Analyse this…

As we embark on our second season of data collection in Lithuania, we highlight what we learned from analysing our first season’s data.

While raw figures might make interesting reading, when it comes to thinking about bycatch, we need to analyse our data to draw useful conclusions about how effective our net panels might be in reducing seabird mortality in gillnet fisheries.

One of the difficulties with almost all bycatch data, irrespective of fishery or accidentally captured species, is that it is usually a rare, sporadic event – this means that our data set contains lots of zeros, when there was no bycatch at all. Most means of analysis don’t cope particularly well with this – but thankfully, there are ways!

Without getting into the details (we will aim to publish our results in full once we have completed our next field season), the mean number of birds caught per set was about a third lower in our experimental sets with net panels (mean of 0.37 birds/set) than control sets (0.54/set). While this is an encouraging result, this difference was not statistically significant. Given this outcome, we are undertaking further trials this winter in Lithuania, continuing to conduct paired trials to bottom-out whether these net panels might have utility in reducing seabird bycatch in the Baltic. The signs are encouraging, but more work is required!

One interesting (and statistically significant!) result is that total fish catch was actually higher in the nets carrying panels compared to standard gillnets (a graph below if you’re interested!). This is an important result, as technical mitigation is unlikely to be popular with fishermen if it negatively affects catch. We’ll continue to keep a close eye on how net panels affect target catch…

total catch

 Total fish catch in control and experimental nets. Horizontal lines are the median, boxes the interquartile range, error bars the 95% CI, and dots are final outliers

Thanks to Alex Bond of RSPB for carrying out the analysis!

Feeding back to fishermen and gearing up for another field season!

To be effective, our seabird bycatch teams all over the world need to be in regular contact with fishery stakeholders. Of course, spending time on boats and in port means we frequently speak to fishermen, but it’s important to take the opportunity to step back and talk about some of the big issues with fishermen, scientists and national fisheries departments. The Seabird Task Force in Lithuania did just that this past summer, by holding a workshop to present our preliminary project results on gillnet bycatch mitigation and plan the next steps for our field work – which is beginning again as we write!

At the workshop, the Task Force team presented the results of our winter 2015/16 mitigation trials. A total of 78 fishing trips were conducted to compare the levels of bycatch in standard nets with our experimental nets, carrying black and white ‘net panels’.  Both fishermen and our observers collected data on fish and bird catch to help us test whether the panels could reduce bird bycatch while maintaining the catch of target fish.

During this field season, participating fishermen caught 89 birds, with the most common species being the Velvet Scoter. Long-tailed Duck, Red-throated Diver and Common Scoter. As is often the case with seabird bycatch, it was highly variable day to day – many days could pass with no birds caught; on one day, a single trip caught 36 birds and just 9 kg of fish- demonstrating the severity of bird bycatch and the need to find solutions!

Our high contrast panels have shown promising preliminary results- while we need to carry out more trips to be able to have stronger statistical evidence to back up our findings- there are indications that nets carrying panels catch fewer birds. The raw data also indicate that most birds where caught in water depth of 10 meters. Very interestingly, the fish catch in the nets with high contrast panel increased compared to the normal nets. We hope to post more details of our analysis on this blog shortly! These results were well received during the workshop by both fishermen and government representatives.

One of the participating fisherman also gave a presentation and he shared his own positive experience of using the panels, collaborating with LOD and his hopes for working towards a reduction in seabird bycatch. In the last session of the day, the Ministry of Agriculture (Department of Fisheries) provided a presentation on their vision for bycatch reduction and opportunities for funding- providing the framework for a very useful discussion on the next steps for this work. The team outlined that in the next field season we will keep testing the same panels more widely and will examine the utility of new methods, such as underwater net lights. As this work is now underway, look out for another blog soon about what we’ve been up to this winter!

Early results from our mitigation trials in Lithuania

The winter has brought the usual mix of seabirds to coastal Lithuania – we recently counted more than 8,000 waterbirds in our winter census. Most of these were threatened Velvet Scoters, with around 6,000 counted in sandy-bottomed sea areas off the beautiful Curonian Spit. Sadly, not all these ducks will see the Spring. We have already recorded Velvet Scoters, Red-throated Divers, Long-tailed Ducks, and Common Scoters as bycatch in the cod fishery. Since late October, we have collected 80 drowned birds from the 10 fishermen we are working with.

