“If they only knew.” That was the thought that ran through my mind as I surfaced at 12:40 a.m. on New Year’s morning on a dive that had began in the final hour of the previous year. It was an extremely clear night, and from my vantage point as we hit the surface I could see the bright lights of the ritzy coastal community of La Jolla. I feel certain that the terrestrial party animals thought they were having a wild time ringing in the New Year, but I couldn’t help but think that they had no idea what kind of wild blizzard they were missing in the water only a few hundred yards away.

We had been diving with an uncountable number of market squid, Loligo opalescens, and the wonderful variety of creatures that their presence brings. We were in “whiteout” conditions, with squid everywhere — at the surface, in the water column, and hovering just over the sandy sea floor below. Also known as common squid, these foot-long denizens of the deep are strongly attracted to dive lights, and at times several hundred squid mobbed our lights, completely engulfing us. 
To control a mob of these mollusks and regain some visibility all you have to do is cover the beam of your dive light for a few seconds and the mob will quickly dissipate. Shine the light into the water column, and here they come again. 
Although the squid are the feature attraction during mating events known as “squid runs” they are not the only show in town. All kinds of scavengers and predators come to feast on the squid. In terms of an absolutely thrilling and wild scene, full on squid runs are all but impossible to top. 
Squid Stats
As adults, common squid live in waters outside of the continental shelf where they can be found down to depths in excess of 1,600 feet. At night during most of their life the adults gather in shoals and rise to the surface to feed under the cover of darkness. But sometime during the fall and winter that pattern is broken as the adults move into on shore waters where they gather in aggregations that can number into the hundreds of thousands in order to mate and for the females to lay their eggs. 
Exactly when and where the squid will gather near shore varies from year to year. But as a general rule the squid tend to begin their mating runs in the fall in northern and central California, while heavy runs usually don’t occur in the southern part of the state until late fall and winter where they sometimes extend into spring.
However, this year the commercial squid boats were already successfully fishing the squid at the southern Channel Islands and off the mainland coast as far south as San Diego by early fall. While there are no guarantees how long squid runs will last, all signs seem to point toward a squid-filled fall and winter all along the California coast.
When the squid come into near shore areas they congregate over areas of sandy bottoms. This means that particular locales at the Channel Islands, various costal canyon sites including several off Monterey, Los Angeles and San Diego are areas that are often squid central. And when the squid show up there is a good chance that there will be squid in those areas for extended periods of time.
As is the case with all squids, market squid are types of mollusks that are further described within the class Cephalopoda, a grouping that includes all octopods, cuttlefishes, nautiluses and squids. Members of this class are considered to be among the most intelligent of all invertebrates. 
The term cephalopod is derived from the Greek words meaning head and foot. This reference is made in acknowledgement of their two most prominent physical features, their extremely enlarged head and foot-like arms. In cephalopods the foot has been modified into sucker-bearing arms that are used for mobility, ensnaring prey, and handling and manipulating objects they encounter. The hard shell that is characteristic of so many mollusks is missing or greatly reduced in cephalopods. In fact, the protective shell is entirely missing in octopods, while it is relatively small and internal in squids and cuttlefishes. 
The arms of squids are covered with one or more rows of suckers. Each sucker is equipped with a number of small hooks or other adhesive structures used to ensnare prey, most of which lives in mid-water. While octopods possess eight arms, squids and cuttlefishes are equipped with ten appendages, eight arms and two tentacular-clubbed arms. Nautiluses have as many as 90 arms. 
As is the case with most cephalopods, common squid are also equipped with a hard, parrot-like beak. The beak serves to bite prey and to help deliver immobilizing toxin that is released into the body of prey when they are bitten.
Market squid occur in the eastern Pacific in waters that range from Alaska in the north well into areas off of Mexico’s Baja peninsula in the south. Within their range these squid are usually found within 200 miles of the coast of the mainland. 
