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A morphological and functional basis for maximum prey size in piscivorous fishes, Michalis Mihalitsis [et al.]

A morphological and functional basis for maximum prey size in piscivorous fishes, Michalis Mihalitsis [et al.]

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Assessing the Population Structure and

Characterizing Spatio-temporal

Distributions of a Red Hind (Epinephelus

guttatus) Spawning Aggregation in St.

Croix, U.S. Virgin Islands

Jonathan Brown

1



2



∗† 1



, Richard Nemeth 2 , Virginia Shervette



3



Master of Marine and Environmental Studies, University of the Virgin Islands – 2 John Brewers Bay

St. Thomas, Virgin Islands 00802-9990, U.S. Virgin Islands

Center for Marine and Environmental Sciences, University of the Virgin Islands – 2 John Brewers Bay

St. Thomas, Virgin Islands 00802-9990, U.S. Virgin Islands

3

Fish/Fisheries Conservation Lab, University of South Carolina Aiken – Aiken, SC 29801, United

States



Red hind, Epinephelus guttatus, form fish spawning aggregations (FSA) within a seasonal

no-take marine protected area (MPA) in St. Croix, U.S. Virgin Islands. To examine changes in

population structure after ten and twenty years of seasonal protection differences among length,

sex ratio and density were tested between baseline data and this study. Additionally, telemetry

data collected over two consecutive spawning seasons tested if fish regularly cross the western

MPA boundary. Results showed signs of a recovering spawning population with a significant

increase in total length (TL) and a return from a leptokurtic to a bimodal size distribution.

Female-to-male sex ratios also showed improvement from 1:1 to 4:1, representing an appropriate

ratio for this haremic spawning species. Conversely, mean density decreased by 55%. Telemetry

recorded few detections along the MPA’s western boundary, but instead, sequential detections

along its northwestern boundary revealed a migratory corridor not previously documented. Detections also revealed high site fidelity within the MPA during primary spawning months, which

concurs with the peak reproductive period for this species in the U.S. Virgin Islands. Although,

numerous detections were also recorded within the MPA after the no-take period, suggesting

temporal variability among known spawning months. Age structure data collected the following

spawning season yielded a 9:1 female-to-male sex ratio with a mean age of 7 years at 33.8 cm

TL. Findings emphasize the need to continue studies for understanding the density decrease and

improving spatio-temporal resolution for better MPA design and FSA protection.









Speaker

Corresponding author: Jembrwn@yahoo.com



186



Behavioral indicators provide insight into a

fish’s perception of coral reefs: implications

for management.

Margaret Malone

1



∗ 1



, Christopher Whelan 1 , Joel Brown



1



University of Illinois at Chicago (UIC) – 845 West Taylor Street (MC 066) Chicago, IL 60607-7104,

United States



Fishes have long been suggested as indicators of coral reef quality. Traditionally, population

surveys are used to measure and assess the effects of habitat degradation. While we learn a great

deal through these assessments, they are unfortunately a trailing indicator, indicating a problem

only after populations or communities have already changed. Coral reef managers can benefit

from an assessment technique that is a leading indicator of the status of fish populations and

communities. Foraging behavior may signal changes that occur prior to shifts in fish communities. We apply foraging theory to supplement standard population and benthos assessments of

patch coral reefs in Kane’ohe Bay, Hawaii. This approach allows us to gain insight into coral

reef quality from the fish’s perspective and incorporates an assessment of ecological processes,

such as predation. We hypothesize that a core habitat reef will have high fish density and high

foraging intensity, while reefs of inferior value to the fish will have low density and low foraging

intensity. Differences in foraging intensity among coral reefs reveals perceived predation risk and

missed opportunities reflecting differences in background food availability. We selected study

reefs of high and low quality using Hawaii’s Department of Aquatic Resources (DAR) survey

data of invasive algae. Fish communities and substrate types, along with the foraging behavior

of the abundant and widespread generalist invertivore, Thalassoma duperrey (saddle wrasse),

were surveyed. We quantified foraging intensity as the giving-up density (GUD) from experimental food patches. Among reefs, we found that saddle wrasse density and foraging intensity

was lower in low quality reefs. Based on our findings, we classified reefs into categories of core

habitat, refuge, food for predators, and inferior habitat through the combination of behavioral

indicators and population surveys. This information can be used to help maintain coral reef

ecosystems and the populations and communities they support.







