It takes a baby abalone twelve to fifteen years to make it to seven inches across at the widest measure, the minimum size for legal capture under normal conditions. As an abalone diver for the last forty-odd years I always look forward to April 1, the abalone season opener. Often the ocean would not settle down enough for a safe dive until May, with many exceptions. According to many newspaper accounts the wild abalone population was teetering on the edge collapse. By personal observation there were as many abalone as ever, unless you dive in the easy access coves and shallow water, something under fifteen feet. There were barren spots where over fishing and massive poaching made the underwater rocks barren of this delicious shellfish. Today the situation is very different.
The near decimation of the red abalone on the north coast the last eight years has resulted in a massive reduction in the population due to a perfect storm of environmental factors. Understand first that the kelp forests of the near shore environment support a wide range of sea life. The kelp forest provides protection from predators, the basic structure of the food chain that supports fish and invertebrate, kelp is the primary food source for the herbivore abalone.
Environmental stressors included impacts from a toxic algae bloom off the Sonoma coast in 2011, a widespread sea star disease in 2013 that was followed by an explosion in the sea urchin population and the warm water conditions that have persisted offshore since 2014. The first major impact to the region occurred in August 2011 when a harmful algal bloom released a toxin into Sonoma County waters, killing large numbers of marine invertebrates. Millions of abalone were poisoned and washed up on shore to rot in place. The state department of fish and wildlife (DFW) responded with an emergency closure of the sport take of abalone until the resource could be assessed.
Two years later in 2013 Sea Star Wasting Disease killed large numbers of sea stars on the West Coast of North America, from Mexico to Alaska. Sea stars are important predators of invertebrates that live in the kelp forests. This opened the door to an exploding population of the primary food source of red sea stars, the purple urchin. CDFW researchers have discovered that purple sea urchin densities are now greater than 60 times their historic density in northern California. This unprecedented expansion of urchin populations spans hundreds of miles of coastline. Purple sea urchins are voracious consumers of kelp. In large numbers, these small but hardy herbivores can easily wipe out vast expanses of kelp and other algae, changing the landscape from a lush and diverse kelp forest ecosystem to what is known as an “urchin barren”.
The kelp forest ecosystem suffered another series of shocks in 2014 and 2015, when coastal water temperatures along the West Coast rocketed upwards due to a combination of oceanographic features: the “Warm Blob” in 2014, combined with a strong El Niño that began in 2015. Kelp and many other marine species are very sensitive to changes in water temperature, and warm water holds few of the nutrients required for kelp growth.
Divers today report vast areas of the underwater structure are either barren or overrun by purple sea urchins. The solution is elimination of the purple urchin mass to more typical levels that can support kelp growth. Today abalone continue to starve to death.
Until nature or man provides a remedy to purple urchin over abundance our kelp forests will remain beaten down. We must hope another factor adverse to the red abalone does not take a toll on the remaining abalone, thus slowing down recovery for years to come. At this time there is no intervention by man that can push recovery forward.
As pointed out in the beginning of this report, once stabilized, it will take a minimum of fifteen years for a sustainable crop of sport-take abalone to grow up. More likely twenty to thirty years after the kelp forest recovers.
Bill Hanson is a Sonoma County native and a lifelong sportsman. He is the former president of the Sonoma County Mycological Association. Look for his column in The Community Voice each week.