Tuesday, November 25, 2014

Mussel transfer: Overwintering

Blue mussels grow naturally off the coast of N.H., filtering the ocean water to feed on tiny plankton. There have been previous efforts to grow and market N.H.'s blue mussels, but various issues have halted their production over the past few years. With help from NHSG/UNHCE marine aquaculture specialist Michael Chambers and UNH professor of zoology Hunt Howell, N.H. fishermen are renewing efforts to raise and harvest blue mussels.

A new team of fishermen have joined forces to culture mussels offshore from N.H. on submerged long lines. Pete Flanagan and Vinnie Prien have formed the Isles of Shoals Mariculture, LLC that will have mussels for sale by next summer. To help jump start their mussel farm, mussel seed was made available to them from an integrated multi-trophic aquaculture (IMTA) project at UNH.  Mussel seed was collected from the IMTA platform and then transferred a grow out raft under the UNH pier for six months, filtering water from the Piscataqua River. The river has relatively high levels of nutrients for the mussels to extract and grow. They have grown so much that they needed to be reset at a lower density and placed offshore for their final grow out near Rye, N.H. They will remain in this colder ocean water until early summer, then harvested and sold to local restaurants and at seafood markets around the Seacoast.

The process of moving the mussels took three days. Day one consisted of pulling up the lines and stripping the mussels from the lines into tote boxes, and the second day was spent size grading and setting the seed into cotton tube sock for stocking offshore. More than 4,000 lbs. of seed were set into the sock at rate of one pound/foot. A total of 4,150' of seed was transferred to a submerged long line on the third day located three miles offshore.

Fishermen first inspected the lines for growth:

The lines were very heavy, weighing as much as 150 lbs. Fishermen pulled them over to a hydraulic stripping machine that pulled the lines up into a bin to separate the mussels from the line.

A hydraulic wheel pulls the mussel line through a narrow opening that separates the mussels from the line.

Fishermen inspect the stripped lines and remove any other mussels that were left behind.

The mussels that are removed from the line slide down a ramp into a tote.

The result: Muddy mussels from the Piscataqua River, which are then rinsed and size graded.

Thirty-three totes were filled with mussels prior to cleaning and grading.

The mussels were then placed into a hopper where they funneled into cotton tube sock for grow out offshore.

The blue tanks were filled with cotton tube sock filled with mussel seed

The next steps involved placing the mussels onto new line. The mussels use bissel threads to attach to ropes, lines and other structures under the water. Although mussels can settle on lines without any assistance, there are ways to ensure a more even distribution. Fishermen placed a biodegradable tube, sometimes called a sock, around the line and filled the sock with the mussels they had previously stripped off the old lines.

The newly filled lines were taken out to the offshore mussel site the next day. In total, fishermen moved over 4000 pounds of mussel seed, and they will grow to weight approximately 30,000 pounds at harvest time next spring.