Date of Award



© 2018 Brett Sweezey

Document Type


Degree Name

Master of Science in Marine Sciences


Marine Science

First Advisor

James A. Sulikowski

Second Advisor

Woon Yuen Koh

Third Advisor

John W. Mandelman


Atlantic cod, Gadus morhua, in the Gulf of Maine has experienced heightened fishing-induced mortality since the 1990s, leading to the lowest population abundances in recorded history. Unaccounted discard mortalities within Gulf of Maine commercial fisheries may be impairing recovery efforts in this and other cod populations. With over 4 million actively fished lobster traps, the Maine commercial lobster fishery has been suggested to be a significant contributor to cod mortality rates within this region. Therefore, the discard mortality rate of Atlantic cod captured by commercial lobster gear was examined to assess its potential influence on recovery efforts using acoustic transmitters and observations of individual viability. In total, 111 cod were captured over 105 fishing trips in 2016-2017, consisting of 18,853 individual trap hauls. A subsample of 54 cod were externally tagged with acoustic transmitters and observed post-release. The observed frequency of injuries following trap hauling included: uninjured (60.0%), slight injured (32.2%), severely injured (2.5%), and deceased (9.3%). Through the use of a mixture-distribution parametric model the discard mortality rate within the southern Maine commercial lobster fishery is estimated to be 24.8%.


Master's thesis