HOMING and SPATIAL USE of GAG GROUPER, Mycteroperca Microlepis

Home , Graysby, Mycteroperca, Mycteroperca microlepis

HOMING AND SPATIAL USE OF GAG GROUPER, Mycteroperca microlepis

BRIAN L. KIEL

A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE

UNIVERSITY OF FLORIDA

2004

Brian L. Kiel

To my parents

ACKNOWLEDGMENTS

I am very grateful to my wife, Patricia Mergo, for her love, patience, and support.

It’s been a journey and during this work-in-progress, my two children, Casey and Kaitlyn were born. I have truly enjoyed my time spent with them as a stay-at-home father as I have come to learn about the important things in life.

I would also like to thank my chairman, Dr. William J. Lindberg, for his patience, advice, constructive criticism, and offshore and financial support. Many thanks also go to the members of my committee, Drs. Debra Murie and Tom Frazer, for their patience, advice, and critical review that were necessary to help guide me to this point. I thank Dr.

Chris Sistrom of the U.F. Shands Hospital, Radiology Department, for statistical advice and expertise. To Loren Kellogg, Jim Loftin, Jason Hale, and Allen Heck, I also owe a great deal of gratitude for the long field days they endured to help complete this project.

Financial assistance was also provided by the Florida Fish and Wildlife

Conservation Commission, Marine Resources Grants Program (Grant No. MR-073), and the National Marine Fisheries Service MARFIN Program (Grant No. NA57FF0288).

TABLE OF CONTENTS

page

ACKNOWLEDGMENTS ...... iv

LIST OF TABLES...... vii

LIST OF FIGURES ...... viii

ABSTRACT...... x

CHAPTER

1 INTRODUCTION ...... 1

2 MATERIALS AND METHODS ...... 8

Suwannee Regional Reef System (SRRS)...... 8 Study Design...... 8 Telemetry Equipment and Tagging Methods ...... 10 Telemetry Relocation Techniques ...... 12 Gag Spatial Utilization ...... 13 Individual Displacements of Ultrasonically Tagged Gag...... 13 Mass Displacement Experiments...... 14 FLOY Tagging ...... 14 Fish Traps and Trapping...... 14 Mass Displacement Trials ...... 15 U/W Surveys ...... 16 Statistical Analysis ...... 16

3 RESULTS...... 19

Gag Spatial Utilization ...... 19 Hourly Tracking ...... 21 Tracking session #1...... 22 Tracking session # 2...... 23 Tracking session # 3...... 24 Individual Displacements of Ultrasonically Tagged Gag...... 25 Mass Displacement Experiments and U/W Surveys ...... 31 Trial 1: 3000 and 4000 Meter Displacements ...... 32

v Trial 2: 2000 and 3000 Meter Displacement...... 33 Combined Trials ...... 34

4 DISCUSSION...... 61

Spatial Utilization ...... 61 Adaptive Significance...... 63 Homing Mechanisms...... 65 Fisheries Management Implications...... 67 Future Work...... 68

LITERATURE CITED ...... 70

BIOGRAPHICAL SKETCH ...... 79

LIST OF TABLES

Table page

1 Marine teleosts that are believed to possess homing ability...... 4

2 Relocation summary of 5 gag tagged with internally placed ultrasonic tags...... 19

3 Relocation summary of 9 gag tagged with externally placed ultrasonic tags...... 20

4 Gag sizes and dates tracked...... 21

5 Summary of diel tracking of ultrasonically tagged gag...... 22

6 Summaries of displacement distances and homing success...... 26

7 Homing status and size of individually displaced gag...... 27

8 Gag displacement distances, averages and range of sizes...... 32

9 Gag size categorized by mass displaced fish from both trials...... 33

10 Parameter estimates for the significant regression equation: ...... 35

vii

LIST OF FIGURES

Figure page

1 Map of Florida showing the mouth of the Suwannee River ...... 17

2 A Suwannee Regional Reef System (SRRS) array...... 18

3 Relocations of gag # 365...... 36

4 Relocations of gag # 456...... 37

5 Relocations of gag # 338...... 38

6 Relocations of gag # 2435...... 39

7 First hourly tracking session of two gag, # 2435 and # 02...... 40

8 Second hourly tracking session of gag # 2435...... 41

9 Third hourly tracking session of one gag, # 15...... 42

10 1000 meter displacement of gag # 10...... 43

11 2000 meter displacement of gag # 11...... 44

12 3000 meter displacement of gag # 15...... 45

13 3000 meter displacement of gag #17...... 46

14 Relocations of gag # 01...... 47

15 233 meter displacement of gag # 05...... 48

16 300 meter displacement of gag # 07...... 49

17 300 meter displacement of gag # 06...... 50

18 450 meter displacement of gag # 08...... 51

19 Relocations of gag # 08...... 52

20 600 meter displacement of gag # 09...... 53

viii 21 1000 meter displacement of gag # 03...... 54

22 Relocations of gag # 15...... 55

23 Relocations of gag # 17...... 56

24 4000 meter displacement of gag # 13...... 57

25 4000 meter displacement of gag # 18...... 58

26 8000 meter displacement of gag # 12...... 59

27 Prediction probabilities of gag homing over displacement distances of 0, 2000, 3000, and 4000 meters...... 60

Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science

HOMING AND SPATIAL USE OF GAG GROUPER, Mycteroperca microlepis

Brian L. Kiel

August 2004

Chair: William J. Lindberg Major Department: Fisheries and Aquatic Sciences

The homing ability and spatial use of gag grouper, Mycteroperca microlepis, in the northeastern Gulf of Mexico were studied between June 1997 and November 1998.

Fourteen ultrasonically tagged gag were relocated to determine spatial area usage (0.01 to

26.68 Ha) before displacing gag to determine homing ability. Gag maintained a close association with a small core area within the spatial area they occupy. Gag expressed strong site fidelity, as demonstrated by homing to capture locations. Ultrasonically tagged gag displaced up to 8000 m (N=18) demonstrated their capacity to home from as far as

3000 m. Homing can occur quickly. For example, three gag homed after displacements of

600, 1000, and 2000 m within 65, 134, 122 minutes, respectively. Homing ability was tested at 2000, 3000, and 4000 m using externally tagged gag (N=90) and SCUBA to record homing success. Gag can home up to 3000 m, but as displacement distance increases the probability of homing decreases.

x CHAPTER 1 INTRODUCTION

Movement is a behavioral response to an animal’s ecological circumstances and physiological needs. Movement helps integrate the acquisition of food, shelter, and mates, yet is often overlooked in ecological studies.

In addition to improving our understanding of animal ecology, knowledge of spatial requirements and movement patterns can play an important role in effectively managing fisheries and wildlife populations. By understanding species’ spatial requirements, the consequences of management practices (e.g., management areas, preserves, and sanctuaries) might be more accurately predicted. For fisheries, knowledge of spatial requirements and movement patterns are important in the planning and development of marine sanctuaries, fishery reserves, and artificial reefs as fishery management tools. For instance, this information can help predict and evaluate the effectiveness of marine reserves in retaining adult fish biomass and exporting adult fish biomass to adjacent fisheries (Roberts and Polunin, 1991; Russ and Alcala, 1996).

Knowing the movement patterns of a protected species will also make it easier to determine the area needed to design effective marine reserves (Rowley, 1994; Chiappone and Sealey, 2000). Artificial reefs that enhance recreational fishing success may also increase fish productivity when designed with spatial requirements of target species in mind (Lindberg and Loftin, 1998). This may occur when reefs are deployed with adequate spacing between patch reefs, thereby decreasing competitive interference from residents that occupy nearby reefs. Competitive interference can influence density-

1 2 dependent responses such as increased emigration rates due to resource degradation by concentrations of consumers and competitors. Population distribution and community structure may be better understood (Zeller, 1997), and fisheries managers might gain more accurate population and stock assessment estimates by incorporating immigration, emigration, migration, and residency patterns (Gerking, 1959; Winter, 1977; Huntsman et al., 1999). Shapiro (1987) suggested that hermaphroditic groupers use social and environmental factors to regulate sexual transition. If this is the case, then homing may play a role since conspecific relationships have likely been established, possibly over extended time periods. It has also been suggested that homing may play a role in the range extension of animals that display exploratory behavior (DeBusk and Kennerly,

1975). Knowledge of a species homing ability may be an important consideration in determining whether to restock an area that has been over-harvested or otherwise threatened. At least one restocking management plan for lingcod has met with failure without considering this behavioral capability (Buckley et al., 1984). In this instance, lingcod were transplanted to an overfished area only to have no lingcod observed at the release location. However, some were caught close to the capture site 190 km away.

Homing refers to the choice that a fish makes between returning to a place formerly occupied rather than to other equally probable places (Gerking, 1959). In fishes, this is most often associated with diadromous families, yet homing occurs in a variety of settings and can range from only meters to many kilometers (Quinn and Dittman, 1992).

Homing may allow individuals to venture beyond an established home range, and then return to it’s original location in the event that more favorable conditions are not found.

For this study of gag grouper, Mycteroperca microlepis, homing was operationally

3 defined as the return, within 10 days after displacement, to the reef(s) where residency was presumed to have been already established (the accepted common name, gag, is both singular and plural). Home range is “the area over which an animal normally travels in pursuit of its routine activities” (Jewell, 1966, pg 103). This ecological concept is important for understanding species’ ecology and to help establish informed management policies (Sanderson, 1966; Winter, 1977; Bekoff and Mech, 1984). For the purpose of this study, the term spatial area serves as a proxy for the measure of home range size because homing per se was the focus, and only a rough estimate of home range was needed for an adequate test of homing.