Speaker



187



Collective Aggressiveness of Fish Social

Groups Contributes to Variation in Coral

Replenishment

Sally Holbrook



∗ 1



, Jonathan Pruitt 2 , Russell Schmitt



1



1



University of California Santa Barbara – Marine Science Institute and Dept of Ecology, Evolution

Marine Biology University of California Santa Barbara Santa Barbara, California 93106 USA, United

States

2

University of California Santa Barbara – Department of Ecology, Evolution and Marine Biology

University of California Santa Barbara Santa Barbara, CA 93106, United States



Many animal societies exhibit stable intergroup differences in their collective behavior, yet

the degree to which such differences impact broader ecological phenomena remains unclear,

particularly on coral reefs. Farmerfish live in groups and collectively defend their gardens of

palatable algae from intrusion. In French Polynesia, farmerfish (Stegastes nigricans) provide

settlement and nursery habitats for coral because they mob corallivorous fish that attempt

to enter their territories. Their role in providing nursery habitat for young branching corals

(Acropora, Pocillopora) via territorial defense has been recognized for several decades – and

has been argued to play a critical part in recovery of coral following disturbances. We tested

for stable intergroup differences in collective vigilance and mobbing behavior in colonies of

farmerfish in Moorea, French Polynesia. Our behavioral assays revealed large among-colony

differences in collective aggression towards intruder fish. We examined whether the territories

of aggressive groups provided greater protection to corals than non-aggressive groups. Surveys

revealed that territories of aggressive groups naturally harbored greater numbers of branching

corals than non-aggressive groups. Field experiments revealed that survival and growth of

outplanted staghorn coral nubbins were positively correlated with levels of collective aggression,

and with adequate protection, they can develop into a staghorn thicket. Our findings highlight

the potential for significant ecological impacts of intergroup differences in collective behavior,

and suggest that factors that increase the collective aggressiveness of farmerfish groups could

enhance the protective value of their territories for the replenishment of coral populations.







Speaker



188



Coral-damselfish mutualism: effects on

photosynthesis and links to predation risk

Sebastian Ferse



∗ 1



, Robin Gauff 1,2 , Sonia Bejarano 1 , Nur Garc´ıa

Herrera 1,3



1



Leibniz Centre for Tropical Marine Research (ZMT) – Leibniz-Zentrum fă

ur Marine Tropenforschung

GmbH, Fahrenheitstr. 6, 28359 Bremen, Germany

2

Oceanography and Marine Environments department, Universit´e Pierre et Marie Curie – Universit´e

Pierre et Marie Curie (UPMC) - Paris VI – 4 Place Jussieu, 75252 Paris cedex 05, France

3

Alfred-Wegener-Institut, Helmholtz-Zentrum fur Polar- und Meeresforschung (AWI) – Am Alten

Hafen 26, Bremerhaven 27568, Germany



Close associations with live corals are widespread among fish species on coral reefs. A large

number of species selectively recruit to living corals, and several maintain a strong bond with

live coral as adults. Fish utilise their host coral as shelter from predators and for egg deposition

and feeding, while corals benefit from the nutrients excreted by fish and the ventilation by

sleep-swimming fish among coral branches at night. Nocturnal ventilation by fish has been

demonstrated to mitigate oxygen depletion inside the coral colony. Current flows are beneficial

for coral photosynthesis, and some photosynthetic cnidarians actively induce flow across their

surfaces. However, the effects of fish ventilation on coral photosynthesis have not been studied

to date. Shelter-seeking behaviour of coral dwelling fish is usually linked to predation risk,

implying that changes in predator abundance may affect the extent of benefits corals derive

from sheltering fish. Here, we report the results of respiration chamber measurements of the

obligate coral-dwelling damselfish, Dascyllus marginatus, and its host coral, Stylophora pistillata.

When the damselfish was allowed to swim among the coral branches, net oxygen production was

22% higher than when the fish and coral were separated by a mesh barrier. Ventilation by D.

marginatus may augment coral photosynthesis by 3-6%, depending on the amount of time fish

spend seeking shelter among coral branches on the reef. The relationship between predation

risk and shelter-seeking behaviour was assessed in a field study of the coral-associated lemon

damselfish, Pomacentrus moluccensis. Large damselfish ventured further away from their host

coral than small ones. Unexpectedly, predator activity was positively related to the distance

swum by large fish away from their host coral. This may indicate that P. moluccensis displays

a form of sentinel behaviour, and implies that cascading effects of predation on host corals are

complex and depend on the ontogenetic stage of individuals and social structure of the species.







Speaker



189



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