Florida Fish and Wildlife

Conservation Commission 

National Park Service

U.S. Department of the Interior

South Florida Natural Resources Center

Everglades and Dry Tortugas National Parks 

Prepared by the 

National Park Service and the 

Florida Fish and Wildlife Conservation Commission

2010

Implementing the

Dry Tortugas National Park

Research Natural Area Science Plan

The 3-Year Report

Implementing the

Dry Tortugas National Park

Research Natural Area Science Plan: 

The 3-Year Report

Prepared by the

National Park Service

and the

Florida Fish and Wildlife Conservation Commission

2010

South Florida Natural Resources Center

Everglades and Dry Tortugas National Parks

Homestead, Florida

National Park Service

U.S. Department of the Interior

Florida Fish and Wildlife Conservation Commission

Tallahassee, Florida

Cover photograph of black grouper by Douglas Morrison, NPS.

Cover satellite photograph of the Dry Tortugas by NOAA.
ii
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 iii

EXECUTIVE SUMMARY

In 2007, the National Park Service (NPS) and the Florida Fish 

and Wildlife Conservation Commission (FWC) developed a 

science plan, “Assessing the Conservation Efficacy of the Dry 

Tortugas National Park Research Natural Area,” specifically 

to assess the effectiveness of a 46-mi2

 Research Natural Area 

(RNA). The Dry Tortugas National Park (DRTO) RNA is a 

no-take, no-anchoring marine reserve that was implemented 

to protect shallow water habitats and reef fish species in conjunction with two nearby existing marine reserves, the Tortugas Ecological Reserves, North and South. This three-year 

interim report summarizes the progress of the science plan 

activities to date. Progress in implementing the science plan 

has been facilitated by a number of cooperative relationships 

between federal and state agencies, academic scientists, and 

coordination by the FWC and NPS. While the results presented are part of a three-year effort, most contributing scientists went through the process of preparing project proposals 

and competing for grant funding prior to being able to initiate work. Nevertheless, work has begun on all 6 major topic 

areas described in the science plan. A total of 18 projects are 

underway. A summary of progress on each of these projects is 

provided here.

RNA Topic 1: Quantify changes in the 

abundance and size-structure of exploited 

species within the RNA relative to 

adjacent areas.

Fishery-independent visual assessment of resource status of 

the reef fish community in DRTO – Jerald S. Ault et al.

In 2008 and 2009, synoptic diver visual surveys were conducted at a number of random sites both inside and outside of 

the RNA. Divers collected biological and environmental data 

on reef fishes and associated habitats to serve as a baseline 

characterization of fish abundance and sizes inside and outside the RNA. After additional surveys are conducted in 2010 

and 2011, data will be available to analyze changes in abundance and sizes of a variety of important reef fish species. 

Examining the efficacy of the newly established RNA for protecting coral reef fishes within DRTO – Theodore S. Switzer 

et al.

Seasonal (spring and fall) fish trapping and hook-and-line 

surveys of reef habitat within DRTO were initiated in 2008 

and will continue through 2011. Preliminary results indicate 

that non-lethal ageing methods may be generally effective 

for groupers and certain snappers. Numerous exploited reef 

fishes (primarily yellowtail snapper, lane snapper, red grouper, gray snapper, button snapper, and black grouper) were 

collected in both the RNA and adjacent open-use area; thus, 

indicating that the study methodology will be useful to monitor changes in the abundances and size structures of these 

species. 

Characterization of fish assemblages associated with seagrasses within the newly established RNA and adjacent 

open-use zones at DRTO – Theodore S. Switzer et al.

Fish trapping surveys of seagrass habitat within DRTO were 

initiated during the spring and fall season in 2009 and will 

continue through 2010. Juveniles of several exploited reef 

fishes (yellowtail snapper, red grouper, and black grouper) 

have been collected in seagrass habitat as have numerous 

non-exploited fishes. Results from this project may help to 

capture early benefits for smaller size classes of fish in seagrass habitats. 

RNA Topic 2: Monitor the immigration and 

emigration of targeted species in the RNA.

Fine-scale and net migration patterns of selected reef fish 

species from the RNA to adjacent fished areas in the DRTO 

region – Michael W. Feeley et al. 

A study was initiated in May 2008 to determine patterns and 

essential habitat ranges of selected adult snapper and grouper species within the RNA using analysis of movement and 

habitat use from telemetry data. A total of 26 mutton snapper, 

13 black grouper, and 18 yellowtail snapper were acoustically 

tagged within the RNA and DRTO in 2008 and 2009 and an 

array of acoustic receivers was deployed. Fish movements 

inside and outside the RNA may demonstrate the spillover 

benefits of the RNA in DRTO and throughout the region. 

Reef fish movements and flux around the RNA – Nicholas A. 

Farmer and Jerald S. Ault 

An array of hydroacoustic receivers was deployed along the 

northwestern boundary of the RNA to track movements of 

acoustically tagged grouper, snapper, and amberjack. Grouper tended to move less frequently than snapper. Home range 

estimates were made for each species. The study demonstrated that exploitable grouper and snapper crossed RNA 

boundaries, particularly when the boundaries were in contiguous coral reef habitats or near home range centers. 

Implementing the Dry Tortugas National Park Research Natural Area 

Science Plan: The 3-Year Report 2010
iv

Use of protected areas by threatened and endangered marine turtles in the Dry Tortugas – Kristin M. Hart 

To understand sea turtle movements and habitat use in DRTO, 

satellite and acoustic tracking of green, hawksbill, and loggerhead turtles were initiated in 2007. Movement data help to 

characterize the proportion of time tagged turtles spend in 

various areas of the park, including the RNA, while nesting, 

feeding, and migrating from one habitat to another. Satellite 

tracking results are also revealing connections between turtles 

tagged at DRTO and other nesting and feeding grounds in the 

Caribbean region.

RNA Topic 3: Monitor changes in species 

composition and catch rates of exploited 

species throughout the surrounding 

region.

Extended creel census development for DRTO – Jerald S. Ault 

and Steven G. Smith

A study to review the historical creel survey data for DRTO 

from 1981 to the present was initiated in fall 2009. Historical 

data will be used to refine the existing creel survey design to 

help estimate fishery statistics. The improved creel census will 

be calibrated with data collected through the reef visual census described under RNA Topic 1 and made compatible with 

the regional Marine Recreational Fisheries Statistics Survey. 

DRTO vessel permit system – Dave Walton 

A vessel permit system was developed in 2009 to help quantify 

boating and recreational activities in DRTO. Permit applications will be available online, in Key West, and at DRTO. Data 

from the permit system will be used to estimate total fishing 

effort (RNA Topic 3), understand the relative impacts of diving on designated dive sites (RNA Topic 4), and provide information for the social science survey that will be implemented 

in 2010 (RNA Topic 6). 

RNA Topic 4: Evaluate the effects of 

RNA implementation on marine benthic 

biological communities.

Assessing the effects on corals of SCUBA and snorkeling 

use at RNA designated (mooring buoy) dive sites – Douglas 

Morrison et al. 

Using underwater video, transects were monitored for stony 

coral damage and coral loss at four RNA designated dives 

sites and three reference sites. Monitoring performed in 2009 

will serve as a baseline to compare future levels of stony coral 

damage that may be induced by divers or natural causes. In 

2010, mooring buoys will be installed at designated dive sites 

and the vessel permit system (RNA Topic 3) will be in place to 

assess total use of designated dive sites and analyze potential 

correlations between diver use and benthic impacts. 

Coral reef community monitoring at Bird Key Reef and sites 

inside and outside the RNA at DRTO – Jeff Miller et al. 

In 2004 and 2005, monitoring was initiated at Bird Key Reef to 

determine if percent cover of stony corals, algae, octocorals, 

sponges, coral species diversity, community structure, and 

rugosity are changing through time. Monitoring was recently 

expanded to include randomly selected sites inside and outside the RNA. Results will help determine long term trends in 

benthic cover at Bird Key Reef and random sites inside and 

outside the RNA.

Trophic relationships on coral reefs of DRTO: Inside and outside of the RNA – Ilsa B. Kuffner et al. 

A study was initiated to examine the potential impacts of 

reduced abundance of exploited reef fish species on herbivores, macroalgae, and corals. Surveys were performed inside 

and outside of the RNA to characterize relationships between 

different trophic level organisms inhabiting the coral reef ecosystem. Additional surveys will be conducted in 2011 to determine if changes have occurred in the proportions of major 

coral reef ecosystem components and to help determine if the 

implementation of the RNA results in balanced benthic communities at DRTO. 

Coral reef monitoring with underwater video camera. Photo by 

Rob Waara, NPS-SFCN.
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 v

Assessing the effects of creating the RNA no-anchor zone on 

seagrass beds – Douglas Morrison 

Because the RNA does not allow anchoring, anchor impacts 

on seagrass should be minimized. A replicated sampling 

design with reference sites was implemented to monitor 

seagrass and macroalgae percent cover. Over time, monitoring results may demonstrate the benefits of no anchoring in 

maintaining high value seagrass habitats. 

RNA Topic 5: Assess reproductive potential 

of exploited species by evaluating egg 

production and larval dispersal.

Reproductive potential of exploited reef fishes within the 

newly established Dry Tortugas RNA and adjacent open-use 

areas – Theodore S. Switzer et al.

An opportunistic examination of reproductive potential for 

exploited reef fishes was conducted on specimens obtained 

through trapping and hook-and-line surveys. To date, there 

has been no evidence of reproductively-active individuals 

within the RNA, although the probability of obtaining reproductively-active individuals was limited due to current levels 

of sampling effort as well as seasonal limitations of existing 

surveys (late spring and early fall only). The study may be 

expanded to collect reef fish during winter and early spring 

to increase the probability of capturing reproductively active 

animals. 

Immigration and emigration of selected reef fish species 

from the RNA to the Tortugas South Ecological Reserve – 

Michael W. Feeley et al. 

Spatial and temporal rates of movement of acoustically tagged 

snappers and groupers are being measured to observe movements during annual spawning migrations between Riley’s 

Hump, the Tortugas Ecological Reserves, and DRTO, including the RNA, by a multi-agency managed array of approximately 80 acoustic receivers. Twenty-three mutton snapper, 

and 8 groupers, including 3 black grouper, 2 Nassau grouper, 

and 3 red grouper, were acoustically tagged within the Tortugas South Ecological Reserve in 2008 and 2009. Preliminary 

results indicate a possible corridor exists for the seasonal 

movements of mutton snapper between the DRTO/RNA 

and the Tortugas South Ecological Reserve, providing a link 

between marine protected areas.

Larval transport modeling from the Dry Tortugas – Jerald S. 

Ault et al. 

A physical oceanographic model is being used to study 

physical transport and fate of reef fish eggs and larvae that are 

spawned in the DRTO region and transported to other areas 

of the Florida Keys and south Florida region. The study utilizes the Hybrid Miami Isopycnal Coordinate Ocean Model 

and information on spawning characteristics, e.g., timing 

locations, depths, and larval behavior of snapper and groupers species. Future model simulations will explore a full 

range of physical and biological conditions and results will 

help demonstrate the benefits of protecting reef fish species 

and spawning habitats in and around the RNA to fisheries 

throughout south Florida. 

RNA Topic 6: Incorporate social sciences 

into the research and monitoring 

program.

A survey of visitor demographics, attitudes, perceptions, and 

experiences in the RNA – David Loomis

A survey was designed to help managers understand demographics, attitudes, perceptions, and experiences of park 

resources among visitors who boat, fish, dive, snorkel, and 

conduct other recreational activities at DRTO. The survey is 

now in the review process with the Office of Management 

and Budget. Once approved for use, the survey will be implemented through contacting visitors that received permits 

(RNA Topic 4) and results will help to improve education 

and outreach messages, encourage compliance with the RNA 

regulations, and enable visitors to help protect natural and 

cultural resources at DRTO.

Law enforcement in DRTO – Dave Walton

DRTO law enforcement staff works to enforce the special regulations associated with the RNA. Recent activities 

include collaboration with the U.S. Fish and Wildlife Service 

to stop illegal fishing activities and other illegal activities in the 

region including the largest lobster poaching case in Florida, 

“Operation Freezer Burn.” Future activities include plans to 

establish cross deputization between National Park Service 

and Florida Fish and Wildlife Conservation Commission law 

enforcement personnel. 

Submerged cultural resource condition assessment project – 

David l. Conlin et al. 

Numerous submerged cultural resources exist inside and 

outside the DRTO RNA. A survey in 2009 relocated over 40 

of 50 submerged cultural resources and condition assessments were performed at each site. Work in 2010 will include 

the investigation of magnetic anomalies and development 

of more detailed documentation techniques to help provide 

educational materials and assist in protection of sensitive submerged cultural resources. 
vi

Diver conducting visual survey. Red grouper in foreground. Photo by Jiangang Luo, Univ. of Miami/RSMAS.
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 vii

TABLE OF CONTENTS

ACKNOWLEDGEMENTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii

INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

STATUS OF DRTO RNA PERFORMANCE PLAN ACTIVITIES BY TOPIC

RNA Performance Topic 1: Quantify changes in the abundance and size-structure of exploited species within the 

RNA relative to adjacent areas

Fishery-independent visual assessment of resource status of the reef fish community in Dry Tortugas National Park. . . . . . . . 2

Examining the efficacy of the newly established Research Natural Area for protecting coral reef fishes within 

Dry Tortugas National Park. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Characterization of fish assemblages associated with seagrasses within the newly established Research Natural Area and 

adjacent open-use zones at Dry Tortugas National Park. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

RNA Performance Topic 2: Monitor the immigration and emigration of targeted species in the RNA

Fine-scale and net migration patterns of selected reef fish species from the Research Natural Area to adjacent fished 

areas in the Dry Tortugas National Park region. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Reef fish movements and flux around the Research Natural Area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Use of protected areas by threatened and endangered marine turtles in the Dry Tortugas. . . . . . . . . . . . . . . . . . . . . . . . . . 12

RNA Performance Topic 3: Monitor changes in species composition and catch rates of exploited species throughout 

the surrounding region

Extended creel census development for Dry Tortugas National Park. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Dry Tortugas National Park vessel permit system. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

RNA Performance Topic 4: Evaluate the effects of RNA implementation on the marine benthic biological communities

Assessing the effects on corals of SCUBA and snorkeling use at Research Natural Area designated (mooring buoy) 

dive sites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Coral reef community monitoring at Bird Key Reef and sites inside and outside the Research Natural Area at 

Dry Tortugas National Park. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Trophic relationships on coral reefs of Dry Tortugas National Park: Inside and outside of the Research Natural Area. . . . . . . 22

Assessing the effects of creating the Research Natural Area no-anchor zone on seagrass meadows. . . . . . . . . . . . . . . . . . . 24

RNA Performance Topic 5: Assess reproductive potential of exploited species by evaluating egg production and 

larval dispersal

Reproductive potential of exploited reef fishes within the newly established Dry Tortugas Research Natural Area and 

adjacent open-use areas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Immigration and emigration of selected reef fish species from the Research Natural Area to the Tortugas South 

Ecological Reserve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Larval transport modeling from the Dry Tortugas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

RNA Performance Topic 6: Incorporate social sciences into the research and monitoring program

A survey of visitor demographics, attitudes, perceptions, and experiences in Dry Tortugas National Park . . . . . . . . . . . . . . . 32

Law enforcement in Dry Tortugas National Park. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Submerged cultural resource condition assessment project. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
viii

Comments and Questions on the RNA Science Plan and 3-Year Report: 

Contact David_Hallac@nps.gov or John.Hunt@MyFWC.com

Report produced by Science Communications, Everglades National Park. 

