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RESEARCH ARTICLE
Contents Vol 30(1)

Red eyes in juvenile bull sharks (Carcharhinus leucas) from Fiji

Kerstin Glaus https://orcid.org/0000-0001-9985-2243 A * , Franziska Genter https://orcid.org/0000-0001-5867-4671 B and Juerg M. Brunnschweiler https://orcid.org/0000-0002-9901-3279 C
+ Author Affiliations
- Author Affiliations

A School of Agriculture, Geography, Environment, Ocean and Natural Sciences, SAGEONS, The University of the South Pacific, Suva, Fiji.

B Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland.

C Gladbachstrasse 60, Zurich 8044, Switzerland.

* Correspondence to: kerstin.glaus@usp.ac.fj

Handling Editor: Andrew Chin

Pacific Conservation Biology 30, PC23009 https://doi.org/10.1071/PC23009
Submitted: 7 February 2023  Accepted: 25 September 2023  Published: 13 October 2023

© 2024 The Author(s) (or their employer(s)). Published by CSIRO Publishing

Abstract

The bull shark (Carcharhinus leucas) is an apex predator with a wide distribution in tropical and warm temperate waters. This species is known to utilise freshwater systems and estuaries as nursery grounds. During a wider bull shark tagging survey in the Rewa River, Fiji, in 2017 and 2018, 27 neonate bull sharks with red eye pupils were recorded. This opportunistic observation prompted an examination of water quality parameters in the Rewa River to collect preliminary data on the potential cause of pollution. Water samples were analysed for faecal indicator bacteria (Escherichia coli), ammonia, total nitrogen, and various metals. Results indicated high levels of E. coli contamination, as well as elevated ammonia and total nitrogen concentrations. However, due to the limited sample size and the likelihood of additional underlying causes, a definitive causal relationship could not be established. Hence, this finding stands as an opportunistic observation, detailed here for documentation and stimulation of discourse.

Keywords: ecology, elasmobranchs, essential habitats, eyeshine, Fiji islands, organismal biology, sharks.

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