The Atchafalaya River Basin in south-central Louisiana (USA) comprises the largest contiguous river-floodplain swamp in North America and functions as a distributary for the Mississippi River to the Gulf of Mexico. We assessed the impact of the annual flood pulse on fisheries production at a basin-wide scale. We modelled flood duration (days/year Butte LaRose gauge height >3.6 m) and magnitude (mean daily gauge height) against long term ) fishery-independent and fishery-dependent data on largemouth bass (Micropterus salmoides), crappie (Pomoxis spp.), blue catfish (Ictalurus furcatus), buffalofish (Ictiobus spp.), gizzard shad (Dorosoma cepedianum) and crayfish (Procambarus spp.). When the Atchafalaya River at Butte LaRose is at flood stage (≥ 3.6 m gauge height) for approximately 121-157 days/year, then annual relative abundances of largemouth bass, crappie, blue catfish and buffalofish are optimized during the fall (October-December). In contrast to the tenets of the flood pulse concept, gizzard shad abundance was optimized during low flow years, when flood duration is ≤10 days/year. Annual proportion of age-1 largemouth bass was associated positively with flow magnitude during the previous year, whereas proportions of age-2 largemouth bass and crappie were associated positively with flood magnitude 2 years prior to the fish sample. Results for commercial production metrics were ambiguous. Crayfish catches were associated positively with flood magnitude and duration, whereas gizzard shad landings peaked at a relatively small flood magnitude level and were not related to flood duration. Blue catfish and buffalofish annual landings were not influenced by the annual flood pulse. The annual flood pulse can be managed to optimize the availability of recreational (largemouth bass and crappie) and some commercial fisheries resources (blue catfish and crayfish). We estimate that a minimum discharge of 8807 m 3 s À1 is required at the river's source for approximately 4-5 months during the winter-spring months to optimize fisheries production. Figure 1. The Atchafalaya River Basin showing the study area and sample locations for the electrofishing, gill net and commercial crayfisher creel surveys. This figure is available in color online at wileyonlinelibrary.com/journal/rra MANAGING FLOODS TO OPTIMIZE ATCHAFALAYA BASIN FISHERIES Only stock-size fish were included (TL ≥ 200 mm for largemouth bass and 150 mm for crappie). b All buffalo species (Ictiobus spp.) were included. MANAGING FLOODS TO OPTIMIZE ATCHAFALAYA BASIN FISHERIES 283
No abstract
The pressures of urbanization place demands on city infrastructure and connections between cities. The rapid urbanization in the latter half of the 20th century was carried out against a backdrop of depletion of limited natural resources, generation of wastes, including greenhouse gases, and inefficient use of energy. The Brundtland Commission and subsequent 1987 report recognized this behavior as globally unsustainable. Over the past 25 years, much effort has been expended to establish carbon emissions on a country-by-country basis in order to demonstrate reductions against a baseline. There has been a transformation in energy consumption in commercial and residential buildings as a result of concerted efforts in energy conservation. However, the construction of buildings and infrastructure, and the operations and maintenance of infrastructure have received comparatively little attention, despite being responsible for significant proportions of global greenhouse gas emissions. This paper concentrates on the use of carbon accounting and embodied energy methods for a wide range of ground engineering construction activities. The authors examine concepts of Capital and Operational Carbon and associated payback period, and provide examples that show how this holistic approach can result in design changes and considered choices in construction and maintenance means and methods.
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