New Understanding of Lobster Shell Disease


The conversations on the dock and in the papers this summer about lobster focused on the quantity of softshell lobsters that arrived along the entire coast virtually simultaneously in July, and the resulting drop in price that led to tie-ups and concerns about fishermen’s ability to turn a profit even as they landed record quantities. But below the clamor, fishermen were voicing another concern: the increasing appearance of shell disease in lobsters from Maine’s western and southern coastal waters. Shell disease contributed to the decimation of the lobster fishery south of Cape Cod. In June, scientists from a host of institutions, from Virginia to Maine published results of a multi-year research effort into the causes and impacts of shell disease in Southern New England in a special issue of the Journal of Shellfish Research.

Marta Gomez-Chiarri and J. Stanley Cobb, both at University of Rhode Island, synthesized the study results, and wrote that the major outbreak of Epizootic Shell Disease (ESD) in Rhode Island, Buzzards Bay, and eastern Long Island Sound occurred after a period of exceptionally high lobster population density (and fishery volume). According to Chiarri and Cobb, these conditions were similar to those that occurred in Western Long Island Sound directly before the major mortality event in 1999-2001, which researchers believe was caused by a combination of warm water, low oxygen, excess nutrients and pollutants stressing the lobsters, so that they became susceptible to a parasite which actually caused the mortality.

The new set of studies confirm what has been called the “host susceptibility” hypothesis (Tlusty et al. 2007), which, Gomez-Chiarri and Cobb explain, “states that ESD is an emerging disease caused by one or several opportunistic bacterial pathogens that take advantage of a host that is susceptible either through physical damage to the shell or other factors leading to stress and immunosuppression.” The relative importance of changes in temperature, pH, high population density, and pollutants in causing stress in the Rhode Island lobsters remains to be determined, but the findings do provide important lessons for Maine. Gomez-Chiarri and Cobb highlight the potential economic devastation that shell disease could cause if it spreads into the Gulf of Maine, and recommend development of rapid response management action plans, including, potentially, a complete cull of the lobster population in an affected area, in order to control spread of the disease.

Researchers, and others, monitor changes with the dismantling of Penobscot Dams


In June, construction crews from Ellsworth-based R.F. Jordan began dismantling the Great Works Dam on the Penobscot River, watched over by members of the Penobscot Nation, a partner in the Penobscot River Restoration Trust. The dam, which stretches across the river’s full width from the Old Town Fuel & Fiber mill to Bradley, was removed as part of the unprecedented Penobscot River Restoration Project. Over the course of the summer, excavators clanged away on the concrete footing and dismantled the walls that have blocked fish migrations for over a century and severed the Penobscots’ cultural and spiritual connections to the river. By September, the Great Works Dam was all but gone and the river’s currents quickly erased the footprints of demolition crews. Scientists have been monitoring the river since 2009 to evaluate baseline conditions before dam removal, including changes in river shape, wetlands along the banks, water quality, and of course fisheries. The project is likely the most-studied dam removal in Maine and one of the most-watched around the nation and the world, because scientific evaluation is lacking in many habitat restoration projects. Next summer, work begins on removal of the Veazie Dam, which is downstream of the Great Works site and is the first (or last) dam on the river. With removal of the Veazie Dam, salmon, sturgeon, river herring, striped bass, eels, etcetera will have access to thousands of miles of native homeground.

Continued progress with razor clam
aquaculture methods


Earlier this year, reporter Muriel Hendrix wrote about a new project to culture razor clams, a native species with high value as food (Story #14858 on The razor or Atlantic jackknife clam (Ensis directus) could provide for diversification in the $50 million Northeast shellfish aquaculture industry. Since that story, the researchers successfully spawned razor clams in the hatchery of the Darling Marine Center, resulting in between 50,000 and 100,000 juvenile clams with lengths of a half-inch or greater. Shellfish specialist Dana Morse of the University of Maine’s Marine Extension Team reported that some of the clams will be planted in the tidal flats of the Damariscotta River before year’s end.

Bright outlook for aquaculture integrating finfish, shellfish and seaweed


Ropes implanted with baby mussels are dangling from rafts around Cooke Aquaculture’s salmon pens in Machias Bay as part of an integrated multitrophic aquaculture study reported in an earlier column (Story #14525 on University of Maine researchers Deborah Bouchard, Ian Bricknell, Sally Malloy, and Mike Pietrak have been conducting laboratory and field studies to examine the ability of mussels to reduce the infectious pressure of sea lice. “The results have not yet been analyzed, but appear to show a trend of decreasing infectious pressure with mussels compared to no mussels,” said Pietrak. While the research team is still waiting to harvest fully-grown mussels, much has already been learned about integrating different types of marine aquaculture. “The experience has highlighted several potential issues, such as the difficulties in procuring local mussel seed and mussel handling equipment. These issues have fostered additional research throughout the state to try and find sustainable solutions,” said Pietrak. Additional research is being conducted by Brian Beal of the Downeast Institute for Applied Marine Research and Education, who has spawned mussels and is currently growing the seed out to a size suitable for mussel rafts in both Machais and Cobscook bays.

This article is made possible by funds from Maine Sea Grant.

Heather Deese holds a doctorate in oceanography and is the Island Institute’s vice-president of strategic development. Catherine Schmitt is communications coordinator for Maine Sea Grant.