Identification of key chemical components responsible for attracting American lobster (Homarus americanus) to Atlantic herring (Clupea harengus) bait

Atlantic herring (Clupea harengus) is the principal bait used to capture American lobsters (Homarus americanus) in North America. The American lobster fishery is amongst the most lucrative fisheries in both the USA and Canada. However, there are emerging economic and environmental concerns regarding the long-term viability of the Atlantic herring supply chain. The depletion of the forage fish stock, subsequent frozen storage and transport for it to be deployed as bait in the American lobster fishery results in a negative environmental impact. Additionally, growing competition from other sectors for a limited supply of forage fish has led to the bait supply becoming increasingly costly and uncertain.An alternative bait that utilises off-the-shelf attractants to lure American lobsters into traps would remedy the emerging concerns regarding the use of forage fish as bait. To facilitate the development of a synthetic bait, this study sought to identify the key chemical components responsible for attracting American lobsters to the traditionally used bait, Atlantic herring. Firstly, a bioassay was developed to observe whether a given substance is capable of attracting lobsters towards an odour source and retaining their interest. This assay was utilised in various ways to obtain a greater understanding of the attractive properties of Atlantic herring throughout this thesis.Attractive components in herring were characterised as stable to decomposition, as herring samples were aged for up to 14 days and found to retain their attractive properties, both in the laboratory and in the field. The natural extract was then purified using a bioassay-guided purification approach. Based on the information gathered in the characterisation and purification, amino acids were deemed the primary candidate class of compounds. The key amino acids responsible for distinguishing between attractive and less attractive tissues were identified by combining chemical profiling procedures with chemometric analysis techniques. The resulting understanding then advised the formulation of a synthetic baiting solution. This solution comprised of eight amino acids in the natural ratios observed in the profile of herring muscle tissue. This synthetic solution was then trialled under laboratory conditions and found to attract a greater number of subjects than whole Atlantic herring in flowing water conditions. The synthetic solution developed in the present study is the first step towards developing a more sustainable bait to replace the environmentally damaging and economically unstable practice of using forage fish as bait.

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