Much of our current understanding of fish movement patterns and the use of space has been largely derived from tag and recapture studies. This methodology, however, has limited the resolution of what scientists can infer. Recent technological advances in satellite navigation systems and telemetry equipment have now allowed scientists to more closely examine how fish use space (Nielsen, 1992). Today, telemetry plays an important role in fish movement studies (Zeller, 1998a). Despite being labor-intensive, telemetry studies yield large amounts of data on relatively small numbers of individuals while having a minimal impact on the behavior of those animals (Nielsen, 1992; Winter, 1996).

One growing body of behavioral research concerns the homing ability of fish.

While much work has been done on the homing abilities of salmonids, other marine fishes are also believed to possess such abilities (Table 1). In this study, ultrasonic telemetry was used to determine aspects of the homing ability and spatial behavior of gag grouper in the northeastern Gulf of Mexico.

Table 1. Marine teleosts that are believed to possess homing ability.

Family Species Author(s)

Apogonidae Apogon doederlini Marnane 2000 Cheilodipterus artus Smith Cheilodipterus quinquilineatus

Cheilodactylidae Cheilodactylus fuscus Lowry and Suthers 1998

Cottidae Clinocottus analis Williams 1957 Clinocuttus globiceps Girard Yoshiyama et al. 1992 Oligocottus snyderi Greely Oligocuttus maculosus Green 1971; Yoshiyama et al. 1992

Gobiidae Bathygobius soporator Beebe 1931

Haemulidae Haemulon flavolineatum Ogden and Ehrlich 1977 Haemulon plumieri Tulevech and Recksiek 1994; Ogden and Ehrlich 1977

Hexagrammidae Ophiodon elongatus Matthews 1992

Kyphosidae Girella nigracans Williams 1957

Labridae Oxyjulis californica Hartney 1996 Tautogolabrus adspersus Green 1975

Pomocentridae Chromis punctipinnis Hartney 1996

Scaridae Scarus croicensis Bloch Ogden and Buckman 1973

Scorpaenidae Sebastes chrysomelas Hallacher 1984 Sebastes flavidus Carlson and Haight 1972 Sebastes inermis Mitamura et al. 2002 Sebastes taczanowski Markevich 1988 Sebastes caurinus Matthews 1990 Sebastes maliger Sebastes auriculatus

Table 1. Continued. Family Species Author(s) Serranidae Epinephelus afer Beets and Hixon 1994 Epinephelus cruentatus Corless et al. 1997 Epinephelus fulvus Lembo et al. 1999 Epinephelus marginatus Epinephelus guttatus Bardach 1958; Jimenez and Fernandez 1999 Epinephelus striatus Bardach 1958; Beets and Hixon 1994

Stichaeidae Ulvaria subbifurcata Green and Fisher 1977

Tripterygiidae Forsterygion varium Thompson 1983

Of those marine reef fishes that exhibit homing behavior, one unifying

characteristic they share is fidelity to a known area. Jakob et al. (2001) states that site-

faithful animals reduce the risk that they will not find an appropriate new site, and site

fidelity may also provide important ecological advantages such as: (1) stability in a

turbulent environment (Gibson, 1982; Yoshiyama et al., 1992); (2) well known resource

and refuge locations (Greenwood and Harvey, 1982; Ellis-Quinn and Simon, 1989); and

(3) reduced territorial defense costs with familiar neighbors as compared to with strangers

(Eason and Hannon, 1994).

For serranids, past tagging studies have indicated that some Mycteropercan and

Epinephelin groupers in nearshore environments exhibit reef fidelity (Moe, 1966; Beets

and Hixon, 1994; Corless et al., 1997; Heinisch and Fable, 1999). Not surprisingly, some

studies have also documented either strong homing tendencies or homing abilities

(Bardach, 1958; Beets and Hixon, 1994; Corless et al., 1997; Lembo et al., 1999).

As an economically important serranid, gag grouper supports a large commercial and recreational fishery along the Atlantic coast and the eastern Gulf of Mexico (Smith,

1971; Huntsman and Dixon, 1976). The biology and life history of gag are generally well known. Despite reported movement information (Topp, 1963; Beaumariage, 1964;

Beaumariage and Wittich, 1966; Moe, 1966; Beaumariage, 1969; Moe et al., 1970;

Collins et al., 1990; Van Sant et al., 1990; Heinisch and Fable, 1999), however, uncertainty exists concerning spatial use and movement behaviors. It is widely accepted that gag exhibit, throughout their life, an ontogenetic developmental offshore movement associated with their increasing size (Bullock and Smith, 1991). In the fall, young-of-the- year gag leave estuarine grassbeds and other nearshore structural habitats and move offshore to deeper water (Ross and Moser, 1995; Koenig and Coleman, 1998). Offshore, gag remain closely associated with hard-bottom areas and establish residency upon these reefs. Gag are also believed to remain as reef residents for extended periods of time and exhibit a high degree of site fidelity. Recently, Lindberg and Loftin (1998) in a telemetry study of 80 gag, found that the average residency time on experimental artificial reefs was 298 days (9.8 months), with a maximum residency of at least 951 days (2.6 years).

Gag site fidelity was also believed to be significant since tagged gag movements were minimal during two other short-term movement studies (Lindberg and Loftin, 1998).

Information pertaining to homing ability and home range size has yet to be reported.

Based on the gregarious nature of gag (pers. obs.), long residence on artificial reefs in the northeastern Gulf of Mexico and apparent site fidelity (Lindberg and Loftin, 1998),

I hypothesized that gag also possess an ability to home. The specific objectives of this study were: 1) to examine, at a pilot scale, spatial area utilization and diel patterns of

7 movement, 2) to determine whether or not juvenile-to-adult gag have the ability to home after experimental displacement, and 3) to test over what distances juvenile-to-adult gag demonstrate that capability.

CHAPTER 2 MATERIALS AND METHODS

Suwannee Regional Reef System (SRRS)

This study was carried out from June 1997 through November 1998 on the

Suwannee Regional Reef System (SRRS), a series of 22 experimental artificial reef sites ranging from 32 to 36 km offshore from the Suwannee River along the 13-m depth isopleth in the northeastern Gulf of Mexico (Lindberg and Loftin, 1998) (Fig. 1). Each reef site consists of 6 patch reefs of either 4 or 16 cubes (89 cm3) arranged in a hexagon with patch reefs separated by either 25, 75, or 225 m (Fig. 2). Of the 113 gag tracked in this study, 111 originated on 16-cube patch reefs spaced at 225 m. Two gag were tagged from 4 and 16-cube patch reefs spaced at 75 m. All 113 gag tagged and released were assumed to be residents of the reefs on which they were captured.

The general public is not aware of specific study reef locations, hence Figures 3 through 26 use axes, Easting and Northing, without coordinate values so reef locations are not divulged. Additionally, plots of relocations and displacement tracks encompass large distances, and as a consequence x and y dimensions may be compressed and not to scale. For reference, horizontal and vertical scale bars are included in the figures.

Study Design

The overall study design was executed in three phases, as detailed in subsections below. The first phase, gag spatial utilization, used ultrasonically tagged gag relocated on a daily basis to estimate the spatial area used by resident gag; home range has never been reported for gag. To invoke homing by animals experimentally displaced from their

8 9 home site, displacements should occur outside the home range of resident animals

(Gerking, 1959; Kleeberger and Werner, 1982). Doing so decreases the likelihood of an animal’s familiarity with the area and is a better test of homing abilities. Twenty-four hour tracking studies were also conducted to gain an understanding of diel use of space.

The second phase, individual displacements of ultrasonically tagged gag, estimated the distances over which gag can home following experimental displacements. Beginning with short distance displacements, individual gag were displaced at increments within the range of 5 m to 8000 m. Gag were then relocated with telemetry to determine their routes and ultimate homing status.

Given the estimates of homing distances derived from individual displacements, the third phase entailed mass displacement experiments to statistically test those distances. Gag were captured, tagged with FLOY tags, and displaced at prescribed distances. Underwater surveys of patch reefs by SCUBA divers ascertained which gag homed, and the results were statistically tested as described below.

Spatial area was estimated using the Minimum Convex Polygon (MCP) method, which is a non-statistical method of calculating an animal’s home range size. This method first used by Mohr (1947) describes the areal boundary, which contains all positional fixes of the animal, including those outside the main area of activity. This method is advantageous in that it is comparable among studies (Harris et al., 1990).

Minimum Convex Polygons were calculated using the home range analysis software

Ranges V (Kenward and Hodder, 1996) and spatial area calculations used only the first

10 relocation of the day for each gag. Spatial use figures use the Universal Transverse

Mercator (UTM) system for plotting relocations.

Telemetry Equipment and Tagging Methods

Sonotronics Tracking Tags were used to relocate and track gag to measure spatial area and examine movement patterns. Of the 113 tagged gag in this study, 18 gag were externally tagged with Sonotronics model CT-82-3 ultrasonic tags weighing 8 grams and emitting unique pulsed signals at 75 kHz and frequencies between 38 to 40 kHz. Five additional gag (from an ongoing study) were also tracked and relocated, but were internally tagged with Sonotronics model CT-82-2 and CT-82-3 tags each weighing 8 grams and emitting pulsed signals at 75 kHz (Lindberg and Loftin, 1998). Ultrasonically tagged gag were relocated with a Sonotronics DH-2 directional hydrophone and USR-5W digital receiver and their locations were recorded using a Garmin 75 Global Positioning

System (GPS) equipped with a Garmin GBR-21 differential receiver on an 8-m research vessel. Gag were also tracked underwater by a SCUBA diver using a Datasonics DPL-

275 underwater ultrasonic receiver to determine initial direction heading after release.

To determine the error of measurement associated with tag relocation, five trials were conducted under conditions likely to be encountered while tracking. In each trial, an ultrasonic tag was placed by an impartial observer in a location unknown to the person tracking. The tag was then sonically relocated using the same practices as used for fish relocation as noted below. After the tag was relocated a weight was dropped to the bottom at the estimated tag position. A diver then measured the distance from the weight to the tag. The trials resulted in an average error of 7.7 m (± 4.9 m).