It’s heartbreaking to see such wonderful (and threatened!) bird perish, but these fishermen are at the forefront of our collaborative efforts to see if we can reduce this toll by testing high-visibility net panels. In spite of some tough sea conditions, we have managed to collect data from around 30 paired sets so far – a pair being a set of modified nets with panels versus a ‘normal’ set of nets.

While the data needs to be fully analysed, the preliminary results are encouraging – bycatch is around 20-30% lower in the modified nets, and there does not appear to be a significant difference in the fish catch.

Arunas Grigaitis, one of the skippers we are working with, said: “We do not want to catch birds, our aim is fish…it’s sad to see birds drowned into nets; they also damage the nets, and it takes additional time to take them out. I’d use modified nets – there is only a slight difference in fish catch”

We still have more data to collect from the cod fishery over the next few weeks while winter draws to a close. In Spring, we’ll analyse all the data collected across the season and see if the bycatch reductions and any catch impacts are significant.

Personally speaking, I’m glad that conservationists and fisherman have found a way of communicating and working shoulder to shoulder. It’s been especially great to have the cooperation of the recently-formed coastal fisheries and recreation association. The trusting relationship we have means that many of the smaller vessels owners self-report their bycatch, doing the data collection themselves. When fishermen start to see bird bycatch as a problem not just in their own nets, but more widely, they start to think about how to reduce it, even suggesting their own ideas. For me, that’s really inspiring!

Next autumn/winter, the Seabird Task Force team will probably explore some other types of bycatch mitigation. As there is still no best practice for reducing bird bycatch in gillnets, the more we can learn about new potential measures the better.

In the meantime, if your Lithuanian is good, it’s worth checking out some of the news coverage we got in some of the main news webpages and daily newspapers in Lithuania (links below). Best of all, there was some great coverage on the project on national TV-  – skip to around 20:50.

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Current field season with modified nets in action

The Seabird Task Force team in Lithuania (Lithuanian Ornithological Society (LOD), has been preparing all summer and autumn for the winter fishing period. The aim of our project (and the focus of our field work this season) is to reduce by-catch of sea birds during the wintering season.

For this purpose, we have made 800 high contrast ‘panels’ to attach to 47 nets which we hope will alert the birds to the nets in the water- (ie. scaring them away). Each of the modified nets has 10 to 13 black and white striped panels placed every 4 meters. Another very important aspect this field season will be to test the efficiency of the modified fishing nets- to see if they manage to catch fish as well as the normal nets. The ideal outcome for the project would be to find new fishing measures which do not harm seabirds and do not reduce fish catches!

In late October, we began testing the modified nets with coastal fishermen at sea. Ten fishermen in total are working with us; seven inshore fishermen started fishing cod with the modified and control nets, covering almost all of the Lithuanian coastal zone, and we hope to commence fieldwork with three larger gillnet vessels imminently. Along the Curonian Spit, where currently there are already abundant numbers of wintering birds, the trial fishing trips will be more frequently than in other areas.

Fishing with the modified nets uses exactly the same principle as normal fishing. Nets tend to be left in the sea overnight and the next day they are hauled back in. Nets are deployed 100m to 3 kilometers from the shore in depths of between 10 and 22 meters. Later, when nets are hauled, the fishermen operating smaller vessels calculate catch from both the modified and the unmodified nets. The fishermen add all their records on fish size to specially designed forms, where they also can make remarks on bird bycatch and the fate of them, as well as things like seal damage to fish and nets. On vessels larger than 8 meters in length, the fishermen carry one of the Seabird Task Force observers who collect data on fish catch and bycatch from nets, and also count wintering seabirds to understand the areas with the highest density, where interactions with gillnets are likely to have the greatest impact.

Fish luring lights used in the net lighting measures in Poland.

Preparing for the Bird Wintering Season

Winter is approaching, and lots of sea ducks that have bred further north will gather in the Lithuanian Baltic Sea. Before the colder period sets in, many Baltic Sea gillnet fishermen are focussed on catching plaice – when colder weather arrives, fishermen will switch to catching cod as they come closer to shore, and it is in this fishery that wintering birds are at risk of bycatch.

