Octopus Mercatoris (Caribbean Pygmy) Adam, 1937


Staff member
Sep 4, 2006
We have noticed a decline in the availability of O. mercatoris since the last el nino but I found this interesting paper about a previous decline in their numbers and a different reason:

Disappearance of a population of pygmy octopus following a harmful algal bloom in a northwestern Florida bay, U.S.A.Bridget Nicole Tiffany, Nann A. Fangue*, and Wayne A. Bennett
Department of Biology,University of West Florida, Pensacola, Florida 32514, U.S.A., [email protected]
- full PDF available from link

Note: The first paragraph gives a short presentation on the differences between O.joubini and O.mercatoris and I have included it after the abstract. Additional information in the paper gives a summary of the natural habitat and habits.

Abstract: St. Joseph Bay, Bay County, Florida, U.S.A. is 1 of 4 locations at which the pygmy octopus, Octopus cf. mercatoris, is known to occur. Octopus densities of 1 per 33 m2 were measured and values of catch per day ranging from 1-70 animals were consistently reported between 1972 and 1999. From 17 August 1999 through 14 October 1999, St. Joseph Bay experienced a severe and prolonged harmful algal
bloom (HAB) with cell counts reaching 1,000,000 cells/L at its peak. Populations of Octopus cf. mercatoris were devastated during the bloom. Repeated and extensive sampling from September 1999 through February 2004 resulted in the collection of only a single brooding female in February 2003. The molluscs' relatively low fecundity (50-320 eggs/clutch) and benthic early life history reduce the probability of distant
re-colonization and slow repopulation by surviving octopus within the Bay. Ongoing changes in land use and loss of critical habitat may further stress the remaining, remnant population, leaving them vulnerable to eradication should another HAB event occur.

Octopus joubini (Robson, 1929) had been the only resident
species of pygmy octopus within the Gulf of Mexico
(Robson 1929, Pickford 1945, Voss 1956, Roper et al. 1984)
until Forsythe and Toll (1991) demonstrated that the pygmy
octopus population of the Gulf of Mexico is actually comprised
of two distinct species-Octopus joubini and a second,
similar species that is either a synonym of Octopus mercatoris
(holotype collected in the Virgin Islands) or an undescribed
species. Although both species are morphologically similar,
egg size, fecundity, hatchling type, and habitat preference
differ markedly (Forsythe and Toll 1991). Female individuals
of O. cf. mercatoris deposit 50 to 320 eggs ranging in size
from 6.0-8.0 mm and emerging young are benthic. Conversely,
females of O. joubini deposit 150-3000 eggs ranging
from 2.3-2.9 mm in length and hatchlings are planktonic.
Furthermore, individuals of O. joubini are typically limited
to sandy or muddy substrates in depths greater than 10 m,
whereas individuals of O. cf. mercatoris favor shallow seagrass
beds less than 5 m deep. Within the Gulf of Mexico,
O. cf. mercatoris is thought to be resident in several shallow
Florida bays including Biscayne Bay, Palmetto Key, Pine
Island, and St. Joseph Bay (Pickford 1945, Forsythe and Toll
1991). Forsythe and Toll (1991) concluded that previously
published accounts of pygmy octopus collected from shallow
waters in Biscayne and St. Joseph Bays, and widely cited in
the literature as O. joubini, were in fact O. cf. mercatoris.
Historic taxonomic ambiguities make it difficult to know if
O. joubini have ever been collected from St. Joseph Bay ...

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