An Interim Draft Report Exploratory Analysis of the Occurrence of Kemp’s Ridleys in Inland Waters of Texas and Louisiana A report of the Texas A&M Research Foundation pursuant to U.S. Fish and Wildlife Grant No. 1448-00002-94-0823 Submitted by the Texas A&M Research Foundation Box 3573 College Station, Texas 77843 to the U.S. Fish and Wildlife Sevice Ecological Services Branch P.O. Box 1306 Albuquerque, New Mexico 87103-1306 Prepared by André M. Landry, Jr., David T. Costa, F. Leonard Kenyon, Marc C. Hadler, Michael S. Coyne, Lisa A. Hoopes, Lisa M. Orvik, Karen E. St. John, and Katharine J. VanDenburg Department of Marine Biology Institute of Marine Life Sciences Texas A&M University at Galveston Galveston, Texas 77551 March 1996 i Table of Contents List of Tables............................................................................................ ii List of Figures........................................................................................... iii List of Appendix Tables................................................................................ iv Introduction.............................................................................................. 1 Identification of Problem...................................................................... 1 Project Goals and Objectives................................................................. 3 Methods.................................................................................................. 3 Description of Work........................................................................... 3 Study Area............................................................................. 3 Sea Turtle Capture and Related Activities................................................... 4 Entanglement Netting................................................................. 4 Turtle Work-Up....................................................................... 4 Tagging Protocol......................................................................6 Blood Sampling/Sex Determination.................................................6 Habitat Characterization........................................................................7 Hydrographic Monitoring.............................................................7 Trawl Surveys..........................................................................7 Results.....................................................................................................8 Sea Turtle Capture Effort......................................................................8 Sea Turtle Population Dynamics..............................................................8 Other Turtle Captures.......................................................................... 23 Tag and Recapture..............................................................................28 Sex Ratio........................................................................................ 29 Prey Availability................................................................................29 Entanglement-Net Bycatch.................................................................... 37 Hydrographic/Meteorologic Conditions..................................................... 37 Discussion................................................................................................40 References................................................................................................43 Appendix Tables.........................................................................................45 ii List of Tables T a ble P a ge 1 Monthly entanglement netting effort (hours:minutes) at Sabine Pass habitats during March-October 1995. ............................................................. 9 2 Sea turtle captures at all monitoring sites during March-October 1995. ............. 10 3 Monthly number of sea turtles netted at Sabine Pass habitats during March- October 1995. .............................................................................. 11 4 Monthly number of Kemp' s ridleys netted at Sabine Pass during March-October 1995. ........................................................................................ 12 5 Monthly sea turtle CPUE (# turtles/km-hr) at Sabine Pass habitats during March- October 1995. .............................................................................. 15 6 Monthly Kemp' s ridley CPUE (# ridleys/km-hr) at Sabine Pass habitats during March-October 1995. ...................................................................... 16 7 Monthly abundance and CPUE for sea turtles and blue crabs at Sabine Pass habitats during March-October 1995. ................................................... 19 8 Straight carapace lengths (cm) for sea turtles captured at monitoring sites in 1995. 22 9 Sex of sea turtles captured at all monitoring sites in 1995. ........................... 30 10 Monthly gender abundance for sea turtles captured at all monitoring sites in 1995. 32 11 Demersal taxa collected in trawls at Sabine Pass during 1995. ....................... 34 12 Dominant (≥5% of total catch) taxa in trawl tows at Sabine Pass jetty sites (1,4) during 1995. ................................................................................ 35 13 Dominant (≥5% of total catch) taxa in trawl tows at Sabine Pass beachfront sites (3,5) during 1995. ......................................................................... 36 14 Monthly entanglement netting soak time (hours:minutes), bycatch (# individuals), and hydrographic measurements at Sabine Pass during April-October 1995. ...... 38 iii List of Figures F i gure P a ge 1 Sabine Pass study area. ................................................................... 5 2 Monthly number of Kemp' s ridley sea turtles captured by entanglement netting operations at Sabine Pass during 1995. ................................................. 13 3 Monthly catch-per-unit of effort (# turtles/km-hr) for Kemp' s ridley and loggerhead sea turtles at Sabine Pass during 1995. .................................... 14 4 Overall sea turtle catch-per-unit of effort (# turtles/km-hr) for jetty and beachfront habitats at Sabine Pass during 1995. .................................................... 18 5 Sea turtle catch-per-unit of effort (# turtles/km-hr) as a function of crab catch-per- unit of effort (# crabs/trawl tow) at all study areas/habitats during 1995. ........... 20 6 Straight carapace length (cm) frequency for Kemp' s ridleys netted at Sabine Pass during 1995. ................................................................................ 21 7 Monthly straight carapace length (cm) for Kemp' s ridleys netted at Sabine Pass during 1995. ................................................................................ 24 8 Monthly range and mean straight carapace length (cm) for Kemp' s ridleys netted at Sabine Pass during 1995. .............................................................. 25 9 Straight carapace length (cm) frequency for Kemp' s ridleys netted at Sabine Pass habitats during 1995. ...................................................................... 26 10 Range and mean straight carapace length (cm) for Kemp' s ridleys netted at Sabine Pass during 1995. ......................................................................... 27 11 Serum testosterone concentration (pg/ml) and sex of Kemp' s ridley and loggerhead sea turtles captured at all monitoring sites in 1995. ...................... 31 12 Predicted sex for different size classes of Kemp' s ridleys netted at Sabine Pass during 1995. ................................................................................ 33 13 Hypoxic/anoxic zone in the Gulf of Mexico 1995. .................................... 39 iv List of Appendix Tables A p pendix Table P a ge 1 Sea turtle captures during 1995. ......................................................... 45 2 Sea turtles recaptured at Sabine Pass and Calcasieu Pass habitats during 1995. ... 47 3 Sex determination information for sea turtles captured at all monitoring sites during 1995. ................................................................................ 48 4 Abundance and size of nekton species in trawl tows at Sabine Pass jetty sites (1,4) during 1995. ......................................................................... 49 5 Abundance and size of nekton species in trawl tows at Sabine Pass beachfront sites (3,5) during 1995. ................................................................... 58 6 Hydrographic measurements at Sabine Pass during March-October 1995. ......... 67 7 Sea and meteorological conditions at Sabine Pass during March-October 1995. .. 70 1 INTRODUCTION Identification of Problem The Kemp’s ridley (Lepidochelys kempii) is a critically endangered sea turtle whose nesting population has been reduced to about 1% of its 1947 abundance at its only nesting beach, Rancho Nuevo, Mexico. Ridley nests declined at about 4% per year from 1978 through the 1980’s, with the number of nesting females ebbing to as low as 350. This loss of reproductive potential plus recent estimates of 500 to 5000 conspecifics killed annually in shrimp trawls render Kemp’s ridleys the twelfth most endangered animal species in the world (Weber 1990) and a candidate for extinction (Magnuson et al. 1990). The Texas and southwestern Louisiana coasts are the annual recipients of 200 to 500 stranded sea turtle carcasses and, as such, the Gulf leader in documented Kemp’s ridley deaths (Ms. Donna Shaver,