Oral Presentation Australian Society for Fish Biology Conference 2024

Age and growth of kawakawa (Euthynnus affinis) in the Indian Ocean (109371)

Irwan Jatmiko 1 2 3 , Naomi Clear 2 , Kyne Krusic-Golub 4 , Caleb Gardner 1 , Klaas Hartmann 1 , Campbell Davies 2
  1. UTAS, Taroona, TAS, Australia
  2. Oceans and Atmosphere, CSIRO, Hobart, Tasmania, Australia
  3. Centre for Fisheries Research, National Research and Innovation Agency, Jakarta, Indonesia
  4. Fish Ageing Service, Queenscliff, Victoria, Australia

Kawakawa (Euthynnus affinis) is an important resource for fishermen in the Indian Ocean. Studies on age and growth are important information to support fisheries management. The objective of this research is to determine the suitability of otolith-based age methods for estimating age and growth of kawakawa in the Indian Ocean. These otolith samples were collected in a related project from Seychelles, Maldives, Indonesia, and Australia between 2017 and 2022. Annual and daily growth increments (which are assumed to be annual and daily) were used to estimate fish age.  Of the 87 samples, 76 were suitable for annual increments, 36 for daily increments, and 25 were suitable for counts of both annual and daily increments. Fitting the most suitable growth model (von Bertalanffy) to the resulting length at age data resulted in Linf = 71 cm, K = 0.47/yr, and t0 = -0.79 yr. These results show that kawakawa have speedy growth at the beginning of their life, reaching a length of 50 cm in the first 2 years. This swift growth shows that kawakawa could reproduce more offspring quickly to maintain the health of their population and to minimise predation before reaching maturity. However, good fisheries management with the precautionary principle must be carried out to preserve this resource.