Scales of spatial variation in demography of a large coral-reef fish: an exception to the typical model?

Spatial variation in demographic parameters of the red throat emperor (Lethrinus miniatus) was examined among 12 coral reefs in three geographic regions (Townsville, Mackay, and Storm Cay) spanning over 3° of latitude of the Great Barrier Reef, Australia. Estimates of demographic parameters were based on age estimates from counts of annuli in whole otoliths because there was no significant difference in age estimates between whole and sectioned otoliths. There were significant regional differences in age structures, rates of somatic and otolith growth, and total mortality. The Townsville region was characterized by the greatest proportion of older fish, the smallest maximum size, and the lowest rates of otolith growth and total mortality. In contrast the Mackay region was characterized by the highest proportion of younger fish, the largest maximum size, and the highest rates of otolith growth and total mortality. Demographic parameters for the Storm Cay region were intermediate between the other two regions. Historic differences in fishing pressure and regional differences in productivity are two alternative hypotheses given to explain the regional patterns in demographic parameters. All demographic parameters were similar among the four reefs within each region. Thus, subpopulations with relatively homogeneous demographic parameters occurred on scales of reef clusters. Previous studies, by contrast, have found substantial between-reef variation in demographic parameters within regions. Thus spatial variation in demographic parameters for L. miniatus may differ from what is assumed typical for a coral-reef fish metapopulation.

Turtle excluder devices -- Are the escape openings large enough?

All five species of sea turtles in continental U.S. waters are protected under the Endangered Species Act of 1973 and the population sizes of all species remain well below historic levels. Shrimp trawling was determined to be the largest source of anthropogenic mortality of many of the species. As a mechanism to reduce the incidental catch of turtles in trawl nets, turtle excluder devices have been required intermittently in the shrimp fishery since 1987, and at all times since 1994. The expanded turtle excluder device (TED) regulations, implemented in 1994, were expected to reduce shrimp trawl capture of sea turtles by 97%. Recent evidence has indicated that the sizes of turtles stranding were not representative of the animals subjected to being captured by the shrimp trawlers. The purpose of our study was to compare the sizes of stranded sea turtles with the size of the TED openings. We compared the sizes of stranded loggerhead (Caretta caretta), green (Chelonia mydas), and Kemp’s ridley (Lepidochelys kempii) sea turtles, the three species most commonly found stranded, to the minimum widths and heights of TED openings. We found that annually a large proportion of stranded loggerhead turtles (33–47%) and a small proportion of stranded green turtles (1–7%) are too large to fit through the required minimum-size TED openings. The continued high mortality of sea turtles caused by bottom trawling is reason for concern, especially for the northern subpopulation of loggerhead turtles, which currently is not projected to achieve the federal recovery goal of reaching and maintaining prelisting levels of nesting.

Simulation and diagnosis of large-scale atmospheric moisture and surface hydrology over North America

We describe a preliminary investigation into large-scale atmospheric and surface moisture variations over North America. We compare large-scale hydrologic budgets in the Los Alamos general circulation model (GCM) to observed precipitation and vertically integrated atmospheric moisture fluxes derived from the National Meteorological Center's operational analyses. THe GCM faithfully simulates the integrated flux divergence and P-E differences. However, the integrated moisture content is too low, and precipitation and evaporation are too high. The model produces summertime soil moisture dryness, which supports previous studies showing increased droughts under warmer conditions.

Anomalous atmospheric circulation and large winter floods in six subregions of the southwestern United States

EXTRACT (SEE PDF FOR FULL ABSTRACT): We examined atmospheric circulation conditions conducive to occurrence of winter floods that exceed the 10-year peak discharge on rivers in six hydroclimatic subregions in Arizona, southern Utah, Nevada, and California. ... This relationship between flooding and broad-scale atmospheric patterns in the modern record will aid in paleoclimatic interpretations of paleoflood records over the last few thousand years.

Climatological aspects of the large-scale hydrologic cycle in the United States

We describe a 2.5-degree gridpoint atmospheric hydrology/climatology of precipitable water, precipitation, atmospheric moisture convergence, and a residual evaporation or evapotranspiration for the coterminous United States. We also describe a large-scale surface hydrology/climatology of a residual soil moisture, streamflow divergence, or runoff, as well as precipitation and evaporation. Annual and seasonal means and interrelationships among various components of the hydrologic cycles are discussed.