1156556_Roberts,B_2021.pdf (1.23 MB)
Faster juvenile growth promotes earlier sex change in a protandrous hermaphrodite (barramundi Lates calcarifer)
journal contributionposted on 2023-01-16, 05:43 authored by BH Roberts, JR Morrongiello, DL Morgan, Alison KingAlison King, TM Saunders, David CrookDavid Crook
The relationship between growth and sexual maturation is central to understanding the dynamics of animal populations which exhibit indeterminate growth. In sequential hermaphrodites, which undergo post-maturation sex change, the size and age at which sex change occurs directly affects reproductive output and hence population productivity. However, these traits are often labile, and may be strongly influenced by heterogenous growth and mortality rates. We analysed otolith microstructure of a protandrous (i.e., male-to-female) fish (barramundi Lates calcarifer) to examine growth in relation to individual variation in the timing of sex change. Growth trajectories of individuals with contrasting life histories were examined to elucidate the direction and extent to which growth rate influences the size and age individuals change sex. Then, the relationships between growth rate, maturation schedules and asymptotic maximum size were explored to identify potential trade-offs between age at female maturity and growth potential. Rapid growth was strongly associated with decreased age at sex change, but this was not accompanied by a decrease in size at sex change. Individuals that were caught as large females grew faster than those caught as males, suggesting that fast-growing individuals ultimately obtain higher fitness and therefore make a disproportionate contribution to population fecundity. These results indicate that individual-level variation in maturation schedules is not reflective of trade-offs between growth and reproduction. Rather, we suggest that conditions experienced during the juvenile phase are likely to be a key determinant of post-maturation fitness. These findings highlight the vulnerability of sex-changing species to future environmental change and harvest.
The research team acknowledge Traditional Owners across our study region, and recognise their continuing connection to land and water. We are grateful to the Murdoch University researchers, volunteers, many recreational fishers and the commercial fisher Ferdy Bergmann who provided fish frames that were used in this study. We would specifically like to thank Joe Duncan, Mark Herbert, Jim Kelly, Big Barra's One Stop Shop (Derby), Dean Thorburn, Mark Allen, Simon Visser, Howard Gill, Stephen Beatty, Mervin Street, Mary Aitken, Kevin Tromp, Mark Horstman, Patsy Bedford, the Kimberley Land Council, Mary Island Fishing Club and the people of the West Kimberley for assistance with the collection of barramundi samples. We thank Osmar Luiz and Derek Ogle for assisting with the otolith back-calculation model. The research was supported through funding from the Australian Government's National Environmental Science Program (Northern Australia Environmental Resources Hub), Charles Darwin University, Murdoch University and an Australian Government Research Training Program Stipend Scholarship to BR.
Article NumberARTN 2276
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