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American Lobster Settlement Index (ALSI) - American Lobster Settlement Index

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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
University of New Brunswick
PEI Fishermen’s Association
Guysborough County Inshore Fishermen’s Assn.
Fishermen and Scientist Research Society


 National Science Foundation
NOAA National Undersea Research Program
NOAA Fisheries and the Environment (FATE) Program
Maine Sea Grant
Maine Department of Marine Resources
Rhode Island Division of Fish and Wildlife
Fishermen and Scientists Research Society
University of New Brunswick
Commercial Fisheries Research Foundation

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.

YoY All Years 2014
YoY All Years 2014

Map displaying ALSI sampling sites and Young of Year lobster densities from 1989 to 2014.

greater than YoY All Years 2014
greater than YoY All Years 2014

Map displaying ALSI sampling sites and older than Young of Year lobster densities from 1989 to 2014.


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.

Suction Sampling                          Young of Year Lobster                       Passive Collector deployment


Annual Update (PDF’s):


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.


For a map of ALSI sites and plots of ALSI data:

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