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

Section 5: Exploration of potential mitigation strategies with Industry

5.1 Introduction

The purpose of this section of the project was two-fold: firstly, to collate and summarise the detailed trip notes collected by the onboard observer who has undertaken the data collection in the fishery for over ten years and secondly, to obtain the views and knowledge of skippers on bycatch in a more formal way than had been done previously. Initially we planned to hold a small workshop or series of meetings with skippers, but due to restrictions from the Covid-19 pandemic that was not achieved and as an alternative we developed a questionnaire (see Annex 1) that was circulated to skippers in the fleet to complete. The results of both elements are described below.

5.2 Summary of observer notes

In addition to gathering data on sensitive species bycatch rates, observers working under the UK Bycatch Monitoring Programme often collect supplementary information on fishing operations, animal behaviour around vessels, summaries of discussions with skippers and provide other insights into possible reasons for observed bycatch rates. Although these may be considered anecdotal in nature, they provide useful information for contextualising and understanding the factors that may lead to bycatch events occurring.

As a first step we collated the observer notes and insights formed across 23 trips in the fishery into a short informal report. The notes are based on first-hand observational experience and in-depth discussions during sea trips with skippers and crews from several vessels in the UK longline fleet. A summary of this information is provided below.

Vessels in the UK offshore longline fleet set about 150 line units per day. Each line unit has about 80 hooks normally with frozen pilchard or herring as bait. Hooks are attached to the main line on 1m snoods, which are spaced 2.5 meters apart with alternating 2kg weights and small floats approximately every 20 hooks. This characteristic is what gives rise to the name “piedra bola” (“stone float”) by which this longline configuration is commonly known. Figure 15 provides a schematic of a section of longline.

Depending on the seabed conditions and the depth at which the target species (mainly hake, and occasionally ling) are more abundant, different configurations of weights and floats may be used. Lines are clustered into sections called “claros” which contain five units of about 400 hooks, with heavier weights (25 kg) in between each claro. Lines are normally set in one single continuous operation and typically follow the optimal depth contour. However, if there are several vessels in an area and full line setting is not possible, the longline can be split into two or three shorter sections that are set and hauled independently. These shorter sections are normally deployed fairly close together.

When the vessel reaches the area where the lines will be set, the skipper will normally wait until it is dark before deploying them. The line setting process can take several hours. After the lines have been deployed, line retrieval normally starts in the late morning and the hauling operation will last for around twelve or thirteen hours, during which time the crew will process the catch and prepare the lines to be set again. When all the lines are on board (sometimes after midnight), the vessel often moves for one or two hours to the position where the lines will be deployed again, and line setting normally starts between 3am and 5am. This daily routine continues until the vessel is ready to land the catch and is normally only interrupted by severe weather conditions.

It has been observed several times that bycatch sometimes occurs in clusters and the skipper’s insight might explain this. Some skippers are of the view that when seabird bycatch occurs it makes the lines less effective, as bycaught birds tangle the line and don't allow it to sink as it should. Furthermore, a bycaught bird will generally keep the other adjacent baits at the surface for longer which can lead to bycatch of other birds in the same section of line.

Based on discussions with skippers, to try and avoid bycatch, most of the vessels (in the UK fleet) set their longlines at night when skippers feel seabirds are less active, and some vessels use home-made scarers (which consists of a rope with some coloured ribbons hanging from it) as deterrents during line setting. Scarers can help prevent bycatch, but they also cause problems if they tangle with the fishing line. This happens more frequently in bad weather conditions and can lead to the line breaking which causes significant delays in line setting and retrieving operations.

Some bycatch occurs during line setting, and all birds that are securely hooked at that point in the fishing operation will drown prior to line retrieval. Birds are also caught during line hauling and most of these are released alive. These birds are generally hooked in their beak or wing. Most attempts by seabirds to grab baits during line hauling do not lead to birds getting hooked and often they manage to take the bait successfully.