Before the tracking and displacement experiments, tagging methods were developed and tag retention times determined. Stomach insertion (Kenward, 1987) failed

11 with two gag regurgitating the ultrasonic tags within 12 hours. External attachment of tags to the dorsal surface following Holland et al. (1985) resulted in tag retentions of at least 23 days under laboratory conditions for four gag between 500 and 750 mm total length (TL). Three of the 4 gag had retentions up to 38 days, after which all tags were removed. Later, when observed by divers on the SRRS, externally tagged gag displayed similar behavior as their nearby conspecifics.

Gag were captured on patch reefs by SCUBA divers using handlines with size 12/0 circle hooks baited with squid. Circle hooks were preferred over J-hooks since circle hooks are less prone to swallowing and gag tended to hook themselves with no effort from the diver (Horst, 2000; pers. obs.). Once hooked, gag were brought to the surface and placed aboard the research vessel. The hook was removed, TL was measured, and the fish was placed in a cooler filled with seawater. Prior to tagging, attachment loops on the tags were prepared by inserting 20.4 kg (tensile strength), 0.711-mm diameter,

Steelon® nylon coated cable through pre-existing holes at the tag ends, and crimping both cable ends with number 3 connector sleeves to form a small loop. Loops served as attachments for two 22.7 kg plastic cable tie wraps. Tie wraps were cut to 20 cm leaving a sharp point at the tip to aid insertion through the dorsal musculature. During the surgical tagging procedure, an assistant placed the gag on a fish board and maintained physical control of the fish. An ultrasonic tag was then placed below the insertion of the dorsal fin and was used as a template to determine where the plastic tie wraps should be inserted. A surgical scalpel was used to nick the skin after which the plastic tie wrap was placed through the tag loop and pushed through the skin and dorsal musculature between the pterygiophores until the skin on the opposite side bulged. A second nick was made

12 on the bulging area with a scalpel to allow the tie wrap to exit the body. Next, the dorsal fin membrane was cut where the tie wrap would lay to allow continued function of the dorsal fin. The tie wrap was then secured and tightened over the back of the fish and trimmed flush with the locking portion of the tie wrap. The same surgical procedures were used to secure the posterior end of the tag. The average time for the procedure was

3.3 min (± 34 s). An antibiotic cream, Panalog®, was applied topically to the four wounds, and the tagged gag was placed back into the seawater filled cooler as the vessel moved to the release point. Fresh seawater was added to the cooler at ten-min intervals and tagged gag remained in the cooler for 30 minutes prior to displacement.

Telemetry Relocation Techniques

To relocate ultrasonically tagged gag, the tracking vessel would slow to an idle approximately 450 m away from the last known location of a tagged gag to reduce the noise made on approach and lessen the chance of interfering with gag behavior. The directional hydrophone was placed in the water, and once the tag’s signal was detected, the vessel would idle toward the signal. While approaching the signal the hydrophone was constantly turned side-to-side to refine the signal’s location. As the vessel approached, the tag signal strength would increase along with the angle of tag reception.

Directly over the tagged fish, the signal strength would be uniformly strong in a 360º degree arc. The driver of the vessel would then motor over and beyond the gag and make a sharp turn back over the gag, intersecting the boat’s wake at a ninety-degree angle. The latitude and longitude would then be recorded. Daily boat time was divided among several studies, often kilometers away from telemetry sites. Hence, the majority of relocations were made during early daylight hours and may not accurately describe the diel use of space by tagged gag.

Gag Spatial Utilization

Fourteen gagged were relocated daily to determine spatial area utilization (i.e.

Home Range). Gag were relocated following telemetry relocation methods described above. Three 24-h diel tracking sessions were also conducted to characterize diel spatial area and movement. Tagged gag were relocated on regular intervals, hourly or on the half hour.

Individual Displacements of Ultrasonically Tagged Gag

From September 1997 to July 1998, 18 gag were ultrasonically tagged, displaced up to 8000 m away from their capture sites, and tracked to determine the distances over which gag might home. A successful homing was defined as a return to the capture site, as determined by ultrasonic telemetry, within 10 days. At the release site, a buoy was deployed, and the latitude and longitude recorded. Each tagged gag was then placed in a dark, covered 60-L plastic container and taken to the bottom by divers for release. Prior to release, water temperature, visibility, bottom type (sand, rock, live bottom), and current direction were noted and recorded. The gag was then released facing a randomly determined direction and was observed to the visual limit to determine the vanishing point. An underwater hydrophone was then used to determine the direction of gag movement, with records made every minute for approximately 10 min. Onboard the research vessel, the gag was relocated and surface tracked using a directional hydrophone deployed from the vessel. In an effort to minimize interference with the gag, relocations were made approximately every 30 min, or in the case of rough conditions as often as necessary to ensure staying with the fish. Tracking continued until personnel had to return to port, bad weather intervened, the gag was lost, or homing occurred. Of the displaced gag that homed, some were speared to recover the transmitter for reuse.

Mass Displacement Experiments

A total of 90 gag were tagged with FLOY Disc tags, with 45 displaced in each of

two displacement experiments to statistically test distances over which homing may

occur. The gag displaced were divided into groups of 15, some as controls, which were

released upon their resident reef, and as groups that were displaced 2000, 3000, and 4000

m away from their resident reef. Of those gag displaced, all were released individually at

predetermined release sites separated by 100 m.

FLOY Tagging

Prior to conducting any FLOY Disc tagging, a SCUBA diver determined the most

suitable tag colors and shapes to be combinations of white, orange, yellow, and blue, and

circles and squares. All tags were of similar size, i.e. approximately 2.54-cm across.

FLOY tags were applied to gag by first pushing a plastic backing plate, followed by a

numbered disc tag, onto a stainless steel pin. This pin was then inserted through the

dorsal musculature and another numbered tag and plastic backing plate was threaded on

the opposite side. The tag was then secured by grasping the pin with small pliers and

turning 360º to form a small tight loop. While tagging, the boat was moving to the

displacement sites.

Fish Traps and Trapping

To capture gag for tagging, 14 homemade fish traps were constructed using hog

rings and 2.54-cm2 gap 14-gauge plastic coated wire with a fish door attached with dissolving twine. Trap size was 92-cm long by 61-cm wide and 61-cm tall. Traps were placed on patch reefs that were previously identified to have the most gag. After a 24-h soak the traps were sent to the surface by a diver-deployed lift bag. On board, the traps were opened and gag between 45 and 90-cm TL were placed in aerated coolers. All other

fish were released. To prevent oxygen depletion a maximum of four gag were held per

128 qt cooler. Upon placement in the cooler, all gag would float on their sides or upside

down due to air bladder distention. Gag were vented by inserting an 18 gauge

hypodermic needle into their air bladder and releasing the pressure until air bubbles were

no longer observed from the needle. Frequent water exchanges were made to remove

stomach contents regurgitated by the gag. Prior to tagging, gag were measured for TL

and randomly assigned a displacement distance. All gag were handled the same, held for

similar durations of approximately 30 minutes after tagging, and released at the surface.

Mass Displacement Trials

Two trials of this tag-release-resight experiment were conducted. The first trial comprised 3 days of trapping, spanning six days from July 23 to July 28, 1998, during which time 45 gag were trapped, tagged and released; 15 gag as controls and 15 gag each displaced 3000 and 4000 m away from their capture sites (16 gag trapped, tagged, and released on July 23, 16 gag on July 24 and 13 gag on July 28). Trapping was completed on July 28, however, due to inclement weather the underwater surveying commenced 3 days later. Two complete surveys were completed over an 8-day period with additional sightings noted periodically over a total of 26 days.

The second trial comprised 2 days of trapping, on October 7 and October 8, 1998, during which time 45 gag were trapped, tagged and released; 15 gag as controls and 15 gag each displaced at 2000 and 3000 m away from their capture sites. On the first day of trapping (October 7) 37 gag were tagged and released and on October 8, eight gag were tagged and released. Complete underwater surveys began on October 9 with 6 surveys completed over a 36-day period.

U/W Surveys

Twenty-four hours after the release of the last displaced gag in both trials, paired

SCUBA divers returned to the collection sites and conducted visual counts of tagged gag recorded on waterproof paper. Upon descent, one diver surveyed the periphery of the patch reef, while the second diver remained on the patch reef and surveyed those gag on or near the patch. Surveys lasted 10 to 15 min per patch depending upon visibility and gag density. Surveys were conducted only if underwater visibility exceeded five m.

Statistical Analysis

SAS version 9.0 (SAS Institute, Cary, NC) was used to statistically test displacement distances, fish length, homing, and the absence of homing from both mass displacements trials. Multiple logistic regression following the LOGISTIC procedure generated homing probabilities and 95% prediction intervals for the displacement distances.

Figure 1. Map of Florida showing the mouth of the Suwannee River and the 22 artificial reef arrays of the Suwannee Regional Reef System (SRRS).

N 225 meters North

NW NE

SW SE

Figure 2. A Suwannee Regional Reef System (SRRS) array comprises six 16-cube patch reefs, which are arranged in a hexagonal configuration. The study patch reefs are each separated by 225 meters. Patch reefs are denoted north, northeast, northwest, south, southeast, and southwest.

CHAPTER 3 RESULTS

Gag Spatial Utilization

Minimum Convex Polygons (MCP), as determined from five gag with internal ultrasonic tags ranged from 0.42 to 10.86 Ha and had maximum widths from 171 to 582 m (Table 2). Gag relocations suggest reef fidelity to specific patch reefs (Figs. 3, 4, 5, 6).

