The fish pens in the Piscataqua River that normally hold steelhead trout are now teeming with another form of life — sugar kelp. This native species is being grown on lines this winter for eventual harvest in late spring when they reach 2-3 m in length. NHSG/UNHCE marine aquaculture specialist Michael Chambers says he expects to grow almost 50 kelp plants per meter of line, leading to a potential harvest weight of 1800 kg total — that’s almost 4,000 lbs of seaweed.
Above: Aquaculture technician Jess Cranney holds a blade of sugar kelp near the pier at the UNH Judd Gregg Marine Research Complex in New Castle, N.H.
While they grow, the kelp will help extract excess nutrients like ammonia, nitrite and nitrate in the river. And for a waterway like the Piscataqua already impaired by too many nutrients, any bit of help is welcome. But the kelp’s final destination will be select markets for human consumption: once harvested, the kelp will be sent to Ocean Approved for processing and distribution as kelp slaw and kelp noodles.
But how exactly do you grow kelp on lines?
Sugar kelp “gametophytes” — the reproductive tissue in the kelp blade that releases spores into the environment — were collected from naturally occurring kelp growing on the fish pens under the pier. Once collected, the gametophytes were brought to Ocean Approved in Portland, Maine, where they were spawned in captivity. The kelp spores settled onto spools of twine and grown in tanks for two months. These spools were recently brought back to N.H. with the help of Sarah Redmond, marine extension associate from Maine Sea Grant and Paul Dobbins, co-owner of Ocean Approved.
Above: Sarah Redmond and Paul Dobbins demonstrate techniques for setting the seeded kelp twine onto a submerged grow-out line.
The spore lines were wrapped around a weighted rope and deployed into the empty fish pens.
Above: Kelp spore line is wrapped around a Polyester line with weights.
Chambers says there is potential for local oyster farmers to grow kelp or other seaweeds on their sites in Great Bay, both as a way to increase revenue and decrease nutrient levels.