Testing Methods to Minimize Herring Spawning Events on Alaska Kelp Farms

Herring roe on farmed ribbon kelp. Credit: Seagrove Kelp Company.

Each spring, Alaska kelp farmers have the potential to run afoul of commercial herring fisheries when wild herring spawn in kelp farms. A new studyhelps evaluate different deterrents to prevent herring from spawning on their farms. This research addresses the emerging need to reduce negative interactions between aquatic farms and a species of commercial and regulatory importance.

Alaska Kelp Farming

Worldwide, ocean farmers grow millions of metric tons of seaweed each year. A growing number of seaweed farms are sprouting up in the United States, including in Alaska. Along with increasing sustainable seafood supply, seaweed farms can keep working waterfronts vibrant. They provide important economic opportunities in coastal areas around the nation. The coastal waters of Alaska may be particularly well suited to seaweed farming due to an extensive coastline with clean, cold, and nutrient-rich waters.

Need for Herring Deterrence Tools on Kelp Farms

As the kelp aquaculture industry grows in Alaska, so do the opportunities for interactions between farms and marine life. For example, kelp farmers plant tiny kelp seeds on long lines submerged 10 feet below the water's surface during the fall. By late spring, the kelp has grown large enough for harvest. This coincides with the spring spawning season of Pacific herring.

Herring spawn in nearshore areas and deposit their eggs on intertidal and subtidal vegetation, such as kelp. The State of Alaska recommends avoiding known herring spawning locations when siting kelp farms. However, herring can spawn in new areas or areas that predate state survey information, so avoidance may not be possible.

"Kelp farmers recognized a burgeoning need to improve our understanding of herring interactions with kelp farms, and NOAA scientists designed an intelligent methodology for testing deterrents, all with the goal of helping the farmers and the herring," said Ky Friedman, who worked on the project through the Ernest F. Hollings Undergraduate Scholarship Program.

Pacific herring are a critical food source for many marine animals and a vital subsistence and fisheries resource in many communities. In Alaska there is a commercial fishery (Herring Pound Fishery) for herring eggs that involves capturing herring in floating pens and harvesting their eggs on kelp. Seaweed farming in Alaska is intended to harvest seaweed only. Alaska regulations prevent the harvest of farmed kelp or herring eggs if herring have spawned on a farm.

In spring 2020, a spawning event on farmed kelp destroyed most of the crop from one of the largest kelp aquaculture operations in the country, worth approximately $300,000. The fate of herring eggs on farmed kelp is unknown.

"Seaweed aquaculture is a relatively new industry for Alaska, so it is important that we bring together groups with diverse expertise to find solutions to challenges such as herring spawning, and ensure that this industry develops with environmental sustainability at the forefront," said Jordan Hollarsmith, Lead Macroalgae and Mariculture Research Biologist at the Alaska Fisheries Science Center.

There is a critical need for methods that safely deter herring but do not interfere with nutrient supply, harass marine mammals, or result in excessive fouling or cost. This will ensure continued sustainability and expansion of these aquaculture operations in Alaska and help meet the goals set forth by the Alaska Mariculture Task Force.

Left: herring roe on kelp. Right: Herring roe on kelp lines. Credit: Seagrove Kelp Company

Herring Deterrent Experiment at Little Port Walter

The herring deterrent experiment took place at the NOAA Fisheries Little Port Walter Biological Field Station, located 110 miles southeast of Juneau, Alaska. Little Port Walter is the oldest year-round biological research station in Alaska. It has been host to a wide variety of fisheries research projects since 1934.

Net pen setup at Little Port Walter where herring were exposed to deterrents. Credit: NOAA Fisheries/Ky Friedman

Researchers caught and placed herring in a net pen. Herring were exposed to four different experimental treatments, including:

1. Underwater LED lights
2. Aeration system (bubbles)
3. Banana pingers (3kHz-20kHz)
4. Commercial fishing flashers (moving and stationary)

Seining at Mist Cove to catch herring. Credit: NOAA Fisheries/Ky Friedman Chris Taylor (NCCOS) with herring caught from the beach seine. Credit: NOAA Fisheries/Jordan Hollarsmith

Researchers gathered data on herring movement and location in the net pen. Responses to treatments were gathered using sonar.

Bubble Curtain

Across the methods tested, the aeration system elicited a clear behavioral response in the herring.

"We found that herring stayed far from bubble curtains, which mimics how humpback whales hunt herring. However, there are challenges to putting bubbles around ocean farms. We look forward to getting feedback from farmers and community members on this work and what our next steps should be," added Hollarsmith.

In application on a kelp farm, the bubble curtain created by the aeration system would be established before herring arrival. The intention is to exclude herring from the farm entirely and minimize the potential for herring to be on the kelp farm. However, deploying this technology at remote farm sites may be a logistical and financial challenge. Pacific herring under spawning conditions also may respond completely differently to these treatments. Further research into developing low-cost strategies to minimize negative interactions between this type of aquaculture and wild organisms is necessary for the sustainable growth of the industry.

Other Deterrent Systems Less Successful

Lights and pingers had no effect on the location of herring in the net pen. Suspended moving or stationary fishing flashers either had no effect or attracted herring. But, there is the potential for pingers at untested and different frequencies and decibels to have a deterrent effect.

The aquaculture industry and NOAA Fisheries' managers and researchers worked together to address an emerging industry need and help sustainably advance this type of aquaculture in Alaska.

"Part of NOAA Fisheries' mission is fostering responsible aquaculture development while conserving our trust resources," said Alicia Bishop, NOAA Fisheries Alaska Regional Aquaculture Coordinator. "This project was a great example of collaboration on a real-world problem and trying to meet the needs of farmers and fishermen while minimizing impacts to habitats and protected resources like marine mammals."

The collaborative research was conducted by scientists from:

• Alaska Fisheries Science Center
• Alaska Regional Office
• National Centers for Coastal Ocean Science
• Florida International University