11th ICRS Abstract book - Nova Southeastern University

22-37
Pacific-Wide Reduction Of Reef Fish Biomass Near Human Population Centers
Robert SCHROEDER* 1 , Benjamin RICHARDS 1 , Marc NADON 1 , Brian
ZGLICZYNSKI 2 , Russell BRAINARD 2
1 Coral Reef Ecosystem Division, JIMAR-University of Hawaii and NOAA-Pacific
Islands Fisheries Science Center, Honolulu, HI, 2 Coral Reef Ecosystem Division, NOAA-
National Marine Fisheries Service, Pacific Islands Fisheries Science Center, Honolulu,
HI
Reef fishes comprise the most important renewable resource sought on Pacific coral
reefs. Healthy reef fish assemblages are essential for maintaining ecosystem integrity that
supports sustainable reef fisheries. Many of these resource species are particularly
vulnerable to overfishing, especially targeted large/predatory species, with negative
ecosystem consequences. Biennial assessments of coral reef fish assemblages were
conducted around 50 U.S. Pacific Islands (from Guam to Hawaii to Samoa) from 2002 to
2007 using two complementary visual-census methods: (belt-transect [all fish] and
towed-diver survey [large fish]). At the island level, regression analysis showed a strong
trend of decreasing total fish biomass density with increasing human population (~proxy
for fishing pressure). Highest total fish biomass density (>6.4 t/ha) was found at
uninhabited Jarvis Island in the U.S. Line Islands and lowest (30 cm
TL). The level of regulation of fishing pressure suggests that C. urodeta and C. argus
can attain larger sizes in the MPAs such as those in Tubbataha. Aside from fishing
pressure, other patterns of distribution were confounded by the habitat preferences of the
species (e.g. C. boenak, E. fasciatus and E. coioides) that showed some association with
distinct habitat types, depth, and their biogeographic location range. These findings
suggest that bigger MPAs need to be established for critical life history stages such as
spawning aggregation sites since there are still records of moderate to high abundance
despite the high fishing pressure.
Oral Mini-Symposium 22: Coral Reef Associated Fisheries
22-39
Red Hind (epinephelus Guttatus) Spawning Aggregations in The U.s. Virgin Islands:
Movement And Migratory Patterns
Elizabeth KADISON* 1 , Richard NEMETH 1 , Jeremiah BLONDEAU 1
1 Center for Marine and Environmental Studies, University of the Virgin Islands, St. Thomas,
Virgin Islands (U.S.)
Spawning aggregations of commercial reef fish are extremely vulnerable to over fishing and
have been decimated in tropical systems throughout the world. Seasonal and permanent fishery
area closures are effective for protecting spawning aggregations however adequate size and
placement of closures is dependent on accurate knowledge of the location of the aggregation
site as well as movement patterns of fishes immediately before, after and during spawning. The
Marine Conservation District (MCD) is a 41 km2 reserve on the Puerto Rican shelf edge that
has been closed for ten years to all bottom fishing. Red hind (Epinephelus guttatus) spawn
annually in the eastern quarter of the reserve in numbers estimated to be greater than 80,000
over a 0.35 km2 area. Tag returns of fish tagged on the spawning site indicate that red hind
move west and northwest to home ranges outside of the protected area when spawning ends.
The aim of this study was to determine migration routes to the aggregation site as well as
movement patterns of fish while on the site between spawning events. Hydro-acoustic
transmitters were inserted into red hind of both sexes caught in the aggregation area over two
spawning seasons. Receivers were deployed in curtain arrays around the site and along the
shelf-edge of the insular platform to detect tagged fish up to 300m away. Little significant daily
movement was detected while fish were on the aggregation site over the two month spawning
period indicating that the MCD was adequate in size and location to protect fish during this
time. Overall spatial and temporal movement patterns were differential between sexes, however
specific migratory routes were identified. These followed particular habitat types and could
serve as predictors for migratory patterns of red hind in similar aggregations, influencing
decisions for other marine reserve boundaries.
22-40
Effects Of MPA Status On The Population Structure And Age-Based Demography Of A
Heavily Exploited Reef Fish, Lethrinus Harak
Brett TAYLOR* 1
1 Marine Laboratory, University of Guam, Hagatna, Guam
Marine protected areas (MPAs) have been considered the most practical fishery management
option for small island nations where imposing size/effort restrictions on fisherman is
problematic. The success of this management option in facilitating recovery of heavily fished
stocks has been well documented with numerous examples of increased abundance and biomass
of target species within well protected areas. However, the success of MPA implementation in
preserving exploited fish stocks for the longer-term can only be evaluated through the collection
of more detailed information such as demographic parameters and accurate abundance
estimates. In this study I compared total abundance, growth, age, length frequency, mortality
and biomass of Lethrinus harak between two marine preserves and two fished sites on the
pacific island territory of Guam. This fish is among the most important food fishes on Guam
and is heavily exploited in both the commercial and recreational inshore fisheries. Given that
landed biomass of L.harak has decreased significantly in the past decades despite increases in
fishing intensity, I set out to test whether (1) there were significant differences in the population
parameters I measured and (2) whether these results were correlated with the degree of
protection from fishing. Abundance data collected by visual census, using an optimized
sampling design stratified by habitat, has revealed a clear ontogenetic shift in habitat preference
at all sites. Juveniles are restricted to seagrass areas while adults occupy numerous backreef
habitats. For one MPA-nonMPA pair, density was greater in the fished site due to a greater
abundance of juveniles, while overall biomass and spawner biomass were 4 and 142 times
greater in the MPA, respectively. As habitat preferences differ among the life stages of L.harak,
those MPAs on Guam which contain little or no juvenile habitat play a greater role in protecting
older individuals with a higher reproductive potential.
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