April 18, 2012
[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. For the complete story on the best squid patterns, and where and when to find the best fishing for 20-pound-plus stripers, see author John Field's story "Squid in the Rips" in the June-July 2012 issue of Fly Fisherman. The Editor.]
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.