Octopus and Squid (Class Cephalopoda)
Steve O'Shea and Franz Smith
Octopus and squid are a key group of predators in both pelagic and benthic habitats, with the majority of species characterised by soft bodies, numerous (eight) arms (octopus) and two tentacles (squid), well-developed eyes, and complex life cycles and behaviours. Their size ranges from small squid, Heteroteuthis serventii, not exceeding 5 cm total length, to giant squid, Architeuthis dux, known to reach 13 m total length.
At higher latitudes pelagic squid possibly replace teleosts as the most significant predators in mesopelagic waters. In shallow-water reef and soft-sediment systems, squid and octopus are also key predators of invertebrates and fish; in pelagic systems their diet consists of small fish, such as myctophids, crustaceans, and other squid. Cephalopods also represent important prey items for a number of seabird species, including albatross and penguins, and marine mammals.
The life cycle of many octopods, in particular squid, involves a short lifespan, typically 12-18 months, and semelparous reproduction (ie, spawn once and die). Species fecundity varies widely, with some producing tens of eggs (the rare deep-sea octopus, Thaumeledone zeiss), to those that produce hundreds of thousands of eggs (Architeuthis); a number of octopuses are known to brood young. A number of pelagic squid are known to release large gelatinous egg masses (diameter 1.5-2 m), each containing several thousand individual eggs. These egg masses are released by the female directly into the water column, where they drift in shallow water (10-30 m) for several weeks prior to egg hatching; the paralarval squid then swim to the sea surface where they dine on macro-zooplankton. These egg masses are extremely susceptible to damage by trawl.
Major concentrations of squid in upwelling and convergence regions of high primary productivity indicate their close linkage to oceanographic processes. Because of the dependence of vision for mating success in some species, population fluctuations of some inshore species have been related to storm conditions and water visibility; population dynamics might also inadvertently be affected by disintegration of the pelagic egg mass by trawling.
In tropical waters the global-scale decline of finfish fisheries has been followed by a corresponding rise in the total catch of cephalopods, particularly in the past 25 years. The same does not appear true of deep-water, higher-latitude squid and octopus. For many species, there is still little information available about their distribution, abundance, and life history characteristics.
The New Zealand cephalopod fauna comprises 119 reported species, representing 34 families in 5 orders; a further 13 species await description from New Zealand waters. About one-quarter of reported species are endemic to New Zealand waters, several species are common to southern Australia and Japan, and a number of pelagic octopus and squid species are of cosmopolitan distribution. At the family level, the octopuses (family Octopodidae) are represented by 22 species, two-thirds of which are endemic to the New Zealand region. The nine cirrate (finned) octopuses known from New Zealand waters are all endemic; New Zealand has the highest diversity of cirrates known worldwide, at both species and family levels.
New Zealand represents one of the key areas for the distribution and spawning of several deepwater squid species, including the giant squid Architeuthis dux-a species that is not considered to reside in New Zealand waters, but to migrate into them at two times and locations in order to breed. Many other pelagic squid are possibly migratory also.
The lack of quantitative information on the life history, growth, and distribution of the 119 species makes it difficult to determine the threat status of any species/population. Currently, five species of octopus and squid have been identified as having some threat status according to the DoC invertebrate classification system: Opisthoteuthis chathamensis, O. mero, Cirroctopus hochbergi, Octopus kaharoa, and Idioteuthis cordiformis. All occur at depths in excess of 350 m, restricted to seamount habitat or soft-sediment foraminiferal oozes. Each has shown a marked decline in abundance in places where they were once common. Two species of octopus have been identified as being threatened: Cirroctopus hochbergi, known from deep seamount habitat, is considered nationally critical, while an inshore species, Octopus kaharoa, is considered to be in serious decline. More information is required in order to evaluate the conservation status of other species.
