275
16 Loligo vulgaris and Doryteuthis opalescens
Loliginid females lay their egg capsules over other egg masses of the same species, forming egg masses that can vary greatly from small clusters of a few capsules to very large ones. In L. vulgaris, each capsule contains from 130 to 180
eggs (Mangold-Wirz 1963) and newly laid eggs measure 2.0–2.2 mm in length by
1.5–1.6 mm in width (Boletzky 1974a). The size of eggs are close to those of D.
opalescens (2.0–2.5 mm in length by 1.3–1.6 mm in width), although in this species
the number of eggs per egg capsule ranges from 180–300 as indicated by Hixon
(1983). In summary, these two loliginid species form oocytes of roughly similar
size, much larger than, e.g. Doryteuthis pealeii (Hanlon et al. 1979).
16.3 Broodstock Acclimatization to Captivity
Broodstock acclimatization is necessary when juvenile, subadult or adult individuals are captured from the sea and transferred to holding facilities where reproduction can be achieved.
In a brief section on ecological characteristics of L. vulgaris, Bauer (1909,
p. 154) had already stated the following: ‘Loligo is pelagic like most of the decapods and in general lives in shoals. In the aquarium the animals are in continuous
movement, swimming intermittently forward and backward without turning; indeed
all the individuals in a swarm move simultaneously in the same direction’.
Tardent (1962) summarized earlier experience (e.g. Grimpe 1928) with squid
maintenance at the Naples Aquarium (which used an open seawater circuit, functioning as a closed circuit during stormy periods with high water turbidity), where
groups of individuals have been kept continuously for periods lasting up to 2
months, being fed mainly on live and dead fish. Freshly caught individuals were
acclimatized in circular rubber tanks (inflatable splash pools; see Neill 1971) before
being transferred to a rectangular show tank, where they formed well-organized
‘schools’. Bentivegna (1987) indicated maximum survival time of 3 months for
small individuals of L. vulgaris in the Naples Aquarium, under optimal feeding
conditions (live prawn).
For highly active swimmers such as loliginid squids (Neumeister et al. 2000),
which begin schooling at an early juvenile stage, sufficient tank space accommodating relatively large groups is a major requirement (Neill 1971; Neill and Cullen
1974). Hanlon and Messenger (1996, p. 151) drew attention to a distinction between shoaling and schooling: ‘Shoaling emphasises the social behaviours related
to aggregating as distinct from the physical synchrony (velocity and direction) and
polarization (parallel swimming) of individuals in the group, which are termed
schooling’.
Visual landmarks in their artificial environment (e.g. striped tank walls or curtains, or entirely black-walled cylindrical tanks, as described by Mladineo et al.
2003) may help the animals to avoid contact with technically imposed barriers in
their artificial environment (Hanlon 1978, p. 10). But even when a high water quality (cf. Gilly and Lucero 1992), a regular supply of appropriate prey (DeRusha et al.
16 Loligo vulgaris and Doryteuthis opalescens
Loliginid females lay their egg capsules over other egg masses of the same species, forming egg masses that can vary greatly from small clusters of a few capsules to very large ones. In L. vulgaris, each capsule contains from 130 to 180
eggs (Mangold-Wirz 1963) and newly laid eggs measure 2.0–2.2 mm in length by
1.5–1.6 mm in width (Boletzky 1974a). The size of eggs are close to those of D.
opalescens (2.0–2.5 mm in length by 1.3–1.6 mm in width), although in this species
the number of eggs per egg capsule ranges from 180–300 as indicated by Hixon
(1983). In summary, these two loliginid species form oocytes of roughly similar
size, much larger than, e.g. Doryteuthis pealeii (Hanlon et al. 1979).
16.3 Broodstock Acclimatization to Captivity
Broodstock acclimatization is necessary when juvenile, subadult or adult individuals are captured from the sea and transferred to holding facilities where reproduction can be achieved.
In a brief section on ecological characteristics of L. vulgaris, Bauer (1909,
p. 154) had already stated the following: ‘Loligo is pelagic like most of the decapods and in general lives in shoals. In the aquarium the animals are in continuous
movement, swimming intermittently forward and backward without turning; indeed
all the individuals in a swarm move simultaneously in the same direction’.
Tardent (1962) summarized earlier experience (e.g. Grimpe 1928) with squid
maintenance at the Naples Aquarium (which used an open seawater circuit, functioning as a closed circuit during stormy periods with high water turbidity), where
groups of individuals have been kept continuously for periods lasting up to 2
months, being fed mainly on live and dead fish. Freshly caught individuals were
acclimatized in circular rubber tanks (inflatable splash pools; see Neill 1971) before
being transferred to a rectangular show tank, where they formed well-organized
‘schools’. Bentivegna (1987) indicated maximum survival time of 3 months for
small individuals of L. vulgaris in the Naples Aquarium, under optimal feeding
conditions (live prawn).
For highly active swimmers such as loliginid squids (Neumeister et al. 2000),
which begin schooling at an early juvenile stage, sufficient tank space accommodating relatively large groups is a major requirement (Neill 1971; Neill and Cullen
1974). Hanlon and Messenger (1996, p. 151) drew attention to a distinction between shoaling and schooling: ‘Shoaling emphasises the social behaviours related
to aggregating as distinct from the physical synchrony (velocity and direction) and
polarization (parallel swimming) of individuals in the group, which are termed
schooling’.
Visual landmarks in their artificial environment (e.g. striped tank walls or curtains, or entirely black-walled cylindrical tanks, as described by Mladineo et al.
2003) may help the animals to avoid contact with technically imposed barriers in
their artificial environment (Hanlon 1978, p. 10). But even when a high water quality (cf. Gilly and Lucero 1992), a regular supply of appropriate prey (DeRusha et al.