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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
NOAA/NURP
NOAA/NESDIS
NSF
DFO
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 11 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 2010 by suction sampling, passive collectors, or both. Numbered boxes surround suction sampling sites used for regional averages in annual timeseries.
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:
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.
Selected Related Publications:
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.
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 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., R.A. Wahle, JS. Cobb. 1997. Quantitative relationships between postlarval supply and benthic recruitment in the American lobster. Mar & Freshw. Res. 48: 729-743.
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.
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, 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.
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.
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.
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.