Oral Presentation Australian Society for Fish Biology Conference 2024

More than one way to build a fish – how functional divergence of Australian smelt challenges the form-function relationship   (111456)

Daniel P Svozil 1 , Robyn J Watts 1 , R Keller Kopf 2 , Lee Baumgartner 1 , Christopher Fulton 3
  1. Gulbali Institute, Charles Sturt University, Thurgoona, New South Wales, Australia
  2. Research Institute for the Environment and Livelihoods (RIEL) Faculty of Science and Technology, Charles Darwin University, Darwin, Northern Territory, Australia
  3. Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia

River impoundment has transformed flowing environments into lentic systems. According to conceptual form-function models, differences in flow velocity can influence body shape divergence among fish populations in modified habitats such as reservoirs (Langerhans, 2008, Pavey et al 2010, Webb, 1975). However, the consequences of morphological trait divergence on swimming performance in isolated populations remain unclear. 

In experimental comparisons of river and reservoir populations of Australian smelt, we tested the predictions from conceptual models, that river populations would have narrower, fusiform bodies, higher critical swimming speed (Ucrit), fin aspect ratio (fin shape) and metabolic activity than reservoir conspecifics.

Instead, river populations had deeper, more robust bodies contrary to conceptual models, but higher Ucrit, fin aspect ratio and metabolic activity than reservoir conspecifics, as expected. As such, morphological divergence and its influence on swimming performance across the studied populations was inconsistent with the form-functional relationship in conceptual models and other species.

We conclude that alternative patterns of trait divergence may give rise to the same swimming performance outcomes, and divergence of populations due to contrasting hydrology in modified habitats may depend more on biomechanics and physiology (Sfakiotakis et al 1999, Odell et al 2003, Pink and Fulton, 2014). Further understanding of the form-function relationship and selective pressure are required for further understanding ecological impacts of river modification on fish populations.

  1. Langerhans, R. B. (2008). Predictability of phenotypic differentiation across flow regimes in fishes. Integrative and Comparative Biology, 48 (6), 750–768.
  2. Pavey, S. A., Nielsen, J. L., MacKas, R. H., Hamon, T. R., & Breden, F. (2010). Contrasting ecology shapes juvenile lake-type and riverine sockeye salmon. Transactions of the American Fisheries Society, 139(5), 1584–1594.
  3. Webb, P. W. (1984). Form and function in fish swimming. Scientific American, 251(1), 72–82.
  4. Sfakiotakis, M., Lane, D. M., & Davies, J. B. C. (1999). Review of fish swimming modes for aquatic locomotion. IEEE Journal of Oceanic Engineering, 24(2), 237–252
  5. Odell, J. P., Chappell, M. A., & Dickson, K. A. (2003). Morphological and enzymatic correlates of aerobic and burst performance in different populations of Trinidadian guppies Poecilia reticulata. Journal of Experimental Biology, 206(20), 3707–3718.
  6. Pink, J., & Fulton, C. (2014). Right tools for the task: Intraspecific modality in the swimming behaviour of coral reef fishes. Marine Biology, 161(5), 1103–1111.