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Peterson N.P.,West Fork Environmental | Simmons R.K.,West Fork Environmental | Cardoso T.,Terrastat Consulting Group | Light J.T.,Plum Creek Timber Company
North American Journal of Fisheries Management | Year: 2013

We conducted a series of volitional trials with wild-caught resident Coastal Cutthroat Trout Oncorhynchus clarkii clarkii in a 12.2-m-long, 1.8-m-diameter culvert test facility to develop a probabilistic model for predicting rates of upstream passage over a wide range of average velocities. The results of the passage trials indicated that the percentage of fish attempting passage and the percentage of fish successfully passing decreased as the trial target average velocity increased. At our highest trial average velocity of 2.4 m/s, 31% of test fish that chose to attempt passage passed after two nights of observation. Passage performance was generally better for larger fish, but this pattern was only statistically significant for a single trial (1.9 m/s). Fish ascended through the pipe more quickly as velocity increased. At higher test velocities fish favored the left side of the pipe (looking downstream), which contained a reduced-velocity zone created by the slightly oblique orientation of culvert corrugations. Our data provide the basis for a logistic model describing the probability of passage for Coastal Cutthroat Trout through bare corrugated metal culverts with no outlet drop. Empirical studies testing fish passage, such as this one, can inform culvert assessment protocols currently in use. © 2013 Copyright Taylor and Francis Group, LLC. Source


Irvine G.V.,U.S. Geological Survey | Shelly A.,Terrastat Consulting Group
Environmental Monitoring and Assessment | Year: 2013

Probability-based designs reduce bias and allow inference of results to the pool of sites from which they were chosen. We developed and tested probability-based designs for monitoring marine rocky intertidal assemblages at Glacier Bay National Park and Preserve (GLBA), Alaska. A multilevel design was used that varied in scale and inference. The levels included aerial surveys, extensive sampling of 25 sites, and more intensive sampling of 6 sites. Aerial surveys of a subset of intertidal habitat indicated that the original target habitat of bedrock-dominated sites with slope ≤30 was rare. This unexpected finding illustrated one value of probability-based surveys and led to a shift in the target habitat type to include steeper, more mixed rocky habitat. Subsequently, we evaluated the statistical power of different sampling methods and sampling strategies to detect changes in the abundances of the predominant sessile intertidal taxa: barnacles Balanomorpha, the mussel Mytilus trossulus, and the rockweed Fucus distichus subsp. evanescens. There was greatest power to detect trends in Mytilus and lesser power for barnacles and Fucus. Because of its greater power, the extensive, coarse-grained sampling scheme was adopted in subsequent years over the intensive, fine-grained scheme. The sampling attributes that had the largest effects on power included sampling of "vertical" line transects (vs. horizontal line transects or quadrats) and increasing the number of sites. We also evaluated the power of several management-set parameters. Given equal sampling effort, sampling more sites fewer times had greater power. The information gained through intertidal monitoring is likely to be useful in assessing changes due to climate, including ocean acidification; invasive species; trampling effects; and oil spills. © 2013 Springer Science+Business Media Dordrecht (outside the USA). Source


Melvin E.F.,University of Washington | Guy T.J.,University of Washington | Read L.B.,Terrastat Consulting Group
Fisheries Research | Year: 2013

