Four-Hour Tows Beat Five for Value, BIM Trial Confirms
Commercial fishermen chasing Nephrops in the Irish Sea are getting little extra for hauling longer, according to a second BIM trial that found no meaningful gain in catch beyond four hours of towing around slack water, while fuel costs for the fifth hour comfortably outweigh the extra prawns landed.
The trial, led by BIM’s Matthew McHugh, Fisheries Conservation Technologist, aboard the MFV Margaret Mary (DA56) in the western Irish Sea during June and July 2026, tested 2-, 3-, 4- and 5-hour tows across fourteen valid hauls using a quad-rig Nephrops trawl. It repeats, with a different vessel and skipper, the pattern BIM first flagged in a 2025 trial.
Catches barely move with extra hours
Nephrops made up 70 to 82 per cent of total catch weight across all treatments. Mean catch rose only modestly with tow length, from 240 kg on 2-hour tows to 284 kg on 5-hour tows, a spread of less than 20 per cent despite tow times varying by up to three hours. Statistically, the difference between the 3-, 4- and 5-hour treatments was not significant.
Figure 1: Mean Nephrops catch by tow duration, 2026 BIM trial. Source: BIM Fisheries Conservation Report, September 2026.
Four hours is the sweet spot for value
The economics point the same way. Four-hour tows generated the highest average landed value, at €1,974, ahead of €1,799 for 5-hour tows, €1,663 for 2-hour tows and €1,602 for 3-hour tows. Larger Nephrops turned up in greater numbers in the 4-hour catches, lifting the average grade value even though total weight was similar to the 5-hour treatment.
Figure 2: Mean Nephrops value per tow, 2026 BIM trial. Source: BIM Fisheries Conservation Report, September 2026.
The fuel math doesn’t add up for hour five
BIM’s report puts a hard number on the trade-off. Stretching a tow from four to five hours added just 6.3 kg of Nephrops on average, worth about €43. A vessel of this size burns roughly 80 to 100 litres of fuel an hour while towing, and with marine diesel at €1.13 a litre in early September, that fifth hour costs up to €113 in fuel alone, over two and a half times what the extra catch is worth.
Fuel prices have climbed sharply this year, up to 70 per cent higher than in 2025, adding pressure on skippers to cut wasted steaming and towing time wherever the data allows it.
Matthew McHugh said reducing tow duration can lower fuel consumption per trip while maintaining fishing performance, adding that it can also cut carbon emissions and gear wear, delivering both economic and environmental benefits for fishing businesses.
Gear stowed on deck between hauls during the trial.
Second trial backs up 2025 findings
The result echoes BIM’s 2025 study, which also found no significant difference in catch between 3-, 4- and 5-hour tows. Researchers say the consistency across two trials, run on different vessels and in different conditions, strengthens the case that Nephrops catchability drops off as tidal currents pick up, with most of the available catch taken during the central slack-water window.
The report’s authors conclude that fishing for 3 to 4 hours around slack water offers a better balance of catch, fuel use, profitability and gear wear than routinely running tows out to five hours. The full report, Shorter Tows, Similar Catches? A Commercial Assessment of Nephrops Fishing Around Slack Water, was announced by BIM on 23 September 2026 and funded by the Irish Government and the European Union through the EMFAF Operational Programme.
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