“Spawn Till You Die” 
During heavy squid runs millions of squid gather in sandy coastal canyons and at steep sand drop-offs at our offshore islands. They gather in great numbers with a single focus; they’re here to spawn. A single squid run can last for weeks with mating and egg-laying activity occurring every night during that period. 
Driven by strong instincts, the squid pay little attention to outsiders, whether predators or divers, as they search for mates. The missile-shaped mollusks are capable of swimming forward, backward and sideways with equal rapidity as they ‚”jet-propel” themselves with a directable siphon while using their undulating tail fins as they maneuver in an effort to find a mate. It is generally believed that the vast majority of mating occurs at night with the courtship and mating activity being accompanied by a stunning light show as the squid pulsate from creamy white to purple, green, brown and blotched combinations. 
When a male successfully latches onto a female his tentacles immediately blush a scarlet warning to deter other males from attempting to woo or steal his mate. Once engaged with the female, the male adeptly passes a packet of sperm underneath the mantle of the female who then uses the contents to fertilize her eggs.
At some point after mating the captivating color shows slow and eventually cease, and the squid take on a sickly pallid hue and their tentacles become grossly disfigured. It was long believed that all of the adults die shortly after they mate, an easy assumption to make after one sees piles of dead adults on and around the egg beds on the sea floor. However, some specialists now believe that adults might live for several weeks to several months after their first mating and egg-laying events, and that the squid spawn repeatedly during that period. The deterioration of the adults makes them easy prey for the variety of creatures that come to feed on the dead and dying squid. 
Most eggs are laid on sand bottoms although the eggs sometimes are attached to kelp stipes near predominantly sandy areas. The eggs are encapsulated inside of whitish egg casings that are roughly 8 to 14 inch long. Firmly attached to the sea floor, each egg casing contains approximately 200 eggs. 
In many places the density of the planted egg casings is so thick that they completely obscure the sea floor, and the once brown sandy bottom takes on the appearance of a luxurious, creamy-white, shag carpet. Five to seven days after the egg casings are deposited you can see the bright red eyes of the embryonic squid. The eggs take somewhere between three and five weeks to hatch, and when they do the newborns instinctively head for deep water, although no one knows exactly where they go. Specialists maintain that only a handful (at best) of hatchlings ever become adults as the youngsters are heavily preyed upon by a variety of carnivorous fishes and crustaceans.
Roughly two months after hatching juvenile squid begin to gather and swim in shoals. Some two to six months later the animals reach sexual maturity. And by the time they are approximately nine months old the squid will have returned to near shore waters to mate and for females to lay their eggs as the mollusks complete their life cycle.   
The Party Crashers
The market squid aren’t the only ones in a festive mood. Along the sea floor diverse collections of scavengers and predators feast on the dead and dying squid as well as healthy squid that have yet to mate. Animals such as bat rays, horn sharks, thornback rays, guitarfish, and angelsharks often stuff themselves with so many squid that they end up coming to rest on the bottom virtually immobilized by their consumption. Rockfishes, black sea bass, cabezon, sculpin and a multitude of other fishes routinely join the fray. Lobster and crabs leave the protective crevices of the reef to forage on the dead and dying adults. And even with all of these animals gorging themselves to their limit, the squid often die off so fast that in places their bodies get stacked up in piles. 
Interestingly, the seemingly vulnerable egg casings are not heavily preyed upon. It is believed that this lack of predation is due to the presence of proteins that are repulsive to potential predators. That said, it should be noted that bat stars and some snails do readily prey on the eggs.
High up in the water column creatures such as sea lions and harbor seals join the feast. On some occasions shortfin pilot whales and blue sharks take advantage of the abundance of easily captured prey.  And quite often gatherings of opportunistic sea birds that number into the thousands can be seen on the surface. 
While some divers are quick to put their dive gear away in the winter by doing so they miss out on some potentially wonderful diving. During the winter in California we might not have days on end with great diving conditions. But every winter we seem to get some stretches of days and occasionally weeks with absolutely wonderful conditions. Combine a squid run with great conditions, and you have a phenomenon that is not to be missed.