April 18, 2012
By John Field
This article provides background information and natural history on longfin squid, an important spring and early summer prey for striped bass and bluefish feeding in the rips of New England. Click here for the complete story on the best squid patterns, and where and when to find the best fishing for 20-pound-plus stripers.
According to NOAA (National Oceanic and Atmospheric Administration), longfin squid (Loligo pealeii) inhabit the Atlantic coastal waters from the Caribbean to Newfoundland, but the highest concentration in U.S. waters extends from Cape Hatteras northward to Georges Bank. In the spring, during April and May, the squid come into shallow water to spawn. Federal trawl surveys indicate their highest catches occur between 50 and 54 degrees water temperature in spring.
Longfin squid are harvested by recreational and commercial fishermen in locations such as Long Island Sound, Buzzards Bay, Vineyard Sound and Nantucket Sound. Early in the season, netters concentrate on the 40- to 70-foot depths to catch them. One famous spot anglers jig squid at night for the table is the 1,000-foot-long lit Goat Island Causeway, near Newport, RI.
Dr. William Macy and Dr. Jon Brodziak, published a landmark study in ICES Journal of Marine Science in 2001, indicating the Longfin is an annual species capable of spawning year-round and lives less than 12 months, usually 6-9. The adults usually reach the length of 14 to 24 inches long, including their arms, or tentacles. The males are larger than females and neither suffer mortality as a result of reproduction, as rumored; this was also confirmed by extensive diving studies conducted by Roger Hanlon and his colleagues. Squid group according to size class and juveniles born in spring may become forage for larger predators like stripers, bluefish, Atlantic bonito and Little Tunny in later August when they reach the size of 3- 6 inches in length.
Longfin squid are very capable swimmers and can propel themselves forward or backward, but swim fastest mantle first using their jet propulsion with arms closed rearward in a slipstream shape. They can also undulate their fins for mobility and stability. This movement is common when they are near the bottom feeding or breeding. Their daily movements, when not traveling to breed, are diel vertical migration (DVM) and follow the food chain from bottom during the day, to the upper water column and shallows at night. They are generally considered (benthic) bottom dwellers and are a major flounder forage.
Squid have acute polarization vision, which enables them to see small translucent larval fish and crustaceans underwater, other species without it cannot. The question has been posed, but the subject not fully understood, whether squid might be able to use visual intraspecific communication undetectable to their predators and other species that cannot see the polarization aspect of light. Longfin aren't known to have acute hearing but a new study from marine biologist T. Aran Mooney, a post-doctoral scholar at the Woods Hole Oceanographic Institution (WHOI) in Massachusetts, confirms that squid can hear low-frequency sounds. Dr Mooney speculates that the squid would probably be able to hear waves in open water, or breaking on reefs and other environmental sounds. This is yet to be studied.
Squid Defense & Communication
Think about it, this squid has no real weapons or external armor as many fish or crustaceans do. If it wants to survive, it either has to deter detection, or successfully flee its prey. The most fascinating and romanticized aspects of the squid are its defensive and communication capabilities.
Generally, deep-water squid and fish depend more on low-light visibility and bioluminescence, than shallower ones. The Longfin spends most of its life in less than 60ft of water and according to Dr. Hanlon, do not have the capability of bioluminescence at all. Longfin do however, rapidly change colors, produce patterns and adjust iridescent reflective cells. Flashing contrasting colors with wide reflective values allows them to camouflage near the bottom or to communicate with other squids during spawning season.
Other accounts of Longfin bioluminescence by fishermen may also have been the disruption or consumption of other small bioluminescent organisms while swimming, described as "fire in the water." In Ed Mitchell's book, Fly Rodding the Coast, Stackpole Books 1995 pg. 272, Ed writes, "The flashing light of a squid is larger (than the light of small invertebrates), more the size of your hand, and often moves rapidly like some underwater shooting star." The colors, shades and patterns squid produce are some of the most beautiful in the natural world. Here's how the color changes, patterning and iridescence work and when Longfin use them.
The skin of the squid contains chromatophore organs that are neurally controlled by the brain to produce the color and extremely complex patterns it shows to camouflage itself and communicate with other squid and predators. These organs contain pigment granules and are surrounded with radially arranged muscle fibers that open and close the pigment sac to conceal or expose various colored pigments. These pigments include, yellow, red, and brown. The most effective use of these abilities for the Longfin is to camouflage itself to match bottom habitat and substrate when hunting for food, or hiding from certain predators. This habitat is typically sand, gravel seaweed or boulders. The chromatophores can even display large banded patterns to match the similar patterns of the bottom. Conversely, chromatophores may be sparse or absent in deep water squid. The other three color-altering organs are grouped as "reflecting cells."
The most important of these cells are called iridophores, containing little platelets which reflect polarized light to produce the iridescence of squid. The color of reflected incident light depends on the arrangement of the platelets and the angle they are viewed. Their spectrum includes pinks, yellows, greens, silver and white.
