The first time I heard the term “marine heatwave,” I said we call that El Niño. A marine cold snap is called La Niña. Actually, those two related events are the flip sides of what scientists call El Nino-Southern Oscillation which is a well-known climate pattern in the Pacific Ocean, and one we fisherfolk have figured out how to adjust to and take advantage of.
The El Nino Southern Oscillation is the most famous, infamous and sometimes unpredictable of a global phenomenon referred to as marine heatwaves or MHW. These occur when ocean temperatures are much warmer than usual for an extended period of time. They are specifically defined by differences in expected (normal) temperatures for a given location and time of year.
There have been numerous MHWs, and we have been surprised and perplexed by some, such as the infamous “Blob” which emerged about 2013 in the northeast Pacific Ocean and persisted through 2016. It led to shifting fish stocks, harmful algal blooms, entanglements of endangered humpback whales, and thousands of starving sea lion pups washing up on beaches.
The Blob served as a wakeup call to researchers and ocean harvesters because it messed up our typical patterns and caused widespread damages and disruption of fishing opportunities. A NOAA public statement said this marine heatwave led to an ecological cascade in which whales’ prey was concentrated unusually close to shore, and a severe bloom of toxic algae along the coast delayed opening of the valuable Dungeness crab fishery.
The Blob was not alone, and marine heatwaves are on the rise globally. According to NOAA, the global annual number of MHW days has risen by 54% over the past century, with eight of the 10 most extreme MHWs ever recorded occurring after 2010.
MHWs are forceful agents of disturbance with wide-ranging impacts on marine ecosystems, including driving species range shifts and mass mortalities and altering food webs and species interactions.
Impacts of marine heatwaves have been documented in ecosystems around the world, particularly in the past decade. NOAA says these include:
Fish and shellfish declines that caused global fishery losses of hundreds of millions of dollars.
Shifting distributions of marine species that increased human-wildlife conflict and disputes about fishing rights.
Extremely warm waters that have caused bleaching and mass mortalities of corals.
Biological responses to MHWs can increase human-ocean interactions, providing benefits and opportunities for sporting enthusiasts and therefor coastal industries and communities. For example, cyclic El Nino events have taught anglers to happily expect their local waters to hold fish that they typically have to travel far to the south to find, (such as dorado showing up off CenCal and NorCal and even offshore from Oregon) thereby increasing tourism and fishing opportunities.
During El Niño and other MHW events, swimmers, divers and surfers may find the water to be a little more comfortably warm than usual. This tends to entice people to enjoy visits to the sea more often which in turn benefits coastal economies as locals and visitors alike spend more on gear such as surfboards and dive equipment. I benefitted from that as the previous owner of Hook, Line & Sinker in Santa Barbara.
— Capt. David Bacon operates WaveWalker Charters and is president of SOFTIN Inc., a nonprofit organization providing seafaring opportunities for those in need. Visit softininc.blogspot.com to learn more about the organization and how you can help. Click here to read previous columns. The opinions expressed are his own.