Alice Clarke, Managing Editor, with the editorial support of Ellen Hardy. Desktop design and publishing by Joy Brunk and Larry Perez. 

Please reference the RNA 3-Year Report as follows:

Hallac, D. E. and J. Hunt, editors. 2010. Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 

2010. South Florida Natural Resources Center, Everglades and Dry Tortugas National Parks, Homestead, FL, and the Florida Fish and Wildlife 

Conservation Commission, Tallahassee, FL. 37 pp. 

Printed on 30% post-consumer waste paper with vegetable-based inks. Fiber sourced from responsibly managed forests.

Science activities in the Dry Tortugas National Park Research Natural 

Area are guided by the science plan prepared in 2007 by the National 

Park Service and the Florida Fish and Wildlife Conservation Commission.

ACKNOWLEDGEMENTS

We are grateful for the services provided by the captain and crew of the M/V Fort Jefferson. In particular, Clay “Blue” and Janie 

Douglass have provided exceptional research and monitoring support for a large number of projects described within this report. 

We thank Pat Walton, Brion Schaner, Tree Gottshall, Kayla Nimmo, and Chris Ziegler for their support at Dry Tortugas National 

Park.

Editors:

David E. Hallac, National Park Service, Everglades and Dry Tortugas National Parks 

John Hunt, Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 1

INTRODUCTION

In 2007, the National Park Service (NPS) and the Florida Fish 

and Wildlife Conservation Commission (FWC) established 

the 46-mi2

 Research Natural Area (RNA) of Dry Tortugas 

National Park (DRTO) and also developed a science plan 

specifically to assess the effectiveness of the marine reserve. 

This three-year interim report summarizes the progress of the 

science plan activities to date. 

 First established as Fort Jefferson National Momument 

in 1935, the site was reauthorized in 1992 as a national park. 

Congress established DRTO to “preserve and protect for the 

education, inspiration, and enjoyment of present and future 

generations nationally significant natural, historic, scenic, marine, and scientific values in south Florida.” The enabling legislation stipulates that the park be managed to protect, among 

other values, “a pristine subtropical marine ecosystem, including an intact coral reef community.” The RNA marine reserve directly supports the mission of the park as it is designed 

to restore ecological integrity and capacity for self-renewal by 

minimizing the effects of human activities on marine resources (see map of RNA on inside cover). Together, the RNA and 

the larger, adjacent Tortugas Ecological Reserve (TER) of the 

Florida Keys National Marine Sanctuary (FKNMS) will help 

to ensure the success of both marine and terrestrial ecosystems (see map of the regional reserve network on the inside 

back cover), and thereby contribute to a region-wide effort to 

strengthen resource protection. 

 The DRTO RNA was established to protect shallow water 

marine habitat, ensure species diversity, and enhance the productivity and sustainability of fish populations throughout the 

region. While boating, swimming, snorkeling, scuba diving, 

hiking, research, and education activities are allowed within 

the RNA, anchoring and fishing are prohibited. 

 The NPS and the FWC are committed to working together to conduct research, education, enforcement, and 

adaptive management of the Dry Tortugas ecosystem. The 

RNA provides a unique unexploited area that can be used 

to help assess the effects of fishing on exploited areas. Longterm studies and monitoring will serve to document existing 

baseline conditions and analyze how park natural resources 

respond to the protection provided. 

 The RNA science plan identifies six areas of RNA performance to be evaluated: 

1. Quantify changes in the abundance and size-structure 

of exploited species within the RNA relative to adjacent areas; 

2. Monitor the immigration and emigration of targeted 

species in the RNA; 

3. Monitor changes in species composition and catch 

rates of exploited species throughout the surrounding region; 

4. Evaluate the effects of RNA implementation on marine benthic biological communities; 

5. Assess reproductive potential of exploited species by 

evaluating egg production and larval dispersal; and

6. Incorporate social sciences into the research and 

monitoring program.

 Because ecosystems take time to respond to management 

actions, the developers of the assessment plan have included 

a variety of indicators that will help evaluate benefits both in 

short and long time-frames. Natural variability in sea temperature, weather events such as hurricanes, and other factors can 

affect many of the indicators described in the science plan and 

thereby have the potential to complicate RNA assessment. 

The full benefit of the RNA to the Tortugas region will only 

be measurable in the long-term. Therefore, this initial threeyear assessment, reports primarily on progress implementing 

science projects that begin to monitor baseline conditions. A 

five-year assessment report will be prepared for release in the 

spring of 2012. 

Black grouper. Photo by Douglas Morrison, NPS.
2 RNA Performance Topic 1: Quantify changes in the abundance and size-structure of exploited species within the RNA relative to 

adjacent areas

RNA Performance Topic 1

Fishery-independent visual assessment of resource status of the reef fish 

community in Dry Tortugas National Park

Investigators

Jerald S. Ault1, Steven G. Smith1, James A. Bohnsack2, Matt 

Patterson2

, Ben Ruttenberg3, and John Hunt4

1

University of Miami, Rosenstiel School of Marine and 

Atmospheric Science

2

National Oceanic and Atmospheric Administration, 

Southeast Fisheries Science Center

3

National Park Service, South Florida/Caribbean Inventory 

and Monitoring Network

4

Florida Fish and Wildlife Conservation Commission, Fish 

and Wildlife Research Institute

For further information contact: jault@rsmas.miami.edu

Project Description

The goal of this study is to monitor and statistically assess 

coral reef fish resource status (species composition, frequency-of-occurrence, size-structured abundance, and spatial distribution) in Dry Tortugas National Park. The study 

conducts synoptic diver visual surveys following a statistically 

robust stratified random sampling design to collect biological 

and environmental data on reef fishes and their habitats both 

inside and outside the Research Natural Area (RNA) in the 

park. Spatial and temporal trends in estimates of species-specific abundance metrics (e.g., occurrence, density, abundance, 

biomass, size composition) and fish community metrics (e.g., 

species diversity) are then statistically evaluated from surveys 

conducted before and after implementation of the RNA.

Accomplishments 

Intensive sampling surveys were conducted in spring-summer 

of 2008 and 2009, one and two years post-implementation of 

the RNA. Divers using SCUBA collected biological data following a standard, non-destructive, and in-situ monitoring 

protocol in which a stationary diver records reef-fish data 

while centered in a randomly selected circular plot 15 m in 

diameter. The field research team was comprised of scientific 

personnel from NOAA Fisheries, the University of Miami, the 

National Park Service, and the State of Florida. The statistical field design partitioned Dry Tortugas National Park into 

subregions or strata based on reef habitat characteristics (i.e., 

complexity and patchiness of reef structures, depth) and spatial management zones (i.e., inside and outside the RNA). This 

habitat-based survey design was developed in 1999 and 2000, 

and has been shown to provide accurate and precise abundance metrics for reef fishes in the Tortugas region in a costeffective manner. In 2008, 392 stations (i.e., statistical observations) were sampled, and 409 stations were sampled in 2009 

(one station represents the pooled stationary plot counts for 

a buddy-pair of scientific divers). Sample sizes ranged from 

approximately 200-350 per survey conducted in 1999-2000, 

2002, 2004, and 2006, prior to implementation of the RNA.

Gray angelfish, red grouper, and a bluehead wrasse swim beside great star coral in Dry Tortugas National Park. Photo by 

Jiangang Luo, Univ. of Miami/RSMAS.
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 3

Preliminary Results

In theory, establishment of a no-take marine reserve such as 

the RNA should reduce fishing pressure on exploited species, resulting in increases in relative abundance of fishes in 

the exploited life phase (i.e., individuals larger than the minimum legal length of capture) inside the reserve as compared 

to areas outside the reserve. For long-lived species such as 

snappers and groupers, these changes in abundance and size/

age-structure are expected to take 10 to 20 years to reach their 

full potential. However, our previous research in the Florida 

Keys and Dry Tortugas regions has been able to statistically 

detect these changes in as little as 3 to 5 years after reserve 

implementation. 

As an example, preliminary results are shown in Figures 

1 and 2 for red grouper (Epinephelus morio), a highly prized 

species by both commercial and recreational fishers. For 

the pre-exploited life phase (length<50 cm), average density 

(number per unit area) has been stable since 2004, but appears 

to have declined somewhat from the 1999-2002 period (Fig. 1, 

top panel). Abundance of pre-exploited animals generally depends on the status of the spawning stock along with general 

environmental conditions. For the exploited life phase (>50 

cm), average density fluctuated to some extent inside and outside the RNA prior to implementation in 2007 (Fig. 1, bottom 

panel). Post-implementation, densities were not statistically 

different inside and outside the RNA, but the average has been 

consistently higher inside the RNA compared to outside. The 

proportion of individuals larger than 50 cm, the legal minimum capture size, has also generally increased throughout the 

park post-implementation of the RNA, with an even higher 

proportion of exploited phase red grouper inside the RNA in 

2009 compared to outside (Fig. 2). Although our results are 

not conclusive at this early stage of RNA establishment, the 

changes in relative abundance and size structure for red grouper seem to be moving in the expected direction.

Future Work

A robust monitoring and assessment program has been firmly 

established to track changes, should they occur, in reef fish 

species abundance and community metrics in response to 

implementation of the RNA in Dry Tortugas National Park. 

An intensive 20-day regional cruise of visual surveys is scheduled for the Tortugas during spring-summer 2010. Cruises 

should also occur in 2011 and 2012 to ensure that the final 

analyses are rigorous and detect all possible states of regional 

resource condition and ultimately determine the effectiveness 

of the RNA in building a sustainable recreational reef fishery 

within the park. In addition, complementary analyses will be 

conducted to compare the state of park resources with those 

of the broader Tortugas region, and the entire south Florida 

coral reef ecosystem.

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Figure 1. Visual survey time-series of red grouper mean density 

and associated standard error inside (dark circles) and outside 

(white squares) the RNA in Dry Tortugas National Park for preexploited (top panel) and exploited (bottom panel) life phases. 

The RNA was established in 2007.

Figure 2. Relative length-frequency histograms for red grouper 

inside (dark bars) and outside (white bars) the RNA in Dry 

Tortugas National Park for surveys conducted in 2006, 2008, and 

2009. The RNA was established in 2007. Lc

 denotes the minimum 

legal capture length.
4 RNA Performance Topic 1: Quantify changes in the abundance and size-structure of exploited species within the RNA relative to 

adjacent areas

Investigators

Theodore S. Switzer1, Alejandro Acosta1, Michael W. Feeley1, 

John Hunt1

, Sean F. Keenan1, Brett Pittinger1, David E. Hallac2, 

Douglas Morrison2

, and Carole C. McIvor3

1

Florida Fish and Wildlife Conservation Commission, Fish 

and Wildlife Research Institute 

2

National Park Service, Dry Tortugas National Park 

3

U.S. Geological Survey

For further information contact: Ted.Switzer@MyFWC.com

Project Description

This study was designed to address explicitly several priority 

research areas identified by the National Park Service (NPS) 

and the Florida Fish and Wildlife Conservation Commission 

(FWC) in the Research Natural Area (RNA) science plan, 

including (1) the implementation of a stratified-random sampling survey using baited fish traps and hook-and-line gear 

to evaluate changes in the relative abundance, frequency of 

occurrence, and size structure of exploited reef fishes within 

the RNA and adjacent open-use areas, (2) the development 

of an external tagging study to monitor broad-scale ingress/

egress of exploited reef fishes across RNA boundaries, and 

(3) the examination of size-age structure of exploited reef 

fishes within the RNA and adjacent open-use areas. Sampling 

methods follow a seasonal (spring and fall) stratified-random 

survey (SRS) approach within the southern portion of Dry 

Tortugas National Park (DRTO) (south of 24o 40’ N; Fig. 1) 

in which sampling effort is randomly allocated among three 

generalized reef habitat types (isolated reef, continuous reef 

– spur and groove, continuous reef – non-spur and groove) 

common to both the RNA and adjacent open-use areas. At 

each sampling station, a survey of structure-oriented fishes is 

conducted through the use of baited chevron traps; an ancillary hook-and-line survey targeting exploited reef fishes is also 

conducted at a subset of trapping sites. Each individual collected is identified, enumerated, and measured. For exploited 

reef fishes, a small number of individuals (n = 10 per family 

per season) are sacrificed for life-history studies; the remainder are implanted with an external dart tag prior to release. 

