11th ICRS Abstract book - Nova Southeastern University

Poster Mini-Symposium 10: Ecological Processes on Today's Reef Ecosystems
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Ichthyological Colonization On The Coral Reefs in The French West Indies
Yann FREJAVILLE* 1 , Yolande BOUCHON-NAVARO 1 , Max LOUIS 1 , Lionel
REYNAL 2 , Claude BOUCHON 1
1 Laboratoire de biologie marine, Université Antilles-Guyane, Pointe-à-Pitre, Guadeloupe,
2 Laboratoire de ressources halieutiques, IFREMER, Le Robert, Martinique
Reef fisheries in the Caribbean exhibit regularly decreasing CPUE during the last
decades. In order to better understand the reef fish dynamics, the aim of the present work
was to study the colonization of coral reef fishes after a pelagic larval development stage.
The success of settlement governs the post larval supply of the reef fish stocks. Monthly
samplings of post-larval fishes settling on a coral reef of Guadeloupe Island were carried
out with a crest net over 15 months. In complement, samplings of pelagic patches of
micronekton were realized with a mesopelagic trawl (30 tows) off the coasts of
Martinique Island.
A total of 3867 settlers belonging to 50 families were sampled on the reef of Guadeloupe.
An average colonization of 9 individuals by linear meter of the reef front and per hour
was recorded. The colonization on the reef is close to the “competition” model, based on
the hypothesis that the fishes settle in excess relatively to habitat and resources provided
by the reef. The most abundant families of settlers are the Gobiidae (50% of total
number, 43% of relative occurrences), then the Clinidae and the Scaridae. The main
environmental factor governing the colonization is the nycthemeral cycle and the most
prefered period is located between 3:00 am and 5:00 am. The other favourable factors
are: strong hydrodynamic conditions, nebulosity, wind direction and abundance of
drifting debris.
A total of 678 post-larvae belonging to 54 families were collected off Martinique coasts.
A phenomenon of nycthemeral vertical migration was observed. Fish colonization
revealed to be actively controlled by the behaviour of the competent post-larvae.
The results of this study suggest that predation and competition during the settlement
stage, combined to the degradations of the habitat, are among the main factors limiting
the stocks of adult coral reef fishes.
10.330
The Effect Of Fisheries Management On Species-Composition Of Crustose
Coralline Algae, With Implications For Coral Recruitment
Jennifer O'LEARY* 1 , Juan Carlos BRAGA 2 , Tim MCCLANAHAN 3
1 Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz,
CA, 2 Departamento de Estratigrafía y Paleontología, Universidad de Granada, Granada,
Spain, 3 Coral Reef Conservation, Wildlife Conservation Society, Mombasa, Kenya
Fishing can change species composition at lower, un-harvested trophic levels and alter
ecological processes. We demonstrated (in other work) that fishing reduces the cover of
crustose coralline algae (CCA) in Kenya by changing the dominant grazers. Here, we
test whether species composition of CCA is impacted by fishing. CCA is thought to be
the primary settlement substrate for coral recruitment; however, some CCA species
induce coral settlement but others actually inhibit it. Thus, changes in CCA species
composition can profoundly impact coral recruitment. We compared CCA composition
along line-intercept transects in 3 management regimes in Kenya: fully fished, gearrestricted,
and marine protected (with 3 sites/regime). We expected fished areas to have
primarily thin CCA able to withstand low-intensity but frequent sea urchins grazing and
protected areas to have primarily thick CCA able to withstand deep, but infrequent fish
grazing. We sampled, photographed, and described each visually different CCA along
three 10 m transects at each site. We grouped CCA into 60 groups that were visually
similar using external morphology and conceptacle size, shape, and spacing (using a 25x
scope). We did a preliminary analysis to determine which groups distinguished between
management regimes. Twenty-two groups were important, and from each of these
groups we randomly selected 6 samples and identified them to species level. We had
correctly grouped specimens of the same species for 11 of the 22 groups (using a cutoff
of 75% correctness). These 11 groups contained 6 CCA species. We are now using these
6 species to determine whether their relative abundance differs based on management.
