J. A. Keinath

Bio: J. A. Keinath is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 28 citations.

The Horseshoe Crab, Limulus polyphemus: 200 Million Years of Existence, 100 Years of Study

Abstract: (2002). The Horseshoe Crab, Limulus polyphemus: 200 Million Years of Existence, 100 Years of Study. Reviews in Fisheries Science: Vol. 10, No. 1, pp. 39-73.

Compensatory growth in oceanic loggerhead sea turtles: response to a stochastic environment

Abstract: Compensatory growth (CG, accelerated growth that may occur when an organism that has grown at a reduced rate as a result of suboptimal environmental conditions is exposed to better conditions) is considered an adaptation to variable en- vironments. Although documented thoroughly under captive conditions, CG has rarely been studied in wild populations. In their first years of life, oceanic-stage loggerhead sea turtles (Caretta caretta) have relatively little control over their geographic position or movements and thus have an extremely stochastic lifestyle with great variation in food availability and temperature. This environmental variation results in variable growth rates. We evaluate somatic growth functions of oceanic-stage loggerheads from the eastern Atlantic based on skeletochronology that allowed us to assign age and cohort to each individual. We demonstrate CG in these turtles based on three different analytical approaches: changes in coefficients of variation in size-at-age, generalized additive model regression analyses of somatic growth, and linear regression of age-specific growth rates. As a result of CG, variation in size-at-age in these juvenile loggerheads is substantially reduced. Thus, size is a better predictor of age than expected based on variation in growth rates. CG decreases with age, apparently as loggerheads gain greater control over their movements. In addition, we have evaluated for the first time in wild sea turtles the time-dependent nature of somatic growth by distinguishing among age, year, and cohort effects using a mixed longitudinal sampling design with assigned-age individuals. Age and year had significant effects on growth rates, but there was no significant cohort effect. Our results address critical gaps in knowledge of the demog- raphy of this endangered species.

The Ecology and Migrations of Sea Turtles 8. Tests of the Developmental Habitat Hypothesis

Abstract: The existence of ontogenetic shifts in habitat by marine turtles, and of immature-dominated assemblages in “developmental habitat,” were important concepts first proposed by Archie Carr in 1956. Results of long-term, in-water capture programs in Caribbean Panama (17 yr) and Bermuda (37 yr) allow the testing and refinement of these ideas, in particular the developmental habitat hypothesis for Chelonia mydas, Eretmochelys imbricata, and Caretta caretta. A literature survey reviews worldwide studies on these species, and also incorporates Lepidochelys kempii. The studies in Panama and Bermuda reported in this paper use netting, mark/recapture, laparoscopy, and satellite telemetry to investigate size distributions, maturity status, residency, site fidelity, and developmental migrations of three species of sea turtles at three study sites. Characteristics of benthic developmental habitat of C. mydas, E. imbricata, L. kempii, and, to a lesser extent, C. caretta in the Atlantic Ocean usually include ben...

Sea Turtles in North Carolina Waters

Abstract: Until the turn of the century the inshore waters of North Carolina harbored populations of sea turtles large enough to support a commercial fishery. Based on a 4- to-5-year record of sighting reports by the public, interviews of recreational fishermen, and records kept by commercial fishermen the waters continue to provide important developmental habitats for loggerhead, green, and Kemp's ridley sea turtles. Leathertback and hawksbill sea turtles infrequently entered the inshore waters. Reports from the public and commercial fishermen indicated that sea turtles were present offshore North Carolina all year and were present in inshore waters April through December. Sea turtles were encountered most frequently in the Atlantic Ocean, but seasonal encounters in some inshore waters, such as Core and Pamlico Sounds, often were greater. In early May large numbers of leatherbacks were sighted in the ocean and moved northward along the beach. Reported sightings of leatherbacks declined markedly by late June. Based on incidental captures by commercial fishermen loggerhead turtles were the most numerous species in Pamlico and Core Sounds (80%), followed by green (15%) and Kemp's ridley sea turtles (5%). Most captured turtles were immature, and all were released alive. The abundance of immature sea turtles in North Carolina inshore waters serves to emphasize that southeast U.S. estuaries are important habitats for these threatened and endangered species. This recognition supported the decision of the U.S. National Marine Fisheries Service to extend the requirement for turtle excluder devices in shrimp trawls to inshore areas during the entire year, full implementation of these requirements was achieved by December 1994. Las aguas costeras de Carolina del Norte (EEUU) acogieron poblaciones de tortugas marinas lo suficientemente grandes como para sostener una pesqueria comercial hasta principios de siglo. Basados en 4 a 5 anos de registros de reportes de avistamiento por et publico, entrevistas a pescadores deportivos, y registros mantenidos por pescadores comerciales, es posible inferir que las aguas continuan proveyendo importantes habitats de desarrollo para las tortugas marinas cahuama, verde y lora de Kemp. Las tortugas marinas laud y de carey entraron en las aguas costeras en forma poco frecuente. Los reportes del publico y pescadores comerciales indicaron que las tortugas marinas estaban presentes en las aguas de alta mar frente a las costas de Carolina del Norte todo et ano y se encontraban en las aguas costeras entre abril y diciembre. Las tortugas fueron encontradas mas frecuentemente en et Oceano Atlantico, pero los encuentros estacionales en algunas aguas costeras, tales como los Estrechos de Core y Pamlico, fueron en muchos casos, mayores. A principios de Mayo se avistaron grandes numeros de tortugas laud en el oceano las cuales se movian en direcion al norte a lo largo de la costa. Los avistamientos de tortugas laud reportados declinaron marcadamente hacia finales de Junto. En base a las capturas incidentales por pesqueros comerciales se puede inferir que las tortugas cahuama fue la especie mas abundante en los Estrechos de Pamlico y Core (80%), seguidas de las tortugas verdes (15%) y las tortugas loras de Kemp (5%). La mayoŕia de las tortugas capturadas eran inmaduras y todas fueron liberadas con vida. La abundancia de tortugas marinas inmaduras en las aguas consteras de Carolina del Norte sirven para enfatizar que los estuarios del sudeste de los Estados Unidos son habitats importantes para estas especies amenazadas y en peligro. Estos reconocimientos fundamentaron la decision de extender el requerimiento de dispositivos de exclusion de tortugas en la pesca de arrastre del langostino hacia las areas costeras todo el ano; una implementacion completa de estos requerimientos fue alcanzada en diciembre de 1994.

Historical Diet Analysis of Loggerhead Sea Turtles (Caretta Caretta) in Virginia

Abstract: Digestive tract contents were examined from 297 Loggerhead Sea Turtles (Caretta caretta) in Virginia during 1983–2002. Analyses revealed a shift from predominantly Atlantic Horseshoe Crab (Limulus polyphemus) during the early to mid-1980s to predominantly Common Blue Crab (Callinectes sapidus) during the late 1980s and early 1990s. Diet in the mid-1990s and in 2000–2002 was dominated by finfish, particularly Atlantic Menhaden (Brevoortia tyrannus) and Atlantic Croaker (Micropogonias undulatus). These diet shifts suggest that horseshoe crab and blue crab population declines have caused loggerheads to forage in nets or on discarded fishery bycatch.