Working aboard a hake longliner in Namibia is a tough life for everyone aboard. The hours are long and gruelling. I would say longline crew are amongst the hardest working people in Namibia and always battling against difficult sea conditions. I have just spent the last two weeks on board to compare the traditional concrete weights used in this fishery with 5 kg steel weights, to demonstrate how denser weights can help reduce seabird bycatch.
These vessels set up to 22 miles of line at a time, either as a single long line or two parallel shorter lines, with about 27,000 baited hooks deployed per day. Line setting operations commence anytime between 03:00 to 05:00 hours and finish at around 07:00 to 07:30 hours. This allows time for a quick breakfast and a couple of hours sleep before starting to haul the line at around 10:30. The hauling operation continues from 10:30 to around midnight. This process is repeated every day for the duration of the trip. The vessels usually dock to unload their catch early in the morning and sail again the following afternoon.
The image below shows the crew hard at work, setting our steel weights from the aft deck
My tasks aboard are to observe the line set and deploy Time Depth Recorders (TDR’s), which provide data on how fast the gear sinks out of the reach of foraging seabirds. I also record any bird interactions as they attempt to take baited hooks at the water surface. I then observe the line retrieval to count and record any bird mortality and where exactly on the line they are caught in relation to line weighting.
I am planning on doing five trips in total, but so far the first two trips have shown some positive results for the heavier steel weights.
It is now mid-winter in Namibia which means that the birds are congregating in the over-wintering feeding grounds looking for any food they can find. Of course a fishing vessel provides easy pickings for hungry birds. We were at-sea over the full moon period which improves night visibility making it easier for the night foraging White-chinned petrels to see the baits as they are set behind the longliner. This is the most dangerous period in terms of seabird bycatch.
Over the two trips 194 nautical miles of line was set with a total of 228,000 hooks. The really sad part of all this was that 92 birds were hooked and drowned. That is the reality of what happens when vessels fish without mitigation measures such as bird-scaring lines and appropriate line-weighting. However, my results show bycatch is greatly reduced by using the 5 kg steel weights.
The image below shows White-chinned petrels in the hauling bay. these birds were caught on the line where concrete weights were in use
Conducting this experimental work is critical to convincing the skipper and crew of the efficiency of best practice mitigation measures. My observations on where the birds are being caught in relation to line weighting are vital to this process. Using the TDRs means we can also identify the sink rate of fishing gear and therefore define the area behind the vessel that must be protected with a bird-scaring line.
It is hard to watch birds being pulled up dead on a fishing line. However, the skipper and crew now see the difference that good line weighting can make and are all very positive about the results. Other longline skippers have been on the radio daily asking about the weights and how they work.
By the time I finish another two or three trips we will have a really strong case for implementing bird-scaring lines and improved line weighting in combination with night setting as the best practice suite of mitigation measures for this fishery. We are confident that this combination will dramatically reduce seabird bycatch.