Tag: Mitigation

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!

Lithuania

nets-to-be-used

Shedding light on seabird bycatch

By Tomasz Linkowski & Anetta Ameryk, Polish National Marine Fisheries Research Institute NMFRI

For the first time in EU waters, we want to test net lighting in Polish gillnet fisheries to minimise seabird bycatch, thanks to a new project coordinated by BirdLife International and funded by the European Commission to specifically look at gillnet bycatch mitigation. As part of BirdLife’s existing work in the Baltic (Lithuania), testing of net panels is already being carried out, so it only made sense to examine the efficacy of an alternate measure in Poland. While it was relatively easy to come up with a solution, actually implementing it turned out to be a challenge!

At the beginning of December,  we decided together with BirdLife International that due to light conditions prevailing in the winter season in the the South Baltic, net lighting instead of the high contrast panels (see below) already tested in Lithuania should be more effective in protecting birds against their accidental bycatch in gillnets.

  • High contrast panel being tried out in Lithuania.
  • Fish luring lights used in the net lighting measures in Poland.
Images above: On the left, fish luring lights used in the net lighting measures in Poland. On the right, high contrast panel being tried out in Lithuania.

The effectiveness of lamps produced by the Korean company CENTRO had already been documented to reduce seabird bycatch in the Southern Pacific. So why would the same measures not be as effective in the Baltic? Once the decision was taken, we thought it’d be easy enough to start trying out the idea.

It turned out CENTRO lamps were not available either in Europe or at the manufacturer in Korea in time to start our project in the present season. In the end, we only managed to buy two pieces of CENTRO lights so we had to look for alternatives. We successfully found appropriate lights and after some trouble we managed to buy 350 lamps of Korean production type YML-1000 (photo below) of a very similar design and parameters with respect to the original CENTRO product.

Lights © Anetta Ameryk/Morski Instytut Rybacki

Once we had the lamps in our hands, we came across another issue. The proposed lamps had been developed for longline or angler catches of swordfish, so adapting them for our project needs was not so obvious. Luckily, we eventually got around that issue too!

Mounting the lights © Anetta Ameryk/Morski Instytut Rybacki

The lamps reached the NMFRI in mid-February and they were immediately installed on previously prepared net sets by owners of two boats with whom the NMFRI had earlier signed relevant agreements on cooperation within the project.

After negotiations with fishermen, they considered that they could try with automatic lamps which should not significantly slow down the process of fishing and would hopefully be effective in minimizing seabird bycatch.

  • nets-to-be-used
    Nets ready for use © Anetta Ameryk/Morski Instytut Rybacki
  • Mounting the lights © Anetta Ameryk/Morski Instytut Rybacki

The lamps have been installed by each fisher on two sets of nets with a length of approx. 300 m. Two identical net sets have been left with no lights as control sets. The next step will be to examine any operational issues with the lights so we can eventually deploy them in big numbers.

Now that we are ready to set sail, we are eager to share our next steps with you!

Poland