Underwater Observation of Behavior of Roundfish and Flatfish near Trawl Bridles: Measures to Reduce Flatfish Catch in Haddock Trawls

As much as two-thirds of fish that arrive at the mouth of an otter trawl might have been herded by trawl bridles and sweeps that connect the doors and the wingends of the net. Typical heavy bridles composed of wires or rubber disks (cookies) provide good bottom contact that effectively herd species such as flounders and other bottom-dwelling species into the trawl path through physical contact or visual response to suspended sediment. Depleted yellowtail flounder (Limanda ferruginea) and winter flounder (Pseudopleuronectes americanus) biomass on Georges Bank has elevated the technical and management importance of measures to reduce flounder catch while maintaining catch of the healthy haddock (Melanogrammus aeglefinus) stock.  By field testing the replacement of heavy bridles with floating synthetic bridles, this project attempts to answer the following questions: Can floating synthetic bridles reduce or eliminate flatfish bycatch while maintaining catch of haddock? What are the differences in behavior between flounders and haddock in response to a moving bridle and sweep assemblage? Fish behavior observations using underwater cameras installed at the bridle area and comparative fishing trials will demonstrate that floating synthetic bridles may be used to replace traditional cookie bridles for haddock trawls and reduce catch of yellowtail and winter flounders. We will discuss how a positive result may provide fishing industry and fishery management a simple, cost-effective, and easy-to-manage modification for harvesting and managing multispecies in the Northeast USA.