From general observer observations several factors appear to influence the bycatch rates:

• Time of year - bycatch rates appear to be lower in winter, spring and late autumn, and higher in summer and early autumn.
• Location - bycatch rates appear to be lower to the south and west of Ireland and to the west of Scotland, but higher to the north of Scotland.
• Performance of the scarer - sometimes in side-winds the scarer is blown away from the line as it is being set and this appears to be associated with higher bycatch rates than when the scarer is vertically above the lines.
• Timing of line setting - Lines that are set across the dawn period appear to have higher bycatch rates. One skipper commented that sometimes on bright moonlit nights, bycatch can also occur even if the full line is set during darkness.
• Behavior of the birds - there are always birds around the vessel during line setting and hauling but sometimes they do not appear to be interested in the bait. However, at other times they are much more eager and aggressive which leads to more seabirds getting caught. This behavioral observation may partially explain the highly variable bycatch rates observed in the fishery.

During discussions with skippers some questioned whether certain birds have become more reliant on foraging around the fishing fleet than others. Skippers had also noticed that sometimes the birds are calmer and less interested in the baits, while at other times they are more determined to grab them. Some skippers wondered if this changing behaviour is related to the abundance of other food, or to the fish catch rates and how much offal and discards are available during the day. The observer concludes that there seems to be a complicated ecological relationship between the birds, the vessels and bycatch levels.

5.3 Discussions with industry on bycatch and bycatch mitigation

The intention at the outset of the project was to hold one or more informal meetings or small workshops with skippers from the fishery to obtain their views on bycatch and bycatch mitigation in the fishery. Initial discussions took place with industry representatives to that effect early in 2021. However, due to travel restrictions and various other uncertainties related to the Covid-19 pandemic, and because most of the skippers are at sea for large parts of the year and are rarely all ashore at the same time, it was determined that a group meeting or workshop would not be feasible in the project timescales. Consequently, other possible routes for directly obtaining skippers input were discussed and resulted in the development of a questionnaire that could be circulated throughout the fleet.

A first draft of the questionnaire was completed by the skipper of a vessel while our observer was aboard in autumn 2021. Several significant adjustments were made to the draft, based on the skipper’s feedback and some further consideration by the project team. A final draft was submitted to the University of St Andrews Ethics Committee in December 2021 and received ethical approval shortly afterwards. As part of the ethics requirement, a participants information sheet was also provided to all participants along with the questionnaire. The questionnaire and information sheet are provided in full in Annex 1.

The final questionnaire was sent to the main industry representatives in early 2022, and responses from the skippers (and in one case also the chief mate) of four vessels (approximately 30% of the UK fleet) were received. Responses are summarised below.

5.3.1 Summary of the skippers’ responses

Fisher experience: All respondents have significant experience in the hake longline fishery. Three skippers have over ten years’ experience, and one skipper and the chief mate of one of the vessels have five to ten years’ experience. Collectively, the respondents have at least 40 years of first-hand experience as skippers in the fishery.

Fishing effort: Overall, most of the fishing effort of the four vessels occurs in 4a. However, there are some differences in where and when the vessels fish. One vessel works all year in ICES Division 4a (Northern North Sea). The three other vessels split their time between 4a and 6ab (West of Scotland) and one of those vessels also spends limited time working in 7cbkj (West/Southwest of Ireland).

Estimated bycatch: The skippers were asked to provide estimates of their annual seabird bycatch. Estimates of bycatch resulting in mortality ranged from 1-5 to 80 birds per year. Estimates of live bycatch (caught during line hauling) ranged from 10 to over 200 birds per year. There was some variation in the skippers’ views regarding bycatch trends: one skipper felt bycatch levels were generally increasing, another felt levels were decreasing, and two skippers and the chief mate of one vessel felt bycatch levels were stable.

Factors affecting bycatch: All respondents felt that fishing area and season had an influence on bycatch levels. In Division 4a, four respondents indicated that bycatch is highest in quarter 3 (July - September) and one respondent indicated highest bycatch in quarter 2 (April - June). In 6ab, two respondents indicated that bycatch was highest in quarter 2 and two indicated it was highest in quarter 3.

