximately equal to the bone conduction limits of human skull. Finally, the attenuation estimates derived in this study werc less than comparable data published by the respective manufacturers.展开更多
文摘Whale age at sexual maturity is one of the most important biological parameters that can be used in stock management and population analysis. Earplugs have been widely used as an indicator of age among rorquals. It has also been accepted that the transition phase in the earplug can be used as an indicator of age at sexual maturity in fin whales, sei whales, and Antarctic minke whales. This study aimed to provide further insight into the utility of the transition phase as an indicator of age at sexual maturity in the North Pacific common minke whales, which has not yet been clarified. The relationship between sexual maturity and transition phase in earplugs was examined using 981 readable earplugs from common minke whales that were sampled at the JARPN and JARPN II scientific permit survey platform in the western North Pacific from 1994 to 2011. The transition phase was recognized in 53.2% of mature males and in 58.6% of mature females. Most whales in which the transition phase was recognized in the earplug were sexually mature. A significant correlation was found between the number of corpora and time after sexual maturation, as revealed by the transition phase, demonstrating that the transition phase is a valid indicator of age at sexual maturity in common minke whales. However, it was difficult to recognize the transition phase in whales that had recently attained sexual maturity because insufficient time had elapsed since its formation. To avoid potential bias, the use of earplugs as an indicator of age should be restricted to whales more than 12 years old.
文摘This article deals with subjective measurements of attenuation characteristic of three earmuffs (A, B, C) and two earplugs (foam and molded). The measurement was carried out through the real-ear attenuation at threshold (REAT) under freefield condition. The five devices were examined singly, and four of them in combination. The performance of double hearing protection (earplug plus earmuff)were investigated experimentally using the same method for a number of combinations. All tests were conducted on 7 subjects, and two replications per subject. The obtained data of the earmuffs tested show that earmuff (A) posscsses the lowest attenuation and is characterized by highest standard deviation. On the other hand, the foam plug provides the higher attenuation and the lower standard deviation. When the foam plug was combined with either carmuff (B or C) an improvement of attenuation was similar, i. e. the choice of earmuff is not important. This combination yields higher attenuation than that produces for either device alone, but does not simply yield overall attenuation equal to the sum of the individual of each device. However, when situation was reversed, the combination of either earplug (foam or molded) with single earmuff yields variation in attenuation below 2 kHz. At and above 2 kHz, the combination results were comparcd to the bone conduction limits which was reported by different authors. At these frequencies, all tests of plug plus earmuff combinations that were studied provided attenuation approximately equal to the bone conduction limits of human skull. Finally, the attenuation estimates derived in this study werc less than comparable data published by the respective manufacturers.
