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Depth and benthic habitat influence shallow and mesophotic predatory fishes on a remote, high-latitude coral reef
journal contribution
posted on 2022-01-01, 00:00 authored by Kristy Brown, J Monk, Joel Williams, Andrew Carroll, David Harasti, Neville BarrettPredatory fishes on coral reefs continue to decline globally despite playing key roles in eco-
system functioning. Remote atolls and platform reefs provide potential refugia for predator
populations, but quantitative information on their spatial distribution is required to establish
accurate baselines for ongoing monitoring and conservation management. Current knowl-
edge of predatory fish populations has been derived from targeted shallow diver-based sur-
veys (<15 m). However, the spatial distribution and extent of predatory fishes on outer
mesophotic shelf environments has remained under described. Middleton Reef is a remote,
high-latitude, oceanic platform reef that is located within a no-take area in the Lord Howe
Marine Park off eastern Australia. Here we used baited remote underwater stereo video to
sample predatory fishes across lagoon and outer shelf habitats from depths 0–100 m,
extending knowledge on use of mesophotic depths and habitats. Many predatory fish dem-
onstrated clear depth and habitat associations over this depth range. Carcharhinid sharks
and Carangid fishes were the most abundant predators sampled on Middleton Reef, with
five predatory fishes accounting for over 90% of the predator fish biomass. Notably, Galapa-
gos shark (Carcharhinus galapagensis) and the protected black rockcod (Epinephelus dae-
melii) dominated the predator fish assemblage. A higher richness of predator fish species
was sampled on reef areas north and south of the lagoon. The more exposed southern
aspect of the reef supported a different suite of predator fish across mesophotic habitats rel-
ative to the assemblage recorded in the north and lagoonal habitats, a pattern potentially
driven by differences in hard coral cover. Biomass of predatory fishes in the more sheltered
north habitats was twice that of other areas, predominantly driven by high abundances of
Galapagos shark. This work adds to the growing body of literature highlighting the conserva-
tion value of isolated oceanic reefs and the need to ensure that lagoon, shallow and meso-
photic habitats in these systems are adequately protected, as they support vulnerable
ecologically and economically important predator fish assemblages.
system functioning. Remote atolls and platform reefs provide potential refugia for predator
populations, but quantitative information on their spatial distribution is required to establish
accurate baselines for ongoing monitoring and conservation management. Current knowl-
edge of predatory fish populations has been derived from targeted shallow diver-based sur-
veys (<15 m). However, the spatial distribution and extent of predatory fishes on outer
mesophotic shelf environments has remained under described. Middleton Reef is a remote,
high-latitude, oceanic platform reef that is located within a no-take area in the Lord Howe
Marine Park off eastern Australia. Here we used baited remote underwater stereo video to
sample predatory fishes across lagoon and outer shelf habitats from depths 0–100 m,
extending knowledge on use of mesophotic depths and habitats. Many predatory fish dem-
onstrated clear depth and habitat associations over this depth range. Carcharhinid sharks
and Carangid fishes were the most abundant predators sampled on Middleton Reef, with
five predatory fishes accounting for over 90% of the predator fish biomass. Notably, Galapa-
gos shark (Carcharhinus galapagensis) and the protected black rockcod (Epinephelus dae-
melii) dominated the predator fish assemblage. A higher richness of predator fish species
was sampled on reef areas north and south of the lagoon. The more exposed southern
aspect of the reef supported a different suite of predator fish across mesophotic habitats rel-
ative to the assemblage recorded in the north and lagoonal habitats, a pattern potentially
driven by differences in hard coral cover. Biomass of predatory fishes in the more sheltered
north habitats was twice that of other areas, predominantly driven by high abundances of
Galapagos shark. This work adds to the growing body of literature highlighting the conserva-
tion value of isolated oceanic reefs and the need to ensure that lagoon, shallow and meso-
photic habitats in these systems are adequately protected, as they support vulnerable
ecologically and economically important predator fish assemblages.