Data from seasonal SRS trapping surveys will be used to 

compare overall community structure between the RNA and 

open-use areas as well as among habitat types. Data from both 

the SRS trapping and hook-and-line surveys will be used to 

compare abundance, frequency of occurrence, size structure, 

and habitat use of exploited reef fishes between the RNA and 

open-use areas. Data from life-history studies will be used to 

validate non-lethal ageing methods and conduct comparisons 

of age-structure for exploited reef fishes between the RNA 

and open-use areas. In addition, this study will provide data 

that can be compared to the reef visual census techniques that 

are also being used to understand changes in abundance and 

size structure of exploited reef fish species in the RNA.

Accomplishments

To date, seasonal stratified-random surveys, using both baited 

chevron traps and hook-and-line gear, were successfully conducted during both spring and fall in 2008 and 2009. In 2008, 

trapping surveys were conducted at a total of 112 stations 

including 58 stations within the RNA and 54 stations within 

adjacent, open-use areas of DRTO. Hook-and-line surveys 

were conducted at a total of 65 stations, including 30 stations 

within the RNA and 35 stations within open-use areas. In 

2009, trapping surveys were conducted at a total of 121 stations, while hook-and-line surveys were conducted at a total 

of 57 stations.

RNA Performance Topic 1

Examining the efficacy of the newly established Research Natural Area for 

protecting coral reef fishes within Dry Tortugas National Park

Red grouper. Photo by Douglas Morrison, NPS.
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 5

Preliminary Results

During 2008, a total of 3,392 individuals was collected, 

including 1,784 within the RNA and 1,608 within open-use 

areas. Among exploited reef species, the most frequently collected taxa in the trapping surveys were yellowtail snapper, 

lane snapper, red grouper, and gray snapper. Within hookand-line surveys, 522 individuals were collected, including 

209 within the RNA and 313 within open-use areas. Among 

exploited reef species, the most frequently collected taxa 

in the hook-and-line surveys were yellowtail snapper, red 

grouper, mutton snapper, and black grouper. In 2008, a total 

of 2,641 individuals was tagged with external dart tags and 

released, including 1,200 within the RNA and 1,441 within 

open-use areas. Preliminary results indicate that non-lethal 

ageing methods may be effective at ageing groupers collected 

within DRTO. Results from non-lethal ageing methods have 

been mixed for snappers and will require additional data 

before making definitive conclusions. Data entry and processing for 2009 data are ongoing at present; therefore preliminary 

results from 2009 are unavailable.

Future Work

Stratified-random trapping and hook-and-line surveys will be 

conducted in the RNA and open-use areas in spring and fall 

during both 2010 and 2011. We will continue to tag released 

individuals. During future sampling, continued effort will be 

directed toward informing recreational anglers of our reef-fish 

tagging program with the hopes of increasing the numbers of 

recaptured individuals reported by recreational anglers. We 

will also begin to conduct more comprehensive and rigorous statistical analyses of collected data to compare habitatspecific community structure, size structure, and catch rates 

between the RNA and open-use areas. 

Figure 1. Hook-and-line and fish trap sampling sites during fall 2008.
6 RNA Performance Topic 1: Quantify changes in the abundance and size-structure of exploited species within the RNA relative to 

adjacent areas

Investigators

Theodore S. Switzer1, Alejandro Acosta1, Michael W. Feeley1, 

John Hunt1

, Sean F. Keenan1, Brett Pittinger1, and David E. 

Hallac2

1

Florida Fish and Wildlife Conservation Commission, Fish 

and Wildlife Research Institute

2

National Park Service, Dry Tortugas National Park

For further information contact: Ted.Switzer@MyFWC.com

Project Description

This project is designed to fill acknowledged data gaps regarding fish assemblages associated with seagrasses within Dry 

Tortugas National Park (DRTO). The primary objective of the 

study is to characterize community structure of seagrass-associated fish within the DRTO Research Natural Area (RNA) 

and adjacent open-use areas. The newly established RNA 

is the first protected area established in the DRTO region 

to offer direct protection to seagrasses, a habitat known to 

support numerous resident and transient fishes. The relative contribution of these protected seagrass areas related to 

recruitment of reef-associated fish is currently understudied 

in the Dry Tortugas. Additionally, baseline data from which 

long-term changes in community structure in association 

with the establishment of the DRTO RNA will be assembled. 

Potential benefits of the RNA would likely first be detectable 

in either the recruitment of reef fishes or alternately trophic 

cascades; accordingly, it is critical to obtain baseline data for 

these smaller individuals as soon as possible following the 

2007 establishment of the DRTO RNA. Sampling methods 

follow a seasonal (spring and fall) stratified-random survey 

approach within the southern portion of DRTO (south of 24o 

40’ N; Fig. 1) in which sampling effort is randomly allocated 

to areas of known seagrass within both the RNA and adjacent 

open-use areas. At each sampling station, a survey of seagrassassociated fish is conducted through the use of baited Antillean Z-traps. Each individual collected is identified, enumerated, and measured. Data from these seasonal surveys will 

be used to compare overall community structure as well as 

habitat use by exploited reef fishes associated with seagrasses 

within the RNA and adjacent open-use areas.

Accomplishments

In spring 2009, we conducted an exploratory survey to test the 

utility of two sampling alternatives that were chosen based on 

minimizing the potential for damage to seagrass and associated coral habitat: a small diver-deployed seine (DDS) and 

Antillean Z-traps. The DDS has been used effectively in collecting structure-oriented fishes associated with kelp forests 

along the Oregon coast, while Antillean Z-traps have been 

used effectively in monitoring structure-oriented assemblages 

in Australia. A total of 26 stations was sampled in spring 2009, 

including 12 within the RNA and 14 within open-use areas. 

Preliminary results indicated that the DDS was ineffective 

at capturing seagrass-associated fish in the clear Dry Tortugas waters. The Antillean Z-traps were much more effective, 

capturing juveniles of several exploited reef fish taxa (black 

grouper, red grouper, and yellowtail snapper) along with 

numerous other fishes. Beginning in fall 2009, sampling was 

conducted solely with the use of Antillean Z-traps, although 

additional effort was allocated among shallow (less than 10 m 

deep) reef sites to compare relative abundances between seagrass and reef habitats. During fall sampling, we sampled 14 

seagrass stations within the RNA, 12 seagrass stations within 

open-use areas, and 10 reef stations.

Preliminary Results

Data entry and processing for 2009 data are currently ongoing. Qualitatively, catches were greater during fall than spring 

and have been dominated numerically by yellowtail snapper, 

slippery dicks, and white grunt. In addition, Z-traps have collected numerous red grouper and graysby.

Future Work

Stratified-random trapping surveys will be conducted in seagrass and shallow reef habitats in the RNA and open-use areas 

in spring and fall 2010. We will also begin to conduct more 

comprehensive and rigorous statistical analyses to compare 

habitat-specific community structure and catch rates between 

the RNA and open-use areas. This project will assess the value 

of seagrass habitat for juvenile fishes in DRTO. 

RNA Performance Topic 1 

Characterization of fish assemblages associated with seagrasses within the 

newly established Research Natural Area and adjacent open-use zones at 

Dry Tortugas National Park
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 7

Figure 1. Fish assemblage sampling sites within seagrass and reef habitats, spring and fall 2009.

Yellowtail snapper and school of silverside fish. Photo by Douglas Morrison, NPS.
8

Investigators

Michael W. Feeley, Alejandro Acosta, Theodore S. Switzer, 

John Hunt, Paul Barbera, and Danielle Morley

Florida Fish and Wildlife Conservation Commission, Fish and 

Wildlife Research Institute

For further information contact: Michael.Feeley@MyFWC.

com

Project Description

The first marine protected area in the Florida Keys was established in 1963. Since then, numerous protected areas have 

been established and these are widely recognized as valuable 

tools in an ecosystem-based approach to marine resource 

management. However, to establish biologically relevant 

boundaries and eventually define management benefits, the 

scale on which ecological processes function must be determined. Therefore, a study using analysis of movement and 

habitat use from telemetry data was initiated in May 2008 

to determine patterns and essential spatial range of selected 

adult snapper and grouper species. Ongoing research efforts 

are focused in the southern half of Dry Tortugas National 

Park (DRTO; south of 24o 40’ N) with an array of Vemco VR2 

receivers positioned in the southeastern corner of a newly 

established no-take marine reserve, the Research Natural 

Area (RNA), including coverage within both the RNA and 

adjacent open-use areas (Fig. 1). The receiver array covers a 

total area of approximately 10 km2

 and is centralized along 

the low-relief/high-relief spur and groove habitat within and 

adjacent to the southeastern corner of the RNA, a habitat 

known to support a rich and diverse assemblage of exploited 

reef fishes. This low-relief and high-relief spur and groove 

habitat borders low-relief hard bottom and seagrass habitats 

to the northwest and sand habitat to the south, allowing for 

the examination of fine-scale patterns of habitat use among 

a variety of habitats. Additionally, the array comprises both a 

western and an eastern component separated by a deep (30 

meters sea water) sand plain. The area covered by the western 

component of the array straddles both the RNA and adjacent 

open-use areas of the Special Use Zone (SUZ) and southern 

Natural Cultural Zone (NCZ), while the eastern component 

is concentrated within the eastern NCZ and adjacent sand 

plain. Combined, these two components will allow us to 

examine fine-scale rates of movement across RNA boundaries as well as test for potential movement across two separate 

RNA boundaries: one with a natural barrier and another with 

uninterrupted contiguous habitat.

Accomplishments

Thirty-two VR2 acoustic receivers were placed in DRTO, 

within and outside the borders of the RNA in May 2008. 

Receivers were deployed using a subsurface buoy system to 

minimize the probability of receiver loss. These receivers were 

first downloaded and redeployed in October 2008. Following 

the passage of Hurricane Ike in September 2008, all receivers were recovered with the exception of those located along 

RNA boundary lines in less than 15 m of water. These stations 

were subsequently repositioned in deeper water (greater 

than 20 m) and 100%of all receivers were downloaded and 

redeployed in May and October 2009. Selected reef fish 

were caught by hook-and-line or fish trap within DRTO and 

the RNA and surgically implanted with coded transmitters 

(Vemco V9 or V16) in May and October 2008 and 2009. This 

study is complemented by ongoing research being conducted 

by Mote Marine Laboratory, the U.S. Geological Survey, and 

Florida Fish and Wildlife Conservation Commission that 

includes: a nurse shark project (Principal Investigator (PI): 

Dr. W. Pratt/Mote); a sea turtle project (PI: Dr. K. Hart/USGS) 

and our spawning aggregation project (see RNA Topic 5). We 

are coordinating closely with these organizations with respect 

to exchange of data obtained from the various arrays. These 

complementary studies extend regional coverage to the east 

and north within DRTO and throughout the region, including the Tortugas North Ecological Reserve (TNER) and the 

Tortugas South Ecological Reserve (TSER), located 25 km 

southeast of Garden Key.

RNA Performance Topic 2: Monitor the immigration and emigration of targeted species in the RNA

RNA Performance Topic 2

Fine-scale and net migration patterns of selected reef fish species from the 

Research Natural Area to adjacent fished areas in the Dry Tortugas National 

Park region

Mutton snapper. Photo by Douglas Morrison, NPS.
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 9

Preliminary Results

A total of 26 mutton snapper (Lutjanus analis), 13 black grouper (Mycteroperca bonaci), and 18 yellowtail snapper (Ocyurus chrysurus) was acoustically tagged within the RNA and 

DRTO in 2008 and 2009. The telemetry database is currently 

under review and will be used to elucidate fine- and broadscale habitat utilization patterns. We are tracking a significant 

number of mutton and yellowtail snapper; however, we presently can account for only 3 of the total black grouper tagged 

within the array. Preliminary analyses in 2008 determined that 

one mutton snapper tagged inside the RNA migrated 25 km 

during a 10-day period. This fish returned to the RNA after 

it was detected on a receiver approximately 6 km east of the 

TSER. An array of offshore receivers established at Riley’s 

Hump, within the TSER, later confirmed that mutton snapper tagged within DRTO and the RNA repeatedly undertake 

seasonal spawning migrations to the TSER. The final measure 

of conservation benefits of the RNA likely will depend on 

data collected with acoustic receivers throughout the region 

in order to understand fully the spatial patterns and habitat 

utilization of selected species within the region.

Future Work

We will continue our acoustic tagging efforts within DRTO 

and the RNA through May 2010. Although extensive efforts 

are ongoing to describe habitat utilization patterns across 

protected and non-protected zones through spatially explicit 

randomized sampling designs, life history and seasonal movement patterns still remain to be determined. During 2010, 

additional field efforts will be directed toward acoustically 

tagging black grouper to complement static habitat utilization studies (PI. T. Switzer/FWC; PI. J. Ault & J. Bohnsack/

UMiami & NOAA) and our acoustic spawning aggregation 

study (see RNA Topic 5). Since multi-year transmitters were 

implanted in fish, we will continue to download data semiannually on receivers through 2011. Data analyses will establish 

the degree of connectivity between habitats and the network 

of management areas in the Dry Tortugas and determine the 

efficacy of current management zones on commercially and 

recreationally valuable reef fish. Data collected on fish species 

from DRTO and the RNA will be evaluated from a seascape 

perspective at a scale appropriate to regional ecosystem processes.

Figure 1. Locations of acoustic receivers in the Dry Tortugas region during summer 2009.
10

Investigators

Nicholas A. Farmer and Jerald S. Ault

University of Miami, Rosenstiel School of Marine and 

Atmospheric Science

For further information contact: jault@rsmas.miami.edu

Project Description

Quantifying reef fish movement patterns and space use is 

critical in determining the effectiveness of no-take marine 

reserves (NTMR) in conserving adult spawning stock biomass for subsequent recruitment, and providing exploitable 

biomass to adjacent fisheries areas. Movements of exploited 

coral reef fishes are largely unknown, but knowledge of the 

distance and frequency of movement in and out of reserves is 

essential for management decision-making. To better understand population flux for exploited reef fishes and evaluate 

the contention that reserves are a sink for fisheries production, a multi-year acoustic telemetry study was conducted in 

the Research Natural Area (RNA) of Dry Tortugas National 

Park. Empirical data on long-term movement patterns and 

space requirements are essential in assessing resource protection and to account for the scale of animal movements and 

the locations of core habitats that may lead to high levels of 

spillover that prevent the reserve from functioning effectively 

as a buffer against fishing mortality.

