The Wahle Lab






Wahle Lab                                                                                                          

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   The American Lobster Settlement Index (ALSI) is an annual monitoring program that quantifies the pulse of newly settled lobsters that repopulate rocky coastal nursery grounds in New England and Atlantic Canada. Quantifying this segment of the life history is especially valuable because it is the only time when one can identify with certainty the strength of an individual year class. It is a pivotal life stage that both sheds light on the ocean processes that deliver larvae to nurseries, and is useful as a predictor of future trends in recruitment to the fishery.  


University of Maine

Maine Department of Marine Resources

Massachusetts Division of Marine Fisheries

Rhode Island Division of Fish & Wildlife

New Hampshire Department of Fish & Wildlife

Department of Fisheries & Oceans Canada

Funding(Since 1989): 

NOAA/Sea Grant





State marine resource agencies




Young of year lobster

Figure 2. Complete time series of settlement, expressed as mean densities of Young of year lobsters at 13 regions with five or more years of suction sampling data. Number in parentheses is number of sites sampled


Figure 1.   Lobster settlement data were collected in 2012 by suction sampling, passive collectors, or both.

   Initiated in 1989, the survey has expanded from a few sampling sites in coastal Maine to encompass more than 100 sites in other lobster-producing regions of the Northeast United States and Atlantic Canada (Figure 1) (e.g., Incze et  al. 1997, Incze et al. 2010). Two sampling methodologies are in use: Diver-based suction sampling (Photo 1) (Wahle and Steneck 1991, Incze and Wahle 1991), and more recently, passive postlarval collectors (Photo 2) (Wahle et al. 2009b). Both methods quantify recently settled young-of-year (YoY) (Figure 2) and older juvenile lobsters at the end of the larval settlement season between August and October. 


Photo 1.  Suction sampling



Photo 2.  Passive postlarval collector

for more information see:

Collector Project page




Timeseries Graphing:

   Complete timeseries of young-of-year settlement density and older juvenile lobster density at the 11 numbered regions above (Figure 1) can be accessed by interactive graphing.

Young of year

Older juveniles


Annual Updates:

2013 Update

2012 Update

2011 Update

2010 Update

2009 Update

2009 Settlement Workshop Report

2008 Update

2007 Update

2006 Update

2005 Update

2004 Update

2003 Update

2002 Update

2001 Update



Selected Related Publications:

Wahle, R.A., C.E. Bergeron, J. Tremblay, C. Wilson, V. Burdett-Coutts, M. Comeau, R. Rochette, P. Lawton, R. Glenn, M. Gibson. 2013. The geography and bathymetry of American lobster benthic recruitment as measured by diver-based suction sampling and passive collectors. Mar. Biol. Res.

Pershing, A., R.A. Wahle,  P. Meyers, and P. Lawton. 2013.   Large-scale coherence in New England  lobster settlement  associated with regional weather. Fisheries Oceanogr. 21: 348-362.  doi:10.1111/j.1365-2419.2012.00629.x

Wahle, R.A., J.S. Cobb, L.S. Incze, P. Lawton, M. Gibson, R. Glenn, C. Wilson, J. Tremblay. 2010. The American lobster settlement index at 20 years: looking back - looking ahead. J. Mar. Biol. Ass. India. 52: 180-188.

Incze, L., H. Xue, N. Wolff, D. Xu, C. Wilson, R. Steneck, R. Wahle, P. Lawton, N. Pettigrew, and Y. Chen. 2010. Connectivity of lobster (Homarus americanus) populations in the coastal Gulf of Maine: part II. Coupled biophysical dynamics. Fisheries Oceanography 19: 1-20.

Wahle, R.A., M. Gibson, M.J. Fogarty. 2009a. Distinguishing disease impacts from larval supply effects in a lobster fishery collapse. Marine Ecology Progress Series 376: 185–192.

Wahle, R.A., C. Bergeron, C. Wilson, M. Parkhurst. 2009b.  A vessel-deployed passive post-larval collector for the American lobster.  New Zealand  J. Mar. Freshw. Res. 43: 465-474.

Xue, H., L. Incze, D. Xu, N. Wolff, and N. Pettigrew, 2007. Connectivity of lobster population in the coastal Gulf of Maine. Part I: Circulation and larval transport potential. Ecol. Modelling, doi:10.1016/j.ecolmodel.2007.07.024.

Incze, L. S, R. A. Wahle, N. Wolff, C. Wilson, R. Steneck, E. Annis, P. Lawton, H. Xue, and Y. Chen. 2006. Early life history and a modeling framework for lobster (Homarus americanus) populations in the Gulf of Maine. Journal of Crustacean Biology: 26: 555-564.

Wahle, RA., Incze, l.S., Fogarty, M. 2004.  First projections of American lobster Homarus americanus recruitment from a settlement index. Bull. Mar. Sci. 74: 101-114.

Incze, L. S., R. A. Wahle, and A. T. Palma . 2000. Advection and settlement rates in a benthic invertebrate: recruitment to first benthic stage in Homarus americanus. ICES J. Mar. Sci. 57:430-437.

Incze, L.S., R.A. Wahle, JS. Cobb. 1997. Quantitative relationships between postlarval supply and benthic recruitment in the American lobster. Mar & Freshw. Res. 48: 729-743.

Wahle, R.A. and L.S. Incze. 1997. Pre- and post-settlement processes in recruitment of the American lobster. J. Exp. Mar. Biol. Ecol. 217: 179-207.

Incze, L.S. and R.A. Wahle. 1991. Recruitment from pelagic to early benthic phase in lobsters Homarus americanus. Mar. Ecol. Prog. Ser. 79: 77-87.

Wahle, R. A., and R. S. Steneck. 1991. Recruitment habitats and nursery grounds of the American lobster Homarus americanus: a demographic bottleneck? Mar. Ecol. Prog. Ser. 69:231-243.










Darling Marine Center, 193 Clark's Cove Rd, Walpole, Maine 04573