This dataset contains presence/absence information of infaunal bycatch from seed mussel stock (Mytilus edulis) assessment surveys off the Outer Ards Peninsula in Northern Ireland. The seed mussel survey is carried out each year and this particular dataset contains the bycatch information from initial ground truthing (dredge) on these surveys from 2017-02 to 2018-07. The dredge samples are taken from the DAERA Fisheries Protection Vessel Queen of Ulster (formally Banrion Uladh). The main aim of the seed mussel survey is to carry out a stock assessment of seed mussel in areas that are fished for these mussels. The stock assessment surveys use acoustic ground discrimination system (AGDS), dredge surveys (ground truthing) and then in areas where there appears to be high levels of seed mussel an underwater video camera sledge is towed from the RV Corystes for more ground truthing. In total there were 42 dredge tows carried out that contained bycatch in this dataset. It is important to note that the information in this dataset was not the key focus of these surveys. The most common species found were Laminaria species.