Accomplishments

A calibrated array of 75-80 omnidirectional hydroacoustic 

receivers were used to examine home range, activity patterns, 

site fidelity, and habitat preferences for acoustically-tagged 

adult reef fish in Dry Tortugas National Park. The receiver 

array was located near the northwestern section of the RNA 

and covered about 50 km2

. Acoustic tagging included black 

grouper (Mycteroperca bonaci), red grouper (Epinephelus 

morio), mutton snapper (Lutjanus analis), gray snapper (Lutjanus griseus), yellowtail snapper (Ocyurus chyrsurus), tiger 

shark (Galeocerdo cuvier), and greater amberjack (Seriola 

dumerili).

Preliminary Results 

In general, grouper movements detected in this study were 

relatively small and infrequent, whereas mutton snapper and 

yellowtail snapper moved more frequently, and the gray snapper made daily movements associated with an apparent nocturnal migration. Relative frequency of detected movement 

varied between species. Distances moved, presented here as 

mean distance with standard errors (SE), varied significantly 

between species, with significant (p < 0.001) differences for 

all interspecies comparisons except for red grouper and mutton snapper. The majority of yellowtail snapper (mean: 137.5 

± 0.11 m) movements were less than 400 m in distance. The 

majority of movements by black grouper (mean: 210.71 ± 0.35 

m), red grouper (mean: 400.63 ± 0.02 m), and mutton snapper 

(mean: 363.42 ± 0.14 m) were less than 600 m in distance. All 

observed movements by gray snapper (mean: 1215.16 ± 0.13 

m) exceeded 1,000 m. A 274 cm total length (TL) female tiger 

shark ranged broadly, but was detected in the array on a daily 

basis for two months prior to disappearing. Of particular note, 

a 125 cm greater amberjack tagged in Dry Tortugas National 

Park in February 2007 was detected about 30 times between 

February and May, and then left the array permanently in midMay 2007. Surprisingly, that fish was recaptured off Cancun, 

Mexico in October 2009, at a size of approximately 145 cm. 

We found that exploited-phase groupers and snappers 

occasionally crossed RNA boundaries. They were generally 

more likely to do so where boundaries overlay contiguous 

reef, and when home range centers were close to reserve 

boundaries. Flux rates across reserve boundaries detected 

by acoustic telemetry varied by species and by year. In 2006, 

only 2 of 31 (6%) grouper were detected moving across RNA 

boundaries. During 2007, 4 of 14 (29%) red grouper moved 

across RNA boundaries. No black grouper (but sample size 

was small) were detected moving across reserve boundaries in 

either year. Only 1 of 5 of the tagged yellowtail snapper moved 

RNA Performance Topic 2: Monitor the immigration and emigration of targeted species in the RNA

RNA Performance Topic 2 

Reef fish movements and flux around the Research Natural Area

Figure 1. Acoustic receiver detections by site (triangles) during 

2007 for a sexually-mature mutton snapper tagged on April 25, 

2007, relative to new (closed circles) and full (open circles) moon 

periods. Note lack of detections (shaded vertical bars) between 

May 27 and June 13, and then again during June 28 – July 6. Also 

of interest is the great amount of movements detected prior to 

and immediately following apparent spawning migrations, relative to the remainder of the tracking days. 

2007

3

5

7

9

11

13

15

17

19

21

23

25

27

29

31

33

35

37

39

4/19

4/26

5/ 3

5/10

5/17

5/24

5/31

6/ 7

6/14

6/21

6/28

7/ 5

7/12

7/19

7/26

8/ 2

8/ 9

8/16

8/23

8/30

9/6

9/13

9/20

9/27

10/4

10/11

10/18

Receiver Site
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 11

across the reserve boundary; notably, one fish crossed the reserve boundary 62 times, but spent less than 2% of its total 

time outside the RNA. A gray snapper crossed the boundary 

10 times, spending 3.4% of its time outside the RNA. Only 1 

of 2 mutton snapper moved across reserve boundaries, but it 

did so 702 times, spending more than 9% of its time outside 

the RNA. This sexually-mature fish was continuously tracked 

for 168 d, with two extended absences during the full moon 

in summer presumably related to spawning migrations (Fig. 

1). Direction of travel is implied by the receiver detection 

patterns relative to the full moon (open circles). During this 

period there were spawning aggregations of mutton snapper 

over Riley’s Hump in the Tortugas South Ecological Reserve 

(TSER) during full moons May-July, which strongly suggests 

these absences were associated with spawning activity (Fig. 2).

 Linear regression analysis revealed that log-transformed 

proximity of home range center to RNA boundaries was a 

significant predictor of time spent outside of the RNA for red 

grouper, accounting for 40% of the variance in time spent 

outside the reserve. Average home range sizes were 1.13 ± 0.86 

km2

 (±SE) for black grouper (n = 2, 57-75 cm TL), 1.95 ± 0.33 

km2 for red grouper (n = 33, 45-66 cm TL), 3.19 km2 for gray 

snapper (n = 1, 54 cm TL), 7.64 km2 for mutton snapper (n 

= 1, 70 cm TL), and 2.51 ± 0.17 km2 (n = 4, 48-55 cm TL) for 

yellowtail snapper. Estimated home range size varied considerably between individuals for red grouper (0.01 to 5.76 km2

) 

and black grouper (0.27 to 1.99 km2), but was relatively consistent for yellowtail snapper (2.17 to 2.91 km2

). 

The majority of observed movements of groupers and 

snappers out of the RNA were into the North TER, suggesting the importance of this reserve network as a buffer against 

fishing pressure. The detected movements were biphasic: 

off spawning period; and, during spawning. Generally, the 

distance and frequency of movements were greater during spawning suggesting an increased vulnerability of fishes 

during this time. The RNA may provide some protection to 

mutton snapper that subsequently spawn in the TSER. Finally, 

our observations of extensive movement by both a greater 

amberjack and a tiger shark suggest that the RNA may afford 

important short-term protection for these mobile species. A 

spatially synoptic network of NTMRs would be required to 

protect for these species throughout their lifetimes.

Future Work

Refinement and publication of an individual-based localizing 

tendency model of reef fish movement is needed. It should be 

parameterized from the fine-scale acoustic telemetry data and 

integrated into a Spatial Management Performance Assessment simulation model for reef fish populations developed 

to evaluate quantitatively performance of no-take marine 

reserves in the Dry Tortugas, Florida. 

Figure 2. Receiver detections of an acoustically-tagged 70 cm TL mutton snapper in the RNA portion of Dry Tortugas National Park. 

Routine movements are shown during the period of April 25 to October 10, 2007. Specific spatial movements out of and back into the 

array are shown for the periods May 26-June 12 and June 28-July 6, 2007. These two periods correspond to the vertical bars highlighted 

in Figure 1.
12

Investigator

Kristen M. Hart

U.S. Geological Survey, Davie Field Office

For further information contact: kristen_hart@usgs.gov

Project Description

Dry Tortugas National Park (DRTO) harbors several key foraging and nesting habitats that are important for endangered 

marine species, including federally protected marine turtles. 

Threatened loggerheads (Caretta caretta) forage in hard bottom areas on spiny lobsters and crabs, endangered hawksbills (Eretmochelys imbricata) forage on reefs and consume 

sponges, and endangered green turtles (Chelonia mydas) 

graze on seagrasses and marine algae. 

To characterize the population of sea turtles in DRTO and 

quantify the proportion of time individuals of each species 

spend in the RNA compared to other areas of the park, I am 

conducting a turtle capture, tagging, and tracking project. 

Turtle captures are accomplished by intercepting reproductive females on nesting beaches and capturing turtles in the 

water. Using satellite and acoustic telemetry techniques, I 

am determining daily locations and movement patterns for 

tagged turtles, calculating home ranges and core use areas, 

and statistically summarizing the extent of overlap of these 

areas with that of the RNA. 

Accomplishments

During 2008, I tagged six turtles (three loggerheads on East 

Key, three hawksbills from Bird/Long Key flat) with satellite 

and acoustic tags; three of these tags are still transmitting 

daily location data as of November 11, 2009. I also captured, 

tagged, and sampled 23 juvenile green turtles on the Bird/

Long Key flat. In May 2009, I delineated the 50% core use 

areas for loggerheads and hawksbills tagged in 2008 to create transects through these areas to be photographed in June 

2009 using the USGS’s underwater Along Track Reef Imaging 

System (ATRIS). In June 2009, I satellite-tagged four reproductive female loggerheads and six subadult and adult green 

turtles. To date, I have satellite tagged 16 sea turtles (seven loggerheads, six greens, three hawksbills) and acoustic tagged 25 

turtles (10 loggerheads, 13 greens, two hawksbills); 14 of these 

turtles are double-tagged with both satellite and acoustic tags 

(seven loggerheads, five greens, two hawksbills).

Preliminary Results

The size distribution for all 63 sea turtles captured (Fig. 1) in 

the park includes juvenile, subadult, and adult greens of both 

sexes; subadult and adult loggerheads of both sexes; and juvenile, subadult, and adult hawksbills (unknown sex). Green 

turtles were the most common species captured (N=49), 

followed by loggerheads (N=10) and hawksbills (N=4) (Fig. 

1). From October 2007 through August 2009, I observed 

more than 325 georeferenced sightings of sea turtles in various areas of the park. Satellite-tracking results indicated that 

loggerhead females tagged on East Key use core areas outside 

the RNA more frequently than areas within the RNA, and 

hawksbills captured near the Bird/Long Key flat used a core 

area that overlaps with the Natural/Cultural zone “bubble” 

(Fig. 2). Subadult and adult green turtles of both sexes were 

park residents, using an area of lush seagrass near North Key 

Harbor outside the RNA (Fig. 2). In contrast, adult female loggerheads were part-time residents in the park only from about 

May through July/early August. Juvenile/subadult hawksbills 

appeared to be full-time residents of the park, as two tagged 

individuals are each still resident after approximately 460 

tracking days. Migratory pathways and destination points 

RNA Performance Topic 2: Monitor the immigration and emigration of targeted species in the RNA

RNA Performance Topic 2 

Use of protected areas by threatened and endangered marine turtles in the 

Dry Tortugas

Figure 1. Size distribution of sea turtles captured and sampled 

May 2008-August 2009 in Dry Tortugas National Park (N=63).

0

2

4

6

8

10

12

0-10

11-20

21-30

31-40

41-50

51-60

61-70

71-80

81-90

91-100

101-110111-120121-130

# Sea turtles

Straight Carapace Length (SCL, p), in cm

hawksbill

green

loggerhead
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 13

of satellite-tagged loggerhead females indicated that three 

of seven tagged turtles migrated to and took up residence in 

the Bahamas, whereas four migrated to the southwest coast 

of Florida. One hawksbill departed DRTO after 265 days of 

residence and travelled to the north coast of Cuba, where it 

was harvested by fishermen. As of November 11, 2009, I have 

logged 3,262 turtle tracking days (1,446 days for loggerheads, 

618 days for greens, and 1,198 days for hawksbills). In 2009, 

I recaptured 13/29 or 44.8% of juvenile greens (21-50 cm 

straight carapace length (SCL) size class) that were originally 

captured and tagged in August 2008. For these 13 juveniles, 

mean SCL at initial capture was 34.8 cm (5.01 SD; range 26.8-

42.6 cm) and mean annual growth rate was 3.7 cm SCL (2.56 

SD; range 0.9-10.2 cm). Diet of juvenile greens was primarily 

Thalassia testudinum.

Future Work

In 2010-2011, I plan to conduct nesting beach work and inwater turtle captures to increase the sample sizes of tagged/

sampled individuals for all three species and study the internesting habitat where reproductive females spend their time 

between nesting events. I will specifically plan capture and 

tagging efforts to assess (1) whether reproductively mature 

female loggerheads nesting on Loggerhead Key use the same 

internesting habitat (50% core use area) outside the RNA as 

that used by the seven loggerheads previously tagged on East 

Key in 2008 and 2009, (2) where nesting green turtles from 

both East Key and Loggerhead Key spend their time in the 

internesting interval (and whether this area is in the RNA), and 

(3) where additional hawksbills may be found. I also expect 

to be able to determine, through satellite tracking, whether 

reproductive female green turtles nesting at DRTO are resident within the park, or instead migrate elsewhere after the 

nesting season. I have three acoustic data-downloading trips 

planned each year for the next 2 years to service and maintain 

my seven deployed acoustic receivers. I will continue catching 

juvenile greens (and hopefully more hawksbills) in the shallow flat around Bird/Long Key and refine growth rate estimates for these young turtles. Additionally, I will process all 

lavage samples, conduct isotope analysis, and conduct genetic 

analysis to determine stock structure for each species. I will 

continue to update information on residence times for turtles 

residing in and using DRTO. I will also continue to work with 

ATRIS to plan mapping and habitat characterization efforts 

in turtle internesting habitat and other turtle core use areas 

in the park. The combined data sets will provide insight into 

(1) the effectiveness of the RNA for protecting threatened and 

endangered marine turtles and their requisite habitats, (2) 

the condition of those habitats (i.e., seagrass beds), and (3) 

the development of more effective decision-support tools to 

manage coral ecosystems adaptively.

Figure 2. Core use areas (50% kernel density estimates, KDE) for satellite-tagged sea turtles in Dry Tortugas National Park, 2008-2009. 

Colored zones represent the overlap of core use areas for N=3 hawksbills (orange) and N=7 loggerheads (green). Gray zones represent 

individual turtle 50% KDEs for male (dark gray) and female (light gray) green turtles tagged in August 2009. Green turtle core use areas 

are shown for individuals because there was no overlap of all six individual 50% core use areas for this species.
14

Investigators

Jerald S. Ault and Steven G. Smith

University of Miami, Rosenstiel School of Marine and 

Atmospheric Science

For further information contact: jault@rsmas.miami.edu

Project Description

The goal of this study is to improve creel census design performance and evaluate regional fishery-dependent and independent databases as they relate to Research Natural Area (RNA) 

implementation in Dry Tortugas National Park (DRTO).