One gag, #2435, relocated 82 times over a one-year period, demonstrated strong patch reef fidelity over both days and seasons (Fig. 6). Of the 18 gag that were externally ultrasonically tagged and displaced, only nine were relocated enough times to calculate their MCP sizes (Table 3). Minimum Convex Polygon spatial area estimates ranged from

0.01 to 26.68 Ha with maximum widths ranging from 21 to 1058 m for gag tagged with ultrasonic external tags. For spatial comparisons the MCP of a 225 m hexagonal artificial reef array is 13.35 Ha with a maximum width of 458 m. See Table 4 for gag sizes and dates tracked for both groups.

Table 2. Relocation summary of 5 gag tagged with internally placed ultrasonic tags.

Gag # Number of % Relocations Avg. of Relocations Spatial Max Relocations > 25 m > 25 m from Patch (m) Area (Ha) Width (m)

2435 82 34 51 10.86 582 97 19 53 92 1.66 272 365 12 92 61 5.16 466 456 11 73 55 0.94 197 338 10 50 32 0.42 171

19 20

Table 3. Relocation summary of 9 gag tagged with externally placed ultrasonic tags.

Gag # Number of % Relocations Avg. of Relocations Spatial Max Relocations > 25 m > 25 m from Patch (m) Area (Ha) Width (m) 15 27 52 119 26.68 1058 01 16 25 36 0.82 190 17 15 47 37 0.83 208 08 12 50 35 0.19 75 05 7 29 37 0.12 65 06 5 0 0 0.01 21 02 5 40 110 0.37 205 10 4 25 29 0.04 31 07 3 67 30 0.03 34

For the five gag internally tagged, 46% of their relocations were greater than 25 m away from the nearest patch reef, and of those relocations the average distance away from the nearest patch reef was 59 m. The maximum distances away from any patch reef for these gag were measured to be 39, 131, 118, 140, and 206 m (127 m ± 60 m). Of the nine gag tagged with external tags, 36% of their relocations were greater than 25 m away from the nearest patch reef, and of those relocations the average distance away from the nearest patch reef was 78 m. The maximum distances away from any patch reef were measured to be 0, 29, 32, 46, 47, 54, 57, 185, and 596 m (116 m ± 187 m).

Overall, the 14 gag had 42% of their relocations greater than 25 m away from the nearest patch reef, and of those relocations, the average distance away from a patch reef was 66 m. Maximum widths of the MCPs (Table 2 and 3) provide additional insight as to how large of an area gag occupy. Of nine gag with external tags that relocated 10 or more times, the maximum widths of the MCPs averaged 357 m (± 306 m) and ranged from 75 to 1058 m.

Table 4. Gag sizes and dates tracked.

Gag # Total Length (mm) Dates Tracked Ultrasonic Tags Internally Placed 2435 592 June 25, 1997 - July 8, 1998 97 496 June 25, 1997 - September 15, 1997 365 461 June 25, 1997 - August 25, 1997 456 651 June 25, 1997 - July 23, 1997 338 572 June 25, 1997 - July 23, 1997

Ultrasonic Tags Externally Placed 01 507 September 08, 1997 - November 03, 1997 02 609 September 10, 1997 - September 17, 1997 03 482 September 12, 1997 - September 25, 1997 04 575 September 22, 1997 - September 30, 1997 05 590 September 30, 1997 - November 06, 1997 06 562 October 30, 1997 - December 08, 1997 07 724 December 17, 1997 - December 22, 1997 08 662 December 19, 1997 - March 24, 1998 09 564 January 13, 1998 - January 13, 1998 10 610 February 13, 1998 - March 24, 1998 11 761 March 26, 1998 - March 26, 1998 12 705 April 21, 1998 - May 05, 1998 13 597 May 06, 1998 - May 19, 1998 14 717 May 20, 1998 - July 06, 1998 15 679 May 28, 1998 - August 18, 1998 16 728 June 12, 1998 - July 08, 1998 17 723 June 26, 1998 - August 18, 1998 18 621 July 06, 1998 - July 14, 1998

Hourly Tracking

Three 24-h tracking sessions were conducted to characterize the diel spatial utilization by tagged gag (Table 5). In general, during daylight hours, gag exhibited a close association with one core patch reef, and movements during this period were

22 centered around that reef. During the hours of darkness, gag were active throughout the night and early morning hours. Relocations at night were also further away from core patch reefs than during the daylight hours. Most of the longest movements were made during the crepuscular periods and included movements of 66, 270, and 398 m. In two cases, crepuscular movements were directed to an adjacent patch reef. Overall, tagged gag revealed large variations in their diel spatial use. Gag 2435 demonstrated a large variation in diel spatial size over two different tracking sessions (Table 5).

Table 5. Summary of diel tracking of ultrasonically tagged gag.

Tracking Gag # Hours Number of Diel Spatial Max. Session Tracked Relocations Area (Ha) Width (m)

September 16-17, 1997 02 13.5 11 0.23 75 2435 16 23 0.51 112

September 30, 1997 2435 7.5 9 3.77 358

August 10-11, 1998 15 24 23 9.67 726

Tracking session #1

The first tracking session began at 1134 hours on September 16, 1997 and terminated 16 h later at 0346 hours because of a problem with the GPS Differential signal due to storms in the local area (Fig. 7). Two gag were tracked and relocated during this session with Gag # 2435 and #02 relocated on half hour and hourly increments, respectively. Sunset was at 1937 hours and the moon was full.

Gag # 2435 was tracked from 1134 hours to 0346 hours in half hour increments and was relocated 23 times. Overall, this gag stayed near the southeast patch reef and was quite active throughout this period. Of the ten relocations greater than 25 m away from

23 the core patch, the average distance was 43 m. The furthest relocation recorded away from the core patch, 70 m, occurred at 1907 hours, 30 minutes prior to sunset. The diel

MCP spatial area was 0.51 Ha with a maximum width of 112 m.

Gag # 02 was tracked from 1143 to 0114 hours in hourly increments and was relocated eleven times. Prior to the dusk crepuscular period this gag remained close to the northwest patch reef, i.e. within 43 m. Because this gag was relocated hourly, little can be stated concerning crepuscular movement. On the first relocation period following sunset, the tag signal was very faint and the gag could not be relocated until 170 minutes later. Unfortunately, due to an approaching storm, the differential signal was not available. While there was no differential signal during the early morning hours, the southeast and northwest patch reefs were temporarily buoyed with floats and both gag were relocated on or nearby their respective core patch reef from 0600 hours until our departure at 0800 hours. The diel MCP spatial area of gag # 02 was 0.23 Ha with a maximum width of 75 m.

Tracking session # 2

The second tracking session began at 1534 hours on September 30, 1997 and was terminated ~ 8 hr due to bad weather (Fig. 8). Gag # 2435 was relocated approximately every 45 minutes and was relocated 9 times. Five relocations prior to dusk were over 25 m away from its core patch reef, averaging 27 m with the furthest recorded distance equal to 32 m from the patch. The longest movement occurred during the dusk crepuscular period between 1832 and 2007 hours, when this gag moved 270 m from nearby the northeast patch to south of the southeast patch. Four relocations during the hours of darkness averaged 113 m from its core patch reef, with the furthest distance away being

208 m. The diel MCP spatial area was 3.77 Ha with a maximum width of 358 m.

Tracking session # 3

The third 24–hr tracking session began at 1155 hours on August 10, 1998 and finished at 1102 hours on August 11 (Fig. 9). One gag, # 15, was tracked and relocated on an hourly basis and was relocated 23 times. Sunset and sunrise were at 2019 and 0658 hours, respectively. For 9 hours this gag remained close to the northern patch reef. At sunset there was no significant movement. However, during the hours of darkness this gag was quite active and made a number of large movements, one of which placed the gag off the SRRS system. Just after dusk between 2030 and 2100 hours, the tag signal was lost and was difficult to reacquire. Forty-two minutes later the signal was reacquired near the north patch, but the tag was very muted, as if the gag was under something dense. The first large movement, 218 m, occurred between 2143 and 2320 hours when the gag moved from the north patch to the northwest patch.

The second large movement, a total of 346 m, occurred between 0405 and 0629 hours and took the gag away from the SRRS towards a patchy hard-bottom area that was

366 m away from the nearest SRRS patch reef. A third large movement of 249 m occurred during the dawn crepuscular period between 0630 and 0718 hours and placed the gag 588 m from the nearest SRRS patch reef. The next relocation, between 0719 and

0808 hours, revealed another large movement of 178 m. At 1102 hours, the last relocation of the tracking session, the gag was 408 m away from the nearest SRRS patch reef. Of the six relocations during the hours of darkness the average movement was 138 m (± 120 m). The diel MCP spatial area was 9.67 Ha with a maximum width of 726 m.

Interestingly, this gag was relocated two additional times, six and seven days later,

203 and 458 m, respectively, off the SRRS and away from it’s core patch reefs. This gag was not relocated again.

Individual Displacements of Ultrasonically Tagged Gag

Eighteen gag were captured and tagged with external ultrasonic tags to determine if gag can home after experimental displacement (Table 4). Gag were displaced up to 8000 m and demonstrated that they can home up to 3000 m (Table 6). Of 10 gag displaced

1000 m or less, eight homed while the locations of the two other gag were never determined. One gag displaced 2000 m homed, as did 2 of the 3 gag displaced 3000 m.

Displacement distances greater than 3000 m were conducted, but it is unknown whether any of the three gag displaced at 4000 m and the one gag displaced at 8000 m ever homed. See Table 7 for sizes of fish that homed and those whose status remained unknown. Only one individually displaced gag was smaller than 500 mm TL, and the homing status of this gag, 482 mm TL, was uncertain.

There were no discernable patterns as to how gag move immediately upon release at a displacement site. Of the 14 individually displaced gag for which the initial direction of travel could be determined, seven traveled with the direction of tidal movement and seven did not. Plotted routes of individually displaced gag attempting to home showed that gag displaced 1000 m or more did not travel in a straight line and often zigzagged back and forth, sometimes crossing over their previous path (Figs. 10, 11, 12, 13). All gag whether they homed or not, displayed a similar ranging pattern. Two gag displaced

233 and 300 m moved 180 degrees away from their home site only to return home within

5 and 22 hours, respectively. It was not determined why both gag demonstrated this behaviour.

