MAPPING LOBSTER HABITAT WITH SIDESCAN SONAR AND ROV - A GEOLOGIC AND BENTHIC OCEANOGRAPHIC COLLABORATION

Lobsters are a major fishery in much of the northeastern US. Benthic substrate is a critical control from settlement through juvenile stages and into adulthood. While adult lobsters can be found on muddy and sandy bottoms during feeding and migration, cobble and boulder habitat provides critical shelter for many life stages. Cobble and boulder habitats are remnants of glacial deposition, modified by post-glacial marine reworking. The hypotheses tested center around the concept that regional settlement patterns are related to environmental controls: 1) oceanographic: current patterns and temperature, 2) biological: reproductive success, food sources, predation, competition, and disease, 3) habitat: shelter for early post-larval and juvenile phases. Our research plan involves scale-specific tests of habitat and lobster abundance: 1) regional scale: tests of oceanographic and biologic controls, 2) landscape scale: tests availability of habitat, especially pebble, cobble and boulder shelters, and edges adjoining mud bottoms; 3) patch scale: direct sampling and ROV observations of post-larval, juvenile and adult-phase lobsters. We conducted digital sidescan sonar surveys, totaling ca. 72 km², from the R/V Connecticut in July, 2003 at 7 nearshore regions (10-30 m depths): Newport, RI; Buzzards Bay, MA; Cape Cod Bay, MA; Cape Ann, MA; Rye, NH; Casco Bay, ME; Mt. Desert Island, ME; and an 8’th region, Muscongus Bay, ME in the fall, due to weather constraints. ROV dives followed immediately in 3-4 patches in each region to examine cobble-boulder habitats, using the sidescan mosaic as a detailed navigation guide. Preliminary results indicate that cobble habitats are available in all the nearshore regional sampling sites at 10-30 m depth. Buzzards Bay was essentially deserted - no lobsters were found. The peak adult lobster abundance occurred in Casco Bay. Sidescan sonar mapping in geo-referenced imagery allows precise navigation of the ROV, and direct linkage of landscape-scale mapping to in situ observations, enhancing geological and biological research collaboration. This study is funded by the NOAA-National Undersea Research Center, Univ. Connecticut, Avery Point.