The objective of this study was to determine whether juvenile Chinook salmon Oncorhynchus tshawytscha are negatively influenced by the intraperitoneal implantation of acoustic transmitters. We evaluated swimming performance and predator avoidance of juvenile salmonids implanted with acoustic transmitters that weighed up to 6.7% of the fish's body weight in air. Critical swimming speeds (U crit ) of tagged, sham-tagged (surgery but no tag), and control fish were measured in a respirometer to determine tag effects on swimming performance. Swimming performance was similar among treatment groups at 1-d and 21-d postsurgery intervals. Predator avoidance of fish implanted with active tags was evaluated to determine whether tagged fish were impaired by the operation of the tags or predators were attracted to the signals emitted from the tags. Predator avoidance was evaluated by comparing the proportion of each treatment group consumed (active tag, inactive tag, sham, and control) during exposure to piscivorous adult rainbow trout O. mykiss. Surgical implantation of acoustic tags in juvenile fall Chinook salmon did not significantly affect swimming performance. Implantation of acoustic transmitters (active and inactive) did not result in greater predation susceptibility in tagged fish than in untagged fish.

A tag–release study is illustrated using radio-tagged chinook (Oncorhynchus tshawytscha) smolts to concurrently estimate passage rates and survival probabilities through the spillway and turbines of a hydroelectric project. The radio antennas at the forebays of the dam were arranged in double arrays allowing the estimation of route-specific detection probabilities and converting smolt detections to estimates of absolute passage. A maximum likelihood model is presented using the downstream detection histories to jointly estimate the route-specific passage and survival probabilities. In turn, these estimates were combined to estimate smolt survival through the dam, pool, and the entire hydroelectric project. The detailed migration information derived by these techniques can be used to evaluate mitigation programs focused on improving downstream passage of migrating salmonid smolts. At a mid-Columbia River hydroproject, the average spillbay survival calculated across replicate releases of hatchery and run-of-river yearling chinook salmon smolts was 1.000 ( estimated standard error, [Formula: see text] = 0.0144). Average survivals through the two different powerhouses at the hydroproject were estimated to be 0.9409 ([Formula: see text] = 0.0294) and 0.9841 ([Formula: see text] = 0.0119). Project survival after combining the route-specific survival and passage probabilities was estimated across stocks to be 0.9461 ([Formula: see text] = 0.0016).

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Salt diapirism to very shallow depths below seabed in the deepwater Gulf of Mexico Puma appraisal area has extensively tilted, thinned and faulted supra-salt strata, and permitted the migration of asphalt, oil and gas to the seafloor and into the water column. Hydrocarbon migration through the shallow strata has resulted in the formation of extensive areas of authigenic carbonate at, and immediately below, the seabed interface. Active hydrocarbon seepage continues to feed chemosynthetic fauna across much of the Puma area. However, population densities are sparser than might be expected based on the extent of authigenic carbonate interpreted from geophysical data.The integration of surface seismic and autonomous underwater vehicle geophysical data, synthetic aperture radar imagery acquired via satellite, and extensive video acquired in two remotely operated vehicle surveys, has been used to delineate the extent of the above geological and biological relationships to support exploration and appraisal activities in the Puma area. In areas of benign seafloor such extensive site investigation work would not be required. However, the evaluation of areas with complex shallow geology and rugged seafloor that may host environmentally sensitive fauna over extensive areas will benefit from the integrated approach described below.Puma Area. The Puma prospect was successfully tested by the Green Canyon (GC) Block 823 #1 well in 2003 ( Figure 1). The discovery well was followed by two appraisal wells (GC821 #1 and GC866 #1) which finished drilling in 2007. Reservoir level field appraisal, geotechnical studies to quantify the identified shallow geohazards, and investigation of potential development options are underway. The appraisal area is located in the southeast portion of the Green Canyon Protraction Area on the outer continental shelf immediately north of the Sigsbee Escarpment. Water depths in this area

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