Accomplishments

This study commenced in the fall of 2009. Working with park 

personnel we have obtained the historical creel survey database for DRTO dating back to 1981. These data have been 

preliminarily analyzed for trends in catch-per-unit-effort, a 

measure of abundance, for reef fish taxa. These historical data 

will be used to refine the creel survey design to allow efficient 

estimation of fishery statistics and trends as they relate to RNA 

implementation. The new design will be compatible with the 

regional Marine Recreational Fisheries Statistics Survey program and further calibrated against fishery-independent reef 

visual census data.

Preliminary Results

Data have been organized to evaluate the following conditions to facilitate design developments:

6 Spatial and temporal distribution of recreational fishing effort in the park

6 Relationship of catches to the distribution of reef habitats 

within the park

6 Range of vessel sizes and efficiencies operating within park 

waters

6 Range of species targeted by anglers.

Recreational fishers in DRTO captured a wide variety of reef 

fish taxa during the time periods of 1981-84 and 2000-04 

(Table 1). Catches were dominated by grouper and snapper 

species. Historically, creel observers recorded catches of two 

types: (1) captured and kept; and, (2) captured and released. 

The percentage of positive catch trips in which individuals were captured and then released increased between the 

two time periods for grouper and snapper taxa. This may 

be related to management implementation and subsequent 

changes in legal capture size for these taxa in the intervening 

years between the two time periods.

Future Work

We expect these analyses to be completed by fall of 2010 

and will include recommendations for implementing the 

improved creel survey design in DRTO.

RNA Performance Topic 3: Monitor changes in species composition and catch rates of exploited species throughout the surrounding 

region

RNA Performance Topic 3 

Extended creel census development for Dry Tortugas National Park

Graysby. Photo by Jiangang Luo, Univ. of Miami/RSMAS.

Most recreational fishing data are collected from interviews 

of anglers (creel surveys) who land or fish at Garden Key, Dry 

Tortugas National Park. NPS photo.
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 15

Table 1. Preliminary analyses of the percentage of reef fishing trips sampled in the Dry Tortugas National Park creel survey that 

captured fishes of a variety of taxa groups. Positive catch trips were categorized as follows: caught and kept, caught and released, 

and the combined total. 

1981-84 (n=484 reef trips) 

% of Positive Catch Trips

2000-04 (n=229 reef trips)

% of Positive Catch Trips

Taxa Total Kept Released Total Kept Released

Groupers

Graysby 0.6 0.4 0.6 0.0 0.0 0.0

Coney 0.2 0.0 0.2 0.0 0.0 0.0

Rock hind 0.0 0.0 0.0 0.9 0.4 0.4

Red hind 0.4 0.2 0.2 0.0 0.0 0.0

Goliath grouper 0.8 0.0 0.8 1.8 0.0 1.8

Red grouper 19.0 16.9 14.1 69.9 63.8 59.8

Nassau grouper 1.2 1.0 0.6 0.9 0.9 0.9

Black grouper 8.5 6.8 3.5 26.6 21.8 21.0

Gag 1.0 0.8 0.4 4.4 3.1 2.6

Scamp 0.8 0.8 0.2 3.1 2.6 1.3

Yellowfin grouper 0.6 0.4 0.2 0.0 0.0 0.0

Unidentified groupers 32.0 28.5 17.8 1.3 1.3 0.4

Snappers

Mutton snapper 9.7 9.5 0.4 27.5 27.1 9.6

Schoolmaster 0.0 0.0 0.0 0.9 0.4 0.4

Gray snapper 46.7 41.9 22.1 18.8 17.0 10.5

Lane snapper 0.8 0.8 0.0 4.8 3.9 3.1

Yellowtail snapper 25.6 21.7 15.9 65.5 56.3 54.6

Unidentified snappers 11.8 9.3 6.8 3.9 3.1 0.9

Grunts

Margate 0.4 0.4 0.0 0.9 0.9 0.0

French grunt 0.8 0.0 0.8 1.3 0.0 1.3

Spanish grunt 0.4 0.0 0.4 0.4 0.4 0.0

Sailors choice 0.2 0.2 0.0 0.0 0.0 0.0

White grunt 1.7 1.2 0.6 4.4 3.1 2.2

Bluestriped grunt 3.9 2.7 2.3 0.9 0.0 0.9

Unidentified grunts 16.3 7.0 13.2 3.1 1.3 2.2

Other Reef Fishes

Boxfish spp. 1.0 0.0 1.0 0.0 0.0 0.0

Damselfish spp. 1.0 1.0 0.0 0.0 0.0 0.0

Great barracuda 18.8 3.9 17.2 16.2 0.9 15.7

Jack spp. 15.1 9.1 10.1 18.3 8.7 13.1

Parrotfish spp. 1.7 0.2 1.5 1.3 0.0 1.3

Porgy spp. 13.6 9.7 7.0 3.9 2.6 1.8

Shark spp. 6.2 1.7 5.4 14.9 0.4 14.4

Triggerfish spp. 1.0 0.8 0.4 1.8 0.4 1.3

Wrasse spp. 3.3 2.1 1.5 0.4 0.4 0.0
16

Investigator

Dave Walton

National Park Service, Dry Tortugas National Park

For further information contact: Dave_Walton@nps.gov

Project Description

The General Management Plan Amendment of Dry Tortugas 

National Park (DRTO) dictates that a vessel permit plan be 

instituted to protect the resource, minimize human impacts, 

and monitor use. The goal and purpose of the plan is to provide increased protection specifically to the Research Natural 

Area (RNA), the visitor, and to the marine resources outside 

the RNA. The permit system will achieve this goal by providing reliable information to the public about the significance 

of the delicate resources and appropriate practices for RNA 

visitation. The permit system will afford a greater level of 

staff and visitor interaction that will enhance safe boating 

practices, resulting in a reduction of incidents. The system 

will provide park managers reliable information about public 

use and the ability to articulate carrying capacity at recreational dive and snorkel sites. Permit requirements apply to 

all recreational vessels, commercial fishing vessels, and vessels 

operating under a Commercial Use Authorization. It does not 

apply to vessels that are simply transiting through the park. It 

also does not apply to vessels greater than 50 m that require a 

Special Use Permit. Free of charge, a permit application can 

be obtained over the internet through the DRTO website, in 

person at the Key West Eco-Discovery Center or Garden Key 

administrative office, or on the water from park patrol staff.

Accomplishments

The permit system was instituted in September 2009. DRTO 

staff developed an electronic permit system that is utilized 

by the park to generate permits and maintain user statistics. 

DRTO staff has been contacting vessels in the park and issuing permits. A press release has been drafted to inform the 

public of the new requirement. It will be released when the 

electronic permit application is added to the DRTO website. 

The permit will identify park users as well as their activities in 

the park. Presently, every permit holder is a given pamphlet 

concerning the significance of the Research Natural Area, as 

well as a pamphlet that contains the rules and regulations of 

the park. 

Preliminary Results

The program has just begun but has support from the boating public. A social science investigation will be conducted 

using names and addresses that are obtained via the permit 

database.

Future Work

Funding to manage the permit system is being pursued. A 

position to be located at the Eco-Discovery Center on Key 

West is being sought to manage the system.

RNA Performance Topic 3: Monitor changes in species composition and catch rates of exploited species throughout the surrounding 

region

RNA Performance Topic 3 

Dry Tortugas National Park vessel permit system

Commercial fishing vessels anchored in the harbor near Garden Key, Dry Tortugas National Park. Photo by Joy Brunk, NPS.
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 17

Snorkelers over a coral reef near Garden Key, Dry Tortugas National Park. Photo by Brett Seymour, NPS.
18 RNA Performance Topic 4: Evaluate the effects of RNA implementation on the marine benthic biological communities

Investigators

Douglas Morrison1, Meredith Meyers2, and Rob Ruzicka3

1

National Park Service, Dry Tortugas National Park 

2

University of Georgia, Odum School of Ecology

3

Florida Fish and Wildlife Conservation Commission, Fish 

and Wildlife Research Institute

For further information contact: Douglas_Morrison@nps.gov

Project Description

Boat anchoring will not be permitted in the Research Natural 

Area (RNA). Therefore, SCUBA diving and snorkeling activities in the RNA will be concentrated at designated dive sites 

with mooring buoys. Multiple assessments around the world 

have determined that heavy diving activity on coral reefs, in 

most cases greater than 5,000-6,000 divers per year per site, 

have damaged corals. Monitoring the potential effects of diving activity on corals at RNA dive sites is needed.

A RNA resource stewardship target is to have no long-term 

effects of diving activities on corals. The primary performance 

measures are damage to and loss of branching stony coral species, especially Endangered Species Act (ESA)-listed Acropora 

species. Secondary performance measures are damage to and 

loss of plating and foliose (leaf) type and mound, boulder, and 

encrusting type stony coral species. Stony coral species with 

branching morphology (e.g., Acropora species) are most susceptible to damage by diving activities. Acropora species were 

once very abundant but are now relatively uncommon in Dry 

Tortugas National Park (DRTO), and thus are at highest risk. 

Foliose and plating stony corals (e.g., Agaricia species) are 

more susceptible than mound, boulder, and encrusting type 

stony corals (e.g., star and brain corals). 

This project is an element of the DRTO Coral Reef Benthic 

Communities Assessment Program and is conducted jointly 

with the Fish and Wildlife Research Institute (FWRI) of the 

Florida Fish and Wildlife Conservation Commission and the 

University of Georgia as a FWRI subcontractor, via a National 

Park Service cooperative agreement. 

A fully replicated Before–After-Reference–Impact sampling design is used to measure and compare contemporaneous changes at RNA reef dive sites and equivalent reference 

sites with no or little diving activity. Four RNA dive sites, Texas 

Rock, Davis Rock, The Maze, and Off-Ramp, and three reference sites, Mayer’s Peak, Temptation Rock, and Perfection, 

will be assessed annually for stony coral damage and annually 

or biennially for coral loss. Damage, a near-term effects measure, is quantified as the percentage of sampled coral colonies broken or abraded. Two coral damage survey methods 

are used at most sites: eight randomly located 10- x 2-m belt 

transects and four fixed 22- x 2-m belt transects. Coral loss, 

a longer-term measure, is determined by calculating changes 

in live coral percent cover with videographic techniques at 

the four fixed 22- x 2-m belt transects at each site, except 

Perfection and Off-Ramp. The fixed transects were not used 

at Perfection and Off-Ramp sites because of their small size. 

Separate Acropora species colony damage surveys are also 

conducted.

Accomplishments

Stony coral damage and percent cover data were collected at 

all sites in 2009, before dive site mooring buoys were installed 

and the RNA no-anchor regulation was instituted. Thus, preimplementation baseline data at all sites has been established. 

Preliminary Results

Pre-implementation stony coral damage data collected in 

2009 are summarized in Tables 1, 2, and 3; 4,500 coral colonies 

were surveyed. Coral damage, most likely due to storms, was 

observed at all sites. ESA-listed Acropora cervicornis (staghorn coral) is relatively common at Perfection and Off Ramp 

sites. None of the 50 staghorn colonies surveyed at Perfection 

were damaged (0.0% damage); one of the 44 staghorn colonies observed at Off Ramp was damaged (2.3% damage). The 

2009 videography used to determine live coral percent cover 

is still being analyzed.

RNA Performance Topic 4 

Assessing the effects on corals of SCUBA and snorkeling use at Research 

Natural Area designated (mooring buoy) dive sites

Damaged finger coral colony. Photo by Douglas Morrison, NPS.
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 19

Future Work 

RNA dive site mooring buoys will be installed, and the RNA 

no-anchor regulation will be implemented before the 2010 

dive season (May through September). Stony coral damage surveys will be conducted in 2010, 2011, and future 

years, preferably near the end of the dive season. Currently 

we have only two years of funding for the more expensive, 

time-consuming, and logistically complex video surveys 

used to measure live coral percent cover. We will use these 

funds judiciously. For example, if the video surveys cannot be 

performed near the end of the 2010 dive season for logistic 

reasons, we will wait until 2011 to do them (this is a longerterm effects measure). Diver/visitor use data for the RNA dive 

sites are essential for evaluating potential ecological effects of 

diving. These data will be collected via the permit system (see 

Topic 6). This system will need to be operating by the 2010 

dive season.

Table 1. Percent damaged stony coral colonies, by growth form, at future RNA dive sites and RNA reference sites in 2009 pre-implementation random belt transect surveys. Values are mean ± SD.

Table 2. Cumulative data from 2009 pre-implementation stony coral damage surveys, using random transect method, at future RNA 

dive sites and RNA reference sites.

Table 3. Cumulative data from 2009 pre-implementation stony coral damage surveys, using fixed transect method, at future RNA dive 

sites and RNA reference sites.

