Large-scale and long-term, spatial and temporal patterns in demography and landings of the American lobster, Homarus americanus, in Maine

Abstract

The American lobster, Homarus americanus, is abundant (>1/m2) in spatially complex coastal habitats of the Gulf of Maine. Quadrat surveys (stratified by exposure, depth, and substrate) conducted at fixed locations since 1989 revealed consistently higher lobster population densities west and south of Penobscot Bay in central Maine. High-resolution surveys in 1999 at 70 closely spaced dive sites revealed distinct settlement hot spots and cold spots, stable over several years at least. Densest settlement occurred along a 100-km outer coastal region westward from the mouth of Penobscot Bay. A settlement cold spot about 60-km in diameter was evident in the north-east corner of Penobscot Bay. Abundance of older, adolescent-phase, lobsters (40–90 mm carapace length, CL) corresponded with patterns of settlement. Catch rates per trap haul of prerecruits (< 83 mm CL) and catch rates per area for lobsters fully recruited to the fishery (83 mm CL) correspond with local lobster densities. Until recently, populations increased in three of four regions over the past decade, most strongly in north-eastern Maine. Landings per length of coastline corresponded to spatial and temporal patterns of abundance. Consistent spatial and temporal patterns suggest that population densities can be reliably determined from calibrated fisherydependent data.