The great February 1986 flood [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): There were many similarities between the February 1986 storm and that of December 1964 and also December 1955. The 1964 storm hit hardest a little further north and the North Coast took the brunt of that storm. December 1955 also produced higher north coastal area runoff. December 1955 produced greater peaks in the central part of the state than the 1964 flood and is perhaps more comparable south of the Lake Tahoe-American River area. But the real surprise this time was the volume. Four reservoirs, Folsom, Black Butte, Pardee, and Comanche, were filled completely and became surcharged (storing more water than the designed capacity). The 10 day total rainfall amounted to half the normal annual totals at many precipitation stations. The February 1986 flood is a vivid reminder of the extremes of California climate and the value of the extensive system of flood control works in the state. Before the storm, especially in January, there was much concern about the dryness of the water year. Then with the deluge, California's flood control systems were tested. By and large the system worked preventing untold damage and misery for most dwellers in the flat lands.

Changes in frost frequency and desert vegetation assemblages in Grand Canyon, Arizona

The effect of decreasing frost frequency on desert vegetation was documented in Grand Canyon by replication of historical photographs. Although views by numerous photographers of Grand Canyon have been examined, 400 Robert Brewster Stanton and Franklin A. Nims views taken in the winter of 1889-1890 provide the best information on recent plant distribution. In Grand Canyon, where grazing is limited by the rugged topography, vegetation dynamics are controlled by climate and by demographic processes such as seed productivity, recruitment, longevity and mortality. The replicated photographs show distribution and abundance of several species were limited by severe frost before 1889. Two of these, brittlebush (Encelia farinosa) and barrel cactus (Ferocactus cylindraceus), have clearly expanded their ranges up-canyon and have increased their densities at sites where they were present in 1890. In 1890, brittlebush was present in warm microhabitats that provided refugia from frost damage. Views showing desert vegetation in 1923 indicate that Encelia expanded rapidly to near its current distribution between 1890 and 1923, whereas the expansion of Ferocactus occurred more slowly. The higher frequency of frost was probably related to an anomalous increase in winter storms between 1878 (and possibly 1862) and 1891 in the southwestern United States.

Reproductive seasonality, fecundity, and spawning frequency of tautog (Tautoga onitis) in the lower Chesapeake Bay and coastal waters of Virginia

The tautog, Tautoga onitis (Linnaeus), ranges from Nova Scotia to South Carolina and has become a popular target for recreational and commercial fisheries. Although tautog are a multiple spawning species, reproductive potential, measured as annual fecundity, has not been estimated previously with methods (batch fecundity, spawning frequency) necessary for a species with indeterminate annual fecundity. A total of 960 tautog were collected from the mouth of the Rappahannock River in the lower Chesapeake Bay to 45 km offshore of Virginia’s coastline to investigate tautog reproductive biology in the southern portion of the species range. Tautog did not exhibit a 1:1 sex ratio; 56% were females. Male tautog reached 50% maturity at 218 mm TL, females at 224 mm TL. Tautog spawned from 7 April 1995 to 15 June 1995, at locations from the York River to 45 km offshore. Batch fecundity estimates ranged from 2800 to 181,200 eggs per spawning for female tautog age 3–9, total length 259– 516 mm. Mean batch fecundity ±SEM for female tautog ages 4–6 was 54,243 ±2472 eggs and 106,256 ±3837 eggs for females ages 7–9. Spawning frequency was estimated at 1.2 days, resulting in 58 spawning days per female in 1995. Estimates of potential annual fecundity for tautog ages 3–9 ranged from 160,000 to 10,510,000 eggs.

Swimming depth, ambient water temperature preference, and feeding frequency of young Pacific bluefin tuna (Thunnus orientalis) determined with archival tags

We investigated the migration and behavior of young Pacific Bluefin tuna (Thunnus orientalis) using archival tags. The archival tag measures environmental variables, records them in its memory, and estimates daily geographical locations based on measured light levels. Of 166 archival tags implanted in Pacific bluefin tuna that were released at the northeastern end of the East China Sea from 1995 to 1997, 30 tags were recovered, including one from a fish that migrated across the Pacific. This article describes swimming depth, ambient water temperature, and feeding frequency of young Pacific bluefin tuna based on retrieved data. Tag performance, effect of the tag on the fish, and horizontal movements of the species are described in another paper. Young Pacific bluefin tuna swim mainly in the mixed layer, usually near the sea surface, and swim in deeper water in daytime than at nighttime. They also exhibit a pattern of depth changes, corresponding to sunrise and sunset, apparently to avoid a specific low light level. The archival tags recorded temperature changes in viscera that appear to be caused by feeding, and those changes indicate that young Pacific bluefin tuna commonly feed at dawn and in the daytime, but rarely at dusk or at night. Water temperature restricts their distribution, as indicated by changes in their vertical distribution with the seasonal change in depth of the thermocline and by the fact that their horizontal distribution is in most cases confined to water in the temperature range of 14−20°C.