Gag # 01 was captured on the north patch reef of SRRS 09 and displaced 5 m. This initial displacement was to demonstrate that a tagged gag can return to it’s home reef.

Upon release it immediately swam into a cube of its home patch. During a 57 day period

26 this gag was relocated 16 times mostly on or near the northwest patch reef, 75 m from it’s initial capture site. It’s MCP spatial area was calculated to be 0.82 HA with a maximum width of 190 m (Fig. 14).

Gag # 02 was captured on the northwest patch reef of SRRS 13 and displaced 150 m. This gag was relocated one time before tracking was interrupted due to stormy weather and the lack of a Differential GPS signal. The next day, approximately 25 hours later, this gag was relocated at its capture site. A dive on the patch was conducted and the tagged gag was seen suspended above the bottom with other gag and appeared to display behaviour similar to it’s conspecifics. During a twelve day period this gag was relocated five times after which it was speared to recover the tag. It’s MCP spatial area was calculated to be 0.37 HA with a maximum width of 205 m.

Table 6. Summaries of displacement distances and homing success.

Gag # Distance Homing Displaced (m) Success 01 5 Yes 02 150 Yes 05 233 Yes 04 286 Unknown 07 300 Yes 06 300 Yes 08 450 Yes 09 600 Yes 03 1000 Unknown 10 1000 Yes 11 2000 Yes 15 3000 Yes 16 3000 Unknown 17 3000 Yes 13 4000 Unknown 14 4000 Unknown 18 4000 Unknown 12 8000 Unknown

Table 7. Homing status and size of individually displaced gag.

Status N = Average Size SD Range (mm TL) (mm TL) Homed 11 636 80.2 507-724 Unknown 7 632 90.2 482-728

Gag # 05 was captured on the north patch reef of SRRS 13 and displaced 233 m

(Fig. 15). This gag was tracked for four hours and 29 minutes and relocated 8 times.

Upon release this gag made small movements away from both it’s capture and it’s release site. At sometime between 29 and 41 minutes before sunset, this gag made a large movement toward its capture site. At 1939 hours, 17 min after sundown, this gag was relocated at its capture site after having moved 398 m from it’s last known position. This movement was the longest recorded and likely occurred during or near the dusk crepuscular period. During a 37 day period this gag was relocated seven times. Its MCP spatial area was calculated to be 0.12 HA with a maximum width of 65 m.

Gag # 04 was captured on the southwest patch reef of SRRS 11 and displaced 286 m. This gag was relocated once during a 20 minute tracking period, about one third of the distance toward it’s capture site. Because this gag appeared to be heading straight to it’s nearby capture site, it was decided that we would leave the area to finish another ongoing grouper experiment. One hour and 45 minutes later, we returned to the last known relocation point and could not find the tagged gag. An immediate 1.8 km2 search was conducted, but the gag was not relocated. This site was monitored three times during the following eight days, but gag # 04 was never relocated again.

Gag # 07 was captured on the north patch reef of SRRS 13 and displaced 300 m

(Fig. 16). This gag was tracked for two hours and eight minutes, and was relocated four

28 times before tracking was interrupted for the night. The next day, 20 hours and 11 minutes later, this fish was relocated on the north patch. This gag remained on site for six days and was relocated 3 times before it was speared on the north patch to recover the tag. It’s MCP spatial area was calculated to be 0.03 HA with a maximum width of 34 m.

Gag # 06 was captured on the north patch reef of SRRS 11 and displaced 300 m

(Fig. 17). This gag was tracked for a total of two hours and 28 minutes, and was relocated five times before tracking was interrupted for the night. On the next day, 22 hours and 14 minutes later, this fish was relocated on the northeast patch reef of SRRS 11. During a 39 day period this gag was relocated five times, all close to the northeast patch. It’s MCP spatial area was calculated to be 0.01 HA with a maximum width of 21 m.

Gag # 08 was captured on the north patch reef of SRRS 11 and displaced 450 m

(Fig. 18). This gag was tracked for a total of two hours and 31 minutes, and was relocated five times, before tracking was interrupted for the night. At the next opportunity to relocate this gag, three days later, it was relocated on the north patch. During a 95 day period this gag was relocated 12 times, after which it was speared on the north patch to recover the tag. It’s MCP spatial area was calculated to be 0.19 HA with a maximum width of 75 m (Fig. 19).

Gag # 09 was captured on the south patch reef of SRRS 11 and displaced 600 m

(Fig. 20). This gag was relocated two times during a one hour and five minute period, after which it homed to the south patch. After homing, it was immediately speared on the south patch to recover the tag.

Gag # 03 was captured on the northwest patch reef of SRRS 13 and displaced 1000 m (Fig. 21). This gag was relocated 3 times during a three-hour tracking period, after

29 which tracking was interrupted. The next morning this gag could not be relocated. A 9 km2 search was then conducted, with the gag not being relocated. Three days later a second search of 31 km2 did not relocate this tagged gag. The site was monitored five times during the following 13 days, but the gag was never relocated again.

Gag # 10 was captured on the south patch reef of SRRS 11 and displaced 1000 m

(Fig. 10). This gag was relocated 6 times during a two hour and 14 minute period after which this gag returned to the south patch reef. During a 39 day period this gag was relocated four times after which it was speared on the south patch to recover the tag. It’s

MCP spatial area was calculated to be 0.04 HA with a maximum width of 31 m.

Gag # 11 was captured on the north patch reef of SRRS 11 and displaced 2000 m

(Fig. 11). This gag was relocated seven times during a two hour and two minute period, after which this gag homed to the north patch. After homing, it was speared on the north patch to recover the tag.

Gag # 15 was captured on the northwest patch reef of SRRS 13 and displaced 3000 m (Fig. 12). This gag was relocated 9 times during a 3 hour and 45 minute tracking period. At the last relocation, before tracking was interrupted, the fish remained stationary approximately 2089 m away from the capture site. The next opportunity to relocate this gag was the following morning when it was relocated on the north patch of

SRRS 13, nineteen hours and 16 minutes later. During an 82 day period this gag was relocated 27 times, of which three relocations were off the SRRS system up to 596 m away from the nearest patch reef. It’s MCP spatial area was calculated to be 26.68 HA with a maximum width of 1058 m (Fig. 22).

Gag # 16 was captured on the northwest patch reef of SRRS 11 and displaced 3000 m. This gag was relocated four times during a five hour and 33 minute tracking period.

For three hours and 56 minutes it remained in one location 110 m away from it’s release point, after which the signal was lost. A search of the immediate area was conducted, but the tag signal was not reacquired. This site was monitored seven times during the following 25 days, but the gag was never relocated again.

Gag # 17 was captured on the northwest patch reef of SRRS 11 and displaced 3000 m (Fig. 13). This gag was relocated 9 times during a tracking period of three hours and

38 minutes, before tracking was interrupted. I dove to determine the direction of the current and observed the tagged gag swimming two to three meters off the bottom. By the next field day, three days later, the gag had homed to the northwest patch. Twelve days after displacement this gag was videotaped on the northwest patch amongst other gag hovering above the patch reef. During a 53 day period this gag was relocated 15 times.

It’s MCP spatial area was calculated to be 0.83 HA with a maximum width of 208 m

(Fig. 23).

Gag # 14 was captured on the northwest patch reef of SRRS 11 and displaced 4000 m. It was relocated 7 times during a three hour and 20 minute tracking period before the signal was lost. A search was conducted of the immediate area and of the capture site without success. This site was monitored nine times during the following 47 days, but the gag was never relocated again.

Gag # 13 was captured on the north patch reef of SRRS 13 and displaced 4000 m

(Fig. 24). It was relocated 16 times during an 8 hour and 56 minute tracking period after

31 which this tracking session was terminated. This site was monitored five times during the following 13 days, but the gag was never relocated again.

Gag # 18 was captured on the northeast patch reef of SRRS 11 and displaced 4000 m (Fig. 25). It was relocated eight times during a four hour and 4 minute tracking period after which this tracking session was terminated. This site was monitored four times during the following eight days, but the gag was never relocated again.

Gag # 12 was captured on the northwest patch reef of SRRS 11 and displaced 8000 m (Fig. 26). This gag was relocated three times during a 69 minute period. Seventy-eight minutes into this tracking session a pod of dolphins moved into the area and stayed close to the boat. The boat was moved to draw the potentially interfering dolphins away from the tagged gag. The boat was positioned outside of the tracking range with the dolphins nearby. Ninety-eight minutes into the tracking session the boat returned to the last relocation point and the signal was not reacquired. An immediate search of the area was initiated, as was a return to the capture site, with no relocation of the tagged gag. This site was monitored four times during the following 14 days, but the gag was never relocated again.

Mass Displacement Experiments and U/W Surveys

A total of ninety gag were tagged and displaced at 0, 2000, 3000 and 4000 m away from their home site during two mass displacement experiments. Experiments were conducted on two different, but spatially identical 16 X 225 m arrays followed by underwater surveys using SCUBA and paired divers to determine which gag homed.

Trial 1: 3000 and 4000 Meter Displacements

Twelve of the 15 control gag were observed during post-release surveys, while two and zero gag were observed that had been displaced at 3000 and 4000 m, respectively.

See Table 8 for trial results and gag sizes.

On the first day of trapping on July 23, six control gag, five 3000 m displaced gag, and five 4000 m displaced gag were released. On July 24, nine control gag, four 3000 m displaced gag, and three 4000 m displaced gag were released. While working the traps, two control gag and one 3000 m displaced gag were observed after diving all six patches.