According to Dr. Hanlon, squid try to blend in and when longfin are traveling through open water, they show a uniformly patterned "light beige" color. Underwater photographer Mike Laptew describes it as "rubber-band brown." When longfin are swimming over a reef and detect predators, they use several defenses and as Dr. Hanlon describes, their defense is totally unpredictable.
The primary defense against attack is to use erratic jetting to out-run the stripers. If that doesn't work, they might use the "blanch-ink-jet" maneuver. The squid turn the opposite color they started out, eject ink, then jet away. When the squid perform the "blanch-ink-jet" maneuver, they change to the appearance of a translucent, almost clear cylinder. Under close inspection, you can even see their internal organs. When triggered, instantaneously, all of their color changing and light reflecting cells close or orient themselves to let light pass through their body, instead of reflecting it! This makes them less visible to predators. When I've seen them avoiding being eaten, they have this appearance. The squid can eject two types of ink patterns. The first is the pseudomorph, which is a blob of ink which hangs in the water, resembling the form of the squid to deceive the predator, the next is a large cloud of diffuse ink used like a "smoke screen." A captain once told me, longfin turn the color of their ink cloud and disappear into it to avoid stripers. Despite my desire to believe this plausible myth, Dr. Hanlon stated it is unsubstantiated. Squid turn red or dark brown when physically molested by predators, including man. Dr. Hanlon says this deimatic color display is to repel attackers.
When I asked underwater photographer Mike Laptew if he could provide a photograph of squid using these defenses while being chased over a reef by stripers, he said he's been trying to get that shot for ten years! The problem is; the current is too strong to dive safely and visibility is too poor when the conditions are right for a squid blitz. Instead, I asked artist Joe Mahler to illustrate the scene, with Mike consulting. I wanted to show their clear state but most photos I've seen have either been taken when squid were camouflaging near bottom, or already turned red and purple from being caught by humans. [Mahler's illustration can be found on page 34 of the June-July 2012 issue of Fly Fisherman. The Editor.]
The best study available to understand how longfin behave in the presence of predators is the paper published by Michelle Staudinger, while she was a PhD student at the U. of Mass Amherst. The study was performed in a large tank in Hanlon's lab at MBL in Woods Hole. One by one, acclimated bluefish and flounder were added to the squid tank and their behavior was observed. The study says the most effective anti-predator responses of the squid to attack by bluefish were, "alternately freezing and fleeing." When the squid confronted the attacking bluefish with extended tentacles, 88% of the bluefish abandoned attack. This type of warning is called a postural defense. The squid proved they could successfully flee from bluefish using erratic jetting, "blanch-ink-jet" maneuver and jetting out of the water. Inking was effective 61% of the time. If they can flee these aggressive predators, one might surmise they could also counter striper attacks with a good degree of success. One difference between the test conditions and the reef habitat where stripers feed on squid is the lack of strong waves and tidal current. It is unknown how the squid would react to striped bass in a similar study.
Squid Life-cycle and Age Groups
As in many egg-laying creatures, nature insures against reproductive catastrophes by staggering the timing of egg-laying. Likewise, squid are capable of spawning year-round, but the majority is done in spring. When March comes around, Longfin begin their swim to the shallows to spawn.
Most of the fertilization and all the egg laying is performed in shallow water, but there is some breeding that occurs offshore and the females actually store male sperm in a little pocket to combine with their eggs later. When I asked Dr. Roger Hanlon, what drives longfin to spawn: water temperature, photoperiod, or other triggers? He responded, "It's a highly complex question- probably both of those and maybe other factors. No one knows for sure."
He also said, there are no such metrics available to fishery managers to predict the returning numbers of spawning adult longfin using natural population cycles and known variables." Some researches say, part of this question is tied up in the genetic structure of the population. When the squid are within sight of Nantucket, they will be targeted by commercial fishing boats.
The squid have just spawned too and are replenishing all the calories they've expended. The squid cross the reefs where sand eels and juvenile herring are feeding on vegetation, phytoplankton, zooplankton and copepods held in the current eddies formed by the reefs. Remember the newly released squid hearing study I mentioned earlier? I might postulate; if squid can hear waves breaking on reefs, they might use hearing to find the food associated with the reefs too. Longfin in all age classes are also cannibalistic.
The squid in this article is the longfin squid (Loligo pealeii). The major reference source I used was the seminal book entitled, Cephalopod Behaviour, by Roger T. Hanlon & John B. Messenger, Cambridge U. Press- 1996. I've also had the privilege of corresponding and speaking with Dr. Hanlon, of the Marine Biology Laboratory in Woods Hole. (See squid video mbl.edu/mrc/hanlon/video.html) His input blew me away, because it corrects popular misconceptions I had heard for years about Longfin squid. His lab is most interested in studying visual systems, and cephalopods have much to teach us. If the public became more aware of these marine treasures and the potential information we can learn by studying them, I'm sure it would help preserve them from overharvest and support future research. It was also my fortune to meet and fish with Mike Laptew, fisherman and underwater photographer. Mike has more "bottom time" with squid and stripers than anyone I could find and shared his images and experience with me.