In the build up to world fish migration day, we recently publicized that here at the FIRE lab, we would discuss and showcase different migratory tactics of various freshwater species. Within aquatic environments like rivers, lakes and ponds, fauna migrate in a multitude of ways across different scales, from individual meters to hundreds of kilometres. Although this blog series will be understandably dominated by the migration of various iconic fish species, as the invertebrate ecologist within the FIRE lab, I was excited to post today about the movement of different critters supporting fish populations and freshwater ecosystems around the world.

Although invertebrates and their migratory tactics are less studied and discussed compared to fish populations, BBC’s recent ‘Seven Worlds One Planet’ series promoted this topic by showing the unique migration of ‘Tisza mayfly’ (Palingenia longicauda) along the Tisza river, Hungary. Their migration occurs in June, whereby both male and female larvae would emerge from the water as winged adults and mate. Females then proceed fly up to 3 miles upstream to drop their eggs into the water, which slowly sink and are deposited onto the riverbed at the location where their parents emerged hours earlier.

Hungarian mayfly
The Tisza mayfly (photo source).

The migration of invertebrates has been influential within my studies, such as the upstream migration of freshwater shrimp into small streams that have recently started flowing after being previously dry (White et al., 2018); as well as a recent study in the UK where we highlighted that drought conditions facilitate the migration of invasive signal crayfish Pacifastacus leniusculus, which can move along the river or overland (Mathers et al., 2020).

STOTEN image
A conceptual image highlighting the movement of freshwater shrimp into rivers which have recently rewetted (Source: White et al., 2018).

Despite such evidence, some of the research challenges I’ve encountered include directly tracking the migration of freshwater invertebrates, which can prove especially challenging for species with both an aquatic (larvae surviving under water) and terrestrial (overland winged adults) life-cycle phases.

For this reason, I conclude by highlighting the recent impressive work from California undertaken by Hiromi Uno and others, who have tracked the movement of the mayfly Ephemerella maculata across its entire life-cycle. In a recent study, Uno (2019) described that E. maculata larvae grow in larger, open rivers and then emerge as winged adults. Like the Tisza mayfly described above, the female adults then fly to spawning grounds, but unlike the Tisza mayfly, E. maculata seek nearby, shaded tributaries where they then deposit the eggs. After hatching, the small larvae then drift back to the mainstem river and their life-cycle starts over. The same research team highlighted in a previous study that after the E. maculata deposit their eggs  within the shaded headwaters, they die and provide a vital food subsidy for juvenile steelheads (Uno and Power, 2015).

Uno life-cycle picture
A conceptual image highlighting the life-cycle of Ephemerella maculata. (Source: Fig. 1in Uno and Power, 2015. pp. 1013).

So much like the life-cycle of the mayfly, we have come full circle and returned to fish. I hope that you enjoyed learning about the migratory patterns of different invertebrate species.

Stay tuned for our next migratory species blog post in two weeks!

References

Mathers, K.L., White, J.C., Fornaroli, R. and Chadd, R. (2020), Flow regimes control the establishment of invasive crayfish and alter their effects on lotic macroinvertebrate communities. Journal of Applied Ecology. Accepted Author Manuscript. doi:10.1111/1365-2664.13584

Uno, H., 2019. Migratory life cycle of Ephemerella maculata (Traver, 1934)(Ephemerellidae). Aquatic Insects40(2), pp.123-136.

Uno, H. and Power, M.E., 2015. Mainstem‐tributary linkages by mayfly migration help sustain salmonids in a warming river network. Ecology Letters18(10), pp.1012-1020.

White, J. C., House, A., Punchard, N., Hannah, D.M., Wilding, N.A. and Wood, P.J. (2018). Macroinvertebrate community responses to hydrological controls and groundwater abstraction effects across intermittent and perennial headwater streams. Science of The Total Environment, 610-611: 1514-1526.

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