Longfin squid spawn year-round with seasonal and geographic peaks. In New England waters, spawning has been reported from May to August. Egg clusters, or mops, like the one Ellenbogen photographed, act like a hub. As reported by NOAA Fisheries, female squid lay fertilized egg capsules that contain about 150 to 200 eggs each in clusters attached to the ocean bottom. They return repeatedly to deposit multiple clutches of eggs over several weeks, with a typical female laying a total of 3,000 to 6,000 eggs.
Spawning typically occurs in seasonal pulses tied to water temperature and other conditions, sometimes triggering large spawning aggregations — dense gatherings of squid depositing and fertilizing eggs. Males and females gather in the spawning grounds, and density increases until individuals are constantly interacting.
But reproductive biology and behavior are complicated for longfin squid. The NEFSC report highlights unique behavior: Females can store sperm from spawning events for later use, and eggs in the same capsule from a single female may have multiple males from multiple spawning events.
Consort males, typically the larger males, pair up with a single female during spawning. They swim closely alongside her, often guarding her with their arms, and use their size to intimidate competition. Sneaker males, smaller unpaired squid, use stealth and speed to sneak into position with paired females. Males deposit bundles of spermatophores into the female’s mantle cavity or in a pouch located near her head.
The competition is guided by visual and chemical signals, including pheromones indicating reproductive readiness, rapid color and pattern changes, as well as strategic arm postures and whole-body displays. A 1999 paper published by the Marine Biological Laboratory catalogued 34 visual displays involving colors, brightness, spots, stripes, iridescence, and polarization signals, as well as 17 specific positions and movements used by squid on the spawning grounds.
Squid were seen flashing white as a signal to repel other squid. Squid displaying this component are almost always engaged in mate guarding, egg laying, or competitive confrontations. Like humans, female squid can blush, displaying a dark patch on one side of the mantle. But when a squid blushes, it functions as a repellent to courting males. And as captivating as these colorful displays can be, squid communication largely remains an encrypted secret to even the most curious scientists.
“Keith’s rare glimpse of squid in their natural environment beautifully bridges art and science, reminding us that we still have much to learn,” says Hyde, who has centered her research at NOAA on marine ecosystems and fisheries.
For most people, squid are known solely as seafood or as shadowy legends, chameleons of the sea. Yet each spring, beneath the cool waters of Cape Cod, millions of longfin squid gather in this remarkable reproductive event, a reminder of the rich biodiversity and productivity of Massachusetts marine ecosystems.
MIT Sea Grant works to support sustainable fisheries and to promote environmental education and stewardship of our coastal and ocean resources. As MIT Sea Grant’s resident artist, Keith Ellenbogen is working on a long-term project to document extraordinary species and ocean events that unfold just off our coast, revealing hidden moments that few have the opportunity to witness. The longfin squid is one of our region’s most valuable marine resources, and these images help reveal one of the most extraordinary events unfolding right off our coast.