EGRESS OF ADULT SPORT FISH FROM AN ESTUARINE FISH REPLENISHMENT ZONE WITHIN MERRITT ISLAND NATIONAL WILDLIFE REFUGE, FLORIDA

Stevens, P. W., and K. J. Sulak
Florida Integrated Science Center,
U. S. Geological Survey, Gainesville, Florida

Stevens, P.W. and K.J. Sulak.  Egress of adult sport fish from an estuarine reserve within
 Merritt Island National Wildlife Refuge, Florida. Gulf of Mexico Science 2001: 77-89.

Presented at Mar 2000 Benthic Ecology/Southeastern Estuarine Research Society
at Wilmington NC, and Mar 2000 American Fisheries Society at Brooksville, FL

Abstract

A mark-recapture study was conducted within Merritt Island National Wildlife Refuge in the waters surrounding Kennedy Space Center, Florida (where public access has been restricted since 1962) to document egress of adult sport fish from a potential estuarine fish replenishment zone.  A total of 3,358 sport fish were tagged within the restricted areas.  The species tagged were red drum Sciaenops ocellatus (n = 1,366), spotted seatrout Cynoscion nebulosus (n = 927), black drum Pogonias cromis (n = 760), and common snook Centropomis undecimalis (n = 305).  Results showed that adult sport fish moved from the restricted areas within Merritt Island National Wildlife Refuge to surrounding areas open to fishing. The recapture rate based on angler responses outside of the restricted areas were 3.1, 0.7, 2.6, and 16.1 percent for red drum, spotted seatrout, black drum, and common snook, respectively.  In general, red drum, spotted seatrout, and black drum were recaptured in waters adjacent to the restricted areas. Common snook, however, migrated from the restricted areas south to inlets.  Mark-recaptures for red drum, spotted seatrout, and black drum, together with a previous study that found greater abundance and size of sport fish in the restricted areas than in adjacent areas open to fishing, substantiate the fish replenishment zone function of the restricted areas. The restricted areas within Merritt Island National Wildlife Refuge protect fish populations and export large adult sport fish to surrounding waters open to fishing.

Introduction

An estuarine reserve has been in effect within Merritt Island National Wildlife Refuge (MINWR) since 1962, where public access and fishing have been prohibited due to security operations at Kennedy Space Center (KSC) (Johnson et al. 1999). The MINWR 'restricted areas' lie immediately adjacent to heavily fished areas of Indian River Lagoon, Mosquito Lagoon, and Banana River (Fig. 1).  This provides a unique setting within which to test the functions of a no-take estuarine reserve in terms of replenishment of exploited sport fish species. A comparison of fish communities between open and closed fishing areas and a mark-recapture study was undertaken by U.S. Fish and Wildlife Service, 1986 – 1992, to evaluate the effectiveness of MINWR reserve as a fish replenishment zone. Such an evaluation must consider several questions, as follow: 1) Do target fish species increase within the reserve, 2) Does mean adult size increase within the reserve such that protection is being conferred to potential spawners, 3) Do protected fish from within the reserve egress into local and/or more distant areas, contributing to exploited fisheries, 4) Does the existence of the reserve facilitate reproduction and juvenile recruitment in target species.  Johnson et al. (1999) have recently addressed the first two questions, indicating greater abundance and larger mean fish size for selected sport fish within MINWR reserve, compared to data from adjacent areas. Johnson et al. (1999) also provide incidental information concerning question 4, suggesting that sport fish spawn within the reserve.  The present analysis specifically addresses question 3, whether the MINWR restricted areas contribute adult sport fishes to adjacent or more distant areas.

Methods

The target sport fish species for the study were spotted seatrout (Cynoscion nebulosus), red drum (Sciaenops ocellatus), black drum (Pogonias cromis), and common snook (Centropomis undecimalis). Fish were captured by U.S. Fish and Wildlife Service personnel using trammel nets and angling within the restricted area (no public access) surrounding KSC (Fig. 1) from November 1986 to April 1988 and from October 1990 to April 1992.  Captured fish were tagged with either a 7 mm x 26 mm or a 7 mm x 17 mm internal anchor tag with a 55 mm external yellow streamer. Total length (TL), location, tag number, and tagging date were recorded for each tagged fish. For recaptures, tags were imprinted with a return address and tag number on one side and with the wording "$5.00 Reward" on the opposite side. Posters advertising the $5.00 reward were distributed throughout the area.

Discussion

Individuals of each sport fish species tagged during the study egressed from the restricted areas within MINWR to areas open to fishing. However, the MINWR restricted areas may have limited utility in protecting highly migratory species, such as Florida Atlantic common snook, because these species are difficult to protect from exploitation within a small reserve (e.g. Bohnsack 1998).  For the study species with small home ranges, such as spotted seatrout, red drum, and black drum, the restricted areas within MINWR function to replenish the local fishery, by first protecting sport fish populations from exploitation (Johnson et al. 1999), and subsequently exporting adult sport fish to surrounding waters open to fishing.  The restricted areas maintain sport fish species in higher abundance than in adjacent fished areas. The relative abundance (standardized catch per unit effort) of spotted seatrout, red drum, and black drum were 2.4, 6.3, and 12.8 times greater in the restricted areas than in adjacent areas open to fishing (Johnson et al. 1999).  The size of red drum and spotted seatrout in the restricted areas was also greater than areas open to fishing (Johnson et al. 1999). The present mark-recapture results show that large adult sport fish egress from the restricted areas within MINWR to nearby waters, contributing to the recreational fishery of the Indian River Lagoon, Banana River, and Mosquito Lagoon.

The final question that remains with respect to estuarine reserves as fish replenishment zones is whether reserves facilitate reproduction and recruitment in target species. The MINWR restricted areas export large sport fish, and thus add potential spawners to the species spawning pool in adjacent fished areas.  It seems probable, however, that spotted seatrout, red drum, and black drum also spawn within the MINWR restricted areas (Johnson et al. 1999). If so, the greater abundance and size of adult sport fish compared to adjacent fished areas would likely result in greater spawning potential and stock fecundity, potentially increasing egg and larvae production. These benefits are likely to have regional effects, enhancing juvenile recruitment in adjacent fished areas (e.g. Bohnsack 1998). Further research is needed to document spawning behavior, larval dispersal, and juvenile recruitment in target species within the MINWR restricted areas to further determine the effectiveness of estuarine sanctuaries as fish replenishment zones, and to quantify the relative contribution of estuarine reserves to local and regional fisheries.

References

Bohnsack, J. A.  1998. Application of marine reserves to reef fisheries management. Australian Journal of Ecology 23: 298-304. 

Johnson, D. R., N. A. Funicelli, and J. A. Bohnsack. 1999.  The effectiveness of an existing estuarine no-take fish sanctuary within the Kennedy Space Center, Florida. North American Journal of Fisheries Management 19: 436-453.

Acknowledgments

We would like to acknowledge Jim Clugston, Nick Funicelli, Darlene Johnson, Gary Hill, Les Parker, Don Meineke, Steve Traxler, John Noble, and all of the volunteer assistants who conducted the original tagging effort within Merritt Island National Wildlife Refuge.  We would like to thank Merritt Island National Wildlife Refuge and Canaveral National Seashore personnel for their support throughout the study.  The original tagging project was funded by the U.S. Fish and Wildlife Service, grants from the Florida Institute of Government (STAR grant 87-012), and National Marine Fisheries Service.  The analysis was funded, in part, by the U.S. Geological Survey Coastal Restoration Initiative.