On July 26, one diver, configuring the traps to catch gag in anticipation of tagging and displacing gag the next day, observed two of the control gag and one of the 3000 m displaced gag. On July 28, trapping was completed after tagging and displacing six gag at

3000 m and seven gag at 4000 m. The observations made while handling the traps underwater included three of the control gag and no 3000 or 4000 m displaced gag.

However, observations were only made on five of the six patches.

Table 8. Gag displacement distances, averages and range of sizes, standard deviation, and homing success.

Displacement N = Average Size SD Range Homed Condition (mm TL) (mm TL) Trial 1 Control 15 604 45.5 544 - 734 12 3000 M 15 645 108.1 476 - 839 2 4000 M 15 622 108.7 453 - 855 0

Trial 2 Control 15 558 84.8 450 - 719 15 2000 M 15 666 86.3 491 - 826 10 3000 M 15 637 97.6 457 - 799 3

On July 31, the first complete underwater survey was conducted, with eight control gag and one 3000 m displaced gag observed. On August 7, six control gag were sighted

33 and one 3000 m tag was found lying near a patch reef in a depression on the bottom. On

August 18, 21 days after all gag were released, while removing traps from the site, one gag that was displaced 3000 m was observed.

Trial 2: 2000 and 3000 Meter Displacement

All of the fifteen control gag were observed during post-relief surveys, while ten and three gag were observed that were displaced at 2000 and 3000 m, respectively. See

Table 8 for trial results and gag sizes. A summary of gag size categorized by those mass displaced fish from both trials that homed and for those whose status was unknown is shown in Table 9.

Table 9. Gag size categorized by mass displaced fish from both trials that homed and those whose status was unknown.

Mass Displaced Homing Status N = Average Size SD Range (mm TL) (mm TL) Homed Control 27 573 67.6 450 - 719 2000 meter 10 668 66.0 558 - 826 3000 meter 5 682 100.7 573 - 799 4000 meter 0 n/a n/a n/a

Unknown Control 3 653 70.5 610 - 734 2000 meter 5 661 127.5 491 - 765 3000 meter 25 633 101.4 457 - 839 4000 meter 15 622 108.7 453 - 855

On the second day of trapping on October 8, all of the seven control gag were observed that were released the previous day, and four of the fifteen gag displaced 2000 m the previous day were also observed. No gag displaced 3000 m were observed. On

October 9, 13 control gag and three 2000 m displaced gag were observed. No gag displaced 3000 m were observed.

On October 12, the fourth post-release day, twelve control gag, six 2000 m

displaced gag, and one 3000 m displaced gag were observed. On October 30, 22 days

after release, 11 control gag were observed and one Floy disc tag belonging to another

control gag was found lying on the bottom near a patch reef. Seven 2000 m and two

3000 m displaced gag were also observed.

On November 9, 32 days post-release, nine control gag, five 2000 m displaced gag, and one 3000 m displaced gag were observed. On the last observation day, November 12,

35 days post-release, six control gag, five 2000 m displaced gag, and one 3000 m displaced gag were observed.

Combined Trials

Multiple Logistic Regression was used to statistically test the two trials of mass displacements for effects due to distance, trial, and length. Results indicated that distance was significant (p <0.0001) and the distance coefficient (-1.4857) indicated that as distance increases the probability of homing decreased (Fig. 27, Table 10). Trial was also significant (p= 0.0269). However, this likely indicates that the probability of homing was less in trial one than in the second trial. Gag length had no effect and did not influence homing.

The parameter estimates in Table 10 are for the tested model:

log (π(homed) / 1-π(homed)) = β0 + β1distance + β2trial +β3length

Table 10. Parameter estimates for the significant regression equation: log (π(homed) / 1-π(homed)) = β0 + β1distance + β2trial +β3length, where distance is in thousands of meters, trial = 1 for trial 1 and trial = -1 for trial 2, length is TL (mm), and π(homed) = proportion homed.

Parameter Estimate Std Error P Intercept 1.72520 2.30560 0.4543 Distance -1.48570 0.29660 <0.0001 Trial -0.83490 0.37720 0.0269 Length 0.00142 0.00368 0.6995

3.2277e+6

patch reef relocation 3.2276e+6 225 meters

3.2275e+6

g N 3.2274e+6 Northing Northin

3.2273e+6

3.2272e+6 225 meters

3.2271e+6 2.607e+52.608e+52.609e+52.610e+52.611e+52.612e+52.613e+5 EastingEasting

Figure 3. Relocations of gag # 365 showing an MCP estimate of 5.16 Ha with a 466 m maximum width. One relocation per day (n = 12).

3.2277e+6 patch reef relocation 3.2276e+6 225 meters

3.2275e+6 N

3.2274e+6 Northing Northing

3.2273e+6

3.2272e+6

225 meters

3.2271e+6 2.607e+52.608e+52.609e+52.610e+EastingEasting52.611e+52.612e+52.613e+5

Figure 4. Relocations of gag # 456 showing an MCP estimate of 0.94 Ha with a 197 m maximum width. One relocation per day (n = 11).

3.21664e+6

patch reef 3.21662e+6 relocation

3.21660e+6

3.21658e+6

3.21656e+6

N 3.21654e+6 Northing Northing

3.21652e+6

225 meters 3.21650e+6

3.21648e+6 75 meters

3.21646e+6 2.6698e+52.6700e+52.6702e+52.6704e+52.6706e+52.6708e+5Easting2.6710e+52.6712e+52.6714e+52.6716e+52.6718e+52.6720e+5 Easting

Figure 5. Relocations of gag # 338 showing an MCP estimate of 0.42 Ha with a 171 m maximum width. One relocation per day (n = 10).

3.2321e+6 patch reef relocation

3.2320e+6

3.2319e+6 N

3.2318e+6

3.2317e+6Northing Northing

3.2316e+6

225 meters 3.2315e+6 225 meters

3.2314e+6 2.608e+5 2.609e+5 2.610e+5Easting2.611e+5 2.612e+5 2.613e+5 Easting Figure 6. Relocations of gag # 2435 from June 25, 1997 to July 8, 1998 showing an MCP estimate of 10.86 Ha and a maximum width of 582 m. One relocation per day (n = 82).

3.2321e+6 patch reef relocation 0114 hours 3.2320e+6 Gag # 02 N 3.2319e+6

1758 hours g

3.2318e+6 2359 hours Northing Northin Gag # 2435 3.2317e+6

1907 hours 225 meters 3.2316e+6 225 meters

3.2315e+6 2.608e+52.609e+52.610e+52.611e+52.612e+52.613e+52.614e+5 Easting

Figure 7. First hourly tracking session of two gag, # 2435 and # 02. Sunset at 1937 hours.

3232600

patch reef 1841 hours 3232400 relocation Gag # 05

3232200 N

g Gag # 2435 3232000 1939 hours Northing

Northin 1832 hours 3231800

2318 hours 3231600 225 meters 2007 hours 225 meters 3231400 260800 261000 261200 261400 261600 Easting Easting

Figure 8. Second hourly tracking session of gag # 2435. Gag # 05 was also tracked during it’s 233 m displacement, which was running concurrently (Figure 15). The longest movement recorded of both gag coincided with sunset at 1922 hours.

3232250 0718 0844 patch reef relocation 1015 3232200 178 m 0629 0923 1102 3232150 0808 216 m N 3232100

g 0514 N First 3232050 9 hrs 130 m Northing Northin 3232000 218 m 0404 0044 3231950 NW 0256 3231900 225 m 2320 0155 3231850 260300260400260500260600260Easting700260800260900261000261100 Easting

Figure 9. Third hourly tracking session of one gag, # 15. Sunrise and sunset occurred at 2019 and 0658 hours, respectively. Italics represent time and bold represents distance. Only the N and NW patch reefs of the SRRS site are plotted.

3227800 patch reef 225 meters relocation 3227600

3227400 Capture Site 3227200 m 496 ins N 24 m 3227000 1 458 m 3226800 100 mins Northing Northing 326 m 3226600 83 mins

323 3226400 m 46 m ins 39 0 m Release Point 20 3226200 t min ren s Release Point cur 225 meters 3226000 260200 260400 260600Easting 260800 261000 261200 261400 Easting

Figure 10. 1000 meter displacement of gag # 10, which homed within 134 minutes. Italics represent time from release and bold represents distance traveled.

nt 3230000 re Release ur C Point patch reef relocation 3229500 606 m 0 m 12 3229000 850 m N

3228500 529 m Northing Northing 485 m 3228000 m 378 m 205 Capture Site 3227500

225 m

3227000 260100 260400 260700 261000 261300 Easting Easting

Figure 11. 2000 meter displacement of gag # 11, which homed within 122 minutes. Distances between relocations are noted.

3233000

patch reef 3232800 515 m relocation

3232600 370 m 2089 meters 3232400 N Returned to the 3232200 553 m North patch the next morning 356 m Northing

Northing 154 m 3232000 Release Capture Site Point 3231800

t 3231600 ren Cur

3231400 258000 259000 260000 261000 Easting Easting

Figure 12. 3000 meter displacement of gag # 15, which homed by the next morning. Distances between relocations are noted.

3.22765e+6 relocation Release Point 3.22760e+6 122 m 3.22755e+6 t 176 m rren N Cu 3.22750e+6 103 m

3.22745e+6 288 m

Northing Last Relocation 225 m 3.22740e+6 Northing 392 m 3.22735e+6 275 m

3.22730e+6

3.22725e+6 2.571e+52.572e+52.573e+52.574e+5EastingEasting2.575e+5 2.576e+52.577e+52.578e+52.579e+5

Figure 13. 3000 meter displacement of gag #17, which homed within 3 days. Home site is 3000 meters east of the release point. Distances between relocations are noted.

