Age, growth, and reproductive dynamics of striped marlin, Kajikia audax in the southwest Pacific Ocean

Research output: ThesisDoctoral Thesis

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Abstract

Striped marlin, Kajikia audax (Philippi 1887) are the most commercially valuable species of billfish in the family Istiophoridae and are an important recreational and ecological resource in the Indo-Pacific Oceans. This thesis describes the first validated age and growth model for the species and offers new insight into the spatial dynamics of population age structure and reproductive dynamics in the southwest Pacific Ocean (SWPO; 0°-45°S latitude, 145°E-130°W longitude). First dorsal and anal fin spines, paired sagittal otoliths, and gonads were collected from a sample of 489 striped marlin. Fish were caught between January 2006 and December 2008, in commercial longline and recreational fisheries in Australia, New Zealand, Fiji, New Caledonia, and French Polynesia. Back-calculated larval hatch dates estimated from otolith micro-increment counts matched the known spawning period which confirmed daily periodicity of micro-increment formation. The location of the first annulus in dorsal fin spine four was validated by otolith daily micro-increment counts and a marginal increment analysis confirmed yearly periodicity of subsequent annulus formation. Ages ranged from 130 days to 8 years, in striped marlin ranging in length from 990 mm (~4 kg) to 2871 mm (~168 kg) lower jaw-fork length (LJFL). There were no significant sex-specific differences in growth and both sexes attained 75-80% of their maximum estimated body length (male L∞=2494 mm LJFL; female L∞=2609 mm LJFL) during the first two years of life.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Charles Sturt University
Supervisors/Advisors
  • Watts, Robyn, Co-Supervisor
  • Pepperell, Julian , Co-Supervisor, External person
Award date05 May 2010
Place of PublicationAustralia
Publisher
Publication statusPublished - 2010

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