Swinging back from the brink? Polygamous mating strategies revealed for an iconic threatened freshwater fish

Elise M Furlan; Lee J Baumgartner; Meaghan Duncan; Iain Ellis; Bernd Gruber; Katherine Harrisson; Laura Michie; Jason D Thiem; Ivor Stuart

doi:10.1016/j.scitotenv.2024.170808

Swinging back from the brink? Polygamous mating strategies revealed for an iconic threatened freshwater fish

Sci Total Environ. 2024 Apr 1:919:170808. doi: 10.1016/j.scitotenv.2024.170808. Epub 2024 Feb 7.

Authors

Elise M Furlan¹, Lee J Baumgartner², Meaghan Duncan³, Iain Ellis⁴, Bernd Gruber⁵, Katherine Harrisson⁶, Laura Michie³, Jason D Thiem³, Ivor Stuart²

Affiliations

¹ Centre for Conservation Ecology and Genomics, Institute for Applied Ecology, University of Canberra, University Drive, Bruce, ACT 2617, Australia; Gulbali Institute for Agriculture, Water and Environment, Charles Sturt University, P.O. Box 789, Albury, NSW 2640, Australia. Electronic address: Elise.Furlan@canberra.edu.au.
² Gulbali Institute for Agriculture, Water and Environment, Charles Sturt University, P.O. Box 789, Albury, NSW 2640, Australia.
³ Department of Primary Industries, Narrandera Fisheries Centre, Narrandera, New South Wales, Australia.
⁴ Department of Primary Industries, Buronga, New South Wales, Australia.
⁵ Centre for Conservation Ecology and Genomics, Institute for Applied Ecology, University of Canberra, University Drive, Bruce, ACT 2617, Australia.
⁶ Department of Environment and Genetics, La Trobe University, Melbourne, Australia; Research Centre for Future Landscapes, La Trobe University, Melbourne, Australia; Arthur Rylah Institute for Environmental Research, Department of Energy, Environment and Climate Action, Victoria, Australia.

PMID: 38336046
DOI: 10.1016/j.scitotenv.2024.170808

Abstract

Catastrophic fish death events are increasing in frequency and severity globally. A series of major recent fish deaths in the semi-arid lower Darling-Baaka river system (LDBR) of Australia are emblematic of these issues with tens of millions of native fish perishing. In 2018-2019 there was a major death event for Australia's largest freshwater fish, Murray cod (Maccullochella peelii). To aid the recovery and guide restoration activities of local Murray cod populations, it is essential to gather information on the mating strategies and effective population size following the fish death event. After the fish deaths, we collected larvae during the 2020 and 2021 breeding seasons and used single nucleotide polymorphisms (SNPs) to provide insight mating strategies and to estimate effective population size. Larvae were detected in both years along the entire length of the LDBR. Sixteen percent of the inferred breeding individuals were found to contribute to multiple pairings, confirming a complex and polygamous mating system. A high frequency of polygamy was evident both within and between years with 100 % polygamy identified among parents that produced offspring in both 2020 and 2021 and 95 % polygamy identified among parents involved in multiple spawning events within years. Post-larval Murray cod samples collected between 2016 and 2021 were co-analysed to further inform kinship patterns. Again, monogamy was rare with no confirmed cases of the same male-female pair contributing to multiple breeding events within or between seasons. Effective population size based on Murray cod collected after the fish death event was estimated at 721.6 (CI 471-1486), though this has likely declined following a subsequent catastrophic fish death event in the LDBR in March 2023. Our data provide insight into the variability of Murray cod mating strategies, and we anticipate that this knowledge will assist in planning conservation actions to ultimately help recover a species in crisis.

Keywords: Effective population size; Environmental flows; Fish kills; Murray cod; Population recovery; River flows.

MeSH terms

Animals
Australia
Female
Fishes
Fresh Water
Male
Marriage*
Perciformes* / genetics