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Newport, OR, United States

Lefcheck J.S.,Virginia Institute of Marine Science | Marion S.R.,Marine Resources Program | Lombana A.V.,Virginia Institute of Marine Science | Orth R.J.,Virginia Institute of Marine Science
PLoS ONE | Year: 2016

Human-driven habitat fragmentation is cited as one of the most pressing threats facing many coastal ecosystems today. Many experiments have explored the consequences of fragmentation on fauna in one foundational habitat, seagrass beds, but have either surveyed along a gradient of existing patchiness, used artificial materials to mimic a natural bed, or sampled over short timescales. Here, we describe faunal responses to constructed fragmented landscapes varying from 4-400 m2 in two transplant garden experiments incorporating live eelgrass (Zostera marina L.). In experiments replicated within two subestuaries of the Chesapeake Bay, USA across multiple seasons and non-consecutive years, we comprehensively censused mesopredators and epifaunal communities using complementary quantitative methods. We found that community properties, including abundance, species richness, Simpson and functional diversity, and composition were generally unaffected by the number of patches and the size of the landscape, or the intensity of sampling. Additionally, an index of competition based on species co-occurrences revealed no trends with increasing patch size, contrary to theoretical predictions. We extend conclusions concerning the invariance of animal communities to habitat fragmentation from small-scale observational surveys and artificial experiments to experiments conducted with actual living plants and at more realistic scales. Our findings are likely a consequence of the rapid life histories and high mobility of the organisms common to eelgrass beds, and have implications for both conservation and restoration, suggesting that even small patches can rapidly promote abundant and diverse faunal communities. © 2016 Lefcheck et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source

Hannah R.W.,Marine Resources Program | Jones S.A.,Marine Resources Program
Fisheries Research | Year: 2012

The behavior of roundfish excluded from an ocean shrimp (Pandalus jordani) trawl with a deflecting grid was studied using underwater video. The main study objective was to evaluate the condition of escaping eulachon (Thaleichthys pacificus), a species considered " threatened" under the United States Endangered Species Act. Observed behaviors were quantified in relation to a proposed model of an ideal trawl escapement based on an actively swimming fish avoiding contact with the grid. This model of avoidance-based escapement assumed that a roundfish in excellent condition would, (1) maintain distance from the grid, (2) avoid physical contact with the grid, (3) maintain a forward swimming orientation, and (4) maintain an upright vertical orientation. Of the species and size classes of fish encountered, large eulachon (approximately 170-240. mm total length) came closest to the proposed model of avoidance-based escapement, indicating less behavioral impairment than other species. Small eulachon (<150. mm) were not frequently encountered. Almost 80% of the large eulachon maintained an upright vertical orientation throughout their escape and exited the trawl in a forward-swimming orientation. Large eulachon maintained distance from the deflecting grid better than the other species encountered (P< 0.001) and typically showed no contact or only minimal contact with it (63%). Only about 20-30% of the large eulachon showed behaviors indicating fatigue, such as laying on or sliding along the grid. In contrast, both adult and juvenile Pacific hake (Merluccius productus) frequently showed signs of fatigue, including sliding along or laying on the grid, exiting the trawl in physical contact with the grid or failing to maintain an upright vertical orientation throughout their escape. Lingcod (Ophiodon elongatus) and juvenile rockfish (Sebastes) were intermediate in their escape behavior between Pacific hake and large eulachon. They more frequently maintained an upright vertical orientation throughout their escape than Pacific hake, but also showed signs of fatigue, such as sliding along the grid or exiting the trawl in physical contact with the grid. Our data suggest that observing escape behaviors provides additional useful information to evaluate the effectiveness of bycatch reduction devices in reducing fishery-related mortality rates. © 2012 Elsevier B.V. Source

Hannah R.W.,Marine Resources Program | Jones S.A.,Marine Resources Program | Lomeli M.J.M.,Pacific States Marine Fisheries Commission | Wakefield W.W.,National Oceanic and Atmospheric Administration
Fisheries Research | Year: 2011

