Volunteer-based monitoring of juvenile American lobster, Homarus americanus

Abstract

The primary objective of the Juvenile Lobster Monitoring Program is to develop a time series of abundance and distribution of juvenile American lobsters. Between 1997 and 2000, trained volunteers quadrat sampled 1-m² quadrats along fixed 20-m transects monthly from May through October at 24 intertidal sites in the Gulf of Maine. Lobster carapace length ranged from 4 to 82 mm (34.6 0.26 mm, n = 1874). Monthly densities of early benthic phase (≤40 mm CL, EBP) lobsters ranged from 0 to 1.50 lobsters/m² (0.31 0.010 lobsters/m², n = 1417). Peak EBP densities coincided with peak substrate temperatures recorded in situ at low tide. Interregionally, EBP density was highest in Massachusetts and lowest in Penobscot Bay, corresponding with relative regional substrate temperatures. Mean lobster carapace length was greater, and EBP density lower, in eelgrass than in rocky habitat. In a 1999 bay-wide survey of Penobscot Bay, Maine, lobsters were detected in outer, but not inner, regions. A strong correlation between abundances at intertidal and subtidal sites (r = 0.86, P< 0.001, n= 17) indicates similar patterns of abundance in the two zones. A volunteer work-force allows cost-effective long-term research on juvenile lobsters over a wide geographical area.