A new study led by the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science suggests that shark declines can lead to changes in reef fish body shapes. The research team examined neighboring reefs off the coast of northwestern Australia. The reefs are nearly identical biologically and physically, but have one major difference: one reef is protected from fishing and the other reef has been subjected to commercial shark fishing for centuries. Scientists collected hundreds of fish across seven species from the two reef systems. They measured body length, body width, eye area and tail area of each fish.
Conclusions of the study:
At the reef where shark populations have declined, the eyes of fishes are up to 46% smaller compared to the same size of fish at the reef with healthy shark populations.
At the reef where shark populations have declined, the tail fin size of fishes are up to 40% smaller compared to the same size of fish at the reef with healthy shark populations.
These patterns were seen in all seven fish species they examined
Studies examining the cascade effects of depleting an ecosystem of its top predator are well documented, but this study provides the first field evidence of changing body shapes of fish caused by shark overfishing. Watch the video below to learn why these changes may have occurred!
Journal reference:
Hammerschlag, N., S.C. Barley, D.J. Irschick, J.J. Meeuwig, E.R. Nelson, M.G. Meekan. 2018. Predator declines and morphological changes in prey: evidence from coral reefs depleted of sharks. Mar Ecol Prog Ser, 586:127-139. https://doi.org/10.3354/meps12426.
