Population characteristics of Kemp's ridley sea turtles in nearshore waters of the upper Texas and Louisiana coasts

Abstract

Entanglement netting at beachfront, tidal pass, bay, and lagoon habitatsalong the upper Texas and Louisiana coasts was used to characterizespatial/temporal occurrence, relative abundance, size class composition,sex ratio, and growth rate of nearshore Kemp's ridley (Lepidochelyskempii) assemblages in the western Gulf during 1992-98. Nine study areasfrom Grand Isle, Louisiana, to South Padre Island, Texas, were netted atdifferent frequencies and/or years, with capture operations scheduledfor at least 1 week per month at one or more areas. Beachfront habitatsnear Calcasieu Pass, Louisiana, and Sabine Pass, Texas, received 73% ofthe netting effort and accounted for 97% of the 429 ridleys capturedduring the study. Headstarted ridleys comprised 6.8% (29 individuals)of these captures, and all were netted at beachfront habitats. Overallridley catch per unit of effort (CPUE) among all years and study areaswas 0.5 ridley/km-hr. CPUEs at beachfront versus bay/pass habitats were0.6 and 0.1, respectively. Sabine and Calcasieu Pass beachfront habitatsyielded overall CPUEs of 0.7 and 0.5, respectively, while bay/passhabitats produced CPUEs ranging from 0.0 to 0.2. Annual CPUEs at SabinePass, the only area netted each year of the study, ranged from 0.2 to1.1. Ridleys dominated (92%) catches at upper coast study areas. Ridleyoccurrence at Sabine and Calcasieu Passes was generally limited to Aprilthrough September, with May through August producing 92% of the sample.December through February failed to yield ridleys at any study area.Recapture rate for 415 ridleys tagged at Sabine and Calcasieu Passes was2.9%, with the interval ranging from 22 to 364 days. Recaptured ridleysgrew at a mean rate of 0.02 cm/day or 7.3 cm/year. Ridleys ranged from19.5 to 65.8 cm SCL, with 77% < 40 cm SCL. Adults comprised 2.3% ofall captures, none of which were mature males. Sex ratio of wild ridleyswas 1.3F:1M. Nearshore, neritic Gulf waters along the upper Texas andLouisiana coasts provide developmental habitat to juvenile and subadultridleys during late spring through summer when blue crab abundance anddiscarded shrimp fishery bycatch are highest.