Conservation Structures (CANTS)

In the same year (2018) that we co-led the establishment of Kep’s first Marine Fisheries Mangement Area (MFMA), we also officially started the deployment of Conservation and Anti-Trawling Structures (CANTS), also known as conservation structures or “blocks”.

We invented these conservation structures specifically to deter bottom trawling (link to IUU), which was a growing concern at that time. These structures not only block the trawler nets, but also facilitate the regrowth of seagrass (link to seagrass) and marine mammals (link to CMMCP).

We welcome all donations of tools and materials. If you are interested in sponsoring, please let us know!

De-structuring the problem

The original inspiration of the Conservation and Anti-Trawling Structures (CANTS) was to passively fend off the illegal trawlers.

Bottom trawling (link to IUU) was the beginning of a decade-long nightmare for the marine life in the Kep Archipelago. Although we finally co-established Kep’s first Marine Fisheries Management Area (MFMA) in 2018, illegal trawling and fishing activities were still a recurring problem.

Facing a shortage on manpower, we needed more non-confrontational tools to defend against the bottom trawlers.

As time went by, we also realized a second problem in the puzzle.

Our surveys and research showed that the trawled areas have lost its ability to regenerate because most of the basal habitats (e.g., seagrass, seaweed and bivalve reefs) have been destroyed. This affects not just the environment but also the livelihood of the local small-scale fishermen.

Therefore, any sort of hard substrate โ€“ or an artificial reef โ€“ could potentially exponentiate the recovery process.

Hoping to hit two birds with one stone, we started brainstorming a structure that could facilitate conservation and resist trawling at the same time.

One night,

while playing Jengaยฎ after marine patrol, we found inspiration in these wooden Jenga blocks.

Achievement highlights

1. Recorded first avoidance behaviour by trawlers in 2019

2. Continuous increase in species abundance post-deployment, including increase in marine mammal sightings

3. Seagrass regrowth and increase in fish stock and reported catch by fishermen

4. Recorded recolonization of mussels and oysters

Restructuring conservation

Although the deployment process of these conservation structures may appear complicated, in concept they are just a simple interlocking design using concrete blocks.

The individual concrete blocks are easy to make, transport and carry. But after deployment, the assembled structure becomes robust, heavy, adaptable, height-adjustable, and is even strong enough to snag and entangle a passing trawler net.

At the same time, the alternating placement of these blocks creates microhabitats such as crevices and holes that still remain intact even after repeated trawling. It serves as an artificial refuge for the remaining marine life.

After many repeated deployments, these conservation structures collectively harbour the recovery of pioneer seagrass and bivalves.

Then the fishes.

Then seahorses.

And turtles.

And eventually even marine mammals!

These “concrete Jengas” are literally the building blocks of our conservation projects.