Gillnet Configurations and Their Impact on Atlantic Sturgeon and Marine Mammal Bycatch in the New Jersey Monkfish Fishery

Monkfish (Lophius americanus) support a lucrative fishery primarily centered in the waters of the mid-Atlantic and northeast US.  Monkfish are targeted primarily through trawls and sink-gillnets.  Overharvest coupled with habitat loss and alteration lead to a wholesale decline of Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) in the early 1900s. Atlantic sturgeon is currently being considered for listing under the Endangered Species Act.  A formal status review concluded that by catch in otter trawls and sink-gillnets including those used in the monkfish fishery are a significant hurdle to Atlantic sturgeon conservation and recovery.  In an attempt to provide resource managers information on the influence of tie-downs employed in the monkfish fishery on Atlantic sturgeon and marine mammal by catch we employed two gillnet configurations (12 meshes x 30.5cm stretch mesh with tie-downs, 12 meshes x 30.5cm stretch mesh without tie-downs).  Cooperating monkfish harvesters fished paired replicates of each gillnet configuration a total of 120 hauls in accordance to normal monkfish fishing operations.  Atlantic sturgeon by catch was significantly reduced in experimental gillnets (no tie-down) although this net configuration also resulted a number of common dolphin (Delphinus delphis) mortalities which were not encountered in tied-down nets.  Additionally, landings of monkfish and winter skate (Leucoraja ocellata) were significantly reduced in the experimental (no tie-down) gillnets.  Soak times (mean=44.1H (range 2.5-143.8) did not vary significantly by net configuration and appeared to influence the probability of an Atlantic sturgeon by catch event resulting in mortality.  Our findings provide much needed information to managers on the role that net configuration plays in targeted landings and by catch of Atlantic sturgeon and marine mammals in the sink-gillnet monkfish fishery.  Although experimental nets reduced Atlantic sturgeon by catch they also resulted in significantly lower catch rates of targeted species and resulted in unacceptable levels of marine mammal mortalities.