Stony Coral 

Colonies Surveyed

RNA Dive Sites RNA Reference Sites

Texas Rock Davis Rock The Maze Mayer’s Peak Temptation Rock

Damaged 9 9 4 8 5

Total 503 441 415 423 330

% Damaged 1.8 2.0 1.0 1.9 1.5

Stony Coral

Colonies 

Surveyed

RNA Dive Sites RNA Reference Sites

Texas Rock Davis Rock The Maze Off Ramp Mayer’s Peak Temptation 

Rock Perfection

Damaged 14 17 5 8 8 8 7

Total 475 315 359 162 406 379 224

% Damaged 2.9 5.4 1.4 4.9 2.0 2.1 3.1

Stony Coral 

Growth Form

RNA Dive Sites RNA Reference Sites

Texas Rock Davis Rock The Maze Off Ramp Mayer’s Peak Temptation 

Rock Perfection

Branching 5.0 ± 6.6 14.8 ± 3.6 3.5 ± 4.4 5.7 ± 2.7 3.8 ± 3.0 2.3 ± 2.8 3.4 ± 4.7

Plating/

Foliose None 0.0 ± 0.0 0.0 ± 0.0 None None None None

Mound/

Encrust 0.6 ± 1.6 0.0 ± 0.0 0.0 ± 0.0 1.4 ± 3.8 0.0 ± 0.0 0.0 ± 0.0 1.6 ± 4.2

Total 3.1 ± 3.8 5.4 ± 2.7 1.1 ± 1.5 4.4 ± 2.6 2.0 ± 1.7 1.7 ± 2.0 3.0 ± 3.8

Setting up a fixed belt transect for coral damage survey on 

RNA designated dive reef/site (Davis Rock). Photo by Douglas 

Morrison, NPS.
20

Investigators

Jeff Miller, Matt Patterson, Andrea Atkinson, Rob Waara, 

Andy Estep, Andy Davis, Marilyn Brandt, and Ben Ruttenberg

National Park Service, South Florida/Caribbean Inventory 

and Monitoring Network 

For further information contact: William_J_Miller@nps.gov 

Project Description

The South Florida / Caribbean Network (SFCN) is monitoring coral reef communities within Dry Tortugas National Park 

to determine whether the percent cover of stony corals, algae 

(turf, coralline, macroalgae), octocorals, and sponges; coral 

species diversity; coral community structure; and rugosity 

are changing through time within selected coral reef sites and 

inside and outside the newly created Research Natural Area 

(RNA). 

SFCN began monitoring a site at Bird Key Reef in 2004 

and added a second adjacent site in 2005 (Fig. 1). The Bird 

Key (19,765 m2

) and Bird Key-North (25,642 m2) sites are located within a 2-km-long spur-and-groove reef structure and 

were selected for management interest and to compare with 

historical work. Each site consists of 20 permanent, randomly 

selected 10-m transects that are monitored with underwater 

video, capturing 25-35 non-overlapping video images, and 

identifying 10 random points per image (250-350 points/

transect). Percent cover of living coral by species, 

macroalgae, turf algae, crustose coralline algae, 

octocorals, and sponges are calculated. Data 

on coral disease, long-spined sea urchins 

(an important algal grazer), rugosity, and 

water temperature also are collected. The 

Bird Key site straddles a boundary with 

12 transects falling within the RNA and 

8 transects plus 20 transects from Bird 

Key-North site falling inside the traditional Adaptive Use Area.

Monitoring has been expanded to 

include randomly selected sites to complement monitoring at Bird Key Reef. The expansion allows 

a broader assessment of trends in coral reef communities 

(with an initial 5% stony coral cover in waters from 2 to 20 

m in depth) in the park and comparison of trends inside and 

outside the Research Natural Area. These sites are smaller, 

consisting of four 10-m transects providing a cost-effective 

trade-off between evaluating more sites throughout the park 

with effort at a site.

Accomplishments

SFCN staff have annually monitored the 40 transects across 

the two Bird Key and Bird Key-North sites and analyzed the 

results. SFCN investigated 157 randomly selected, potential 

sites using a rapid habitat assessment method that involved 

recording benthic cover in the field every 0.5 m along four 

20-m transect tapes. In 2008, SFCN installed 18 sites that 

met the criteria of having a minimum of 5% initial stony coral 

cover (as determined by the rapid habitat assessment) and 

being from 2 to 20 m in depth. Nine sites are inside the newly 

established Research Natural Area and nine are outside. 

Video monitoring on these transects was conducted in 2008 

and 2009. 

RNA Performance Topic 4: Evaluate the effects of RNA implementation on the marine benthic biological communities

RNA Performance Topic 4 

Coral reef community monitoring at Bird Key Reef and sites inside and 

outside the Research Natural Area at Dry Tortugas National Park

Figure 1. Map of SFCN coral monitoring sites in Dry Tortugas National Park 

showing sites at Bird Key and Bird 

Key-North installed in 2004 and 2005 

respectively and 18 random sites installed in 2008.
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 21

Staff from SFCN were joined by the University of MiamiRSMAS/University of North Carolina Southeast Florida Coral 

Reef Evaluation and Monitoring Program (SCREAM) team, 

who also conducted their coral, sponge, and, algal monitoring protocol on the SFCN transects, allowing comparison of 

methods and the integration of SFCN permanent sites with 

SCREAM team random sites surveyed as part of RSMAS/

National Oceanic and Atmospheric Administration (NOAA) 

fish monitoring. SFCN collected more than 250 randomly 

chosen accuracy assessment points throughout the park to 

evaluate the accuracy of a newly created benthic habitat map 

contracted by the Florida Fish and Wildlife Research Institute 

(FWRI) in partnership with SFCN.

Preliminary Results

Bird Key Reef: Monitoring during 2004-2009 indicated a significant downward trend in stony coral cover at the Bird Key 

site from 13.2 to 10.6% (p<0.0001) but the decrease in coral 

cover at Bird Key-North (11.0 to 9.7%) was not statistically 

significant (Fig. 2). This decrease is a concern as FWRI monitoring data collected using similar methods on selected transects located within the Bird Key study site show stony coral 

cover in 1999 of more than 20%. The octocorals (e.g., sea 

fans, sea whips, etc.) also showed a significant 1-year decline 

at both sites from an average of 20.0% in 2005 to 8.9% cover 

in 2006 (p<0.0001) followed by a slight increase through 2009 

(we suspect the octocorals were damaged by four hurricanes 

that impacted the park in late 2005).

Random Sites: Results in 2008 from video-transect monitoring estimated stony coral cover at 3.6% (SE=1.0) outside 

the RNA and 7.8% (SE=3.4) inside the RNA (within areas 

of from 2 to 20-m in depth and estimated to be initially >5% 

coral cover using the rapid habitat assessment method). Two 

sites inside the RNA fell on an area of exceptionally high coral 

cover called “Loggerhead Forest” of which SFCN and park 

staff were largely unaware. Estimated stony coral cover at 

these sites was 29.9% and 20.3% respectively. Without these 

two sites, coral cover inside the RNA at the remaining sites 

was 2.8% (SE=0.5). Analysis of 2009 video data is pending.

During June and July 2008, SFCN staff observed abovenormal levels of white plague disease, a coral disease syndrome that results in partial or full mortality of affected coral 

colonies. In response, SFCN organized a return trip in July 

2008 with coral disease experts from the U.S. Coral Disease 

and Health Consortium and George Mason University. 

Affected sites were resurveyed and tissue samples collected 

from colonies with active disease. Initial attempts to isolate 

disease agents were unsuccessful, but further analysis is 

pending.

Future Work

SFCN staff are refining the Coral Reef Monitoring Protocol 

and including sections on the random site monitoring design, 

revised coral disease monitoring procedures, Rapid Habitat 

Assessment procedure, and analysis and reporting procedures. A completed document is anticipated in 2010-2011. 

Staff will analyze the annual coral reef community data 

from the random sites for trends and will examine levels of 

variation to determine if sufficient statistical power exists to 

detect changes over time and differences between RNA and 

non-RNA areas of the park. A method comparison will be 

conducted between the SFCN video-transect method and the 

SCREAM team in-situ method on data collected simultaneously on the random site transects in 2008. 

Staff will work to improve the newly created benthic habitat map using a combination of 2009 interferometric side-scan 

SONAR data collected by Dr. Stan Locker of the University 

of South Florida in 2009, LIDAR data collected by the U.S. 

Geological Survey in 2004, accuracy assessment data, rapid 

habitat assessment data, and reef fish visual census data. The 

map will then be compared with the NOAA/UM-RSMAS reef 

fish visual census habitat map grid.

0

5

10

15

20

25

2004 2005 2006 2007 2008 2009 2010

% cover(+/- standard error) .

Stony coral and octocoral cover trends at 2 sites on Bird Key Reef

Coral: Bird Key

Coral: Bird Key North

Octocoral: Bird Key

Octocoral: Bird Key-North

Figure 2. Trends in percent live stony coral cover and octocoral 

(e.g., sea fans, sea whips) cover at Bird Key and Bird Key North 

monitoring sites, Dry Tortugas National Park.

Two SCREAM team divers conducting coral monitoring protocol 

on one of the NPS-SFCN coral monitoring transects. Photo by 

Rob Warra, NPS. 
22

Investigators

Ilsa B. Kuffner1, Valerie J. Paul2, Raphael Ritson-Williams2, 

T. Don Hickey1

, and Linda J. Walters3

1

U.S. Geological Survey 

2

Smithsonian Marine Station, Fort Pierce Florida

3

University of Central Florida, Department of Biology

For further information contact: ikuffner@usgs.gov

Project Description

The goal of the project is to examine trophic interactions 

and the important reef process of herbivory in Dry Tortugas National Park (DRTO). There is inadequate knowledge 

regarding the complex interactions between herbivores, the 

macroalgae they eat, and the stony corals that provide the carbonate structures that act as shelter for most reef organisms. 

The interdependency among these three main components of 

reef ecosystems is quite circular in nature, and the tidy recycling of resources (e.g., space, food) among them has been disrupted during the past century on a global scale. Many of the 

world’s experts believe this is largely a result of the cascading 

effects of overfishing. Coral reefs in the waters of the United 

States are some of the most degraded; overfishing combined 

with the Caribbean-wide die-off of the keystone herbivore, 

Diadema antillarum, are major contributing factors. Protection of reef resources in the United States within no-take 

zones has begun, and there is a critical need to document the 

changes in trophic relationships as protective measures are 

implemented. Because corals are the “ecosystem engineers” 

responsible for producing the topographically complex habitat that defines a coral reef, the perpetuation (or recovery) of 

reef-building corals is of foremost concern to resource managers. Our study aims to understand better the intricate balance 

among herbivores, macroalgae, and corals, and to determine if 

that balance can be restored in protected areas.

Accomplishments

The field work for this study took place during October 15-21, 

2007. We accomplished surveys at 18 sites, including 9 inside 

and 9 outside of the Research Natural Area (RNA) designated 

by the National Park Service in 2007. Sites were chosen 

randomly from a population of possible sites identified to 

fit the criteria of being in the 3- to 5-m depth stratum and 

contained within low-relief reef and hardbottom habitat 

(Fig. 1). We chose these criteria because (1) algal growth 

and herbivory are greatest within this shallow depth range, 

(2) these habitats are very abundant within the park (much 

more so than true coral reef habitat) in the desired depth 

range, and (3) other benthic monitoring efforts are focused 

on deeper coral reef habitat. We conducted detailed specieslevel surveys of macroalgae, scleractinian and gorgonian 

corals, herbivorous and exploited (e.g., grouper and snapper) 

fish species, urchins, and substratum rugosity (topographic 

complexity) at the chosen sites. Our work resulted in a high 

quality data set documenting the status of some important 

resources in the park and will serve as a valuable baseline 

for future comparisons in addressing change in and outside 

of the RNA within DRTO. This work was published in the 

conference proceedings of the 9th International Coral Reef 

Symposium in Ft. Lauderdale, Florida, “Reef communities in 

the Dry Tortugas (Florida, USA): Baseline surveys for the new 

no-take area,” and is at available at http://www.reefbase.org/

resource_center/publication/icrs.aspx. 

Preliminary Results

To understand the current community structure of some of 

the benthic habitats in DRTO, we conducted species-level 

surveys of macroalgae, coral diversity, herbivorous and game 

fishes, urchins, and substratum composition (e.g., rugosity) 

in shallow (3- to 5-m depth) low-relief reef and hardbottom habitats in October 2007. We had particular interest in 

the ecological process of herbivory inside and outside of the 

no-take RNA and in establishing a baseline to assess future 

changes to trophic functioning. Abundance of Diadema 

antillarum and herbivorous fish, percent cover of macroalgae, and species richness of corals and gorgonians at the 18 

randomly selected survey sites were not significantly different 

inside versus outside of the RNA. Coral cover was estimated 

to be between 1% and 5% at these sites. Mean density of D. 

antillarum ranged from 0.01 to 0.54 individuals per m2

, with 

11 of the 18 sites having a density above 0.10 individuals per 

m2

. Both D. antillarum density and coral species richness 

were positively correlated to rugosity of the substratum (Fig. 

2). D. antillarum density also was positively related to the 

percentage of the substratum composed of Acropora cervicornis rubble. Improved trophic functioning and increases in 

D. antillarum density can improve reef condition in the Dry 

Tortugas, and the RNA is an important management tool to 

achieve increases in reef resilience to global-scale stressors.

RNA Performance Topic 4

Trophic relationships on coral reefs of Dry Tortugas National Park: Inside and 

outside of the Research Natural Area

RNA Performance Topic 4: Evaluate the effects of RNA implementation on the marine benthic biological communities
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 23

Future Work

Pending funding, the survey could be conducted again in 2011 

(4 years after the initial survey) to see if any changes are occurring in the populations of exploited fishes, herbivores, algal 

communities, and corals. Changes in proportions of these 

ecosystem components could allow us to make inferences 

about trophic functioning in the reef system, and thus, assess 

the efficacy of the RNA in meeting the goal of restoring benthic communities through no-take protection.

Figure 2. Linear-regression plots of A) Diadema antillarum density (Ln transformed data) and B) scarid (parrotfish) abundance (no. 

cylinder-1) versus substratum rugosity at 18 sites within Dry Tortugas National Park.

Figure 1. Satellite mosaic of Dry Tortugas National Park with the locations of 18 randomly selected sites where in-situ 

surveys were conducted October 16 – 20, 2007. The “no-take” Research Natural Area is within the dashed lines in the NW 

quadrant of the park and does not include the area within the circle.
24

RNA Performance Topic 4 

Assessing the effects of creating the Research Natural Area no-anchor zone 

on seagrass meadows

Investigator

Douglas Morrison

National Park Service, Dry Tortugas National Park

For further information contact: Douglas_Morrison@nps.gov

Project Description 

Implementation of the Research Natural Area (RNA) in Dry 

Tortugas National Park (DRTO) creates a no-anchoring zone 

covering 46% of the park. This action should greatly reduce 

or eliminate any anchor damage to coral reef benthic, other 

hard bottom, and seagrass communities in the RNA. RNA 

resource stewardship targets are to eliminate anchor damage 

to RNA coral reefs and seagrass beds and to enhance recovery of RNA marine benthic communities from any previous 

anchor damage. This project is designed to detect changes in 

the abundance (percent cover) of seagrass and is a component 

of the DRTO Seagrass Communities Assessment Program.

