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Nautilus pompilius life history and demographics at the Osprey Reef Seamount, Coral Sea, Australia.

Dunstan AJ, Ward PD, Marshall NJ - PLoS ONE (2011)

Bottom Line: We found sexual dimorphism in size at maturity (males: 131.9±SD = 2.6 mm; females: 118.9±7.5 mm shell diameter) in a population dominated by mature individuals (58%).Mean growth rates of 15 immature recaptured animals were 0.061±0.023 mm day(-1) resulting in an estimate of around 15.5 years to maturation.Our results provide strong evidence of a K-selected life history for Nautilus from a detailed study of a 'closed' wild population.

View Article: PubMed Central - PubMed

Affiliation: School of Biomedical Science, University of Queensland, Brisbane, Queensland, Australia. andy.dunstan@gmail.com

ABSTRACT
Nautiloids are the subject of speculation as to their threatened status arising from the impacts of targeted fishing for the ornamental shell market. Life history knowledge is essential to understand the susceptibility of this group to overfishing and to the instigation of management frameworks. This study provides a comprehensive insight into the life of Nautilus in the wild. At Osprey Reef from 1998-2008, trapping for Nautilus was conducted on 354 occasions, with 2460 individuals of one species, Nautilus pompilius, captured and 247 individuals recaptured. Baited remote underwater video systems (BRUVS) were deployed on 15 occasions and six remotely operated vehicle (ROV) dives from 100-800 m were conducted to record Nautilus presence and behavior. Maturity, sex and size data were recorded, while measurements of recaptured individuals allowed estimation of growth rates to maturity, and longevity beyond maturity. We found sexual dimorphism in size at maturity (males: 131.9±SD = 2.6 mm; females: 118.9±7.5 mm shell diameter) in a population dominated by mature individuals (58%). Mean growth rates of 15 immature recaptured animals were 0.061±0.023 mm day(-1) resulting in an estimate of around 15.5 years to maturation. Recaptures of mature animals after five years provide evidence of a lifespan exceeding 20 years. Juvenile Nautilus pompilius feeding behavior was recorded for the first time within the same depth range (200-610 m) as adults. Our results provide strong evidence of a K-selected life history for Nautilus from a detailed study of a 'closed' wild population. In conjunction with population size and density estimates established for the Osprey Reef Nautilus, this work allows calculations for sustainable catch and provides mechanisms to extrapolate these findings to other extant nautiloid populations (Nautilus and Allonautilus spp.) throughout the Indo-Pacific.

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Juvenile Nautilus pompilius.A: Juvenile N. pompilius about 70 mm shell length filmedfrom the ROV actively foraging at 608.1 m at North Horn, Osprey Reef. B: Nautilus # 716 with shell length of 89.5 mm captured by trap from 330 m. Note the cessation of color banding lines at the apertural margin and the start of this area becoming a fully white region, indicative of final juvenile stage.
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pone-0016312-g005: Juvenile Nautilus pompilius.A: Juvenile N. pompilius about 70 mm shell length filmedfrom the ROV actively foraging at 608.1 m at North Horn, Osprey Reef. B: Nautilus # 716 with shell length of 89.5 mm captured by trap from 330 m. Note the cessation of color banding lines at the apertural margin and the start of this area becoming a fully white region, indicative of final juvenile stage.

Mentions: Remotely operated vehicle (ROV) observations during six dives at four sites on Osprey Reef (Fig. 1) provided a total of 29.05 hours of video footage and still images from 100 to 800 m depth during daytime only. Sightings of Nautilus were only recorded deeper than 420 m with most between 450–650 m. All Nautiluses were actively moving in foraging mode and many demonstrated some attraction to the ROV. Of the 48 individuals recorded five were juveniles, sighted between 490 and 608.1 m (Table 2 & Fig 5).


Nautilus pompilius life history and demographics at the Osprey Reef Seamount, Coral Sea, Australia.

Dunstan AJ, Ward PD, Marshall NJ - PLoS ONE (2011)

Juvenile Nautilus pompilius.A: Juvenile N. pompilius about 70 mm shell length filmedfrom the ROV actively foraging at 608.1 m at North Horn, Osprey Reef. B: Nautilus # 716 with shell length of 89.5 mm captured by trap from 330 m. Note the cessation of color banding lines at the apertural margin and the start of this area becoming a fully white region, indicative of final juvenile stage.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3037366&req=5

pone-0016312-g005: Juvenile Nautilus pompilius.A: Juvenile N. pompilius about 70 mm shell length filmedfrom the ROV actively foraging at 608.1 m at North Horn, Osprey Reef. B: Nautilus # 716 with shell length of 89.5 mm captured by trap from 330 m. Note the cessation of color banding lines at the apertural margin and the start of this area becoming a fully white region, indicative of final juvenile stage.
Mentions: Remotely operated vehicle (ROV) observations during six dives at four sites on Osprey Reef (Fig. 1) provided a total of 29.05 hours of video footage and still images from 100 to 800 m depth during daytime only. Sightings of Nautilus were only recorded deeper than 420 m with most between 450–650 m. All Nautiluses were actively moving in foraging mode and many demonstrated some attraction to the ROV. Of the 48 individuals recorded five were juveniles, sighted between 490 and 608.1 m (Table 2 & Fig 5).

Bottom Line: We found sexual dimorphism in size at maturity (males: 131.9±SD = 2.6 mm; females: 118.9±7.5 mm shell diameter) in a population dominated by mature individuals (58%).Mean growth rates of 15 immature recaptured animals were 0.061±0.023 mm day(-1) resulting in an estimate of around 15.5 years to maturation.Our results provide strong evidence of a K-selected life history for Nautilus from a detailed study of a 'closed' wild population.

View Article: PubMed Central - PubMed

Affiliation: School of Biomedical Science, University of Queensland, Brisbane, Queensland, Australia. andy.dunstan@gmail.com

ABSTRACT
Nautiloids are the subject of speculation as to their threatened status arising from the impacts of targeted fishing for the ornamental shell market. Life history knowledge is essential to understand the susceptibility of this group to overfishing and to the instigation of management frameworks. This study provides a comprehensive insight into the life of Nautilus in the wild. At Osprey Reef from 1998-2008, trapping for Nautilus was conducted on 354 occasions, with 2460 individuals of one species, Nautilus pompilius, captured and 247 individuals recaptured. Baited remote underwater video systems (BRUVS) were deployed on 15 occasions and six remotely operated vehicle (ROV) dives from 100-800 m were conducted to record Nautilus presence and behavior. Maturity, sex and size data were recorded, while measurements of recaptured individuals allowed estimation of growth rates to maturity, and longevity beyond maturity. We found sexual dimorphism in size at maturity (males: 131.9±SD = 2.6 mm; females: 118.9±7.5 mm shell diameter) in a population dominated by mature individuals (58%). Mean growth rates of 15 immature recaptured animals were 0.061±0.023 mm day(-1) resulting in an estimate of around 15.5 years to maturation. Recaptures of mature animals after five years provide evidence of a lifespan exceeding 20 years. Juvenile Nautilus pompilius feeding behavior was recorded for the first time within the same depth range (200-610 m) as adults. Our results provide strong evidence of a K-selected life history for Nautilus from a detailed study of a 'closed' wild population. In conjunction with population size and density estimates established for the Osprey Reef Nautilus, this work allows calculations for sustainable catch and provides mechanisms to extrapolate these findings to other extant nautiloid populations (Nautilus and Allonautilus spp.) throughout the Indo-Pacific.

Show MeSH
Related in: MedlinePlus