Quality and contribution of food sources to Australian lungfish evaluated using fatty acids and stable isotopes
The Australian lungfish, Neoceratodus forsteri Krefft, 1870, is a threatened species whose long-term persistence is at risk due to land-use intensification, water resource development, and other human pressures. Changes to the hydrology of rivers has the potential to alter the availability of certain high-quality food resources for this species, that may impact recruitment success, and contribute to population declines. This study analysed the fatty acid (FA) composition of lungfish eggs and fin tissues from two locations upstream and downstream of a large dam in the Brisbane River. We tested the hypothesis that river impoundment and flow alteration associated with the dam have altered the dietary composition and the FA composition of important dietary items for N. forsteri which translates to the body tissues and eggs. The contribution of each food source was estimated with mixing models using carbon and nitrogen stable isotopes. The total FA content in lungfish fin and eggs was significantly higher in downstream sites compared to upstream. Few significant differences in FA contents of the nine potential lungfish food sources were found between sites upstream and downstream of the dam. Stable isotope analyses of lungfish fin tissues revealed the most likely food sources were gastropods, bivalves, and crustaceans, however their relative importance differed upstream and downstream of the dam. Collectively, these results indicate that the dam did not negatively affect food quality for lungfish downstream. The most likely mechanism for potential FA deficiency and subsequent impacts on recruitment success in N. forsteri would be due to changes to the availability of high-quality food sources. This study highlights the need for future research to determine whether the low FA contents we observed in lungfish, is a function of broader environmental changes, or if FA contents are naturally low for this sub-tropical species.
KeywordsNeoceratodus forsteri Human disturbance Reproduction Fatty acid Stable isotope Food quality
The authors thank Thomas Espinoza, Andrew McDougall, Christopher Robinson, Stephen Faggotter, Sebastian Knight, Aaron Dunlop, and Jing Lu for their assistance with field sampling. We also thank Katharina Winter and Stefanie Danner for their help with laboratory analysis of FA samples. Lungfish sampling was conducted in accordance with the provisions of Queensland General Fisheries Permit 174232 and the Griffith University Animal Ethics committee (project reference ENV/12/14/AEC). This project was funded and supported by Seqwater, and JT was supported by a Chinese Academy of Sciences Stipend Scholarship and a Griffith University International Postgraduate Research Scholarship.
- Arthington A, Kennard MJ, Mackay SJ et al (2000) Environmental flow requirements of the Brisbane River downstream from Wivenhoe Dam. South East Queensland Water Corporation, and Centre for Catchment and In-Stream Research. Griffith University, BrisbaneGoogle Scholar
- Asil SM, Kenari AA, Miyanji GR, Van Der Kraak G (2017) The influence of dietary arachidonic acid on growth, reproductive performance, and fatty acid composition of ovary, egg and larvae in an anabantid model fish, Blue gourami (Trichopodus trichopterus; Pallas, 1770). Aquaculture 476:8–18CrossRefGoogle Scholar
- Clarke KR, Gorley RN (2006) PRIMER V6: user manual-tutorial. Plymouth Marine Laboratory, PlymouthGoogle Scholar
- Copeman LA, Parrish CC, Brown JA, Harel M (2002) Effects of docosahexaenoic, eicosapentaenoic, and arachidonic acids on the early growth, survival, lipid composition and pigmentation of yellowtail flounder (Limanda ferruginea): a live food enrichment experiment. Aquaculture 210:285–304CrossRefGoogle Scholar
- Kemp A, Anderson T, Tomley A, et al (1981) The use of the Australian lungfish (Neoceratodus forsteri) for the control of submerged aquatic weeds. Queensland Weed Society, pp 155–158Google Scholar
- Kind PK (2011) The natural history of the Australian lungfish Neoceratodus forsteri (Krefft, 1870). In: Jørgensen JM, Joss J (eds) The biology of lungfishes. Science Publidhers, Enfield, pp 61–99Google Scholar
- Olden JD, Fallon SJ, Roberts DT, Espinoza T, Kennard MJ (2018) Looking to the past to ensure the future of the world’s oldest living vertebrate: isotopic evidence for multi-decadal shifts in trophic ecology of the Australian lungfish. River Research and Applications. https://doi.org/10.1002/rra.3369 CrossRefGoogle Scholar
- Sargent JR (1993) Docosahexaenoic acid and the development of brain and retina in marine fish. In: Drevon CA, Baksaas I, Krokan HE (eds) Omega-3 fatty acids metabolism and biological effects. Omega-3 fatty acids; metabolism and biological effects, Basel, Switzerland, pp 139–149Google Scholar
- Sargent JR (1995) Origins and functions of egg lipids: nutritional implications. In: Bromage NR, Roberts RR (eds) Broodstock Management and Egg and Larval Quality. Broodstock Management and Egg and Larval Quality, Oxford, pp 353–372Google Scholar