A fully replicated Before–After-Reference–Impact sampling design is used to measure and compare contemporaneous changes at RNA seagrass sites and equivalent reference 

sites in the Historic Adaptive Use (HAU) Zone (anchoring 

permitted). Three shallow (less than 3 m deep) monitoring 

sites around Loggerhead Key (RNA, future no anchoring) and 

three shallow sites near Garden and Bush Keys in the HAU 

were randomly selected. One HAU site (GK-2) is on the periphery of the Garden Key visitor anchorage. Percent cover 

of seagrass and associated key benthic ecological attributes 

is measured using a 0.25-m2

 quadrat subdivided into 5% sections. About 20 haphazardly located quadrats are sampled annually at each site. Annual visual surveys for potential anchor 

damage, such as dragging anchor scars, are also conducted at 

each site (survey area about 5,000 m2

).

Accomplishments

Annual seagrass, associated macroalgae, and sea urchin 

assessments at the three Loggerhead Key sites (RNA, future 

no-anchoring) and three reference sites near Garden and 

Bush Keys in the HAU (anchoring permitted) have been 

conducted from 2005 through 2009. The RNA no-anchoring 

regulation has yet to be implemented. Hence, five years of 

pre-implementation baseline data have been established. 

RNA Performance Topic 4: Evaluate the effects of RNA implementation on the marine benthic biological communities

Park ecologist surveying seagrass meadow in the Research Natural Area of Dry Tortugas National Park. Photo by Melissa Memory, NPS.
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 25

However, all sites experienced statistically significant seagrass loss caused by four hurricanes in a 4-month period in 

2005; an unprecedented occurrence in the 130 year history of 

Tortugas science. As of May 2007, 19.7 hectares (48.7 acres) 

of seagrass meadows had been destroyed around Loggerhead 

and Bush Keys due to the 2004-2005 hurricanes and subsequent winter and tropical storms (Table 1). This loss is equivalent to nearly one-half of the terrestrial land (island) area in 

Dry Tortugas National Park. Additional seagrass loss from 

Hurricane Ike in September 2009 occurred at two RNA sites 

(LK-1 and LK-2). 

Future Work

It is anticipated that the RNA no-anchor regulation will be 

implemented in 2010. Thus, post-implementation monitoring 

will be conducted at the three RNA and three HAU seagrass 

sites in 2010 and 2011. Annual monitoring is planned to 

continue after 2011 because all sites are part of the Dry 

Tortugas National Park Seagrass Communities Assessment 

Project. Pre- and post- no-anchor implementation seagrass 

abundance data will be compared at each site.

Figure 1. Seagrass percent cover, before implementing no 

anchoring in the RNA, at (A) shallow RNA sites around Loggerhead Key [LK], and (B) shallow sites near Garden Key [GK] where 

anchoring is permitted [HAU Zone].

Example of hurricane (Charley, August 2004) damage to a seagrass meadow off Loggerhead Key in the RNA. There is a white 

one meter stick in the photo for size reference. Photo by Douglas 

Morrison, NPS.

Preliminary Results

Pre-implementation seagrass (all species combined) percent 

cover data are presented in Figure 1. No evidence of anchor 

damage at any RNA monitoring site has been observed in five 

years of pre-implementation surveys. Only two instances of 

probable anchor damage have been observed at the HAU 

sites, both at GK-2, which is on the edge of the Garden Key 

visitor anchorage. 

Island

Seagrass Area Seagrass Loss

April 2003 May 2007 2003-2007

Loggerhead Key 33.5 ha 26.5 ha 7.0 ha [17.3 ac] (20.9%)

Bush Key (north side) 31.9 ha 19.2 ha 12.7 ha [31.4 ac] (38.9%) 

East Key (1 km radius) 105.6 ha 75.8 ha 29.8 ha [73.6 ac] (28.2%)

Table 1. Seagrass loss from 2004-2005 hurricanes around selected islands in Dry Tortugas National Park (ha=hectares, ac=acres). Seagrass 

loss is calculated using satellite imagery.
26

Investigators

Theodore S. Switzer1, Alejandro Acosta1, Michael W. Feeley1, 

John Hunt1

, Sean F. Keenan1, Brett Pittinger1, David E. Hallac2, 

Douglas Morrison 2

, and Carole C. McIvor3

1

Florida Fish and Wildlife Conservation Commission, Fish 

and Wildlife Research Institute 

2

National Park Service, Dry Tortugas National Park

3

U.S. Geological Survey

For further information contact: Ted.Switzer@MyFWC.com

Project Description

In association with a trapping and hook-and-line study titled 

“Examining the efficacy of the newly established Research 

Natural Area (RNA) for protecting coral reef fishes within 

Dry Tortugas National Park (DRTO),” an opportunistic 

examination of reproductive potential of exploited reef fishes 

was conducted. In association with spring and fall trap and 

hook-and-line surveys, a small number of individuals (n = 10 

per family per season) were sacrificed for life-history studies. 

As part of these studies, a macroscopic examination of gonad 

tissues was conducted to assess whether gonads were in an 

advanced stage of development. If so, a sample of gonad tissue 

was preserved for further reproductive analysis.

Accomplishments

Biological specimens have been collected for snappers and 

groupers during spring and fall surveys for 2008 and 2009.

Preliminary Results

Specific catch data are unavailable at present because data 

entry and processing are currently ongoing. Biological 

RNA Performance Topic 5

Reproductive potential of exploited reef fishes within the newly established 

Dry Tortugas Research Natural Area and adjacent open-use areas

RNA Performance Topic 5: Assess reproductive potential of exploited species by evaluating egg production and larval dispersal

Mutton snapper (Lutjanus analis) on Acropora prolifera reef in Dry Tortugas National Park. Photo by Douglas Morrison, NPS.
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 27

specimens have been retained from a variety of snappers 

(primarily yellowtail snapper, gray snapper, and mutton 

snapper) and groupers (primarily red grouper, black 

grouper, and graysby) collected during spring and fall 

surveys conducted in 2008 and 2009. To date, we have yet to 

find evidence of individuals in either an advanced stage of 

development or post-reproduction, and so we do not have 

any estimate of reproductive potential or fecundity.

Future Work

Stratified-random trapping and hook-and-line surveys will be 

conducted in the RNA and open-use areas in spring and fall 

during both 2010 and 2011, and we will continue to examine 

gonad tissue for signs of reproductive development. Given 

the current level of biological sampling (n = 10 individuals per 

family per season), as well as the timing of current sampling 

efforts (late spring and early fall), it is unlikely that we will 

obtain sufficient data to determine the fecundity of reef fishes 

within DRTO. To do so will require either sampling during 

different seasons (i.e., late winter to early spring for groupers) 

or enhanced levels of biological sampling (i.e., for snappers).

Red grouper (Epinephelus morio). Photo by Brett Seymour, NPS.

Gray snapper (Lutjanus griseus). Photo by Brett Seymour, NPS.
28

Investigators

Michael W. Feeley, Alejandro Acosta, Theodore S. Switzer, 

John Hunt, Paul Barbera, and Danielle Morley

Florida Fish and Wildlife Conservation Commission, Fish and 

Wildlife Research Institute

For further information contact: Michael.Feeley@MyFWC.

com

Project Description

Snappers and groupers migrate long distances to specific sites 

to form spawning aggregations of hundreds to thousands 

of individuals at specific times of the year. Unfortunately, 

traditional fishery management strategies have not always 

accounted for the vulnerable nature of spawning events and 

these prime fishery targets are frequently overfished. Recent 

changes in fishery regulations have placed greater emphasis 

on marine protected areas (MPAs) to preserve reef habitat, 

enhance reef fish production, conserve functional ecosystem 

processes, and protect a certain proportion of the population. After years of over-exploitation, the Tortugas South 

Ecological Reserve (TSER) was established in 2001 to protect 

the mutton snapper spawning aggregation on Riley’s Hump 

and the surrounding deep-water habitat. Re-formation of the 

mutton snapper spawning aggregation has been documented 

since closure of the TSER to fishing, but little is known about 

adult reef fish movements in the region or the characterization of transient reef fish spawning aggregations at Riley’s 

Hump. Spatial and temporal rates of movement of acoustically tagged snappers and groupers are being measured in 

the Tortugas region, including annual spawning migratory 

movements between Riley’s Hump, the Tortugas Ecological 

Reserves, and Dry Tortugas National Park (DRTO), including 

the Research Natural Area (RNA). A multi-agency managed 

array of approximately 80 Vemco VR2 receivers will be used 

to assess habitat utilization patterns, residence times, migration patterns, and timing of multispecies aggregations. Results 

will assess the importance of habitat linkages between adjacent MPAs and provide information for an ecosystem-based 

approach to reef fisheries management.

Accomplishments

An array of 64 Vemco VR2 acoustic receivers was deployed 

in three phases between May and July 2008 in the Tortugas region. The array covers approximately 800 km2

 and is 

designed to capture small-scale movement and long-range 

migrations of fishes in water 5 – 50 m deep. In the first phase, 

32 VR2 receivers were placed within DRTO, including within 

and outside the borders of the RNA. The second phase was 

completed in June 2008, with 23 acoustic receivers placed 

throughout DRTO, the Tortugas North Ecological Reserve 

(TNER), and adjacent open-fished areas of the Florida Keys 

National Marine Sanctuary (FKNMS). The final nine receivers were set up in July 2008 on Riley’s Hump. All of our VR2 

receivers were successfully deployed and are operational on 

or near our proposed locations. This array is complemented 

by two collaborative acoustic telemetry projects in the region 

(approximately 20 VR2s); the Mote Marine Laboratory nurse 

shark project (Principal Investigator (PI): Dr. W. Pratt) and the 

U.S. Geological Survey sea turtle project (PI: Dr. K. Hart) (Fig. 

1). Extensive nurse shark and sea turtle data have been collected by the array in addition to valuable long-range movement information on lemon sharks tagged on the east coast 

of Florida near Jupiter. In addition, the presence of a solitary 

white shark near a snapper spawning aggregation was confirmed by a benthic video/acoustic recorder on Riley’s Hump 

in June 2009. During 2008 and 2009, selected reef fish species were tagged inside the TSER from the M/V Spree. All fish 

were surgically implanted with Vemco V16 coded transmitters in-situ to avoid barotrauma induced mortality associated 

with bringing fish to the surface after hook-and-line capture 

from relatively deep water (30 – 45 m).

RNA Performance Topic 5 

Immigration and emigration of selected reef fish species from the Research 

Natural Area to the Tortugas South Ecological Reserve

RNA Performance Topic 5: Assess reproductive potential of exploited species by evaluating egg production and larval dispersal

Mutton snapper spawning event in the late afternoon on Riley’s 

Hump. Photo by Chris Parsons.
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 29

Preliminary Results

Twenty-three mutton snapper, Lutjanus analis, and 8 groupers, including 3 black grouper, Mycteroperca bonaci, 2 Nassau grouper, Epinephelus striatus, and 3 red grouper, Epinephelus morio, were acoustically tagged within the TSER in 2008 

and 2009. The first complete year of acoustically collected 

movement data were downloaded in October 2009. Preliminary results indicate a possible corridor exists for the seasonal 

movements of mutton snapper between the DRTO/RNA and 

the TSER, providing a link between marine protected areas 

(Fig. 1). Individual mutton snapper have been documented 

making repeated migratory round trips (three or fewer trips 

per fish) of as far as 50 km to spawning grounds during the 

spawning season (May to August). Individual fish stay on the 

spawning grounds for as long as 10 days surrounding the full 

moon phase before returning to home forage territory within 

DRTO/RNA. Limited movement has been detected to the 

east or directly north to the TNER; however, one mutton 

snapper tagged at Riley’s Hump was detected in the TNER 

and later at Pulaski Shoals, a movement of 40 km in 2 days. 

Mutton snapper appear to emigrate from Riley’s Hump by the 

end of August, although possible residential mutton snapper 

have been observed there as late as October. A mutton snapper aggregation of thousands (about 4,000) was documented 

on Riley’s Hump in June 2009, along with small subgroups (60 

or fewer) of fish spawning in the late afternoon (about 4:30 

PM EST), 2 days after the full moon.

Future Work

Our current work primarily focuses on mutton snapper utilizing one known spawning site. There are potentially other 

ecologically and economically important species that may 

use Riley’s Hump as an aggregation site (i.e., black grouper) 

and potentially other regionally important spawning sites to 

be discovered. We are funded to acoustically tag fish within 

the TSER in 2010, and future efforts will emphasize tagging 

black grouper. Since multi-year transmitters were implanted 

in fish, we will continue to collect data on receivers through 

2011. Data analyses will establish the degree of connectivity 

between habitats and the network of management areas in the 

Dry Tortugas and determine the efficacy of current management zones. Information will help determine the migratory 

ability of fishes and determine the buffer space required to 

protect fish while in migration to and from a spawning site. 

Preliminary results from this study will be analyzed and a 

scientific presentation and peer-reviewed publication will be 

produced.

Figure 1. Map of the Dry Tortugas region indicating locations of acoustic receivers and offshore migration 

patterns of tagged mutton snapper (arrows).
30

Investigators

Jerald S. Ault, Jiangang Luo, and Steven G. Smith

University of Miami, Rosenstiel School of Marine and 

Atmospheric Science

For further information contact: jault@rsmas.miami.edu 

Project Description 

The goal of this study is to evaluate the expected physical 

transport and fate of reef fish eggs and larvae spawned in 

the Dry Tortugas region to the adjacent waters of the south 

Florida coral reef ecosystem. The study utilizes the Hybrid 

Miami Isopycnal Coordinate Ocean Model (HYCOM) physical oceanographic model along with information on spawning 

and larval life history characteristics of snapper-grouper reef 

fish species.

