The monkfish Lophius americanus fishery has been assessed and managed as two distinct units since the inception of its fishery management plan in 1999, although the fundamental approach (DAS and trip limits) has been the same in both areas. In recent years, further indirect and direct evidence on stock structure has begun to accumulate and still there remain many uncertainties. Evidence suggests that the monkfish stock is a single unit yet the fishery is managed as two separate units. This project will use a sensitive genetic approach, microsatellite DNA analysis, to empirically determine if monkfish constitute a single or multiple stocks over their coast wide distribution from Newfoundland to North Carolina. We will isolate a battery of microsatellite primers specifically from a Lophius americanus genomic library, optimize their use, and test a subset for their levels of genetic variation, and use the 12 most informative loci to evaluate coastwide stock structure. Utilizing a collaborative approach involving multiple academic institutions, commercial fishermen, monkfish wholesalers, the National Marine Fisheries Service (NMFS) Northeast Fisheries Science Center (NEFSC) and Canada Department of Fisheries and Oceans, monkfish biological samples will be collected and monkfish genetic population structure will be analyzed. For the first time, this project will empirically evaluate the coastwide stock structure using sensitive DNA markers. This project will enhance the knowledge of the monkfish fishery resource and contribute to the body of information on which monkfish management decisions are made.
The Fishery Management Plan defines two primary management areas for monkfish (northern and
southern), divided roughly by a line bisecting Georges Bank. The two assessment and management areas for monkfish were defined based on differences in temporal patterns of recruitment (estimated from NEFSC surveys), perceived differences in growth patterns, and differences in the contribution of fishing gear types (mainly trawl, gill net, and dredge) to the landings. (NEFSC, 2010). At this time, the weight of evidence supports a single-stock hypothesis, with the possibility of extensive movement between management areas. Unfortunately, how much exchange occurs and the pathways of migration are very poorly understood at present, making it difficult to judge the implications for management. (MPDT, 2011). A definitive stock definition is crucial at this time in order to determine best management practices for the future of this fishery. Recent empirical genetic evidence suggests that marine fishes exhibit significantly more stock structure than previously thought despite the absence of obvious physical barriers to mixing. Evidence now suggests that, rather than being demographically open, marine fishes exhibit stock structure on fine geographic and temporal scales due to processes that limit dispersal and promote self-replenishment of local populations and that promote spawning site fidelity, natal homing, egg and larval retention and local adaptation (Hauser and Carvalho 2008). Not only have molecular techniques revealed greater levels of heterogeneity of stock structure in marine fishes than previously thought, concomitant variation in ecologically important traits indicate the presence of extensive adaptive differentiation.