Identifying the Effective Brookstock for Coastal Populations of the American Lobster (Homarus americanus): Patterns of Distribution, Abundance, and Body Size in Near-Shore Deep-Water Habitats  (Year 1 of 1) Project Number: NAGL-97-03 Principle Investigators: Steneck, R. S., D. S. Pezzack, and P. Lawton Region(s): Gulf of Maine Project Objectives: 1. To quantify the substrate-specific distribution abundance and body size of lobsters at near-shore deep-water sites off the coast of Maine and southwest Nova Scotia. 2. To compare the abundance of reproductive phase lobsters found in near-shore deep-water sites with those found in coastal regions of Maine, the Bay of Fundy and SW Nova Scotia and offshore regions of Georges Bank and the outer continental shelf. 3. To determine if lobsters are successfully settling to near-shore deep-water habitats. To calibrate traditional stock assessment techniques such as standardized ground-fish trawls and local trap-caught lobsters Summary of Research: We propose to use high resolution, site-specific, in situ techniques to assess lobster population densities, size structure and habitat utilization of large, reproductive phase lobsters at four near-shore deep-water locations along in the Gulf of Maine. We do this to calibrate NMFS trawl survey data and to explore the hypothesis that near-shore deep-water lobsters may be the broodstock for coastal populations of lobsters in the Gulf of Maine. This hypothesis was derived from oceanographic circulation patterns that suggest that larvae from lobsters in other areas of the Gulf may not contribute to coastal stocks. We have used submersibles in deepwater habitats on Georges Bank and intend to use the same techniques in deep water coastal sites. We will use these results as a source of comparison with nearby coastal studies we have and will be conducting and with our off shore research on Georges Bank. We will also use local landings data to calibrate the abundances we measure with those being harvested. All methods for quantifying lobster demographics, size, habitat utilization and recruitment have been field tested in previous years. Preliminary analyses are given below. Significance of Research Our approach intends to augment traditional stock assessment approaches. It considers the stock at an ecosystem level. It is an ecological approach to fisheries management. If we identify the location of a significant component of the effective broodstock for coastal populations of lobsters ' management steps can be taken to preserve them. Certain types of fishing, such as dragging, is incompatible with sustaining viable and productive broodstock, so finding such populations may precipitate important fishing restrictions. From a more basic perspective, understanding the structure and function of huge metapopulations is scientifically fascinating. The American lobster is a large, long-lived invertebrate that may have a breeding population hundreds of miles from its nursery grounds. How life history phases segregate and how their behavior and the physical oceanography of the Gulf of Maine interact presents, a truly unique interdisciplinary study for marine science as well as understanding our marine resources.   Results: The results from our first year of study in deep water, nearshore sites (Fig. 1) indicate that our first two objectives can be answered using submersibles. Our third objective requires detailed substrate specific analyses which are currently underway. We have included results conducted this summer from adjacent shallow-water (10 m) sites. Although weather limited our submersible operation in 1997 and our variances were high, at least the geographic differences we observed in body sizes were statistically significant in our first analysis. To our knowledge, this is the first attempt to obtain comparative demographic data on lobster body size and population densities (i.e., number per meter square) in deep and shallow water habitats. The major points are: 1. We found exceedingly few reproductive-phase lobsters (i.e., 90 mm carapace length CL) in shallow water (10 m) habitats (Fig. 1A). In contrast, we encountered a high proportion of reproductive -phase lobsters adjacent deep water (100 m) sites (Fig. 1 B). 2. Reproductive phase lobsters were significantly more abundant in the eastern sites of Maine (Fig. 1B). 3. Population densities in shallow (10 m) coastal habitats are at least one order of magnitude greater than those found in adjacent deep water (100 m) habitats. 4. Lobster population densities are lower in the eastern sites of Maine in both shallow water (Fig. 1 C) and deep water (Fig. 1 D) habitats. 5. The high densities at the Monhegan Island site may be because it is a lobster conservation zone having the lowest fishing pressure in U.S. waters (zone established over 90 years ago). There are only 12 lobster harvesters lobster in the Monhegan Island conservation zone. The zone is approximately 100 km2, 600 lobstermen fish 600 traps each (half the Maine state limit) and they fish only during the months from January to June. Despite this measurably lower effort, we did not observe significantly larger lobsters there. Leg 1    Begin Date: 9/24/1997   End Date: 10/1/1997   Support Vessel/Platform: R/V Edwin Link System Ops Days Dives Dive Time (hrs) Depth (m) Johnson Sea Link II 8 20 34.66 121.6 Keymap: Location of Project Dives: Legend: Johnson Sea Link II

Home   About   Research   Technology   Centers   News   Funding   Library NOAA's Undersea Research Program 1315 East-West Highway, R/NURP - Silver Spring, MD 20910 Phone: (301) 713-2427   Fax: (301) 713-1967   Email   Contact Info   Privacy Policy   Disclaimer Site Index