3.22468e+6

3.22466e+6 patch reef relocation 3.22464e+6

3.22462e+6

3.22460e+6

3.22458e+6 N 3.22456e+6 Northing Northing 3.22454e+6

3.22452e+6

3.22450e+6 225 meters 3.22448e+6 75 meters

3.22446e+6 2.6285e+52.6290e+52.6295e+52.6300e+52.6305e+52.6310e+52.6315e+5 EastingEasting

Figure 14. Relocations of gag # 01 showing an MCP estimate of 0.82 Ha with a 190 m maximum width. One relocation per day (n = 16).

3232600 patch reef hrs 1 4 relocation 8 1 3232400

Release Point t ren cur 3232200 398 m N Capture Site 3232000 1939 hrs Northing Northing

3231800

3231600 225 meters

3231400 260800 260900 261000 261100 261200 261300 EastingEasting

Figure 15. 233 meter displacement of gag # 05, which homed within 295 minutes. Sunset at 1922 hours.

3232600 patch reef relocation

3232400 74 meters Release Point 3232200 N Capture Site 20 hours later 3232000 Northing Northing

3231800

nt 3231600 e curr 225 meters

3231400 260800 260900 261000Easting261100 261200 261300 Easting

Figure 16. 300 meter displacement of gag # 07, which homed the next day.

228200

225 meters patch reef relocation 228000 Release Point 202 m

227800 Capture Site N

227600 1 day later

g Northing

227400 Northin

t 227200 n e rr u c 225 meters

227000 260700 260800 260900Easting 26100Easting0 261100 261200 261300

Figure 17. 300 meter displacement of gag # 06. Approximately 24 hours later this gag was relocated on the northeast patch reef.

3228200 Release Point patch reef relocation

3228000 298 meters 44 mins

3227800 N 3 days later Capture Site 3227600 Northing Northing 3227400

e r r

3227200 u c 225 meters 225 meters 3227000 260700 260800 260900 261000 261100 261200 261300 EastingEasting

Figure 18. 450 meter displacement of gag # 08. This gag homed within three days after displacement.

3.2278e+6 patch reef relocation

3.2277e+6 225 meters

N 3.2276e+6

3.2275e+6 Northing Northin

3.2274e+6

3.2273e+6 225 meters

3.2272e+6 2.607e+52.608e+52.609e+52.610e+52.611e+52.612e+52.613e+5 EastingEasting

Figure 19. Relocations of gag # 08 showing an MCP estimate of 0.19 Ha with a maximum width of 75 m. One relocation per day.

3227800 225 meters patch reef relocation 3227600

3227400 Capture Site

3227200 65 mins N

m 6

Northing 7 3

3227000Northing

2 4 18 mins 3 3226800 m

t n e 3226600 r r Release u 225 meters c Point 3226400 260700260800260900261000261100261200261300Easting Easting

Figure 20. 600 meter displacement of gag # 09, which homed after 65 minutes. Italics represent time from release and bold represents distance traveled.

3.2321e+6 patch reef relocation

Release 3.2320e+6 Capture Point Site 64 meters 3.2319e+6 N

3.2318e+6 nt Northing Northing rre Cu 3.2317e+6

225 meters 3.2316e+6

400 meters 3.2315e+6 2.596e+52.598e+52.600e+52.602e+52.604e+52.606e+52.608e+52.610e+52.612e+52.614e+5 EastingEasting

Figure 21. 1000 meter displacement of gag # 03.

3.2323e+6 patch reef relocation 3.2322e+6

3.2321e+6

N 3.2320e+6

g 3.2319e+6 Northin

3.2318e+6Northing

3.2317e+6 225 m 3.2316e+6 225 m

3.2315e+6 2.602e+52.604e+52.606e+52.608e+52.610e+52.612e+52.614e+5 EastinEastingg

Figure 22. Relocations of gag # 15 showing an MCP estimate of 26.68 Ha with a maximum width of 1058 m. One relocation per day (n = 27).

3.2277e+6

225 meters patch reef relocation 3.2276e+6

3.2275e+6 N Northing 3.2274e+6Northing

3.2273e+6

225 meters 3.2272e+6 2.607e+52.608e+52.609e+52.610e+52.611e+52.612e+52.613e+5 EastingEasting

Figure 23. Relocations of gag # 17 showing an MCP estimate of 0.83 Ha with a maximum width of 208 m. One relocation per day (n = 15).

3.237e+6 patch reef Release relocation 3.236e+6 Point 580 meters

N 3.235e+6 Current

3.234e+6 Northing Northin

3.233e+6

Capture Site NW NE 3.232e+6

225 meters 3.231e+6 2.608e+5 2.609e+5 2.610e+5 2.611e+5 2.612e+5 2.613e+5 EastingEasting

Figure 24. 4000 meter displacement of gag # 13. Only the north, northeast, and northwest patch reefs are shown.

patch reef Capture relocation 3227600 Site NE Release Point

3227400 225 meters

SE N 3227200

rent Northing Cur 3227000Northin

3226800

1000 meters

3226600 260000 261000 262000 263000 264000 265000 266000 EastingEasting

Figure 25. 4000 meter displacement of gag # 18. Only the northeast and southeast patch reefs are shown.

3.2284e+6 patch reef 200 meters relocation 3.2282e+6

t n e r r u 3.2280e+6

g C N Northin 3.2278e+6Northing

Release 3.2276e+6 Point Capture Site NW 2000 meters

3.2274e+6 2.52e+5 2.54e+5 2.56e+5 2.58e+5 2.60e+5 2.62e+5 EastingEasting

Figure 26. 8000 meter displacement of gag # 12. Only the northwest patch reef is shown.

1 27

0.8

10 0.6

0.4 5 Prob homed

0.2 0

0 -101234 Displacement Distance (x 1000 meters)

Figure 27. Prediction probabilities of gag homing over displacement distances of 0, 2000, 3000, and 4000 meters with upper and lower 95% prediction intervals. The number of gag homed per displacement distance is noted above each upper prediction interval (n=90).

CHAPTER 4 DISCUSSION

Gag grouper have the capacity to home, although not all displaced gag in this study did. Given that gag home from 1000, 2000, and 3000 m, and did not from 4000 and 8000 m, the potential homing distance of gag residing on the SRRS apparently lies between

3000 and 4000 m. The experimental results of gag displaced either as individuals or en mass reflect similar homing distances.

Spatial Utilization

Data from this study show that gag maintain close association with one or more patch reefs, are residents of these reefs, and over time tend not to travel far from them, even after homing from an experimental displacement. This information supports past findings of limited gag movement (Topp, 1963; Beaumariage, 1964; Beaumariage and

Wittich, 1966) and fidelity to small areas (Beaumariage and Wittich, 1966; Moe, 1966;

Lindberg and Loftin, 1998). Multiple relocations of tagged gag on or near a specific patch reef is consistent with their reported tendency to be site specific and to utilize a central core site. Tagged gag were not relocated on all six patch reefs within a reef array, but mostly on one and, less often, on two or more patch reefs. This information when combined with the knowledge of long residency on small artificial patch reefs (Lindberg and Loftin, 1998) demonstrates that gag are strongly site attached, at least for days to months.

Knowing the size of the home range is important in displacement experiments for determining homing ability, but gag home range size is currently not known. Although

61 62 available data from this study cannot adequately establish gag home range size, three observations provide an approximation. First, the maximum distance recorded for resident gag away from their core area was 707 m. Second, the largest MCP width was

1058 m. Third, of the three gag tracked during the diel tracking studies, the maximum distance away from the nearest patch reef and their largest MCP width was 588 m and

726 m, respectively. Although the number of gag tracked was small, these observations indicate that home range size is less than 2000 m at its widest point and the core activity area is very much smaller. Whether or not gag displaced over 2000 m were displaced outside their home range is debatable, based on the semantics of “home range”. With the exception of the three diel tracking studies, it is important to point out that only diurnal relocations were used to calculate spatial area and this may underestimate it since nocturnal relocations were not included (Beyer and Haufler, 1994).

Serranids have long been thought to be crepuscularly active (Starck and Davis,

1966; Randall, 1967; Collette and Talbot, 1972; Potts, 1989; Carter et al., 1990), which is supported by the current study. Two of the three gag tracked for 24 hours were crepuscularly active and moved long distances (up to 270 m) at dusk, movements of which were far longer than those moved during daylight hours. Additionally, a displaced gag, # 02, made a long distance movement coinciding with dusk to return to it’s capture location, 398 m away. This crepuscular movement was much further than those movements it made during daylight hours. Crepuscular periods are characterized by environmental, behavioral, and ecological transitions (Helfman, 1993) and predators like gag probably seek to exploit this short transitional period. After the dusk crepuscular period two of the three gag were active during the hours of darkness. This contrasts with

63 findings by Carter et al. (1990) and Zeller (1997) who found that Nassau grouper,

Epinephelus striatus, and coral trout, Plectropomus leopardus, respectively, were inactive at night.

The ability to home is not unique to gag; six other serranids are known to have homed from tagging and displacement experiments, including Nassau grouper, E. striatus, and red hind, Epinephelus guttatus (possibly up to 350 m displaced) (Bardach,

1958). Mutton hamlet, Epinephelus afer, and E. striatus have also homed following 140 m displacements (Beets & Hixon, 1994). However, it could be argued that all three of these serranids were displaced and released within their home range. The graysby,

Epinephelus cruentatus, and coney, Epinephelus fulvus, have also homed from unspecified distances ranging between 100 and 800 m displacements (Corless et al.,

1997). Similar to the findings in this study, the dusky grouper, Epinephelus marginatus has homed from as far away as 3510 m (Lembo et al., 1999). Additionally, Luckhurst

(1998) captured, tagged, and displaced E. guttatus up to 20.3 km away from spawning aggregation sites and found that they can return to them.

Adaptive Significance

Gag ability to home might be presumed to have adaptive significance.

