Traditionally, when you think of ‘block and tackle’ and fishing, you think of pulley systems designed to help get larger fish out of the water and into a boat. But an alternative use of the term is gaining popularity when it comes to stopping the spread of invasive carp.

In the documentary by Great Lakes Now entitled Against The Current, Tennessee Wildlife Federation employee Michael Butler describes ‘block and tackle’ as the method used across the Cumberland and Tennessee Rivers. 

Fish Guidance Systems provide one of the technologies that helps deliver this method, so let’s look into what it is, how it works, and how it’s helping prevent the spread of invasive carp.

What is Block and Tackle?

Unlike the traditional use of the word, where the block is a crane and the tackle is the pulley system, ‘block and tackle,’ when related to invasive species, is the method of ‘blocking’ the path of the fish by installing deflection systems at locks and dams across the system, and then using commercial fisherman to remove the fish from the river. 

Other names for this system include “the unified method.”

How does Block and Tackle Work?

Invasive carp species (Black, Grass, Silver and Bighead carp) move their way through river networks and thanks to regular shipping on many of these rivers, there is a need to have locks and dams that open to let boats and ships through. This means that fish can swim freely through when the dam or lock is open.

The ‘block’ portion of the system, specifically on the Cumberland River, uses a BioAcoustic Fish Fence, a system that uses series of sound projectors, lights and bubbles to deflect fish away from the lock or dam and create a barrier that ships can pass through, but the invasive carp can’t. This system has been proven in laboratories and a system is installed at Barkley Lock, Kentucky since 2019. Whilst there are only preliminary results, the system appears to be highly effective in preventing fish from crossing the barrier.

In relation to tackle, with nowhere else to go, the fish will remain in the river below the barrier, and will continue to devastate the local ecosystem. Commercial fishermen are paid to remove these fish, and they are then destroyed, or used in commercial processes such as animal food.

Does Block and Tackle Work?

Block and tackle can be highly effective, however it needs to be spread over the whole of the river network. The Kentucky Lock project does show that BAFF reduces the flow of fish upstream. However, earlier this year the TVA highlighted 11 other places across their region where a barrier should be installed. The report also states that BAFF systems are the recommended system for installation.

Systems like ‘block and tackle only work in river systems where there are pinch points. Once invasive carp reach The Great Lakes, there are few remedies to stop their exponential spread. 

If you would like further information on invasive carp, please contact us at [email protected].