Floodplain management: Land acquisition versus preservation of historic buildings in Cambridge,Ontario, Canada

Non-structural adjustments in floodplain management are often avoided because they are seen to infringe on personal rights, adversely affect property values and restrict local tax bases. Land acquisition programs in urban areas encounter a further problem when they lead to demolition of buildings and other structures considered to have historical or architectural value. An experience in Cambridge, Ontario demonstrates that the potential conflict between flood damage reduction and historical preservation objectives can be exacerbated as a result of uncoordinated planning efforts, inflexibility in interpreting mandates, unclear roles for participating agencies, and lack of cooperation Many of these dilemmas can be resolved through consultation and discussion early in the planning process as well as through a willingness to be flexible and to search for a compromise     

Dieldrin, heptachlor, and chlordane residues in soybeans in Illinois 1974, 1980

The Illinois soybean crop was monitored in 1974 and 1980 for dieldrin, heptachlor, and chlordane residues resulting from the use of these compounds for corn soil insect control in the years before extensive soybean cultivation. Residue levels were compared with past published amounts. Dieldrin residue levels in soybeans declined between 1974 and 1980. Heptachlor and heptachlor epoxide levels remained level between 1974 and 1980. Chlorinated hydrocarbon residues were lower in the southern third of Illinois than for the remainder of the state.     

The undulating oceanographic recorder — A new instrument system for sampling plankton and recording physical variables in the euphotic zone from a ship underway

The prototype Undulating Oceanographic Recorder Mark I is an instrumented towed vehicle which can be programmed to undulate between a minimum depth of 8 m and a selected maximum depth between 15 and 70 m, with an undulation length between 3 and 30 km, at any speed between 7 and 15 knots (3.6 to 7.7 m/sec). It takes a continuous series of plankton samples, each integrated over the undulation depth range, and records data on magnetic tape, at a preselected rate between 30/min and 30/h, from which salinity, temperature and depth can be derived with accuracies of ±0.1, ±0.1C° and ±0.5 m, respectively. The instrument is automatic, self-contained and generates its own power supplies. It is towed on about 200 m of unfaired steel cable and can be handled with the winching and lifting equipment found on most research vessels. Examples of processed data from three cruises are presented: temperature and salinity contours on a vertical section through a complex stratified area in the N.W. Irish Sea; results from a survey of the waters over the continental shelf and slope to the north of Scotland, showing the distribution of water masses and associated plankton; and hydrographic data taken in Loch Etive on the west coast of Scotland.     

A DESIGN FOR LOW FLOW CONTROLS1

The determination of the total flow of an alluvial stream by rating a gaging station with a current meter may not be sufficiently accurate for a water yield study. If a large part of the total water yield consists of low flow, a means for accurate measurement must be employed. A technique for the design of a low flow control is described in this paper. Eight low flow controls have been designed on streams of the Southern Plains Watershed Research Center, Chickasha, Oklahoma. Field calibration measurements from these installations have been used to verify the design technique.     

The potential for biodiversity offsetting to fund effective invasive species control

Compensating for biodiversity losses in 1 location by conserving or restoring biodiversity elsewhere (i.e., biodiversity offsetting) is being used increasingly to compensate for biodiversity losses resulting from development. We considered whether a form of biodiversity offsetting, enhancement offsetting (i.e., enhancing the quality of degraded natural habitats through intensive ecological management), can realistically secure additional funding to control biological invaders at a scale and duration that results in enhanced biodiversity outcomes. We suggest that biodiversity offsetting has the potential to enhance biodiversity values through funding of invasive species control, but it needs to meet 7 key conditions: be technically possible to reduce invasive species to levels that enhance native biodiversity; be affordable; be sufficiently large to compensate for the impact; be adaptable to accommodate new strategic and tactical developments while not compromising biodiversity outcomes; acknowledge uncertainties associated with managing pests; be based on an explicit risk assessment that identifies the cost of not achieving target outcomes; and include financial mechanisms to provide for in‐perpetuity funding. The challenge then for conservation practitioners, advocates, and policy makers is to develop frameworks that allow for durable and effective partnerships with developers to realize the full potential of enhancement offsets, which will require a shift away from traditional preservation‐focused approaches to biodiversity management. El Potencial de la Compensación de la Biodiversidad para Financiar Controles Efectivos de Especies Invasoras     

Electrophoretic variants of egg white transferrin indicate a low rate of intraspecific brood parasitism in colonial cliff swallows in the Sierra Nevada,California

Summary The frequency of intraspecific brood parasitism in two colonies of cliff swallows (Hirundo pyrrhonota) nesting in the eastern Sierra Nevada in California was assessed through an electrophoretic analysis of egg white (albumin) proteins. Albumin proteins are maternally derived and are presumed to directly reflect maternal genotype. Thus, a comparison of protein banding patterns produced by eggs collected from a single clutch allows any egg laid by a female other than the putative mother to be detected. Eggs were collected from 13 cliff swallow nests in 1984 and 41 nests in 1987, a total of 54 nests. Of the clutches collected in 1984, one showed evidence of intraspecific brood parasitism, giving a nest parasitism rate of 7.6%. In 1987, one of 41 nests contained a parasitic egg, for a parasitism rate of 2.4%. Over both years combined the rate of intraspecific brood parasitism was 2 of 54 nests, or 3.7%. These parasitism rates are much lower than those estimated for Nebraskan cliff swallows (22–43%) and 2nd-year purple martins (36%). Possible explanations for the discrepancy between parasitism rates in Sierran cliff swallows and other groups of swallows are discussed.Correspondence to: A.P. Smyth     

Movements and swimming behaviour of white sharks (Carcharodon carcharias) in Australian waters

We used a combination of satellite telemetry, archival and conventional tags to show that white sharks made broad-scale movements consistent with mixing of the population across their entire Australasian range. The capture of one of these sharks in New Zealand, some 3,550 km from the point of tagging in South Australia, provides further confirmation that white sharks sometimes move into open ocean waters and cross deep ocean basins. However, most movements were confined to shelf waters, generally in areas of less than 100 m depth and in some cases into waters of less than 5 m depth. Sharks showed considerable plasticity in swimming patterns, which included many of the behaviours reported for other species. One of the archival-tagged sharks showed separate periods of distinct swimming behaviour as it moved into different habitats and travelled between them. The changes in swimming behaviour were abrupt and suggested rapid switching of hunting strategies for different prey types in these habitats. All tracked sharks showed both prolonged periods of directional swimming in coastal waters at swimming speeds of 2–3 km h⁻¹ as well as temporary residency in particular regions. Movements of tagged white sharks, together with data from shark control programs and bycatch records, suggest a seasonal movement northward along the east coast of Australia during the autumn–winter months and south in spring–early summer. The consistency of paths taken by white sharks in Australian waters suggests that they may follow common routes or “highways” in some areas. If so, identifying such areas may assist in reducing interactions with fishing operations and thus reduce bycatch.     

Age-specific survivorship in relation to clutch size and fledging success in California gulls

Summary Data from a natural population of California gulls (Larus californicus) demonstrated that increasing reproductive effort with age was associated with reduced survivorship. Number of offspring fledged but not clutch size was inversely related to adult survivorhip indicating that reproductively induced mortality resulted from the cumulative effects of the entire breeding season. Agerelated increases in fledging success were correlated with increased adult mortality. Young gulls fledged few offspring and had high survival rates. Old gulls tended to fledge more offspring and had low survival rates. However, those old gulls fledging few offspring survived as well as young gulls. Data also invalidate the assumption that survivorship is age-constant in this species.