British Divers Marine Life Rescue
British Divers Marine Rescue
2011-02-24 10:19:49

BDMLR frees Porpoise in Glasgow!

BDMLR frees Porpoise in Glasgow (Photo: Craig Borthwick, BDMLR)Head Office received a call from Strathclyde police late in the afternoon on Monday 21st February 2011 about a harbour porpoise that had been reported as swimming around above the Clyde Tidal Weir, near Glasgow Green, unable to make its way back to open water as the gates were closed.  As our BDMLR Glasgow coordinator Craig Borthwick is on the force as Wildlife Crime Officer and was on duty at time, we put them in direct contact.  As the gates would remain closed on Monday, no action could be taken then.

On Tuesday, Craig organised an attempt to herd the porpoise out when the gates were opened for a short period, with assistance from the Marine Policing Unit and the Maritime Coastguard Agency, and ably assisted by local BDMLR medics Elaine Clark and Laura Davison. Unfortunately, with a very narrow window of opportunity (the gates can only be opened at high tide when the water levels are at the same height above and below the weir) the porpoise didn't go through and remained upstream. It favoured where the salt water from downstream mixes with the fresh water from upstream, and thus when the gates were opened, moved further upstream following the entering salt water.

Although the porpoise seemed to be healthy, the longer it stayed in the brackish water, the more likely it was that its health would fail and it was unlikely that it would have been feeding properly. Our concern heightened when it transpired that it had been spotted in the area on the previous Thursday.  Porpoises are also notoriously easy to shock so it was crucial that the team got the level of intervention right. Police divers advised that it was not safe to enter the water to try and catch the porpoise due to the amount of discarded trash, but this is something that would have created too high a risk to the animal's life, so was never on the agenda.

On Wednesday, we were given a have longer, three-hour period by the City Council for the gates to be open.  These gates are about 24 metres long and just under 4 metres high, opening and shutting vertically.  With advice from colleagues at the Sea Mammal Research Unit at St Andrews, a plan was created to encourage the porpoise to swim through the open gates by banging on scaffolding poles supported in the water from two boats and thus creating an acoustic deterrent. If this didn't work, we were considering playing recordings of killer whales underwater (at low levels) and were trying to source a 'pinger' that salmon farmers use to keep seals away from their farms, that can be set to a suitable frequency for porpoises.

With this new plan and poles in hand, the BDMLR team, on two boats provided by the Maritime Coastguard Agency and the Clyde Rowing Club, located the porpoise upstream and began the operation, lowering the poles into the water and banging on the tops. The porpoise, on hearing the noise, turned tail and headed downstream and about an hour later swam through the open gates with the boats behind.  Once the gates were closed, the porpoise was left alone and was reported to be swimming healthily, on the right side of the weir.  It is expected and hoped that it would follow the deeper water on the outgoing tide and return to open sea.

Film crews from ITV covered the successful operation for a wildlife documentaryFilm crews from ITV covered the successful operation for a wildlife documentary to be aired in June this year. A crew from BBC Springwatch also filmed for a BDMLR special feature to be shown in 2012.

This was yet another successful operation carried out by BDMLR under difficult circumstances, and thanks are due to Craig, Elaine and Laura, as well as the Maritime Coastguard Agency, Clyde Rowing Club, the Marine Policing Unit and friends at Sea Mammal Research Unit at St Andrews for their acoustics advice.

Stephen Marsh
BDMLR Operations Manager