We compared the performance of two bird-scaring line designs (light lines with short streamers vs. hybrid lines with a mix of long and short streamers) deployed in pairs with unweighted branch lines on two joint venture tuna vessels typical of distant-water tuna fisheries in the South Africa Exclusive Economic Zone (EEZ). We also added weight to a subset of branch lines, and compared the effects of line weighting and night vs. day setting in combination with bird-scaring lines on bird and fish catch rates. White-chinned petrels (Procellaria aequinoctialis), a diving seabird, dominated the seabird assemblage; they were the most numerous seabird and they attacked baited hooks and were killed at the highest rates. Secondary attacks - surface foraging albatrosses stealing baits from white-chinned petrels - drove albatross mortality. With hybrid scaring lines deployed, both diving and surface foraging seabirds made fewer attacks (1.5 and 2 times, respectively) within the lines' 100. m aerial extent, where hooks are closest to the surface and birds are most vulnerable to hooking, than with light lines. However, all metrics of comparison between hybrid and light lines were not statistically conclusive, primarily because birds could access baited hooks in areas beyond the protection afforded by bird-scaring lines (aft and to port of their aerial extent). Seabird bycatch rates were 4.6 times higher during daylight hours (2.00 birds/1000 hooks; 52 birds) than at night (0.439 birds/1000 hooks; 28 birds) and night catch rates near the full moon doubled. Bird catch rates were 18 times higher on unweighted branch lines (1.07/1000 hooks; 79 birds) than on weighted branch lines (0.06/1000 hooks; 1 bird) with no detectable effect on fish catch. With respect to streamer lines, our results suggest that in Procellaria petrel dominated systems the aerial extent of bird-scaring lines (of any design) should span the distance that baited hooks are within 10. m of the surface to effectively prevent bird attacks on baits. Overall, results suggest that night setting, adequate branch line weighting, and proper deployment of two bird-scaring lines have the potential to reduce seabird bycatch in pelagic longline fisheries without reducing the catch rates of target fishes. Further development of safe, fast-sinking branch line weighting configurations and bird-scaring lines less prone to tangling on fishing gear is critical to this effort. © 2013. Source


Melvin E.F.,University of Washington | Guy T.J.,University of Washington | Read L.B.,Terrastat Consulting Group
Fisheries Research | Year: 2014

We comprehensively tested combinations of three primary mitigation measures in a pelagic longline fishery with one of the highest rates of interaction with what may be the world's most challenging seabird assemblage (dominated by Procellaria genus petrels), aboard fishing vessels typical of the Asian distant water fleet. Multiple measures were used to compare the performance of weighted vs. unweighted branch lines set with two bird-scaring lines - hybrid lines with long and short streamers - during daytime and nighttime. The weights used were a novel double-weight configuration. Secondary attacks on baits brought to the surface by white-chinned petrels drove albatross mortality. Regardless of time of day, weighted branch lines with two bird-scaring lines, deployed and maintained with an aerial extent of 100. m, reduced bird attacks by a factor of four, and secondary attacks and seabird mortality by a factor of seven, compared to unweighted branch lines, with little effect on fish catch rates and with no injuries to crew. This combination yielded zero bird mortalities when gear was set at night. We conclude that the simultaneous use of two bird-scaring lines, weighted branch lines and night setting meet our criteria for best-practice seabird bycatch mitigation for the joint-venture fleet targeting tuna and related species in the South African EEZ. To be successful, the aerial extent of bird-scaring lines should be aligned with the distance astern that baited hooks sink beyond the foraging depth of the dominant seabird - in this case white-chinned petrels to a depth near 5. m. Given that these measures were successful in one of the most challenging pelagic longline fisheries, they are likely to be widely applicable to pelagic longline fisheries using similar gear. © 2013 Elsevier B.V. Source


Melvin E.F.,University of Washington | Dietrich K.S.,University of Washington | Fitzgerald S.,National Oceanic and Atmospheric Administration | Cardoso T.,Terrastat Consulting Group
Polar Biology | Year: 2011

Effective mitigation measures were developed to reduce high levels of seabird mortality due to warp strikes in southern hemisphere trawl fisheries. However, in northern hemisphere trawl fisheries, little is known about the extent of cable strike seabird mortality or techniques to mitigate it. We compared the rate of heavy seabird strikes by third-wire cables and warps, using three mitigation measures compared to a control of no mitigation. Experiments were conducted aboard two catcher-processor vessels targeting walleye pollock (Theragra chalcogramma) in the eastern Bering Sea: one that rendered offal into fish meal and fish oil (Vessel R) and one that minced offal prior to discharge (Vessel M). More birds attended Vessel M, but the rate of seabird cable strikes was higher on Vessel R due to the greater aerial extent of its cables. Streamer lines significantly reduced heavy seabird strikes by both cable types regardless of discharge characteristics. Reducing the aerial extent of third wires also reduced third-wire strike rates, but this method was less effective than streamer lines. Warp booms designed to divert seabirds from warps failed to reduce seabird warp strikes, but this technique could be improved. These results show for the first time that seabird strikes with modern third-wire trawl sonar cable systems can be reduced through mitigation or gear modification and that warp strikes can be mitigated with techniques similar to those found successful in southern hemisphere fisheries. Mitigation measures and concepts identified in this study should be widely applicable. © 2010 Springer-Verlag. Source

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