Pictures emerge of dead fish found floating on surface of Glasson Dock Marina

The pictures also show excessive algae growth which can cause harm to other organisms including fish, and potentially their death.

The exact cause of the deaths is unknown and could be warm weather but sea water flooding through a broken tidal gate this month could also be to blame, say authorities.

The broken sea gate at Glasson has meant that tides can flow in and out uncontrolled while a connecting canal lock at the marina has been leaking water for months.

Further complications arose after the canal lock gates opened during early September’s high tides due to a broken chain, which could have impacted on fish and water.

Earlier this summer, concerns were raised by Lancaster city councillor Sally Maddocks and parish councillor Nicholas Thorn about low water levels at the marina and Lancaster Canal during dry weather, resulting in feared risks to wildlife.

They also warned of a ‘perfect storm’ of events across Glasson citing the leaking lock and broken sea gate, which is part of wider sea defences.

More recently, high sea tides have put Glasson at risk of flooding and flood defences have been stepped up, with sandbags delivered by the Environment Agency to local homes and businesses,

Now the Environment Agency for Cumbria and Lancashire and Lancaster City Council have issued more information about sea defences and fish deaths.

The agency confirmed recent attempts to fix the broken hydraulic sea gate were unsuccessful. Further work is expected to take 14 weeks.

In an update to households and businesses, the Environment Agency stated: “During high tides of Saturday, September 3, the canal lock gates opened due to a broken chain, allowing salt water into the marina and canal.

"The Canal & Rivers Trust has since replaced the broken chain. Water in the marina rose by about 15cm. While this did not cause any flooding, concerns have been raised about ecological impacts with dead fish and an algal bloom observed.

“The Environment Agency has visited the marina and canal to assess the situation. It believes the fish deaths and algal bloom are likely to be due to a combination of warmer water temperatures and weather conditions, reducing the amount of oxygen in the water.

"The salt water may also have had an impact on the fish.

“The chances of further algal blooms occurring in the marina and canal are low, unless we have similar weather conditions again.”

Environment Agency water samples show there are blue green algae cells present but levels are low, meaning the agency does not need to take any further action.

“We will continue to monitor the blue green algae in the canal and marina,” they said.

"If you spot any further fish deaths, please contact the Environment Agency.”

Regarding the broken hydraulic sea gate, the agency said silt inside hollow spaces of the metal gate and around it are creating problems to raise it.