Assessing the precision of frequency distributions estimated from trawl-survey samples

In trawl surveys a cluster of fish are caught at each station, and fish caught together tend to have more similar characteristics, such as length, age, stomach contents etc., than those in the entire population. When this is the case, the effective sample size for estimates of the frequency distribution of a population characteristic can, therefore, be much smaller than the number of fish sampled during a survey. As examples, it is shown that the effective sample size for estimates of length-frequency distributions generated by trawl surveys conducted in the Barents Sea, off Namibia, and off South Africa is on average approximately one fish per tow. Thus many more fish than necessary are measured at each station (location). One way to increase the effective sample size for these surveys and, hence, increase the precision of the length-frequency estimates, is to reduce tow duration and use the time saved to collect samples at more stations.

Strong, low frequency (decadal) environmental fluctuations during the 20th century in the North Pacific Ocean, on the Washington coast, and in Puget Sound

At decadal period (10-20 years), dynamic linkage was evident between atmospheric low pressure systems over the North Pacific Ocean and circulation in a Pacific Northwest fjord (Puget Sound). As the Aleutian low pressure center shifts, storms arriving from the North Pacific Ocean deposit varying amounts of precipitation in the mountains draining into the estuarine system; in turn, the fluctuating addition of fresh water changes the density distribution near the fjord basin entrance sill, thereby constraining the fjord's vertical velocity structure. This linkage was examined using time series of 21 environmental parameters from 1899 to 1987. Covariation in the time series was evident because of the strong decadal cycles compared with long-term averages, interannual variability, and seasonal cycles.

Inferences from tree rings on low frequency variations in runoff in the interior western United States

EXTRACT (SEE PDF FOR FULL ABSTRACT): Low frequency variations in runoff, AD 1700-1964, in the interior western United States are inferred from smoothed tree-ring series averaged over north, central, and south regions. ... Relative locations of peaks and troughs in streamflow, precipitation, temperature, and tree-ring series suggest that annual precipitation and warm season evapotranspiration variations may both be important to low frequency fluctuations in tree growth and in streamflow.

Assessment of agrobiodiversity resources in the Borotse flood plain, Zambia

Concerns about perceived loss of indigenous materials emerged from multiple stakeholders during consultations to plan and design the CGIAR Research Program on Aquatic Agricultural Systems for the Borotse hub in Zambia’s Western Province. To come to grips with and address the concerns, the AAS Borotse hub program of work included an assessment of agrobiodiversity to inform community-level and program initiatives and actions. The agrobiodiversity assessment comprised three components: key informant and expert surveys complemented by review of grey and published literature, focus group discussions in the communities, and individual household surveys. This working paper reports the findings from assessments of agrobiodiversity resources in the Borotse hub by key informants and local experts working in government ministries, departments and agencies, and non-governmental organizations operating in the communities. This working paper covers the following topics: agriculture in the Borotse flood plain; major agricultural land types in the Borotse flood plain; soils and their uses; production systems; crops, including the seed sector and ex-situ resources; indigenous materials collected from the wild, including non-perennial and perennial plants, aquatic plants, and forest biodiversity; fish resources, including both capture fisheries and aquaculture; livestock resources; dietary diversity; and indigenous and local knowledge on management systems.

Inter-regional correlation in tree-growth variations in the western United States, 1513-1964, at ENSO, sunspot, and longer frequency bands

Cross-spectral analysis of regional tree-ring data suggests the spatial pattern of correlation between moisture variations in the Sierra Nevada of central California and in other parts of the western United States is frequency dependent. Short wavelengths (2.8 to 10.7 years), perhaps associated with El Niño/Southern Oscillation, are strongly coherent both to the north (Oregon) and to the south (Southern California). Longer wavelengths (45 to 75 years) are strongly coherent only to the north. Frequency bands corresponding to annual sunspot series were associated with relatively weak patterns of spatial correlation.