Improving understanding of seabird bycatch in Scottish longline fisheries and exploring potential solutions

Section 4: Collection of whole seabird samples

To support follow-on analyses into the demographic composition, breeding status and colony affinity of seabirds, whole dead bycaught specimens, were collected, safely stored on-board and returned to shore in collaboration with industry representatives.

Processes in relation to the storage and transport of bycaught seabird samples were discussed with the Marine Scotland Licensing Operations Team (MS-LOT) prior to the work starting to ensure that the planned activities complied with all legal requirements, including those contained in the Conservation of Offshore Marine Habitats and Species Regulations 2017.

To ensure that suitable storage facilities were available in relevant ports, Marine Scotland Compliance agreed to provide use of existing freezers in Lerwick and Ullapool. Additionally, a further small chest freezer was purchased and installed in the Marine Scotland Directorate office in Scrabster.

A concise sample collection and storage protocol was developed based, where relevant, on the guidance in Uhart et al.(2020). The protocol included instructions for observers on how to handle, bag, label and store the samples onboard the vessel to minimise damage and sample contamination.

At-sea sampling during 2020 and 2021 was severely impacted by Government restrictions on travel and social mixing resulting from the Covid-19 pandemic. Consequently, an observer did not join a longline vessel until August 2021, which was much later than anticipated, and the trip was only permitted following the development and implementation of a detailed and vessel specific Covid risk management plan that was designed to minimise the risk of cross contamination between the observer and crew. In addition to their normal data collection duties the observer was asked to collect as many dead seabird samples as possible, with a specific focus on northern fulmars but if bycatch rates were low then other species could also be retained.

During five trips totalling 46 days at sea between August and October 2021, four seabird bycatches occurred (two northern gannets and two great shearwaters). One of the shearwaters was released alive, so three whole specimen samples were obtained and stored in a freezer onboard the vessel. No fulmar bycatch occurred during the trips when the observer was aboard, so arrangements were made with the vessels skipper for one of the crew to continue collecting samples during subsequent trips. Sampling equipment and instructions were left on board and regular contact was maintained with the vessel. During two further trips seven seabird samples were collected by the crew; six fulmars and one gull (species yet to be determined). These samples were stored with the initial three samples on board the vessel and then all ten samples were transferred to the freezer in Scrabster. The samples were then transferred to the Marine Laboratory at Aberdeen by a member of the Marine Scotland catch sampling team, before being transferred to a freezer at the University of St Andrews.

During observer trips in May/June 2022 a further 47 fulmar samples were collected and were subsequently transferred to freezers ashore.

Basic details of the samples are provided in Table 4.

Initial basic morphometric examinations of the seabird samples were planned under the project but due to time constraints stemming from the fact that most of samples were obtained late in the project, this was not achieved. Full examinations will take place in due course in collaboration with relevant seabird experts.

This sample collection exercise will continue post-project as it provides a unique source of material for biological and population studies relevant to understanding the full impacts of fisheries bycatch.