Within-Season Homing Movements of Displaced Mature Sunapee Trout (Salvelinus Alpinus) in Floods Pond, Maine

Tagging, displacemenat nd recapture, and ultrasonict racking of displaced mature Sunapee trout (Salvelinusa Ipinus) in Floods Pond, Maine, demonstrated that rapid within-season homing occurs in this relict form of Arctic char. Of the trout displaced about 1.8 km from their spawning ground from 1972 to 1975, 9% to 32% were recaptured one to four times within the same spawning season in trap nets set on the spawning ground. Eight of 14 trout tracked ultrasonically in 1975 homed in 2.5 to 10.0 h. Movements of the homing fish were variable; some trout homed paralleling the shoreline, others homed in open water or used a combination of near-shore and open-water movements. Behavior was similar between the sexes and during day and night, although two fish did begin to move just at sundown. Swimming speeds ranged from 15 to 35 cm s- 1 and averaged about 0 .6 body lengths s -1•. Swimming directions were not influenced by wind and wave direction, nor were swimming speeds within individual tracks influenced by cloud cover, wave height, or water depth. Heavy overcast at night m&y have inhibited movement. Sunapee trout are apparently familiar with the entire lake and travel widely within it. Visual features are postulated as orientational cues, though use of such cues is not clearly demonstrated by our experiments.

Recruitment Habitats and Nursery Grounds of the American Lobster Homarus Americanus: A Demographic Bottleneck?

We have identified benthic recruitment habitats and nursery grounds of the American lobster Homarus americanus Milne Edwards in the coastal Gulf of Maine, USA, by systematically censusing subtidal sediment, cobble, and ledge substrata. We distinguish lobsters between settlement size (5 mm carapace length (CL) to ca 40 mm CL as the 'early benthic phase' (EBP) because they are ecologically and behaviorally distinct from larger lobsters. EBP lobsters are cryptic and apparently restricted to shelter-providing habitats (primarily cobble substratum) in coastal Gulf of Maine. In these habitats we found average population densities of EBP lobsters as high as 6.9 m-2. EBP lobsters were virtually absent from ledge and sedimentary substrata devoid of vegetation although larger lobsters are commonly found there. It is possible that the requirement for shelter-providing substrata by this life phase creates a natural demographic 'bottleneck' to benthic recruitment for the species. Prime cobble recruitment habitat is relatively rare and comprises ca 11 % of the 60.2 km of shoreline at our study area in midcoast Maine. If this low availability of cobble exists throughout the Gulf of Maine, as other studies indicate, it could limit lobster production potential. We verified the geographic extent of recruitment to cobble habitats censused in 3 of 4 regions spanning ca 300 km of the coastal Gulf of Maine (from Nahant, Massachusetts to Swans Island, Maine). Early benthic phase lobsters were absent from cobble censused in the northeastern extreme of our survey (Swans Island). This pattern is consistent with earlier speculation that relatively cool water temperatures may limit larval settlement in this region.