Pioneering sustainable, beneficial change in aquaculture

There is a scientific paper, soon to be in print, that examines 140 fisheries around the world that have either collapsed in the past few years, or are on the brink of doing so. One reason why this is happening to our fisheries is because it is not humanly possible to realistically determine the natural recruitment rate of each species being fished. The ocean is too vast, complex, and dynamic to be that easily determined by mere human beings. Instead of accepting this, the biological managers of each fishery tend to create methodologies for determining natural recruitment that are nothing more than study in jumping to conclusions on insufficient evidence, and camouflage that fact with self-serving, self-deluding, esoteric mathematics.

In 1988, our company Manatee Holdings Ltd. decided to do something about this because we were concerned that the dive fisheries in B.C. harvesting geoducks, sea cucumber and urchins were actually collapsing the stocks. We focused on creating solutions that did away with the necessity to “guesstimate” natural recruitment. We also looked for ways to address natural problems causing excessive mortality.

Urchins, for example,tend to feed on the hold-fast (root) of the weed. The rest of the weed then breaks free, never to return. The reef becomes barren, and the urchin dies.

But if weplant a series of poles along the reef, string a rope along the top of the poles, plant nutritious seed of the types of sea weed the urchins love to eat, and allow it to grow down to the reef to be fed on by the urchin seed we culture in our hatchery the system becomes sustainable. We callthis a “Feed Line Urchin Ranch”.

Geoducks grow in sandy substrate areas, often foundjust below the urchin reefs. Many of these natural geoduck beds have been mined out by the wild fishery. We are replanting these natural beds back up to their natural densities with cultured geoduck seed raised from broodstock taken from the same general vicinity as the beds.

Sea cucumbers are often defined as the, “earthworms of the sea”. Like the earthworm on land, sea cucumbers feed on rotting material in the substrate and help to maintain the ecology. They like to feedon the pseudofaeces produced by both urchins and geoducks.

A healthy adult sea cucumber can move faster than it’s natural predator, the sunstar, just as a healthy caribou can out run a wolf. The problem is juvenile sea cucumbers cannot out run the star, and they get eaten by the millions. So we have creatednurseries for ourcultured sea cucumbers seedwhich are made up of recycled bags of oyster shells placed on the bottom of the ocean where the sandy substrate meets the edge of the reef. When the cucumber seed grows to a size where it has to leave the safety of our nursery refuge they hide out under the weed growing from our planting line on the reef. There they get to feed, not only on the rotting bits dropping down from their protective canopy of weed, they also get to feed on the pseudo faeces of the urchin. Once they are large enough to venture out onto the sandy substrate they also get to feed on the pseudo faeces of the geoducks.“Free ranging” sea cucumber allows them determine their own bestdensity.

This is the system we are championing into place accordingin B.C.

Eric Gant, of Manatee Holdings, is pioneering a new, sustainable model for aquaculture in British Columbia.

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