Two trawl gear modifications for reducing fish bycatch (weight) in ocean shrimp (Pandalus jordani) trawls were tested in June and August-September 2010. The primary focus of the study was evaluating trawl system modifications for reducing bycatch of eulachon (Thaleichthys pacificus) below levels already achieved via mandatory use of bycatch reduction devices (BRDs). An experimental footrope, modified by removing the central one third of the trawl groundline, reduced eulachon bycatch by 33.9%. It also reduced bycatch of slender sole (Lyopsetta exilis), other small flatfishes and juvenile darkblotched rockfish (Sebastes crameri) by 80% or more, but had no effect on bycatch of whitebait smelt (Allosmerus elongatus) or Pacific herring (Clupea pallasii). The experimental groundline also reduced the catch of ocean shrimp (weight) by 22.2% in hauls yielding commercial quantities of shrimp (>194. kg/haul) and by 23.2% in all hauls. Reducing bar spacing in a rigid-grate BRD from 25.4. mm to 19.1. mm reduced eulachon bycatch by 16.6%, with no reduction in ocean shrimp catch. It also reduced bycatch of slender sole, other small flatfish and juvenile darkblotched rockfish by 36.8%, 71.8% and 76.3%, respectively with no effect on bycatch of whitebait smelt or young-of-the-year (YOY) Pacific hake (Merluccius productus). Although both trawl modifications reduced eulachon bycatch, the footrope modification tested, if developed further, has the potential to also avoid trawl entrainment for some demersal fishes, as well as reduce bottom impacts from trawling. © 2011 Elsevier B.V. Source

Hannah R.W.,Marine Resources Program | Blume M.T.O.,Marine Resources Program
Journal of Experimental Marine Biology and Ecology | Year: 2012

We describe the development and practical field testing of a rugged, unbaited video lander as a visual survey tool for fishes inhabiting structurally complex, high-relief, deepwater rocky reefs. Our autonomous, high-resolution, low-light, color video lander system utilized a smooth frame design that incorporated a series of breakaway attachments and inexpensive sacrificial steel bases to maximize the potential for camera system recovery from complex rocky habitats. Initial field tests at five reef complexes off Oregon (n. =. 421) and a larger study evaluating the western boundary of Oregon's Yelloweye Rockfish Conservation Area (YRCA, n. =. 527) showed that the video lander could be deployed and reliably retrieved from high-relief rocky habitat without damage to the camera system and with minimal losses of sacrificial bases. Acceptable visibility for counting fish from the lander video was common at offshore reefs like Stonewall Bank, but less so at nearshore reef complexes. The video lander system was effective for discriminating differences in fish species assemblages at the various reefs surveyed (one-way ANOSIM, P. <. 0.001) and for identifying seafloor habitat types and species-habitat associations for yelloweye rockfish (Sebastes ruberrimus) at Stonewall Bank (P. <. 0.05). The video lander data showed that the area outside and to the west of the YRCA enclosed similar quantities of yelloweye rockfish and their preferred habitats in comparison with the area inside the YRCA (0.179 yelloweye rockfish/station outside, versus 0.144 yelloweye rockfish/station inside, Wilcoxon test, P. =. 0.417). Our visual survey data also showed that the current western YRCA boundary is not optimal for protecting yelloweye rockfish at Stonewall Bank from fishery harvest. © 2012 Elsevier B.V. Source

Hannah R.W.,Marine Resources Program | Blume M.T.O.,Marine Resources Program
Marine and Coastal Fisheries | Year: 2016

We studied how variation in seafloor water clarity, ambient light, and fish fork length influenced the maximum detection range of fish with a stereo-video lander on three temperate reefs of different depths (12–40, 44–91, and 144–149 m). Although the results are somewhat approximate and specific to the camera system, the methods we used can be applied to any stereo remote underwater visual survey system. In the 52 total lander deployments distributed between nearshore, mid-shelf and deep-shelf reefs in Oregon waters, seafloor light levels varied over 4 orders of magnitude, primarily as a function of depth. The seafloor scattering index was higher (low water clarity) and highly variable at the nearshore reef and lower (high water clarity) and less variable at the deeper reefs. In the 15 deployments with sufficient numbers of fish for detection range analysis, the mean maximum range of detection across species varied from3.89 to 4.23 m at the deep-shelf reef, 3.32–5.55 m at the mid-shelf reef, and 1.57–3.42 m at the nearshore reef. Multiple regression analysis of the analyzed deployments showed a strong negative relationship between mean maximum detection range and the scattering index but no relationship with loge of seafloor ambient light. The lack of a light effect showed that the artificial lights were adequately illuminating the field of view in which fish were identifiable, potentially an important system test for sampling across a range of seafloor light levels. Analysis of detection range versus fish fork length for Blue Rockfish Sebastes mystinus and Deacon Rockfish S. diaconus from a single deployment showed a reduction in detection range for 10–20-cm fish of about 1.15 m relative to the detection range of 25–45-cm fish, or about 41%. © 2016, Robert W. Hannah and Matthew T. O. Blume. Source

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