The reason for the higher bycatch in quarters 2 and 3 is considered by all respondents to be related to the increased hours of daylight during the summer months. One respondent noted that this is particularly significant at the more northerly part of the fisheries range around latitude 60^o N. Another respondent indicated that the light levels are important in 6ab when bycatch is higher if lines are shot across the dawn period, but that the same does not appear to happen in 4a when there is almost no darkness during the middle of summer, so the full lines are normally shot in daylight. One respondent indicated that there is more bycatch and less fish catch when lines are set in daylight and when closer to land.

The skippers were asked if they had noticed any other patterns in bycatch. Two respondents indicated that there appear to be less birds around their vessels if there are trawlers working nearby. One respondent indicated that fulmars are more abundant close to land, and in better weather.

Bycatch mitigation: All respondents have a variety of measures in place to try to reduce bycatch levels. All vessels use bird scaring lines routinely. Three vessels set the lines at night as much as possible, and two of those indicated that they also turn off the external deck lights while line setting at night. Three vessels dispose of offal at night after line hauling. One vessel disposes of offal from the opposite side of the vessel to where the lines are hauled. One vessel also prepares bait under cover and never outside on deck.

The skippers were asked if there were other ways it might be possible to reduce bycatch. The respondents suggested the following potential solutions: the use of acoustic deterrents to keep birds away from the vessels, spraying water to keep birds away from the line hauling area, use of a kite simulating a bird of prey to keep birds away from the vessel. Two respondents did not provide any suggestions but said that in their opinion the practices they currently use do reduce bycatch, although they are willing to considering alternative options.

The skippers were asked for their opinion of the efficacy of five different approaches that have been suggested as possible ways of reducing bycatch in other fisheries:

1. Reduce deck lighting during line setting.

All respondents agreed that reducing deck lighting during line setting is a suitable approach for seabird bycatch mitigation in the hake fishery.

2. Bird scaring lines during line setting.

All respondents agreed that the use of bird scaring lines during line setting is a suitable approach for seabird bycatch mitigation in the hake fishery.

3. Increase line sink rates.

Three respondents think that increasing line sink rates is unsuitable for the hake fishery because of health and safety concerns for crew members if weights were increased, possible effects on the behaviour of the fishing gear and fish catch rates with altered weighting regimes and because current weightings are dependent on the line setting system and weighting regimes are sometimes changed to suit working in different areas. One respondent indicated that their current weighting regime has evolved and is appropriate for the fishery. One respondent felt that changing line sink rates would have no influence on bycatch levels. Only one respondent felt that increasing line sink rates would reduce bycatch levels.

4. Change where discards and offal exit the vessel.

Four respondents felt that changing where discards and offal exit the vessel would help reduce bycatch. One of these respondents also suggested that it is better to dispose of all offal/discards after sunset. One respondent felt it would not make any difference as birds caught during line hauling are always released alive.

5. Keep birds away from the line hauling area.

All respondents agreed that keeping birds away from the line hauling area is a good idea. One respondent suggested using acoustics, and another suggested using a water cannon or spray.

Finally, skippers were asked for other comments or personal thoughts about the fishery, the seabirds, seabird bycatch and its possible mitigation. One respondent said that the birds benefit a lot from their fishing activity and that the birds deliberately associate with the vessels, but that they will continue to look for new ways to reduce bycatch and if appropriate ways are identified they will put them into practice. Another respondent said they will continue to work to learn new forms of deterrence and will put them into practice, with the aim of helping the birds and their own fishing operations. Another respondent highlighted that increasing line weightings will increase the workload, which is already large, but asked about possible funding avenues to help automate the longline operations and to re-route offal disposal chutes to the opposite side of the vessel, which would help reduce bycatch. All respondents indicated that they would be prepared to test their own, or other, ideas to reduce bycatch.