ICOLLS - Complex environment, important fish habitat

ICOLLS - Complex environment, important fish habitat © RFA of NSW

With heavy rain and large seas making its impact across our State, NSW Fisheries Officers are out and about on the lookout for attempts to illegally open Intermittently Closed and Open Lakes and Lagoons (ICOLLS) on the NSW coast.

Illegal openings of lakes and lagoons have the potential to lead to large scale fish kills and ongoing environmental impacts.

ICOLLs have evolved to open and close to the ocean naturally in a constant but irregular cycle. When there is sufficient water flowing into a lake or lagoon from the catchment area (usually following heavy rainfall), water levels in the ICOLL will rise. Eventually the water in the ICOLL will spill over the entrance sand berm and drain to the ocean. The force of the backed-up water then quickly scours an entrance channel through the beach and reopens the ICOLL to the ocean.

ICOLLs close when the ocean waves and tides push sand from offshore into the entrance, which gradually closes the entrance channel. Without further large freshwater flows into the estuary from the catchment, the ICOLL will remain closed to the sea.

When ICOLLs are closed and water levels are high there can be concern in the community. Most ICOLLs have existing opening protocols in place, these are developed after extensive consultation with council, the community and Government agencies. They are designed to protect infrastructure and residents from flooding, while still protecting the unique environmental values and fish stocks within these systems.

Opening ICOLLs artificially without appropriate approvals is illegal. Such openings can result in large scale fish kills caused by the sudden drop in water levels and exposure and decomposition of aquatic vegetation leading to depletion of dissolved oxygen levels in the water. Other impacts such as increased closure duration and frequency, acid sulphate leaching and prolonged odours are also linked to openings.

There are an estimated 120 Intermittently Closed and Open Lakes and Lagoons (ICOLLs) on the NSW coast. Where possible, ICOLLS are left to open naturally. Councils can seek permission to artificially open an ICOLL if there is an existing pressure from flooding or to avoid the likely threat of flooding to critical infrastructure. For more information in ICOLLS visit here.

The maximum penalty for carrying out dredging works (such as digging to open an ICOLL) without a permit is $110,000. If you see an attempted illegal opening please contact the Fishers Watch hotline on 1800 043 536 or online here.