Bromfield Street weir to be removed as rare fish found in Merri River

The Bromfield Street weir was constructed in 1907 as part of the Merri scheme to supply town water to Warrnambool, and despite this scheme being decommissioned in 1939, the weir remained in the waterway.

The aging structure of the weir, which has become unsafe over time, has been identified as a key barrier to the natural flow of the Merri River and an impediment to fish passage in the waterway, and will therefore be removed.

The weir removal is being undertaken by the Glenelg Hopkins Catchment Management Authority with funding through the Victorian government's $248 million investment over four years to improve catchment and waterway health across regional Victoria.

During a recent fish survey to assess the impact of the Bromfield Street weir on fish migration in the Merri River, a significant discovery was made by Austral Research and Consulting and the Glenelg Hopkins CMA of a rare Australian grayling, a remarkable find in the waterways of the region.

The Australian grayling is an iconic native fish species that has faced significant decline due to habitat degradation and barriers to migration, such as weirs. It is notable for its requirements for both saline sea water and fresh river water, and when found, it is often identifiable by a distinct smell of cucumber.

"The discovery of the grayling underscores the importance of conducting thorough assessments of waterway ecosystems to understand and mitigate the impacts of human infrastructure," Glenelg Hopkins CMA senior waterways officer Stephen Ryan said.

"The grayling is a migratory fish, it likes to move from the saline estuarine environment up fresh water rivers during their life cycle.

"Removing barriers to assist this is key to the project the CMA is undertaking to remove the Bromfield Street weir and return the Merri River to a more nature flow state."

Mr Ryan said during the fish survey, a total of 15 species were identified downstream of the Bromfield Street weir, while only six species were found upstream.

"This finding highlights the barrier effect of the weir on fish migration, limiting the movement of species upstream and fragmenting their habitats," he said.

"Weirs like the one at Bromfield Street are known to obstruct fish migration, disrupt natural flow regimes, and impede the movement of sediment and nutrients essential for healthy river ecosystems.

"These barriers can lead to decreased biodiversity, diminished fish populations, and ecological imbalances."

Dr Dion Iervasi from Austral Research and Consulting emphasised the importance of removing barriers like the Bromfield Street weir to restore connectivity within river systems.

"The discovery of the Australian grayling in the Merri River highlights the urgent need to address barriers to fish migration. Removing the Bromfield Street weir would not only benefit the grayling but also improve habitat connectivity for a wide range of fish species, promoting healthier and more resilient river ecosystems," he said.

The removal of the Bromfield Street weir is a significant waterway and community project in Warrnambool and extensive modelling and community consultation has been undertaken by the Glenelg Hopkins CMA in preparation for its removal this year.

A community information session held on-site last week gained further feedback from the community about the potential opportunities for re-using the bluestone capping used in the 1900s construction of the weir in and around the Warrnambool community.

"We understand the weir has a long history in the Warrnambool community and we have some ideas about how we will reinstate the site with revegetating the riparian area after its removal, but its always great to get some ideas from the community if there is something specific they would like to see included," Mr Ryan said.