Newport, OR, United States
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Thompson J.E.,Marine Resources Program | Hannah R.W.,Marine Resources Program
Environmental Biology of Fishes | Year: 2010

Since fishery management regulations have shifted much of the groundfish trawl effort in the northeastern Pacific from the continental shelf to the slope, fishery impacts on unassessed demersal slope rockfish species like the aurora rockfish (Sebastes aurora) may have increased. Understanding the life history of these species is a critical first step in developing management strategies to protect them from overharvest. In this study we employ cross-dating methods to validate the annual periodicity of growth increments and investigate the age, growth and maturity of aurora rockfish, a species for which life history information is quite limited. Specimens were collected on an opportunistic basis from Oregon commercial landings and from research cruises, over the years 2003-2006. Age was estimated for 438 individuals using otoliths processed via the break-and-burn method. The maximum estimated age was 118 years for females (n=324) and 81 years for males (n=114). The von Bertalanffy growth function showed that males grow faster and reach a smaller maximum size than females (males: L inf =34, K=0.09, t 0=-1.9; females: L inf=37, K=0.06, t 0=-5.5), though both sexes demonstrate relatively slow growth. Visual assessment of ovaries showed that the aurora rockfish is a synchronous spawner with parturition occurring in May and June off Oregon. Female age and length at 50% maturity were calculated at 12.6 years and 26 cm, respectively (n=307). Maturity and age data provided evidence for a protracted adolescence in this species. © 2010 Springer Science+Business Media B.V.

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.

Hannah R.W.,Marine Resources Program | Rankin P.S.,Marine Resources Program | Blume M.T.O.,Marine Resources Program
Marine and Coastal Fisheries | Year: 2012

We used a caging system designed to minimize the adverse effects of caging fish in marine waters to evaluate the discard mortality of seven species of rockfish Sebastes with barotrauma. Altogether, 288 rockfish were captured, scored for barotrauma, evaluated behaviorally at the surface, and caged individually on the seafloor for 48 h to determine survival. With the exception of three blue rockfish S. mystinus, the condition of surviving fish after cage confinement from 41 to 71 h was excellent. At capture depths up to 54 m, survival was 100% for yelloweye rockfish S. ruberrimus (n = 25) and copper rockfish S. caurinus (n = 10) and 78% for blue rockfish (n = 36). At capture depths up to 64 m, survival was 100% for canary rockfish S. pinniger (n = 41) and quillback rockfish S. maliger (n = 28) and 90% for black rockfish S. melanops (n = 144). Black rockfish survival was negatively associated with capture depth (m) and the surface-bottom temperature differential (°C). Blue rockfish survival was negatively associated with capture depth. Barotrauma signs and surface behavior scores were not good indicators of survival potential across species but were useful within species. In black and blue rockfish, severe barotrauma was negatively associated with survival, while higher scores on reflex behaviors at the surface were positively associated with survival. The high survival rates and excellent condition of some species in this study suggest that requiring hook-and-line fishers to use recompression devices to help discarded rockfish return to depth may increase survival for some species. © American Fisheries Society 2012.

Easton R.R.,Oregon State University | Heppell S.S.,Oregon State University | Hannah R.W.,Marine Resources Program
Marine and Coastal Fisheries | Year: 2015

Abstract: Temperate nearshore reefs along the Pacific coast of North America are highly valuable to commercial and recreational fisheries yet comprise a small fraction of the seabed. Monitoring fisheries resources in this region is difficult; high-relief structural complexity and adverse sea conditions have led to a paucity of information on temperate reef species assemblage patterns. Reliable, inexpensive tools and methods for monitoring are needed, as many traditional tools are both logistically complicated and expensive, limiting the frequency of their implementation over a large scale. Video drop cameras of varying designs have previously been employed to estimate fish abundance and distribution. We surveyed a nearshore rocky reef off the northern Oregon coast with a video lander (a video camera mounted on a landing platform so it can be dropped to the seafloor) over the spring and winter of 2011. We designed a 272-point systematic grid to document the species assemblage and the distribution and habitat associations of the reef species, including two overfished rockfishes: Canary Rockfish Sebastes pinniger and Yelloweye Rockfish Sebastes ruberrimus. Species assemblages differed significantly across the reef by depth and by season for the outer part of the reef. Well-defined habitat associations existed for many species; Canary Rockfish were associated with complex moderate-relief habitat types such as large boulders and small boulders, while Yelloweye Rockfish were associated with high-relief habitats like vertical walls. Species associations were evaluated pairwise to identify nearshore complexes. We compared our site with five exploratory reef sites off the central Oregon coast and found that nearshore reefs differed from our site, while offshore reefs were more similar. Video landers provide a solution to the need for increased sampling of temperate reef systems that are subject to difficult conditions and can contribute to habitat mapping, fish abundance indices, and fish assemblage information for monitoring and management of fisheries resources. © , © Ryan R. Easton, Selina S. Heppell, Robert W. Hannah.

