Estimating The Post-Release Mortality Of Atlantic Cod (Gadus Morhua) In The Southern Gulf Of Maine Commercial Lobster Fishery

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%

Bycatch in a Commercial Lobster Fishery: Effects on Two Benthic Predators, Sea Raven and Longhorn Sculpin

Studying the species‐specific responses to fishing capture is critical for effective management and conservation of bycatch species given that acute stress incurred from capture and handling may ultimately lead to mortality. While species of low commercial value are often overlooked, having accurate information on the effects of capture on all species is necessary for ecosystem‐based management. Sea Raven (SR) Hemitripterus americanus and Longhorn Sculpin (LHS) Myoxocephalus octodecemspinosus are routinely captured in the commercial American lobster Homarus americanus fishery in the Gulf of Maine, and they are discarded due to low commercial value. Despite a lack of economic value, these predatory species play important roles in shaping the benthic communities that they inhabit, highlighting the need to study their stress and mortality due to capture and handling. To help understand the effects of the lobster fishery on these species, the current study evaluated the physical, behavioral, and physiological stress responses of SR and LHS to capture in the state of Maine Zone G commercial lobster fishery. Collectively, our results suggest that although these species appeared to be resilient to capture based on an overt injury assessment, stress responses occurred based on reflex impairment and physiological perturbations, and these responses were species‐specific. Given the prevalence of behavioral and physiological stress in this study, further research into the survival outcomes of SR and LHS following release in the commercial lobster fishery is warranted