Validation of age and growth of the Picasso triggerfish (Balistidae: Rhinecanthus aculeatus ) from Okinawa Island, Japan
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SPECIAL SECTION: ORIGINAL ARTICLE
Towards a cooperative research future in the East China Sea—selected research from the 8th International Workshop on Oceanography and Fisheries Science
Validation of age and growth of the Picasso triggerfish (Balistidae: Rhinecanthus aculeatus) from Okinawa Island, Japan, using sectioned vertebrae and dorsal spines Fabienne Ku¨nzli • Katsunori Tachihara
Received: 1 December 2011 / Revised: 22 February 2012 / Accepted: 15 April 2012 Ó The Oceanographic Society of Japan and Springer 2012
Abstract To understand age and growth of the Picasso triggerfish, Rhinecanthus aculeatus, monthly sampling was conducted from February 2010 to October 2011 on the subtropical Okinawa Island, Japan, using trammel net and speargun. Fish were measured by weight (W) and standard length (SL) and age was determined by examining thinsections of the first dorsal spine and the second abdominal vertebra. A total of 352 fish were caught ranging from 20.9 mm to 209.5 mm (SL). Marginal increment analysis indicated that translucent rings were deposited annually during the colder season from October to January. The relationship of observed SL and age was described by the original form of the von Bertalanffy growth equation. Male and female growth models were significantly different. Overall growth was rapid during the first 2.5 years for both sexes, thereafter growth curves diverged. Males consequently reached larger sizes and greater ages. Maximum age for males and females was 13.5 and 9.5 years, respectively. Regression models of somatic growth (SL) as a function of vertebral and spine radii were significantly correlated (r = 0.98 and r = 0.96, respectively). According to the weight–length relationship, growth in R. aculeatus was negative allometric. Small recruits (SL \ 40 mm) appeared Electronic supplementary material The online version of this article (doi:10.1007/s10872-012-0137-5) contains supplementary material, which is available to authorized users. F. Ku¨nzli (&) Graduate School of Engineering and Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan e-mail: [email protected] K. Tachihara Laboratory of Fisheries Biology and Coral Reef Studies, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan
in high numbers in shallow coastal areas starting from August. This is the first record of age and growth for R. aculeatus. Our data suggest that the Picasso triggerfish is a moderately long-lived balistid and that the observed sex-specific growth pattern is driven by the fish’s polygynous mating system and different reproduction strategies of males and females. Keywords Okinawa Island Balistidae Picasso triggerfish Age and growth Dorsal spine Vertebra Von Bertalanffy Validation Polygynous mating system
1 Introduction The triggerfish family (Balistidae) is a highly modified and advanced group of fish and is well represented throughout the world’s oceans with approximately 11 genera and 40 species described (Nelson
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