11th ICRS Abstract book - Nova Southeastern University

14-6
Modelling Coral Larval Dispersal Patterns Within The Singapore Straits
Ywee Chieh TAY* 1 , Peter Alan TODD 1 , Per Sand ROSSHAUG 2 , Loke Ming CHOU 1
1 Department of Biological Sciences, National University of Singapore, Singapore,
Singapore, 2 Environmental processes, DHI, Hørsholm, Denmark
Despite almost five decades of anthropogenic impacts, the reefs of Singapore’s Southern
Islands support a rich community of scleractinian corals (165 species in just 10km 2 of
reef). Ongoing reef restoration efforts are important for reducing degradation rates of the
remaining reefs, but natural recruitment processes remain poorly understood. Given the
dynamism of the marine environment, broadcast spawners such as scleractinian corals
display great potential for exchange of genetic material. Determining the connectivity
among Singapore reefs is one of the fundamental steps in understanding the sustainability
and viability of coral populations, and would contribute to more informed reef
management decisions.
It is logistically challenging, however, to track the dispersal patterns of millions of
microscopic larvae. Coral larval dispersion patterns were therefore predicted with a 2Dhydrodynamic
flexible mesh (MIKE21 FM) model coupled with a Lagrangian particletracking
module. Neutrally buoyant, passive particles representing the generally passive
coral larvae were released from various coral source reefs in the Southern Islands during
mass spawning events. Particles were also released from the northern coasts of some of
the neighbouring Riau islands of Indonesia at predicted spawning times. Preliminary
findings indicate that the coral reefs of the Southern Islands are mainly self- replenishing.
Most of the input, however, comes from an eastern cluster of islands due to the seasonal
net east-west current that runs through the Singapore Straits during this period. Such
connectivity patterns can be used to predict which reefs are key sources of genetic
material and thus suitable for conservation priorities.
14-7
Larval Dispersal In Archipelagic Basins And Interconnecting Straits Using Particle-
Tracking Models
Cesar VILLANOY* 1 , Marites CANTO 2 , Wilfredo CAMPOS 3
1 Marine Science Institute, University of the Philippines, Quezon City, Philippines,
2 Marine Science Institute, University of the Philippines, Quezon City`, Philippines,
3 OceanBio Laboratory, University of the Philippines in the Visayas, Iloilo, Philippines
Larval dispersal models have been used to investigate marine population connectivity in
the Philippines. The unique archipelagic nature of the seas around the Philippines where
semi-enclosed basins like the Sulu Sea and the Bohol Sea, interconnected with narrow
straits and passages, may define scales of larval dispersal. Surface current velocities from
global and regional models were used to drive particle-tracking larval dispersal models to
gain insights on the role of interconnecting passages and semi-enclosed basins on
dispersal patterns. The location of larval sources were based on coral reef habitat maps
and the magnitude of larval sources scaled according to habitat characteristics,
particularly reef fish biomass and percent live coral from field survey data. The virtual
larvae contain simple behavior involving sensory and swimming capabilities. Survival
rate of settled recruits is also scaled by a simple measure of fishing and environmental
pressure. The results show that while hydrodynamics of straits and basins control
dispersal, spatially varying magnitudes of the larval sources and survival of recruits are
highly influenced by protection and degree of fishing pressure.
Oral Mini-Symposium 14: Reef Connectivity
14-8
A Preliminary Effort in Linking Connectivity Information And Coral Reef Fisheries
Using A Simple Systems Model
Ma. Carmen ABLAN* 1
1 Biology Department, De La Salle University Manila, Manila, Philippines
Connecting connectivity information to reef fisheries management is a major challenge. It
requires the availability and integration of good information and a means of obtaining feedback
from managers and resource users. The need in developing countries is especially urgent
because management interventions to halt the decline and restore productivity of reef fisheries
are increasingly becoming focused on local scales. As policies change, including connectivity in
decision making becomes essential to the success of any intervention. This study presents initial
work on constructing a simple systems model, using Stella 8.0. It integrates available
information on recruitment, spillover and fishing of reef fish to determine fish stocks in three
islands in the Bohol Sea. The effect of introducing estimates of connectivity to the model in
predicting the availability of reef fish was explored in the model and compared to estimates
without information on connectivity. Fish stocks over time in Balicasag, Apo and Sumilon
Islands were first modeled in relation to recruitment, spillover from marine protected areas and
fishing within each of these islands based on published information and data from interviews
with fishers. Estimates of asymmetric migration among islands based on previous work using
microsatellite markers on the sedentary damselfish Dascyllus trimaculatus and the further
ranging Pterocaesio pisang was factored into the model. Values of fish stocks for each area
were recalculated. When conservative estimates of connectivity based on D. trimaculatus were
used, fish stocks in Balicasag and Sumilon declined by 20% and 15% while those in Apo
increased by 22%. Using connectivity estimates from P.pisang, decline of 18-33% in fish
stock was predicted. Results show that different connectivity scenarios have different
consequences for management and raise the question of whether we could actually produce a
measure which can be useful.
14-9
Segregation Of Queen Conch, Strombus Gigas, Populations From Mexico
Claire PARIS* 1 , Dalila ALDANA ARANDA 2
1 Rosenstiel School of Marine and Atmospheric, Marine Biology and Fisheries, University of
Miami, Miami, FL, 2 Recursos del Mar, CINVESTAV IPN Unidad Merida, Merida, Mexico
Despite active conservation measures, slow recovery of Queen conch (Strombus gigas) is a
growing concern in the Caribbean. Although conventional expectations presume that S. gigas
populations are largely connected, we present results of veliger larval drift and survival from the
Yucatan peninsula in Mexico that suggest otherwise. Spatial patterns of observed and simulated
larval stages during the reproductive season revealed isolation of the Alacranes Reef population
on Campeche Bank (North Yucatan) from the Mexican Caribbean coast populations (East
Yucatan). High levels of larval retention on Campeche Bank contrasted to the highly variable
larval transport and survival along the Mexican Caribbean coast into the Yucatan Current, and
eventually into the Loop Current, drive the degree of segregation. In addition, these populations
do not mix downstream. In effect, the probability that S. gigas larvae originating from
Alacranes Reef settle in Florida is insignificant, while a small fraction of larvae produced north
of the Mexican Caribbean coast periodically reaches the Lower Florida Keys. Although this
long-distance dispersal may not be sufficient to replenish the downstream populations, gene
flow could prevent differentiation of the Florida Keys and Mexican Caribbean Queen conch
populations. This study constitutes and essential step in understanding the structure of S. gigas
populations and the needed actions for the recovery of individual populations in Mexico.
Detailed larval dynamics (e.g. behavior, growth, mortality, settlement) and mapping of
populations’ networks at the regional and wider Caribbean scales will be an extension of this
work.
111