DOI: 10.25349/d94617
title: Spatial and Social Behavior of Acanthurus triostegus on Moorea (French Polynesia) and Palmyra Atoll (USA), 2017-2018

description: Human-induced environmental change has directly and indirectly affected
 ecosystems on a global scale, altering the behavior, ecology, and
 evolutionary trajectories of various species. Fishing of marine top
 predators and the cascading effects this may have on marine ecosystems is
 of critical concern. Predators are thought to be an important reason for
 why fish form schools, thus, a reduction in predator populations could
 alter schooling behavior for prey fish. Here, we investigate the indirect
 effects of fishing out predators on the schooling behavior of coral reef
 fishes. We compared the tendency to school for three fish species between
 two Pacific coral reefs: Palmyra Atoll (USA), an unfished reef with high
 predator abundance, and Moorea (French Polynesia), a fished reef with low
 predator abundance. We also specifically characterize movement and
 foraging-associated behaviors of one of these fishes, the convict
 surgeonfish (Acanthurus triostegus), in this same comparative
 context.   
description: <i>Study sites</i> The study was
 conducted on the Pacific coral reefs of Palmyra Atoll (5°53’N, 162°5’W;)
 and Moorea Island (17°32’S 149°50’W). Palmyra Atoll (USA) is a remote
 uninhabited island that forms part of the northern Line Islands
 archipelago in the Central Pacific. Moorea (French Polynesia) is an
 inhabited island (population 17,816 in 2017) that forms part of the
 Society Islands archipelago in the South Pacific (INSEE 2017). Schooling
 surveys and focal follows (described below) were conducted at four sites
 on the backreef of Palmyra Atoll and four sites on the backreef of
 Moorea. Palmyra Sites WT: 5.882234,
 -162.123690 LL: 5.877881, -162.114265
 RP: 5.875142, -162.120279 PS: 5.870679,
 -162.109125 SIB: 5.875445, -162.107227
   Moorea Sites TIAHURA:
 -17.485822, -149.890088 TEMAE: -17.508686,
 -149.763688 TIKI: -17.543092, -149.900736
 PUBLIC: -17.523421, -149.917574 HILTON:
 -17.482513, -149.845671  <i>Schooling behavior
 surveys</i> We conducted 30-min roving diver
 surveys (Rassweiler et al., 2020; Schmitt et al., 2002) to compare the
 <i>prevalence of schooling behavior</i> across both islands.
 An observer snorkeled in a random pattern for 30 minutes and recorded any
 focal species individuals observed. For, <i>A</i>.
 <i>triostegus, C. spilurus </i>, and <i>M.
 flavolineatus</i>, we counted every individual, as schooling
 tendency could be a result of conspecific (Okubo, 1986) and assessed
 whether the fish were in a school (and noted school size) or solitary.
 School sizes were approximated to the number of individuals when possible,
 and approximated in bins of 5, 10, or 50 in larger or fast-moving schools.
 For this study, <i>schooling</i> refers to three or more fish
 exhibiting organized group behavior, and may include synchronized and
 parallel swimming behaviors (as defined by T. J. Pitcher, 1983), but we
 did not include any spawning aggregation behavior. Some
 species of herbivorous fish that form schools are known to use their
 numbers to overwhelm territorial herbivores to force access into their
 guarded territories (Choat & Bellwood, 1985; Eurich et al., 2018;
 Foster, 1985). Thus, to control for the potential of variation in the
 numbers of territorial herbivores affecting schooling behavior
 differentially among islands, we also surveyed the abundance of these
 territorial herbivores (i.e. <i>Acanthurus lineatus, Acanthurus
 nigricans,</i> and <i>Stegastes nigricans </i>on Palmyra
 Atoll and <i>Acanthurus nigrofuscus </i>and <i>Stegastes
 nigricans</i> on Moorea).  <i>Acanthurus
 triostegus behavioral observations</i> We
 conducted 30-60min focal follows on <i>A. triostegus </i>to
 evaluate movement and behavior of schooling and solitary fish subject to
 different predator abundances. We assessed three metrics of fish behavior
 for defined portions of these focal follows: proportion of time spent
 non-vigilant, distance travelled, and area covered via calculation of a
 95% kernel utilization distribution (KUD).  Snorkeling
 observers (four observers on Palmyra Atoll, two on Moorea, lead observer
 (ASG) was present on both islands) followed solitary or schooling
 <i>A. triostegus</i> while towing a GPS device that recorded
 location every 60s. Initial follows were conducted at both islands to
 assess appropriate distance for following fish that would not impact
 normal foraging nor initiate a flight response. Every 60s, the observer
 would note school size (if applicable), and whether the focal
 individual(s) was exhibiting <i>non-vigilant grazing</i>
 behavior, a position in which the fish had their body oriented towards the
 substrate in a nose-down grazing position at time of observation, or
 vigilant behavior with an upright body orientation whether the fish was
 swimming or stationary. This behavior was classified as
 <i>non-vigilant grazing </i>as these nose-down grazing
 positions can reduce a prey fish’s ability to visually scan for predators
 (Krause & Godin, 1996). Observations on schools were done by
 recording behavioral information based on the behavior of 50% or more of
 the individuals in the school (e.g., school was recorded as ‘non-vigilant
 grazing’ if at least half of the school was in a nose-down position at the
 60s mark). If a school was widely dispersed or in a line formation, the
 observer followed the last 1/3 for the school and recorded the information
 for that subset of the school. If an observer lost sight of a solitary
 fish or school of fish, they were able to search for the fish for up to
 two minutes. If after two minutes the fish were not located, the focal
 follow would be terminated.  References: Choat JH, Bellwood DR (1985)
 Interactions amongst herbivorous fishes on a coral reef: influence of
 spatial variation. Mar Biol 89:221–234. doi: 10.1007/BF00393655
 Eurich JG, Shomaker SM,
 McCormick MI, Jones GP (2018) Experimental evaluation of the effect of a
 territorial damselfish on foraging behaviour of roving herbivores on coral
 reefs. Journal of Experimental Marine Biology and Ecology 506:155–162.
 doi: 10.1016/j.jembe.2018.06.009 Foster SA (1985) Group foraging by a
 coral reef fish: a mechanism for gaining access to defended resources.
 Animal Behaviour 33:782–792. doi: 10.1016/S0003-3472(85)80011-7
 Institut national de la
 satistique et des études économiques (2017) Populations légales des
 communes et des communes associées de Polynésie française en
 2017. Krause J, Godin
 J-GJ (1996) Influence of prey foraging posture on flight behavior and
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 10.1016/S0003-3472(83)80087-6 Rassweiler A, Dubel AK, Hernan G,
 Kushner DJ, Caselle JE, Sprague JL, Kui L, Lamy T, Lester SE, Miller RJ
 (2020b) Roving Divers Surveying Fish in Fixed Areas Capture Similar
 Patterns in Biogeography but Different Estimates of Density When Compared
 With Belt Transects. Front Mar Sci. doi:
 10.3389/fmars.2020.00272 Schmitt E, Sluka R, Sullivan-Sealey K
 (2002) Evaluating the use of roving diver and transect surveys to assess
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description: All file metada can be found
 in metada_reef_fish_schooling.rtf