This is the critical time for our project, when months of preparation will come to fruition. Our collaborating fishermen are lined up, we have checked and tested our data collection protocols with them, and our observer team are ready to work with them to test net panels, which we hope will reduce seabird bycatch in gillnets.

The last steps are the production of our modified gillnets with net panels attached and the finalisation of special permissions from the Fisheries Service to conduct our trials. The materials are now ready, and we hope the net maker we are working with will have all 5,600m of these modified nets completed by the end of next week. The nest will be with modification of warning panels 60cm x60xm.

Similarly, the special permissions should be secured in the next fortnight. So, by mid-October, not long before most of the wintering seaducks have arrived, our fisherman will have the chance to test them in real life – some of the first fishermen in the world to work in this sort of trial!

This winter, 10 different fishermen will test our modified nets. Three of them will test nets in the open sea on big boats departing from Klaipeda port, and the remaining 7 will be departing from different areas of the coast with smaller vessels. In addition, the Fisheries Service is offering to help obtain further bird bycatch data from fisherman  not directly involved in our project. This will be supported by our recent engagement with gillnet fishermen at the Costal Fisheries Association annual meeting, where we were able to highlight the bird bycatch issue and encourage fishermen to provide us with records of bycaught birds. Although these ad-hoc reports from fishermen will not form the core basis of our data collection, they will help us build an overall picture of seaduck bycatch in Lithuania.

Diving seabird bycatch assessment in the Lithuanian Baltic Sea- 2014/2015 preliminary information

As summer arrived this year many diving seabirds migrated from the Baltic Sea to breeding grounds in Russian Siberia. But this is just a short period of their life, as they move to their breeding grounds for 4-5 months, and the rest of the year they spend on wintering ground.

The 2014/2015 winter period in the Baltic region was mild, and lots of diving birds stayed further north than usual, where ice-free water was present throughout the entire season. Our colleague Vytautas Eigirdas, in the Lithuanian Ornithological Society found that there were still significant number of wintering Velvet Scoters in the Lithuanian Baltic Sea along the coast of the Curonian Spit. Counts found at least 3500 of this species, which is currently considered endangered globally. During cold winters in the same area you can find more than 5000 wintering Velvet Scoters.

During the 2014/2015 winter we were able to assess the number of these diving birds caught in fishing nets in Lithuania. This is the first time in a number of years that we have been able to do this work. Together with project partners – the coastal fisherman- we collected data on seabird bycatch. Looking at the data collected from this preliminary work, 53 birds were recorded as caught in nets, the majority being Velvet Scoters – 45%, Long-tailed ducks were the second most regularly caught species – 39.6%, and there was also small numbers of Red-throated divers and Common guillemots caught.


For the most part, Velvet Scoters were caught near the Curonian Spit, in depths of 12-30 meters where the sea floor has a sandy bottom. These birds spend the winter in this type of habitat foraging on clams which inhabit the sandy bottom seafloor. In autumn this place is popular for the Cod fishery, which use 50-55mm mesh size nets. As fishermen use nets with big mesh sizes, this could affect the number of birds caught. Long-tailed ducks were mostly was caught near Palanga in water depths of 5-7 meters. In early spring time this region is popular with fishermen catching Smelt, and is also the stopover site for Long-tailed ducks. To catch smelts the fishermen use 18-22mm mesh size nets.

At this stage of our work, the data collected has been different compared to those collected 10-15 years ago, as the most regularly caught species is now Velvet Scoter, which was previously found to be the second most regularly caught species. Previously it was estimated that 2/3 of bycatch was from Long-tailed ducks, which no appears to no longer be the case. These changes could be related to changes of wintering sea ducks number in Baltics, or perhaps to the degradation of the feeding ground habitat. Now large numbers of Long-tailed ducks are common in the Lithuanian coast only during the spring migration. This demonstrates that knowing the key sites and timing of the birds movements and the fishing patterns and bycatch susceptibility in the Lithuanian Baltic sea will help us in trying to change the fishing gears to reduce seabird bycatch in nets.