We will discuss our results in terms of the suitability of available CCA substrate for coral
recruitment. This type of study, linking CCA taxonomy with field ecology, has not
previously been undertaken due to the difficulties of identifying CCA in the field.
10.331
High Biomass Of Fishes in Rarotonga (Cook Islands): Testing Whether High-Fish-
Herbivory Biomass Facilitates Recovery
Teina RONGO* 1 , Dr. Robert VAN WOESIK 1
1 Biological Sciences, Florida Institute of Technology, Melbourne, FL
Protecting coral reefs from over-fishing clearly leads to increases in local fish populations, yet
whether increases in fish biomass, particularly herbivorous fishes, leads to clear cascading and
positive influences on the reef benthos is not clear. We specifically test whether restoring the
biomass of herbivorous fishes facilitates coral recovery following disturbances on Rarotonga, in
the southern Cook Islands. Over the past 15 – 20 years, these reefs have witnessed a cultural
shift away from subsistence fishing because of chronic fish poisoning (ciguatera). The lack of
fishing pressure has led to high herbivorous fish population densities, up to 1 to 3 indv/m2, and
population densities of urchins (1 – 6 indv/m2) suggests some top-down control. Given the
high densities of herbivores we hypothesize that coral recovery is imminent. Over the past 10
years coral recruitment has been relatively high at most sites, but there is no evidence of
significant change in the corals’ size-frequency distribution. The fore reefs of Rarotonga have
remained depauperate of corals and are still dominated by turf algae. Predation pressure by the
coral-eating seastar, Acanthaster planci has been chronic on Rarotonga over the last decade,
preventing coral recovery. Therefore, while herbivory may reduce algal overgrowth and
facilitate post-settlement survival of corals, predation pressure also plays a key role in
understanding the effectiveness of marine protected areas.
10.332
Nutrient enrichment triggers a macroalga to overgrow and a sea anemone to attack coral
Pi-Jen LIU* 1 , Hsing-Juh LIN 1 , Tung-Yung FAN 2,3 , Shiue-Ming LIN 1 , Kwang-Tsao SHAO 4
1 Life Sciences, National Chung Hsing University, Taichung, Taiwan, 2 National Museum of
Marine Biology & Aquarium, National Museum of Marine Biology & Aquarium, Taiwan,
3 National Museum of Marine Biology & Aquarium, Pingtung, Taiwan, 4 Research Center for
Biodiversity, Academia Sinica, Taipei, Taiwan
The coral reefs of Kenting National Park in southern Taiwan have been degrading over the past
decade. Many areas of the reefs have shifted to sea anemone-dominated or macroalgaldominated
reefs. The preliminary results of LTER at Kenting clearly revealed the severe
impacts of anthropogenic factors were hypothesized the causes of the degrading of the coral
reefs. The factors simulation by Ecosim also revealed not only one factor caused coral
degraded. A nutrient-addition mesocosm experiment demonstrated that nutrient enrichment
triggered aggressive competition for space by a macroalga and a sea anemone on coral when the
levels of herbivory and carnivory were reduced as a result of simulated overfishing. The phase
change which occurred during the experimental period replicated what has happened in the field
over the past 10 years. In low-nutrient controls, abundances of alga Codium edule and sea
anemone Mesactinia genesis remained low, and they coexisted with branching coral Acropora
muricata. Combined nitrogen and phosphorus additions markedly increased the photosynthetic
efficiencies of coral, coverage of macroalga, and asexual reproduction of sea anemone. After 35
d of nutrient addition, the macroalga began to overgrow the coral where it was in contact with
live coral, but not with dead coral. The coral finally died after 122 d when totally overgrown by
the macroalga. Within a few days of contact with live coral, sea anemone was observed to
induce and develop acrorhagi tentacles which were used to attack and kill neighboring coral.
Nevertheless, the sea anemone was not observed to attack the macroalga, but avoided the
prolific macroalga in enriched tanks. The response of the macroalga to nutrient enrichment was
more rapid, and its negative impacts on the coral were more severe than those of the sea
anemone. Our results indicate that nutrient enrichment might be a major cause of the phase
shifts from coral- to macroalgal- or sea anemone-dominated reefs.
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