Bluespine unicornfish (Naso unicornis) are both natural control agents and mobile vectors for invasive algae in a Hawaiian marine reserve

Bierwagen, Stacy L., Price, Donald K., Pack, Adam A., and Meyer, Carl G. (2017) Bluespine unicornfish (Naso unicornis) are both natural control agents and mobile vectors for invasive algae in a Hawaiian marine reserve. Marine Biology, 164.

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Abstract

It has been hypothesized that protecting herbivorous fishes within Marine Reserves (MRs) will help these areas to resist algal overgrowth of corals. However, we lack empirical studies demonstrating the validity of key assumptions underpinning this concept, including that herbivorous fishes (1) are permanently resident within MR boundaries, (2) routinely consume the invasive algae of concern at significant levels and (3) are not significant mobile vectors for propagules of the invasive algae. A 46-year-old MR (Hawaii Marine Laboratory Refuge, 21 degrees 27'35 '' N, 157 degrees 48'15 '' W) in waters off Oahu provided a natural setting to examine these factors with the herbivorous bluespine unicornfish (Naso unicornis) and the invasive rhodophyte, Gracilaria salicornia. We acoustically tracked five unicornfish to quantify their residency and habitat use within the MR, conducted field and laboratory observations to confirm N. unicornis consume G. salicornia, and tested the viability of G. salicornia fragments recovered from unicornfish feces. Unicornfish were resident within the MR where they spent most time in reef crest habitat with occasional, brief forays into reef flat habitat. We confirmed unicornfish consume G. salicornia and found a significant positive correlation between algal canopy height and distance from the reef crest, presumably because grazing intensity is lower in less frequently utilized reef flat habitat. We demonstrated that unicornfish egest viable fragments of G. salicornia that resume vegetative growth after several weeks. We conclude that N. unicornis may act as both a natural control agent and a mobile vector for invasive alien algae.

Item ID: 50630
Item Type: Article (Research - C1)
ISSN: 1432-1793
Funders: SeaGrant
Projects and Grants: SeaGrant #UNIHI-SEAGRANT-20101809
Date Deposited: 20 Sep 2017 10:38
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0501 Ecological Applications > 050103 Invasive Species Ecology @ 25%
06 BIOLOGICAL SCIENCES > 0602 Ecology > 060201 Behavioural Ecology @ 50%
06 BIOLOGICAL SCIENCES > 0608 Zoology > 060806 Animal Physiological Ecology @ 25%
SEO Codes: 96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960507 Ecosystem Assessment and Management of Marine Environments @ 25%
97 EXPANDING KNOWLEDGE > 970105 Expanding Knowledge in the Environmental Sciences @ 75%
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