ABSTRACT In 1999, the Long Island Sound lobster fishery suffered a significant mortality event, following 2 years of smaller, more localized, die-offs. A national research initiative investigating the potential cause(s) of the mortalities was undertaken under the auspices of the Steering Committee for Lobster Disease Research, a subcommittee of the Atlantic States Marine Fisheries Commission's Lobster Management Board. More than 20 research efforts investigated the effects of anthropogenic and environmental stressors and disease on lobsters over a 3-year period. The findings of the collective projects were synthesized and presented publicly in October 2004. Lobsters, at an all-time high abundance, and possibly already infected with parasitic amoebae, Neoparamoeba pemaquidensis, were subjected to sustained, stressful environmental conditions, driven by above average water temperature. Physiologically weakened and unable to fend off disease (paramoebiasis), many lobsters died.

KEY WORDS: lobster, mortality, Long Island Sound, disease, pesticides, paramoeba, temperature, Homarus americanus

INTRODUCTION

During the fall of 1999, the American lobster (Homarus americanus H. Milne Edwards, 1837) population in Long Island Sound (LIS) suffered a significant mortality event, particularly in the western and central Sound. Bistate (Connecticut and New York) commercial lobster landings from western LIS (west of Norwalk, Connecticut) declined by as much as 99% from the previous year, and reductions of landings for ports east of Norwalk ranged from 64% to 91% (CTDEP 2000). At the same time, lobstermen in eastern LIS (as well as Rhode Island and Massachusetts) continued to see a rise in the incidence and extent of shell disease in lobsters, which, while apparently unrelated to the mortality event, raised additional concerns about the status and health of the lobster resource and the Long Island Sound commercial fishery.

In late September, the Connecticut Department of Environmental Protection (CTDEP) collected water samples for analysis and contracted with the University of Connecticut to test the samples for a range of materials including pesticides, herbicides, PCBs, semivolatile organic compounds, volatile organic compounds, heavy metals and cyanide. The test results were negative. If pesticides or any other of these materials were present, their concentration levels were less than the parts-per-billion detection limits of the analytical equipment used (CTDEP 2000, DeFur 2000). Samples were also provided to the National Marine Fisheries Service Laboratory in Milford, Connecticut to screen for toxic phytoplankton and bacteria. None were found.

Lobster specimens were sent to the University of Connecticut for gross and histopathologic examination in mid October. By November, the pathology reports indicated that most lobsters examined were infected with what is now known as a strain(s) of the parasitic amoeba, Neoparamoeba pemaquidensis, a facultative pathogen of salmon and sea urchins (French 2000a, 2000b, CTDEP 2000, Mullen et al. 2005). Similar amoebae have caused fatal diseases in crustaceans at other times (e.g., grey crab disease). The parasitic amoebae infecting much of the nervous tissue of lobsters were considered to be the proximate cause of death of the lobsters, but it was unclear whether other factors played a role, setting the lobsters up for infection or suppressing any possible immune response to the infection (French 2000a, 2000b).

During the summer and fall of 1999, the mosquito-borne West Nile Virus (WNV) appeared for the first time in New York and Connecticut. By early September, seven human deaths had been attributed to complications due to WNV. Control programs were undertaken in both states to curb adult and larval mosquito populations. Application methods and pesticides used varied geographically as well as temporally, spanning an interval from early August to mid October, with maximum applications occurring during the last 2 weeks of September (Miller et al. 2005, Wilson et al. 2005, K. Chytalo, NYSDEC, pers. comm.). Malathion was applied in New York only, while pyrethroids (resmethrin and sumithrin) and methoprene were used in both states.

Early on, some lobstermen expressed concern about the apparent coincidental timing of the lobster mortalities, rain events and the application of these pesticides. Local associations of lobstermen retained biologists from the Lobster Institute in Maine to help in the initial investigation of the mortalities during the fall 1999.

By late 1999, the Governors of Connecticut and New York had requested disaster assistance from (then) United States Secretary of Commerce, William M. Daley (CTDEP 2000). On January 26, 2000, Secretary Daley declared the lobster fishery in LIS a "commercial fishery failure due to a resource disaster" under section 312(a) of the Magnuson-Stevens Fishery Conservation and Management Act (US Department of Commerce 2000, CTDEP 2000). Within 6 months, $13.9 million of federal disaster relief funds were authorized to provide economic relief for lobstermen and to support research to investigate the potential cause(s) of the mortality event; $6.6 million was designated for research and $7.3 million for economic relief. (These funds were appropriated in 2001.) The State of Connecticut also authorized bonding to provide $1 million for economic relief and about $1 million for research.