Boom of mysterious invertebrates the latest in recent string of inexplicable episodes
The most unforgettable memories Linsey Sala will come away with from a recent squid-fishing trip won’t merely include the sheer numbers of the slippery invertebrates pulled aboard during a nighttime excursion: 800 squid captured in a 45-minute span, including several that will be used for scientific examinations. Her remembrances also will include images of seeing the creatures in the wild, how they quickly changed colors out of the water from white to deep red, and the dark ink that splattered from them and coated the fishing vessel’s deck, a byproduct of the frenzied hunt.
The excursion occurred during a massive influx of jumbo squid to Southern California’s coast in January, a winter anomaly that generated news headlines across the nation.
The jumbo, or “Humboldt,” squid was first recorded in Monterey Bay in 1935. Scientists know that newborn jumbo squid, called paralarvae, can be just smaller than a grain of rice. Full-grown jumbo squid, which live a year and a half to two years, can span 2.5 meters (8.2 feet) and tip the scales at 50 kilograms (110 pounds).
For the past 12 years, strange influxes of jumbo squid seem to be occurring more commonly. Although fishing boat fleets and their squid-hunting customers are quite happy with such episodes, scientists don’t yet have a clear grasp on why they keep occurring.
Sala, manager of the Pelagic Invertebrate Collection at Scripps Institution of Oceanography at UC San Diego, gathered several new specimens on the excursion in an effort to learn more about these curious invertebrates.
As for explaining the mysterious squid invasions, Sala says there are no foolproof answers, but it may be that the squid populations never leave the area. The majority of their time is spent at depths of 200-700 meters (656-2,296 feet), too deep for scuba-diving scientists to reach and observe the creatures.
One hypothesis is that perhaps something has changed in the environment to make it more beneficial for jumbo squid. This could include changes in the abundance of prey such as fish, other invertebrates, and even each other, which may draw schools of squid en masse to a new area. Alternatively, expanded regions of depleted oxygen in subsurface ocean waters is thought to favor jumbo squid because of their ability to tolerate low oxygen conditions. It’s also possible that predators that feed on jumbo squid are being overfished. Too few swordfish, tuna, marlin, Risso’s dolphins, and sperm whales may allow jumbo squid populations to thrive and open the door to influx events.
The specimens collected on the recent nighttime excursion will be studied and processed for inclusion in the Pelagic Invertebrate Collection at Scripps, a “library” of spineless free-swimming or drifting marine animals cataloged through decades. This collection allows scientists from around the world to piece together clues about marine life such as the jumbo squid.
“Scientific collections allow scientists to study our natural resources and environmental health in terms of our fisheries, provide materials that can be analyzed with new technology, and inspire curiosity in understanding the natural world and life on Earth,” said Sala. “A foundational knowledge of species identification and ecology is often an integral part of many other disciplines in science, and having well-preserved specimens allows us the possibility to access that information.”
– Mario C. Aguilera
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