Sonar image of plowed trench in sea floor along HubLine pipeline.
Sonar image of plowed trench in sea floor along HubLine pipeline.

Post-construction assessment activities of the HubLine pathway are multi-faceted and are intended to address impacts from the construction and evaluate recovery. We are involved in a long term effort through specific assessment and monitoring plans which, in some cases, are associated with mitigation projects. These will help us to understand the broad range of potential impacts which may have occurred.

Monitoring activities were initiated in June 2003 by Algonquin's contractors due to the need to evaluate the effect of surface laid pipe or open trench on the seasonal onshore migration of American lobster. The study did not report higher concentrations of lobsters on the east side of the pipe which would have indicated that the pipe was an impediment to inshore (westward) migration of lobsters. However, since back-fill plowing had already begun, results should be considered inconclusive.

Additional monitoring studies were initiated by MarineFisheries in August 2003 with several localized sampling efforts. MarineFisheries' staff undertook underwater video monitoring including diver transect surveying to describe and quantify biota in and near the trenches of three sections of exposed pipe off Boston. Algonquin's plan to bury these sections with stone raised concerns about the effect on fauna and flora in the trenches and adjacent natural habitat. SCUBA surveys provided baseline data for future recovery monitoring which indicated that significant changes in vegetation and re-colonization of crustaceans and finfish had occurred in a relatively short time since the pipe was laid.

During 2003 MarineFisheries augmented its commercial lobster sea sampling in the general Massachusetts Bay area in order to evaluate potential impacts from construction on the Massachusetts Bay lobster fishery. Standardized catch rate trends will be monitored and updated during the HubLine study period.

Suction Sampling of Early Benthic Phase Lobsters

Suction sampling of early benthic phase (EBP) lobsters was conducted in the Massachusetts Bay area to help evaluate larval lobster settlement relative to previous years. Sampling was conducted using a diver-operated suction device. This time series will be updated annually for the duration of the HubLine Program and augmented with site-specific suctioning of impacted sediments on the pipeline pathway.

Ventless Trap Survey

Commercial lobster trap sampling during ventless trap survey.
Commercial lobster trap sampling during ventless trap survey.

In the fall of 2004 MarineFisheries initiated a pilot random stratified ventless trap survey for American lobster in Massachusetts Bay . This survey was stratified by depth and sediment type to account for their effects on lobster spatial distribution. The survey is therefore designed to monitor lobster relative abundance and size distribution over a variety of habitats. It will help to evaluate lobster abundance and size structure on the impacted HubLine pathway relative to non-impacted areas throughout Massachusetts Bay while taking into consideration the effects of depth and bottom sediment type.

Four commercial lobstermen were contracted to fish experimental ventless traps at pre-defined randomly-selected stations throughout Massachusetts Bay . Traps were constructed of 1-inch wire mesh and were fished in six-pot trawls with alternating vented and non-vented traps. A total of forty trawls were deployed and hauled twice per month in October and November.

Catch per trawl of four size classes; juvenile (30 to 58 mm CL), pre-recruit (59 to 70mm CL), recruit (71 to 82mm CL) and legal (> 83mm CL) of lobsters by sediment type.
Catch per trawl of four size classes; juvenile (30 to 58 mm CL), pre-recruit (59 to 70mm CL), recruit (71 to 82mm CL) and legal (> 83mm CL) of lobsters by sediment type.

A total of 936 trap hauls were sampled during sixteen sampling trips, from which 8,602 lobsters were observed. As expected catches were higher in the ventless traps and >90% of all lobsters caught were sub-legal. Vented traps captured a higher proportion of legal sized lobsters than did the ventless traps. Smaller lobsters were observed more frequently in boulder and cobble habitat than in mud or sandy areas and were more common in shallow water than deep strata.

MarineFisheries will resume this survey in May 2005 and extend the it across seasons. We look forward to working with the four participating Captains once again.

Click here for an informational Coastal Lobster Project Pamphlet .

Acoustic and Optical Surveys of Pipeline Pathway

Long term monitoring of the pipeline pathway began in March 2004 after the schedule of trench back-filling and leveling was projected to be completed. In order to monitor changes in the disturbed area we undertook a sonar and video monitoring effort to provide post-construction baseline information. As-built coordinates of the pipeline pathway were acquired from Algonquin's subcontractor, TRC Environmental Corporation, and baseline imaging of the disturbed sediments using sonar and video equipment aboard the 65' NOAA R/V Gloria Michelle was initiated.

Pipeline pathway recovery assessment was conducted with ROV and sonar imaging throughout 2004. Inshore, shallow water area segments (< 20 ft.), which could not be surveyed due to the R/V Gloria Michelle's draft, were surveyed with the smaller R/V Amphitrite. The work resulted in complete coverage of the back-filled trench across all depths. Countless sonar images were reviewed in order to evaluate sediment type and relief. Permanent sites were established for future occupation and monitoring. These sites are representative of various sediment types, topographical features, and depth along the pipeline pathway.