Source: Morejohn et al. 1978
The recent 15-year absence of L. opalescens is not the first. They were reportedly absent from Puget Sound waters for about a decade in the early 1950s, only to return in considerable numbers in 1958 (Fields 1965). Little is known about these disappearances and the impact they have had on the food web.
Is this cyclic population boom and bust natural, or a result of a disrupted ecosystem? What triggers their absence and return? How did the food web respond to their absence? What role does this fluctuation play in our struggling marine ecosystems? How does this affect other species in the region?
Important questions we hope we can help answer.
Squid Reproductive Cycle
Researchers do know a fair amount about the lifecycle of L. opalescens, however. L. opalescens have four life stages: eggs, paralarvae, juveniles, and adults.
Eggs are encapsulated in a sheath made of many layers of protein, and coated with bacteria, which likely helps prevent fungal infections. Female squid deposit the eggs in sandy bottom substrates, at depths between 10-50 m. The egg capsules are anchored in place with a sticky substance that allows them to be continually aerated without being swept away. Masses of egg capsules are laid together into an egg bed. If the spawning event is large enough, egg beds can cover acres of ocean floor. (Zeidberg 2016)
Paralarvae hatch from their eggs after 3-5 weeks of incubation. At just 2-3 mm long, they must learn to swim and hunt immediately. At this stage, they feed on copepods and other plankton. (Zeidberg 2016)
L. opalescens are considered juveniles when they grow strong enough to swim and hunt in groups, or shoals. This typically occurs when they reach a mantle length of ~15 mm, (at approximately 2 months). As juveniles, they search for food in shoals of approximately ten individuals, and begin to hunt larger prey (as listed above) with the use of their tentacles. They perform a daily vertical migration, swimming to depths pf 500 m during the day, only to return to the surface each night to feed. (Zeidberg 2016)
L. opalescens are considered adults when their sexual organs mature, between 4-8 months of age. As adults, their average mantle length is 19 cm for males and 17 cm for females. Like other squid, L. opalescens have chromatophores in their skin, which are pigment-bearing cells that can change color in order to confuse predators, attract mates, and communicate with others. (Armstrong et al. 2012; Zeidberg 2016)
L. opalescens are mass spawners, with numbers of individuals sometimes reaching into the millions. Shoals of squid move to shallow water to spawn. It is during these mass spawning events that they are most vulnerable to predation. They are known to breed throughout the year, and it has been shown that the presence of egg sacs in an area will stimulate other females to lay eggs. Female squid lay between 100-300 eggs. (Morejohn et al. 1978; Zeidberg 2016).
Squid and Elwha Nearshore Restoration
Squid egg masses were found along the Elwha beach wrack line for the first time in October 2016. The CWI crew have been keeping a qualitative count since then.
Will the Elwha nearshore restoration result in more squid? We don’t know.
As a key player in our region’s marine food web, it’s exciting to witness what may to be a return of L. opalescens to the Elwha system. We encourage and look forward to more work to understanding this fascinating and mysterious component of our nearshore ecosystem.
Armstrong, M.; H. Buchanan and J. Davidson. 2012. (Online), Animal Diversity Web. Accessed November 07, 2016 at http://animaldiversity.org/accounts//
Fields WG. 1965. The structure, development, food relations, reproduction and life history of squid, Loligo opalescens Berry. Calif Dep Fish Game Fish Bull 131:1–108.
Morejohn GV, Harvey JT, Krasnow LT. 1978. The importance of Loligo opalescens in the food web of marine vertebrates in Monterey Bay, California. Calif Dep Fish Game Fish Bull 169:67–98.
Quinn, Thomas P. The Behavior and Ecology of Pacific Salmon and Trout. Bethesda: American Fisheries Society, 2005: 269-270.
Zeidberg, L. 1995-2016. “The Cephalopod Page” (Online). Loligo opalescens, California Market squid. Accessed November 6, 2016 at www.thecephalopodpage.org/Lopal.php.