American lobster nurseries of southern New England receding in the face of climate change

Abstract

Historically, southern New England has supported one of the most productive American lobster (Homarus americanus) fisheries of the northeast United States. Recently, the region has seen dramatic declines in lobster populations coincident with a trend of increasingly stressful summer warmth and shell disease. We report significant declines in the abundance, distribution, and size composition of juvenile lobsters that have accompanied the warming trend in Narragansett Bay, Rhode Island, since the first comprehensive survey of lobster nurseries conducted there in 1990. We used diver-based visual surveys and suction sampling in 1990, 2011, and 2012, supplemented by post-larval collectors in 2011 and 2012. In 1990, lobster nurseries extended from the outer coast into the mid-sections of the bay, but by 2011 and 2012 they were largely restricted to the outer coast and deeper water at the mouth of the bay. Among five new study sites selected by the lobster fishing industry for the 2011 and 2012 surveys, the deepest site on the outer coast (15–17 m depth) harboured some of the highest lobster densities in the survey. Separate fixed site hydrographic monitoring at 13 locations in the bay by the Rhode Island Division of Fish and Wildlife recorded an approximately 2.0°C increase in summer surface temperatures over the period, with 2012 being the warmest on record. Additional monitoring of bottom temperatures, dissolved oxygen and pH at our sampling sites in 2011 and 2012 indicated conditions falling below physiological optima for lobsters during summer. The invasion of the Asian shore crab, Hemigrapsus sanguineus, since the 1990s may also be contributing to declines of juvenile lobster shallow zones (<5 m) in this region. Because lobster populations appear increasingly restricted to deeper and outer coastal waters of southern New England, further monitoring of settlement and nursery habitat in deep water is warranted.

Impact of disease on the survival of three commercially fished species

“…Although lobster populations appear to be growing over most of their range, abundance of lobsters in the southernmost stock, the southern New England stock, is the lowest since the 1980s, despite declining exploitation rates over the last 10 years (Howell , Wahle et al. ). Recruitment has been low since 1998 and the natural mortality rate appears to have increased (Castro et al.…”

“…Study system.-The American lobster is one of the most valuable fisheries in the United States, with annual dockside revenues as high as US$567 million (NMFS 2016). Although lobster populations appear to be growing over most of their range, abundance of lobsters in the southernmost stock, the southern New England stock, is the lowest since the 1980s, despite declining exploitation rates over the last 10 years (Howell 2012, Wahle et al 2015. Recruitment has been low since 1998 and the natural mortality rate appears to have increased (Castro et al 2012, Howell 2012.…”

The cresting wave: larval settlement and ocean temperatures predict change in the American lobster harvest

“…Just as lobster populations have collapsed and receded from historically productive grounds in southern New England, largely due to the adverse effects of warming (Pearce and Balcom , Wahle et al. , ), populations further north in the Gulf of Maine and Bay of Fundy have undergone unprecedented expansion resulting in a three‐ to fourfold increase in total lobster production since the 1990s that has elevated the fishery to its premiere status (NOAA ). In Maine, where lobster comprise approximately three‐quarters of total fishery revenue, harvesters have few alternative fisheries should there be a downturn (Steneck ).…”

The brighter side of climate change: How local oceanography amplified a lobster boom in the Gulf of Maine

“…South of Cape Cod, Massachusetts, USA, entirely different oceanography and thermogeography results in warming temperatures exceeding the 20°C upper threshold and has been associated with physiological stress, rising prevalence of epizootic disease (e.g., Castro & Angell, ; Glenn & Pugh, ), and with mass mortalities (Pearce & Balcom, ). The widespread mortality in southern New England contributed to the reduced reproductive potential and settlement (Wahle, Dellinger, Olszewski, & Jekielek, ). Southwestern‐most parts of the Gulf of Maine occasionally exceed 20°C, but these periods are relatively short in comparison to southern New England where regions can exceed this threshold for over 2 months (Wahle, Bergeron, et al, ).…”