Activities of juvenile green turtles, 

 Chelonia mydas, at a jettied pass 

 in South Texas 



Maurice L. Renaud 

 James A. Carpenter 



Jo A. Williams 



Galveston Laboratory, Southeast Fisheries Science Center 

 National Marine Fisheries Service, NOAA 

 4700 Ave. U, Galveston, Texas 77551 



Sharon A. Manzella-Tirpak 



U.S. Army Corps of Engineers 



2000 Fort Point Blvd., Galveston, Texas 77553 



Green turtles, Chelonia mydas, 

 have a worldwide distribution in 

 tropical and subtropical regions. 

 Primary nesting areas in the Atlan- 

 tic region are located at Ascension 

 Island, Aves Island, Costa Rica, and 

 Surinam. The east coast of Florida 

 has the largest breeding assem- 

 blage in the United States. The spe- 

 cies is listed as endangered by the 

 International Union for the Conser- 

 vation of Nature (IUCN) (Groom- 

 bridge, 1982) and is listed as threat- 

 ened in all areas, except for breed- 

 ing populations in Florida and the 

 Pacific coast of Mexico, which are 

 listed as endangered (National 

 Marine Fisheries Service, 1991). 



During most of the nineteenth 

 century, green turtles were abun- 

 dant throughout Texas, including 

 the lower Laguna Madre (Hilde- 

 brand, 1982; Doughty, 1984). Com- 

 mercial harvest of these turtles 

 peaked in 1890; Texas landings in- 

 creased to about 2,160 turtles 

 (265,000 kg) from an estimated 89 

 turtles (10,909 kg) in 1880. By the 

 early twentieth century the fishery 

 had collapsed (Doughty, 1984). 



Understanding habitat needs has 

 been recognized as an essential el- 

 ement for successful recovery of sea 

 turtle stocks in the Gulf of Mexico 



(Thompson et al., 1990). Distribu- 

 tion, movements, and feeding hab- 

 its of pelagic hatchlings are un- 

 known. Little research has been 

 conducted on sea turtle populations 

 in Texas. Published stranding data 

 suggest that Texas nearshore and 

 inshore waters are important habi- 

 tats for juvenile and subadult sea 

 turtles (Rabalais and Rabalais, 

 1980; Manzella and Williams, 

 1992). Recent tracking and mark- 

 recapture studies on green turtles 

 indicate that jetties and channel 

 entrances along the south Texas 

 coast serve as summer developmen- 

 tal habitats for this species 1,2 

 (Manzella et al., 1990; Shaver, 

 1990, 1994). This is supported by 

 higher numbers of sightings in 

 south Texas versus the upper Texas 

 and west Louisiana coasts (Will- 

 iams and Manzella, 1991). 



Turtles using jetties and channel 

 entrances could interact with hu- 

 man activities, such as channel 

 dredging, shrimping, and recre- 

 ational fishing and boating. The 

 level of such interaction is depen- 

 dent on the nature and degree of 

 jetty and channel utilization. Stud- 

 ies conducted during 1991 1,2 indi- 

 cated that green turtles may utilize 

 jetty habitat to a greater degree 



than other habitats within Brazos- 

 Santiago Pass, on the basis of 

 sightings and the behavior of a 

 single radio-tracked turtle. The 

 objectives of our study were to de- 

 scribe juvenile green turtle move- 

 ments within Brazos-Santiago 

 Pass, Texas. We hypothesized that 

 juvenile green turtles select jetty 

 habitat over other habitats within 

 Brazos-Santiago Pass. 



Materials and methods 



Study area 



The study was conducted in the 

 Brazos Santiago Pass area, South 

 Padre Island, Texas (Fig. 1). The 

 pass, extending from the tip of the 

 jetties to the western edge of Bar- 

 racuda and Dolphin Coves, links 

 the Laguna Madre to the Gulf of 

 Mexico. Landry et al. 1 character- 

 ized habitat types within the pass. 

 Using their data, we designated 

 four habitats in the pass area. 



The jetty habitat extended 10 m 

 from the visible jetty, with water 

 depths up to 3 m. It contained par- 

 tially exposed and submerged gran- 

 ite boulders and rubble, which de- 

 creased in density as distance from 

 the jetty increased. The highest 

 density and concentration of sessile 

 organisms were found in this habi- 

 tat. Barnacles (Balanus sp.), sea 

 urchins (Arbacia punctulata), and 



1 Landry, A, Jr., D. Costa, B. Williams, and 

 M. Coyne. 1992. Turtle capture and habi- 

 tat characterization study. Final Rep. sub- 

 mitted to the U.S. Army Corps of Engi- 

 neers, Galveston District, 2000 Fort Point 

 Blvd., Galveston, TX 77553, 112 p. 



2 Renaud, M., G. Gitschlag, E. Klima, S. 

 Manzella, and J. Williams. 1992. Track- 

 ing of green (Chelonia mydas) and logger- 

 head (Caretta caretta) sea turtles using 

 radio and sonic telemetry at South Padre 

 Island, Texas. June-September 1991. Fi- 

 nal Rep. to the U.S. Army Corps of Engi- 

 neers, Galveston District, 2000 Fort Point 

 Blvd., Galveston, TX 77553, 52 p. 



Manuscript accepted 5 December 1994. 

 Fishery Bulletin 93:586-593 (1995). 



586 



