46 SEP TEMBER 2022 • WORLD AQUACULTURE • WWW.WA S .ORG CPI maintained a crew of 24 employees, five boats and a harvester barge to operate the farm. When the seedlings were 2-4 cm long, they were now big enough to go into the harvest system (Figs. 5 and 6). The older nori did not need daily drying at this point and could be laid out horizontally on the surface of the water. In summer the nori usually began to get pale, which was not a good sign. Chemical analysis showed that the nitrogen content was low. Given that Cobscook Bay and Gulf of Maine are considered extremely productive, this was not expected. I began weekly sampling of the water, sending the samples carefully to a postdoc who was developing a more precise analysis of aquatic nitrogen at the University of Maine, Orono to get accurate measurements. Ambient N in the form of NO3 and NH4 ranged from 0.5 to 3.0 ppm. The standard method of measuring N was over 50 percent greater; the new method was much more accurate and precise, rendering historically reported N levels incomparable and incorrect. In the Sea of Japan, where I visited the nori farm, they measured 100-300 ppm. By bathing the nets in ammonium nitrate solution once per week, I could darken the color and improve nori health. I used the Pantone color guide to monitor the color. This guide consists of thousands of colors and shades, giving a numerical value to each one. I could monitor the color by assessing the value, 469-C was good, 460 was not (Fig. 7). Incidentally, pale nori also had less phosphorus, so there may have been a correlation. As a possible solution, we stretched nori production nets among salmon netpens as part of a Sea Grant project to simultaneously determine the extent nori could reduce the environmental loading of salmon farming waste. The level of success in darkening the nori depended on who was looking. The scientists involved – Charlie Yarish of UConn, Thierry Chopin of UNB, Art Mathieson, and Shan Lu of the Institute of Oceanology, Qingdao, China documented rapid growth and appropriate pigmentation of the nori on nets around the pens, but to my horror Yarish and Chopin selected the biggest and darkest plants from the nets and compared them to wimpy, pale nori on the nori nets at our production sites. I did not find any difference in total production of nets around pens compared to the average at our production sites. But their data helped me get consultation projects, as we all promoted polyculture as environmentally beneficial and the results were published to demonstrate its value. The research with the salmon pens ultimately led to my belief that aquaculture is just plain bad for the environment due to the waste produced. The seaweed does soak up wastes from salmon netpens, but not nearly enough to make any difference, and the amount of seaweed one can harvest from these systems can’t come close to being profitable. The nori grows on the surface, the net pens are 7.6-11.9 m deep, and the salmon wastes and excess feed sank to the bottom. The surface water was only slightly more nutritious. Based on this research, I designed a separate system in Chile for land-based salmon pens, placing the seaweed in the effluent pipes that emptied into the ocean. The seaweed (Gracilaria) grew well, but it didn’t produce enough biomass for economic viability. Harvesting Nori andMaking Nori Sheets for Market When the nori was growing properly, harvesting became the focus. Timing was important. Bright sun between 0800 and 1000 h provided the best conditions, as the plants photosynthesize in the sunlight and produce sugars and starch. Later in the day the sun becomes too intense and the nori reduces chemical production, leaving the harvest with less flavor. A normal harvest can take up to eight hours; therefore most of the nori harvested does not have the optimum conditions. Bright sunny days in Cobscook Bay from July through October are not a given and harvesting in heavy rain further diminishes the quality. Nori is harvested with a machine that looks like an upsidedown, reel-type lawn mower with 5-ft blades. It is placed on a 2.4 × 2.4 m barge that was pulled under the net, the blades slapped the nori off the nets into mesh-lined baskets (Fig. 8). The nori-laden baskets are then brought to the processing plant. The nori had to be harvested directly into clean containers and absolutely kept from gas and oil contamination. This was more of a challenge than was obvious, given that the boats were powered by outboard motors and the nori harvester powered by a gas engine. A few drops of gas or FIGURE 6. Author (foreground) showing growth on nori production net. FIGURE 7. Nori filaments on net, Pantone color 469-C.
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