Advances in octopus culture:
I. Reproduction
European Network for the Dissemination of Aquaculture
RTD Information (Q5CA-2000-30105) and previously FAIR-3837, Aquaflow ref. :
TL2003-191
The common octopus, Octopus vulgaris, is found world wide, from near shore shallows to
as deep as 150m. It is a species with a relatively short life cycle
(approximately 2 years). Following hatching, the paralarvae spend the first
weeks of their life in the plankton. Those that survive settle out and begin
a benthic (bottom dwelling) life.
O. vulgaris
is commercially important and accounts for a large percentage of octopus
fisheries. The common octopus also meets several of the criteria to be
considered as a candidate for industrial rearing: easy adaptation to
captivity, high growth rates (2-4% of body weight per day at 20°C),
high fecundity, and high economic value. Embryonic development and the
description of the early developmental stages have been performed both in
the wild and under laboratory conditions. Several trials have also been
conducted for the breeding and ongrowing of octopus at industrial level. The
objectives of the current project were to obtain paralarvae from broodstock
kept in captivity, to complete the early developmental stages, and to study
the growth pattern of octopus during the ongrowing phase, towards
commercialization of this species.
Individuals of the common octopus were caught at the
Saronicos Bay (Attiki, Greece), sexed, transferred to the installations of
the Zoology-Marine Biology Laboratory (Biology Department, University of
Athens), and placed into 200 l aquariums under a recirculating water system.
Reproduction experiments were conducted at a salinity of 37‰ and
temperature 20°C.
Once
the spawns were obtained, the number of egg clusters, average length, and
the number of eggs per cluster was counted. Embryonic development was
followed in two spawns.
Results indicated that a single male can fertilise
many females and that it is possible that octopus can mate more than once in
their life span. Egg-bearing
females tend to avoid males. Each female deposits clusters of eggs, at a
daily ratio of 10-20 clusters, for a period of 4 to 6 weeks. However, egg
deposit only takes place water temperatures above 10°C. Spawning was monitored in two females. The first female
(197g), produced 9,000 eggs, hatching was partial and lasted for 120h. The
second female (238g), produced 6,500 eggs, hatching lasted 24 hours and all
eggs were hatched. During this period, i.e. between spawning and egg
hatching, the females stay close to the cluster of eggs, protecting them.
The females stopped feeding and showed a weight loss of 14-28% of their body
weight. The females died 20 days after hatching. Newly deposit eggs had an
average length of 2.71mm and an average width of 1.25mm. Following hatching
planktonic larvae were placed in mesocosms containing
phytoplanktonic and zooplanktonic organisms (Dunalliela
tertiolecta, Chlorella
mininutissima, Brachionus
plicatilis, Artemia salina and
wild zooplanktonic strains). Under these conditions the paralarvae increased
their size, but showed low survival rates. At the end of the experimental
larvae rearing mortality was 100%. According to the literature larvae
rearing with several live diets usually results in 100% mortality and in
only one case 5% survival after two months of life.
These preliminary results are similar with other
studies on the artificial propagation of octopus. Reproduction in captivity
is feasible but research should be focused on the quality and the
nutritional profile of the prey for the early developmental stages.
The project is co-financed by the Ministry of
Development, General Secretariat for R&D (G.S.R.D.); co-financing
project – 50% G.S.R.D. and 50% Aquaculture Centre of Acheloos S.A.
(ICHTYKA). The Biology
Department of the University of Athens is implementing the project.
For more information, contact:
G. Verriopoulos
University of Athens,Department of Biology
Greece
Tel.: (030-1)7274 608 - Fax: (030-1)7274 604
E-mail gverriop@biol.uoa.gr