Date of Award


Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)


Marine Biology


Robert C. Bayer

Second Committee Member

William R. Congleton

Third Committee Member

Richard A. Wahle


The American lobster, Homarus americanus, is Maine's most valuable marine fishery. The state of Maine has an economic interest in the protection of this resource. The health of this industry depends on effective management for sustainability. However, there is little quantitative information on American lobsters less than harvestable size. A study was conducted to evaluate the utility of traps modified to catch sublegal lobsters. With the aid of fishernlen fiom six of the eight Maine coastal counties over a four-month time period (July through October, 2000), data were recorded to compare catch rates in experimental traps with no escape vents and standard traps with vents, meeting Maine lobster regulations. The purpose of this survey was to deternline whether non-vented or vented traps are better at (1) detecting spatial and temporal differences in juvenile lobster abundance and (2) predicting patterns in the harvest of legal lobsters. I tested the hypothesis that non-vented traps will be better than vented traps at detecting differences in juvenile abundance by month and county. Furthermore, I evaluated the correlation between catch measured by research traps and statewide landing patterns, an index of patterns in abundance. In this study it was found that vented (standard) traps more accurately reflect statewide spatial patterns of catch than non-vented traps. It was also found that spatial and temporal differences depended on the trap type. Furthermore, catch-per-unit-traphaul provided a better index of abundance than catch-per-unit-trap-haul-set-over-days. Possible sources of error include: not all coastal counties participating in the survey, wide range of soak times, trap saturation and size variations per fishermen and inconsistent participation per county. Implications from the research suggest that sea sampling of standard traps may be a useful predictor of catches. Furthermore, the new method (ventless traps) proved to be worse than the old method (standard, vented traps) in assessing American lobster populations greater than 40 mm CL to harvestable size.