Theoretically, an animal’s ability to evaluate conditions within and beyond its home range, and then determine whether to leave for an area of higher quality or to remain at its present location, should lead to increased fitness. For example, it has been suggested that fitness may be improved by having the ability to return: 1) to familiar areas of refuge

(Metzgar, 1967; Ambrose, 1972; Clarke et al., 1993); 2) to areas of high productivity (i.e. to areas of known food resources (Stephens and Krebs, 1986; Bradbury et al., 1995)); and

3) to areas where habitat conditions result in higher spawning success (McDowall, 2001).

However, for gregarious animals like gag, returning to areas where other conspecifics are concentrated may also increase fitness through anti-predator defenses like increased vigilance, dilution and confusion effects, and other anti-predator advantages for living in groups (Miller, 1922; Bertram, 1978; Milinski, 1979; Barnard, 1983). Homing may also assist in the maintenance of populations of those animals displaced by natural forces, e.g., draughts or floods (Gerking, 1959; Giger, 1973; Yoshiyama et al., 1992).

Homing also suggests that the derived benefits are high or that the costs are low to return to familiar space. In the mass displacement experiments, the propensity to return to or remain on the resident site is evidenced by the 66% return rate from 2000 m and 90% retention of control gag. Within the range of these experiments, intuitively, the cost associated with homing 2000 m is less than homing from 4000 m. Ellis-Quinn and Simon

(1989) suggest that for young lizards the costs of homing may simply outweigh the benefits of establishing a new home range.

One can know the status of re-sighted gag, but one cannot assert the status of those not re-sighted. While gag were able to home from experimental displacements up to 3000 m, why two gag individually displaced at 1000 m or less did not home is not known. One possible explanation could be related to size, as one of the smallest (482 mm TL) of the

18 individually displaced gag did not home. The smallest gag to return from the mass displacement experiments was 558 mm TL. Another gag individually displaced only 286 m, initially traveled 119 m towards its capture site, but never returned to it’s origin. This gag might have been expected to home from the 286 m displacement, given the greater fish movements previously observed. However, the tag signal was lost after only 20 minutes tracking time. Possible explanations include tag failure, consumption by a

65 predator, or emigration from an assumed residence, owing to a weak attachment to the capture site possibly due to a short residence time. In this study, one tag did fail prior to implantation and there have been other tag failures using similar tags (Szedlmayer, 1997;

Lindberg and Loftin, 1998).

The capacity to home may provide behavioral flexibility in an ever-changing environment, which sets the stage for animal choice. Animal choice is an accepted assumption within related theories such as Optimal Foraging (Krebs, 1978), the Ideal

Free Distribution (Fretwell and Lucas, 1970), and Density Dependent Habitat Selection

(DDHS) (MacCall, 1990). To behave optimally, animals need to be able to assess current conditions relative to a number of ever changing factors, including, but not limited to, food availability, predation threat, and competitor density. In this study it could be arguably stated that homing gag made a choice to return to a familiar space, or emigrate, based upon some perceived advantage. The effects of salient factors and mechanisms of perception are yet to be tested in this study system.

Homing Mechanisms

While the homing mechanism(s) of gag grouper remains unknown, observations may offer insights into their capacity. Cognitive maps and pilotage may partially explain how gag homed. Knowledge of local geography, i.e. cognitive maps (Thinus-Blanc,

1987) and pilotage, the ability to find one’s way to a known destination across familiar terrain through the use of landmarks (Baker, 1984) is one method animals may use to home over short distances. Together cognitive maps and pilotage may account for gag homing from 1000 m or less, as gag roamed up to 707 m away from core sites, and hence may be knowledgeable of an area on that scale. Displacements beyond 1000 m exceed the furthest distance any tagged gag was relocated away from it’s home site and two gag

66 were able to home quickly from 1000 and 2000 m displacements within 134 and 122 minutes, respectively. Their ability to return quickly may indicate that gag are familiar with areas larger than their home ranges (as estimated in this study) or that they possess some homing mechanism or navigational skill necessary to return from unfamiliar areas.

As expected, gag homing success declined with increased displacement distances.

Homing studies of reptiles (Weintraub, 1970; Krekorian, 1977; Carroll and Ehrenfeld,

1978; Stanley, 1998), fish (Green, 1975; Ogden and Ehrlich, 1977; Marnane, 2000) and mammals (Hassell, 1963; Bovet, 1972; Cooke and Terman, 1977) also report similar declines with distance. Cognitive maps and pilotage, however, may not account for homing behavior of gag displaced over longer distances, especially those displaced over

2000 m. Gag that homed from distances greater than 2000 m may have homed over areas unfamiliar to them and it is likely that other abilities, possibly including navigational mechanisms, played a role in their homing.

Attempts have been made to determine whether visual recognition and olfaction play a role in the homing abilities of serranids. Bardach (1958) severed the optic nerve of seven red hinds and Nassau groupers before releasing them on a strange reef, however, none were recaptured. Bardach (1958) also firmly plugged with cotton the interior and posterior nares of seven red hinds and Nassau groupers and displaced them. Although the displacement distance was not reported, only one red hind homed and presumably did so without the use of its olfactory abilities. In the present study, gag were able to home while moving with and against the water current. Assuming water current transports olfactory cues down current, olfactory abilities may not be important to help gag home, at least over the distances displaced in these experiments. Three individually displaced gag

67 were able to home from 600, 1000, and 2000 m away, despite being released up-current from their capture point, which should have countered olfaction as a guide home. In contrast, two gag displaced 1000 and 286 m, were not relocated despite being released down current, theoretically permitting the use of olfactory cues. If olfaction is important to homing, then both grouper might have been expected to home. In a homing sensory study of an intertidal fish, Oligocottus maculosus, Khoo (1974) found that olfaction was more important than vision.

Other positional informational sources may be important to homing and may include solar, stellar, lunar, or magnetic information. Papi (1992) stated that animals often rely on two or more sources of information, switching between sources and integrating this information into a homing behavior. Whether sun compass navigation is used by gag remains unknown, however, homing occurred during periods of both clear and overcast skies. Under overcast skies two gag homed within 65 and 134 minutes after displacements of 600 and 1000 m, respectively, while another homed from 3000 m in 24- h. Under clear skies, one gag homed quickly (122 minutes) from 2000 m, but two gag displaced 4000 and 3000 m were never relocated.

Fisheries Management Implications

A sound understanding of fish movement is relevant to fishery management. In the marine environment there has been a growing interest away from reactive single species management to one incorporating proactive spatial management of mixed assemblages, i.e. marine protected areas (MPAs) and marine reserves (Conover et al., 2000). Today, these concepts are gaining momentum as acceptable conservation and management tools, yet uncertainties affect their universal acceptability (Agardy et al., 2003). One such area concerns the paucity of fish movement information (Roberts and Polunin, 1991; Rowley,

1994; Corless et al., 1997). Regarding the efficacy of marine reserves, Rowley (1994) stated that the primary research needs are for studies on fish movement. The paucity of fish movement data and ignorance of fish spatial requirements are two obstacles preventing universal acceptance of marine reserves as a management option. For instance, a “spillover effect” or emigration of adult fish from a protected area to an adjacent non-protected area (Rowley, 1994) is touted as one major benefit of marine reserves. However, pertinent data are scant and thus hypothesized benefits remain largely untested (Roberts and Polunin, 1991; Dugan and Davis, 1993; Russ and Alcala, 1996).

Another obstacle in the design and implementation of MPAs includes an understanding of how much area is needed to be set aside. Bohnsack (1990) suggests that the home range of the species needing protection will likely determine how much area a reserve should incorporate and that the reserve should be sufficient in size to prevent resident animals from being captured outside the reserve during normal movements.

Rowley (1994, pg 240) states, “the effectiveness of a reserve can be greatly increased if we know the movement patterns of species targeted for protection”, as well as determining the appropriate size of a marine reserve (Starr, 1998; Chiappone and Sealey,

2000; MPA News, 2004). Should reserve coupling, links between critical habitat and animal life stages (St. Mary et al., 2000), be considered in designing marine reserves, detailed knowledge of fish movements among life history stages and habitats will also be needed. Clearly, more detailed fish movement information is needed to develop these concepts into useful management tools.

Future Work

This study demonstrates the behavioral capacity to home by gag grouper and provides a general description of their use of space. The next step is to quantify home

69 range size through more rigorous testing over broader spatial and temporal scales, possibly incorporating an array of telemetry buoys monitoring spatial use over lunar and seasonal time scales. Work is also needed in tracking gag to and from offshore spawning aggregations, to determine whether or not gag home after spawning (Hood and Schlieder,

1992). At least two serranids, the coral trout (Zeller, 1998b) and the red hind (Luckhurst,

1998; Jimenez and Fernandez, 1999) are suspected of having homing behavior following their spawning aggregation. In the event that gag do return home from spawning aggregations, fishing pressure upon gag spawning aggregations may impact local gag stocks by practices that occur tens to hundreds of kilometers away (Koenig, 1999).

Shapiro (1987) stated similar concerns for those grouper species that may aggregate and return “home” after spawning.

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BIOGRAPHICAL SKETCH

Brian Kiel was born on July 3, 1961, in Blanchardville, Wisconsin, but for the majority of his childhood lived in Sparta, Wisconsin. After high school he enlisted in the

US Air Force and spent 12 years in the service as a Security Specialist and retraining in

Pararescue (PJ). He was medically retired in 1992 and enrolled in college, finishing an undergraduate degree in zoology at the University of Florida in 1996. He then was accepted into a marine ecology program with the Department of Fisheries and Aquatics

Sciences at the University of Florida in the fall of 1996. Along this journey came a son,

Casey, and a daughter, Kaitlyn, which occupied his time, energy, and focus as he chose to remain at home as a stay-at-home-dad. He will graduate with a Master of Science degree in the summer of 2004.