Research

New Gillnet Roller to Improve Quality

Problem:

Many of Alaska's salmon setnetters are at a competitive disadvantage because some fish they deliver have been subjected to bruising and crushing during net maintenance operations. This can happen when the fishermen motor their setnet skiffs along the net, running the net from bow to stern along the length of the boat. The fishermen do this to facilitate cleaning marine debris and algae from the net. Because the net and its associated lines are often stretched tightly during this process, many salmon get squeezed between the lines and net when everything comes over the skiff's bow.

Approach:

This project seeks to remedy that situation through the deployment of experimental gillnet rollers that will relieve strain on the gillnet web and therefore on the fish. Working with a commercial salmon setnetter in Uganik Bay, Kodiak Island, we designed a custom gillnet roller that had a one-inch deep, four-inch wide notch at one end. The purpose of the notch was to constrain the running, lead, and cork lines, allowing the web, where the fish were located, to roll loosely over the remainder of the roller. In theory, keeping the taut lies away from the fragile salmon would result in fewer occasions when the salmon would be squeezed, and possibly mangled, between the lines and the roller. The experiments lasted for eight days in July-August 2007, during which time samples were taken from one pick of the net each day. Four of the picks were made with the experimental bow roller; the other four were made with the standard, cylindrical bow roller. Each pick saw different weather and tide conditions: windy, breezy, and flat calm; slack tide and tide running. Over the eight days, during the selected picks of the net, the fishermen caught 1,442 salmon. Of those, 200, or 13.9 percent, were filleted and examined for deep or shallow bruising. One hundred fish were selected from the set that came over the standard roller, another hundred came from the set that came over the experimental roller.

Results:

The results appeared to show that the experimental roller had no effect on bruise rates. Of the sampled fish that came over the standard roller, 27 percent were bruised. Of the fish that came over the experimental roller, 29 percent were bruised.

Contact person:

Mr. Mark Buckley: mkbuckley@alaska.com