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.

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.

Watson J.L.,Marine Resources Program | Huntington B.E.,Marine Resources Program
Journal of Experimental Marine Biology and Ecology | Year: 2016

Rocky reefs in the temperate Northeast Pacific constitute a small portion of the nearshore seabed, yet are highly valued as productive habitat for local fisheries. Surveying these structurally complex, untrawlable habitats requires robust gear that can be deployed in rough sea states. Here, a cost-effective, compact video lander was evaluated for its ability to survey the diversity and abundance of nearshore (< 40 m), rocky-reef-associated fish populations (e.g. Sebastes, Cottidae, Hexagrammidae). To determine the application and limitations of surveying complex rocky reefs with this new tool, this study sought to (1) determine the frequency of observation of known nearshore fish species, (2) evaluate the influence of baiting the lander on the observed fish assemblage, (3) identify the optimal deployment time to maximize observed species richness and abundance, and (4) evaluate species-specific behavioral responses to the lander characterized a priori as attractive, avoidance, or neutral. Seventy percent of lander deployments met established requirements of visibility, view, and habitat. Seventy-seven percent of observed fishes were identifiable to species. The method observed 15 species belonging to 5 families; 5 species were classified as common (observed in > 20% of deployments), the remaining rare. Contrary to lander studies in other regions, bait was not found to improve species-specific identification, increase observed species richness or abundance (at the species or feeding guild level), or shorten deployment duration. A deployment time of 8 min on the benthos was determined as optimal for observing maximum species richness and abundance in the nearshore, doubling the previously described lander drop durations evaluated in deeper Oregon, U.S.A., waters. Species-specific behavioral responses to this compact lander were evaluated by viewing trends in species abundance (assessed within 30 s bins) over the deployment duration; no attractive or avoidance behaviors were observed. Results confirm that this simple, cost-effective video lander configuration is suitable for sampling the suite of fish species found in the nearshore, including rockfish species federally designated as “overfished” (Sebastes pinniger and Sebastes ruberrimus). Furthermore, this study illustrates the importance of evaluating the performance of survey tools in the specific environment in which the tool will be used to determine best-practices from long-term monitoring. © 2016

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.

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.

Hannah R.W.,Marine Resources Program | Blume M.T.O.,Marine Resources Program
Marine and Coastal Fisheries | Year: 2014

Abstract: We evaluated how the use of bait as a fish attractant influenced the species and size composition of demersal fishes viewed with a stereo video lander at 160 sampling sites at Stonewall Bank, a deepwater rocky reef complex off the Oregon coast. We also studied the effectiveness of stereo video for generating estimates of fish length and distance from the cameras. Bait altered the species composition of fish encountered, increasing the mean counts of demersal fishes by 47%, with increases of 135–250% for Rosethorn Rockfish Sebastes helvomaculatus, Northern Ronquil Ronquilis jordani, and Spotted Ratfish Hydrolagus colliei. Increases in the mean counts of 35–150% for unidentified sculpins (Cottidae), Yelloweye Rockfish S. ruberrimus, and Quillback Rockfish S. maliger were nonsignificant. The calibrated stereo video lander provided acceptably precise estimates of fish length and camera-to-fish distance (range of three replicate measurements less than 3 cm for length and 20 cm for distance) for 34.3% of the demersal fishes that were counted. The precision of length and distance estimates declined with increased distance; acceptable estimates of distance were typical when fish were within 200 cm and were infrequent when fish were beyond 500 cm. Bait reduced the mean distance at which acceptable estimates of length and distance were obtained from 264 cm to 200 cm, but had no effect on mean fish length for the three most frequently encountered demersal species. The combined effect of bait on demersal fish counts and mean distance more than doubled the efficiency of the stereo video lander for generating fish length and fish–camera distance estimates.Received January 22, 2014; accepted April 9, 2014 © 2014, © American Fisheries Society 2014.

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