Because of the short-lived, fast growth of many cephalopod species, the standing stock (or biomass) of a given area may not necessarily be a good indicator of the exploitation that the population can support. The short overlap in successive generations of many species creates a lack of "buffering" for natural fluctuations in abundance that is driven by oceanographic or climatic factors. The potential impact of commercial harvest of key squid and octopus species on higher-level predators, such as seabirds and marine mammals, has also been raised. Because of the sensitivity of many squid and octopus populations to environmental fluctuations, predators (and also fisheries) must be able to turn to alternate resources in years of low abundance. For many cephalopod specialists, such as sperm whale or penguins, this may not be possible.
Based on information from NIWA's research trawl survey database, the commercially fished squid species, Nototodarus sloanii, a New Zealand endemic, is particularly important along the southern portion of the South Island and Stewart Island, extending over the Chatham Rise and the Campbell and Bounty plateaus. There is another key area for this species on the northwest coast of the South Island. The second species that forms a large part of the commercial catch, Nototodarus gouldi, which also occurs in Australian waters, is largely restricted to the northern portion of the North Island. Other key locations for deep water and offshore species include the shelf break of the east coast of the North Island, Chatham Rise and the Challenger Plateau. For several inshore species where there is information available, the Hauraki Gulf and Cook Strait appear to be key areas, along with embayments and harbours, which are used for spawning grounds for several octopus and broad squid.
Summary of Threats
The single-greatest threat to existing cephalopod species is commercial fishing activity, whether this is directly on the adult/breeding component of a population (retention of mature/submature squid and octopus in fisheries bycatch), destruction of the spawning habitat and egg-deposition structures as a consequence of bottom trawling activity (loss of gorgonian, antipatharian, and scleractinian corals-the substratum upon which many deep-sea octopus and primitive squid deposit their eggs), or disintegration of the pelagic egg masses of squid.
There are no typical cephalopod habitats. Cephalopods occur from the ocean's surface to depths of 9000+ metres; from true pelagic forms to benthopelagic variants; many are truly benthic.
State of Information
Information pertaining to the biology of squid and octopus are largely based on fisheries derived information and studies of anatomical features. Studies of the ecology of non-fished species are comparatively sparse.
Significance for Maori
The general Maori name for cephalopods is whekekorako. There is little information on the significance of these animals to Maori. A tradition tells of the explorer Kupe chasing a giant octopus known as "Te Wheke a Muturangi" from Hawaiki to Raukawa Moana (Cook Strait) where he killed it, placing its eyes on the tapu (sacred) rocks known as Nga Whatu (The Brothers), an area hazardous to navigation. Elsewhere there is reference of some species of octopus being captured by hand and used as bait for line-and-hook fishing or in crayfish pots.
Jackson, G D. 2001. Confirmation of winter spawning of Moroteuthis ingens (Cephalopoda: Onychoteuthididae) in the Chatham Rise region of New Zealand. Polar Biology 24: 97-100.
Jackson, G D, Shaw, A G P and C Lalas. 2000. Distribution and biomass of two squid species off southern New Zealand: Nototodarus sloanii and Moroteuthis ingens. Polar Biology 23: 699-705.
Orbell, M. 1995. Illustrated Encyclopedia of Maori Myth and Legend. Christchurch, Canterbury University Press.
Smith, P J, Mattlin, R H, Roeleveld, M A and T Okutani 1987. Arrow squids of the genus Nototodarus in New Zealand waters: systematics, biology, and fisheries. New Zealand Journal of Marine and Freshwater Research 21: 315-326.
Table 16: Octopus and Squid (Class Cephalopoda) in New Zealand
|Order||Family||Endemic species||Total species|
Figure 43: Mero's umbrella octopus Opisthoteuthis mero annual distribution.
Figure 44: Southern arrow squid Nototodarus sloanii annual distribution
Figure 45: 'Giant' squid Idioteuthis cordiformis annual distribution.
Figure 46: Four-blotched umbrella octopus Cirroctopus hochbergi annual distribution.
Figure 47: Kaharoa octopus Octopus kaharoa annual distribution.