Persistence of Hydraulic Dredge Tracks Following Surfclam Harvesting in Shallow Water

Legare, Bryan; Nichols, Owen C.; Borrelli, Mark

doi:10.2983/035.039.0214

Cited by 2 publications

(9 citation statements)

References 26 publications

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“…The area is dominated by submerged sand flats and banks with a median grain size (D50 1-2 mm) of coarse sand (Borrelli et al, 2019). From November 2014 to April 2015, a series of fishing vessels harvested Atlantic surfclams (Spisula soldidissima) by hydraulic dredge along the Provincetown Hook, for the first time since a moratorium was imposed in 2007 (Borrelli et al, 2012;Myers, 2015;Legare et al, 2020a). The method of fishing employed involved a hydraulic clam dredge, in which high-pressure jets of water fluidize the substrate allowing a cage to sift clams and other objects larger than bar width into the cage.…”

Section: Study Sitementioning

confidence: 99%

“…Fisheries management plans for Atlantic surfclams (Mid-Atlantic Fisheries Management Council, 2016) state that in sand dominated environments, the effects of dredging on benthic communities are short lived (hours to months), and that, in comparison, disturbances caused by strong currents and storm events would be more severe. These conditions are assumed for the nearshore sandy environment along Cape Cod, yet physical alteration to the substrate in nearshore environment has been shown to last multiple years (Legare et al, 2020a).…”

Section: Introductionmentioning

confidence: 99%

“…The area off Herring Cove, has had a local moratorium on hydraulic clamming starting in 2007, in which no hydraulic clamming has been documented between 2007 and the winter of 2014-2015. During the winter of 2014-2015, a series of vessels conducted hydraulic clamming within the study site, extensively covering the area (Legare et al, 2020a). The impacts were thought to be ephemeral allowing the baseline inventory to proceed as planned.…”

Section: Introductionmentioning

confidence: 99%

“…The impacts were thought to be ephemeral allowing the baseline inventory to proceed as planned. Upon inspection (Legare et al, 2020a), significant alteration to the substrate was found. This led us to question if the current survey could be considered a baseline.…”

Section: Introductionmentioning

confidence: 99%

“…The present study focuses on understanding benthic invertebrate communities relative to habitat type and disturbance by hydraulic clamming. Analysis of acoustic surveys identified an area of slow (multiple years) physical recovery to the substrate (Legare et al, 2020a) but no information about the biological impacts exists. Using acoustic survey techniques, benthic invertebrate surveys, grain size analysis, and video surveys, this study documents: 1) the habitat types present; and 2) the differences in benthic invertebrate community composition between areas exposed to hydraulic clamming and areas that have not been exposed to hydraulic clamming.…”

Section: Introductionmentioning

confidence: 99%

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The impacts of hydraulic clamming in shallow water and the importance of incorporating anthropogenic disturbances into habitat assessments

Legare

Mittermayr

Borrelli

2020

Aquat. Living Resour.

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Hydraulic dredging for shellfish is known to create some of the highest levels of disturbance, affecting the benthic microfaunal community and the physical characteristics of the substrate. Properly conducted benthic habitat assessments are complex and time consuming, resulting in assessments not being conducted increasing the uncertainty in post impact studies. Hydraulic dredging for Atlantic surfclams (Spisula soldidissima) took place at Herring Cove, Massachusetts in the winter of 2014–2015 resulting in areas of high impact disturbance of the seafloor. Surveys conducted in the summer of 2015 included hydroacoustics, benthic invertebrate sampling, video, and grain size analysis for the creation of a habitat map of Herring Cove. The four habitats (A–D) identified were a mix of sand, shell, cobble, algae, and eelgrass. Habitat type “D” is a mix of sand, algae and cobble material and occurred at 12 of 18 stations. These 12 stations were distributed across areas of “high” (n = 4), “low” (n = 2), and “no” (n = 6) hydraulic dredge disturbance. Once habitat was accounted for, benthic invertebrate community structure varied significantly (Analysis of similarity; significance level of sample statistic: 0.3%) between areas of “high”, “low” to “no” disturbance. Areas of “low” to “no” dredge track coverage contained high abundances of bivalves, echinoderms, and isopods, whereas highly disturbed areas had highest abundances of polychaetes and oligochaetes. Future mapping efforts, especially surveys with biological components, need to include and quantify the level, type and spatial distribution of anthropogenic alterations. More attention should be given to “reference maps” instead of “baseline maps”. The latter of which omits to acknowledge pre-existing anthropogenic disturbances and has the potential to skew monitoring of restoration and management efforts.

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Section: Study Sitementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The impacts of hydraulic clamming in shallow water and the importance of incorporating anthropogenic disturbances into habitat assessments

Legare

Mittermayr

Borrelli

2020

Aquat. Living Resour.

Self Cite

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Absolute Localization of Targets Using a Phase-Measuring Sidescan Sonar in Very Shallow Waters

et al. 2023

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The detection, classification, and localization of targets or features on the seafloor in acoustic data are critical to many disciplines. This is most important in cases where human safety is in jeopardy, such as hazards to navigation, mitigation of mine countermeasures, or unexploded ordnance. This study quantifies the absolute localization of targets, in the form of inert unexploded ordnance, in very shallow waters (2–3 m) on two intertidal bottom types in a meso-tidal environment (tide range = ~3.0 m). The two sites, a sandy intertidal flat and a mixed sand and gravel beach with abundant cobble-sized material, were seeded at low tide with targets (wax-filled 60-, 81-, 105- and 155-mm, projectile and mortar shells). An RTK-GPS was used to collect positional data for the targets and an unoccupied aerial system (UAS) survey was conducted on both sites. At the next high-tide, a vessel-based acoustic survey was performed, and at the subsequent low tide, the targets were re-surveyed with RTK-GPS. We focus here on the sidescan backscatter from a phase-measuring sidescan sonar (PMSS) and the sources of uncertainty for absolute localization. A total of 1426 calls of acoustic targets were made within the sidescan backscatter data, yielding an accuracy of 0.41 ± 0.26 m, with 98.9% of all calls <1 m from their absolute location. Distance from nadir was the most significant source of uncertainty, and targets between 3–7 m had the lowest uncertainty (0.32 ± 0.23 m) with increasing values toward and away from nadir. Bathymetry and bathymetry-mode backscatter were less useful for the detection and classification of targets compared to sidescan backscatter, but once detected, the accuracy of absolute localization were similar. This is likely due to target calls from these two datasets that were orders of magnitude less and that focused on the larger sized targets, thus more work is needed to better understand these differences. Lastly, the absolute localization of targets detected on sandy and cobble bottoms for all datasets were statistically similar. These acoustic instruments, their datasets, and methods presented herein can better document the absolute localization within acoustic data for many uses in very shallow waters.

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Persistence of Hydraulic Dredge Tracks Following Surfclam Harvesting in Shallow Water

Cited by 2 publications

References 26 publications

The impacts of hydraulic clamming in shallow water and the importance of incorporating anthropogenic disturbances into habitat assessments

The impacts of hydraulic clamming in shallow water and the importance of incorporating anthropogenic disturbances into habitat assessments

Absolute Localization of Targets Using a Phase-Measuring Sidescan Sonar in Very Shallow Waters

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