Accomplishments 

Work commenced on this project in fall 2009. We developed a 

computer interface to link the HYCOM model with a particle 

flux model to simulate larval transport. The model domain 

is the northern Caribbean Sea, Gulf of Mexico, and southRNA Performance Topic 5

Larval transport modeling from the Dry Tortugas

RNA Performance Topic 5: Assess reproductive potential of exploited species by evaluating egg production and larval dispersal

Figure 1. Distribution of “larval particles” at 15 days (light purple) and 30 days (red) simulated with HYCOM model current vectors 

starting from Riley’s Hump on June 15, 2008 at four depth layers: (a) surface; (b) 10 m; (c) 20 m; and (d) 30 m.
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 31

Figure 2. Distribution of “larval particles” at 15 days (light purple) and 30 days (red) simulated with HYCOM model current vectors 

starting from Riley’s Hump on July 15, 2008 at four depth layers: (a) surface; (b) 10 m; (c) 20 m; and (d) 30 m.

eastern United States with a grid spacing of 4 km. The model 

utilizes meteorological and oceanographic data that allow 

“real time” simulations of transport. Biological information 

including spawning timing and duration and larval phase 

durations was compiled for principal snapper and grouper 

species. Preliminary experimental design includes the release 

of thousands of passive larval particles at designated spawning locations, depths (0 to 30 m), and times (winter and 

spring-summer). The particles are continuously tracked for a 

period equal to the larval duration, and the outcome spatial 

distribution is evaluated. 

Preliminary Results

Preliminary Lagrangian simulations of larval drift patterns from a potential spawning site at Riley’s Hump using 

HYCOM model daily outputs are shown in Figures 1 and 2. 

Neutral passive particles were released at two different times, 

June 15, 2008 (Fig. 1) and July 15, 2008 (Fig. 2), and at 4 different depths. Outputs are shown 15 and 30 days after spawning simulations. For a summer-spawning animal with a larval 

duration of about 30 days, both the timing and depth appear to 

be critical factors in the outcome distribution of particles. For 

example, particles “spawned” at different times and depths 

had the potential of ending up on the West Florida Shelf, the 

Florida Keys, or on the Eastern Seaboard as far north as the 

South Atlantic Bight. 

Future Work 

Future research will involve running simulations for a more 

complete range of conditions including timing and depth of 

spawning, larval behavior, and tidal influence. 
32 RNA Performance Topic 6: Incorporate social sciences into the research and monitoring program

Investigator

David Loomis

University of Massachusetts, Human Dimensions of Marine 

and Coastal Ecosystems Program 

For further information contact: loomis@nrc.umas.edu

Project Description

This project surveys visitor demographics, attitudes, perceptions, and experiences of park resources among visitors who 

enjoy recreational boating, fishing, SCUBA diving, snorkeling, and other activities. In addition, the report will provide 

a geospatial assessment of geographic locations of these uses. 

The science plan calls for the identification of human factors 

contributing to behaviors and actions of park visitors that 

have significant impacts on resources and the success of the 

Research Natural Area (RNA). A better understanding of the 

human dimension will greatly inform adaptive management 

efforts by National Park Service (NPS) and the Florida Fish 

and Wildlife Conservation Commission (FWC) in evaluation 

of the RNA and other park management zones. By characterizing visitors’ ecological knowledge and perceptions, NPS and 

FWC will improve education and outreach messages, encourage compliance with fishing and anchoring regulations, and 

enable visitors to protect the resources they enjoy. The geospatial assessment and survey questions will help elucidate 

heavily utilized areas within the park, as well as highlight 

possible areas of user-group conflicts. Another component 

included in the survey instruments will address a travel-cost 

analysis to estimate the value of recreational benefits generated by marine ecosystems. Finally, NPS also seeks to measure 

visitor satisfaction and enjoyment after RNA implementation. 

The project is funded by the NPS service-wide recreational 

fee program and coordinated by the NPS Ocean and Coastal 

Resources Branch of the Natural Resource Program Center 

and Dry Tortugas National Park.

Survey data will be collected through visitor contact and 

mail and internet surveys. Separate surveys will be administered to visitors arriving either by commercial ferry or by private boats. Visitors will be contacted on-site and those agreeing to participate will complete a brief on-site contact sheet. 

The main survey questionnaire will be sent to these identified 

individuals within one month of being contacted and will be 

completed either by mail or internet.

RNA Performance Topic 6

A survey of visitor demographics, attitudes, perceptions, and experiences in 

Dry Tortugas National Park 

Tourist ferries docked at Garden Key in front of Fort Jefferson. Photo by Mike Ryan, NPS.
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 33

Accomplishments

Design of the survey questionnaires was completed. University of Massachusetts and NPS collaborated to develop the 

survey questionnaires and methodology. These efforts have 

improved understanding of the human dimension information needed for the project, as well as the survey methods 

needed for the unique conditions and visitor use patterns at 

this remote marine park. Separate survey questionnaires for 

ferry passengers and private boats were designed and completed in September 2008. These quantitative survey instruments were informed by similar research activities completed 

by the University of Massachusetts for the Florida Reef 

Resilience Program in 2007. In addition, prior research drawn 

from a wide array of social science literature and discussions 

with park management informed the design and format of 

specific questions. 

Progress was made toward Office of Management and 

Budget (OMB) approval and public commenting. Regulations 

under the Paperwork Reduction Act require review by OMB 

on social science surveys as well as two opportunities for 

public notice and comment. The initial public notice was published in the Federal Register on May 6, 2009. (Only one comment was received during the 60-day comment period.) The 

Investigator working with NPS staff submitted justifications 

and copies of the survey questionnaires required by OMB. 

Department of the Interior and OMB must review these materials before publication notice in the Federal Register of the 

second and final 30-day opportunity for public comment and 

before final approval.

Preliminary Results

Each survey instrument is unique because of differences in 

opportunities for visitors arriving by ferry at Garden Key and 

from private boats with greater access to marine resources. 

Each has an identical set of core questions followed by questions specific to primary recreational activity and location. 

The survey questionnaires will provide basic demographic 

information on the respondents, the frequency and extent to 

which they engage in different types of recreational activities, 

their experience levels as anglers, divers, or in other activities, 

their perceptions of the RNA, their views on the ecological 

health of resources and the relative impacts of environmental 

stressors and recreational activities, their preferred sources of 

information, and factors such as ecological health and visitor 

crowding that diminish their enjoyment. 

Future Work

Data collection will continue from February 2010 through 

December 2010. We will then enter the data and perform 

quality control checks during the period of December 2010 

and February 2011. A draft report will be prepared by May 

2011. The final report for the project will be completed by 

October 2011. 

An NPS ranger and visitor snorkel outside the moat wall at Fort Jefferson, Dry Tortugas National Park. Photo by Brett Seymour, NPS.
34 RNA Performance Topic 6: Incorporate social sciences into the research and monitoring program

Investigator

Dave Walton

National Park Service, Dry Tortugas National Park

For further information contact: Dave_Walton@nps.gov

Project Description

The primary law enforcement goals at Dry Tortugas National 

Park (DRTO) are to educate the public and enforce zones 

that do not permit anchoring and fishing. This includes an 

emphasis on enforcing fishing limits in areas where fishing 

is permitted, as well as enforcing laws that protect sensitive 

turtle, coral, and seagrass habitat. At DRTO, it also includes 

the protection of submerged cultural resources. 

Law enforcement also strives to minimize hazards that 

pose a threat to human health and safety. One of the most 

significant aspects of the DRTO law enforcement program is 

to provide education to the user group to build a greater understanding and appreciation of the values the park is working to perpetuate. Building the user group constituency will 

translate into a greater protection of the resource and more 

support for the programs.

Law enforcement must partner with neighboring agencies 

to be effective and maximize enforcement potential. DRTO 

currently partners with a wide range of state and federal law 

enforcement agencies and the military.

Law enforcement is able to account, several times a day, 

for visitor use in the Research Natural Area (RNA). Vessels are 

contacted on the water or, more frequently, when they return 

to Garden Key. Area closures are enforced as are prohibited 

activities in the Research Natural Area, such as fishing. Law 

enforcement personnel also make frequent contact with researchers to identify at-risk areas.

Accomplishments

DRTO was fortunate to be able to capitalize on information 

supplied by a confidential informant concerning illegal fishing activities in the park. DRTO used the information to collaborate with law enforcement personnel from the U.S. Fish 

and Wildlife Service. The goal for this case was to publicize 

that fishing illegally in the park has significant consequences. 

The case yielded jail time and forfeiture. The case also led 

to the largest lobster poaching case in Florida history, called 

“Operation Freezer Burn,” which was widely publicized. The 

case targeted one of the biggest threats to DRTO, which is 

overfishing. 

 There is also commercial pressure from fishing along the 

park and RNA boundary. A case was successfully made when 

a commercial trap line was placed along the boundary that 

was partially in the RNA. As a result of this case, trapping and 

commercial fishing are no longer occurring as close to the 

boundary. 

The majority of commercial fishermen and private boaters 

are contacted and briefed about the values of the resource and 

the rules and regulations that govern their use. This is often 

accomplished with pamphlets written in English and Spanish.

Partnerships with state and federal law enforcement agencies have been made. Deputization with the Florida Fish and 

Wildlife Conservation Commission is being pursued.

Preliminary Results

DRTO has a frequent turnover of law enforcement staff. 

Replacing a law enforcement ranger presently takes longer 

than 6 months. Once replaced, the training time required for 

the position to conduct effective enforcement is about a year. 

The park is frequently staffed below effective levels to execute 

its mission. As a result, the law enforcement actions described 

above are intermittent and dependent on staffing levels. Presently DRTO is relying on seasonal rangers that are limited to 

26 weeks of employment.

Future Work

Continue to develop collaborative relationships with state and 

federal law enforcement agencies and the military. Establish a 

Memorandum of Understanding with Florida Fish and Wildlife Conservation Commission to establish cross-deputization. Maintain the fiduciary agreement with the U.S. Department of Homeland Security for reimbursement of expenses 

related to illegal immigration that would otherwise detract 

from the NPS mission. Fund the hiring of enough rangers so 

that the loss of a position does not severely impact the entire 

program and will allow continuity of the protection function. 

Overcome housing limitations to provide adequate housing 

for needed staff. 

RNA Performance Topic 6 

Law enforcement in Dry Tortugas National Park
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 35

Law enforcement ranger spots a boat from the lighthouse on Fort Jefferson, Garden Key, Dry Tortugas National Park. Top photos by 

David Walton, NPS. Garden Key Harbor Light on top of Fort Jefferson overlooking a fishing boat anchored in the harbor. Bottom photo 

by Joy Brunk, NPS.
36 RNA Performance Topic 6: Incorporate social sciences into the research and monitoring program

Investigators

David L. Conlin1, Andres Diaz1, and Melissa Memory2

1

National Park Service, Submerged Resource Center 

2

National Park Service, Dry Tortugas National Park 

For further information contact: Dave_Conlin@nps.gov

Project Description

This project was designed to conduct current condition 

assessments of known submerged cultural resources in the 

park. Most sites had not been monitored since their discovery 

in the 1970s and 1980s, and implementation of the Research 

Natural Area (RNA) Submerged Cultural Resource Strategy called for baseline documentation and monitoring. The 

goals of the project were to gather baseline data on all sites 

and implement a subsequent monitoring program. The NPS 

Submerged Resource Center (SRC) led the condition assessments and provided training to park divers to develop internal capacity to continue site monitoring. In addition to the 

primary project goals, additional funding allowed follow-up 

investigation of magnetic anomalies discovered during magnetometer surveys by the SRC in the 1990s.

Accomplishments

6 The project achieved its primary goals by either completing condition assessments or determining that submerged 

resources could not be located at 43 sites listed in the NPS 

Archeological Sites Management Information System (ASMIS), including verifying or correcting location data

6 Added 10 sites to the ASMIS database

6 Captured numerous high quality digital and video images of RNA cultural and natural resources and park operations; these will be available for publications and outreach 

efforts

6 Trained the DRTO/EVER dive team on dive operations, 

conducting condition assessments, and underwater mapping techniques that can be used for cultural resource documentation, groundings, etc.

6 Developed a database of all corrected DRTO site data for 

development of the park’s cultural resource management/

compliance database

6 Provided training to maritime archaeologists from South 

Africa researching the history of the international slave 

trade, and set the groundwork for future collaborations on 

this topic of international importance.

Preliminary Results

All but one of the submerged cultural resources inspected 

in DRTO were in good condition. This relatively consistent 

baseline data should provide an opportunity to observe the 

long-term trends of RNA implementation on submerged cultural resources.

Future Work

The SRC plans to return in 2010 to try and relocate sites not 

relocated in 2009 (per ASMIS guidelines). Further investigation of known magnetic anomalies, as well as survey of 

deeper waters, is also planned. Maritime archaeologists from 

South Africa are planning to return to learn documentation 

techniques relevant to their research on the historical international slave trade. Continuation of site monitoring is planned 

for 2011.

RNA Performance Topic 6 

Submerged cultural resource condition assessment project

NPS divers assess cultural resource at Dry Tortugas National Park. 

Photo by Brett Seymour, NPS.
Implementing the Dry Tortugas National Park Research Natural Area Science Plan: The 3-Year Report 2010 37

National Park Service diver records information about a cultural resource near Garden Key, Dry Tortugas National Park. Photo by Brett 

Seymour, NPS.



North

DRY TORTUGAS 

NATIONAL PARK

RESEARCH

NATURAL

AREA

FLORIDA KEYS NATIONAL 

MARINE SANCTUARY

TORTUGAS ECOLOGICAL RESERVE

TORTUGAS NORTH

Naples 

Miami

Key West

Area of Detail

TORTUGAS ECOLOGICAL RESERVE

TORTUGAS SOUTH
South Florida Natural Resources Center

Everglades and Dry Tortugas National Park

950 N. Krome Ave, 3rd Floor 

Homestead, FL 33030-4443

www.nps.gov/ever/naturescience/sfnrc.htm

www.MyFWC.com