304
E. A. G. Vidal and S. von Boletzky
availability is an important regulator of growth and survival. Paralarvae showed
substantial growth plasticity in response to food availability in a very short period
of time (10 days). In addition, paralarvae subjected to 2–3 days of starvation were
able to increase growth rates above that of the continuously fed squid, showing
compensatory growth that mitigated the effects of starvation. Noticeably, starvation
caused a strong selection for faster growing squid, suggesting that discontinuous
feeding regimes would perhaps promote better growth to closer approximation of
the natural environment (Vidal et al. 2006).
16.6.6 Social Behaviour
‘Squids are schooling, social creatures with large brains and complex behaviour’
(Hanlon 1990). During rearing of D. opalescens changes in social interactions between same-aged paralarvae can be often observed. Early paralarvae (0–15 days
old) swim dispersed, holding a certain distance from each another and often display
aggressive behaviour towards one another. About 30–40-day-old paralarvae usually swim at 45–65°- angles, less vertically oriented than the newly hatched squid
and are able to swim against low current speeds (~ 1.4 cm s
−1
), frequently copying
the position of other squid swimming nearby (Vidal 2000). Schooling can be first
noticed in 35–45-day-old paralarvae (6–8 mm ML) and seems to be dependent on
size of squid and flow intensity (Vidal 2000). In fact, Yang et al. (1983a, 1986) first
noticed the ability of D. opalescens to hold position at 40–45 days (10 mm ML), and
to form schools between 60–80 dah (15 mm ML). These authors have used larger
rearing tanks and current speeds.
16.7 Ongrowing
So far, no reports are known to us about large-scale ongrowing culture in the two
species under consideration. Given the rather expensive food required (Tables 16.3
and 16.4), it is not surprising that no industrial squid culture using L. vulgaris and D.
opalescens has ever been achieved. What potential market should be interested in
these two species? The year-round production of squid that must be kept alive until
consumption (e.g. as Sashimi) can be achieved much more easily with other species, especially Sepioteuthis (see Chap. 17). Only for D. opalescens the complete
life cycle was close under laboratory conditions (Yang et al. 1986). For any attempt
to set up a large-scale culture of L. vulgaris or D. opalescens, the following conditions would have to be fulfilled.
E. A. G. Vidal and S. von Boletzky
availability is an important regulator of growth and survival. Paralarvae showed
substantial growth plasticity in response to food availability in a very short period
of time (10 days). In addition, paralarvae subjected to 2–3 days of starvation were
able to increase growth rates above that of the continuously fed squid, showing
compensatory growth that mitigated the effects of starvation. Noticeably, starvation
caused a strong selection for faster growing squid, suggesting that discontinuous
feeding regimes would perhaps promote better growth to closer approximation of
the natural environment (Vidal et al. 2006).
16.6.6 Social Behaviour
‘Squids are schooling, social creatures with large brains and complex behaviour’
(Hanlon 1990). During rearing of D. opalescens changes in social interactions between same-aged paralarvae can be often observed. Early paralarvae (0–15 days
old) swim dispersed, holding a certain distance from each another and often display
aggressive behaviour towards one another. About 30–40-day-old paralarvae usually swim at 45–65°- angles, less vertically oriented than the newly hatched squid
and are able to swim against low current speeds (~ 1.4 cm s
−1
), frequently copying
the position of other squid swimming nearby (Vidal 2000). Schooling can be first
noticed in 35–45-day-old paralarvae (6–8 mm ML) and seems to be dependent on
size of squid and flow intensity (Vidal 2000). In fact, Yang et al. (1983a, 1986) first
noticed the ability of D. opalescens to hold position at 40–45 days (10 mm ML), and
to form schools between 60–80 dah (15 mm ML). These authors have used larger
rearing tanks and current speeds.
16.7 Ongrowing
So far, no reports are known to us about large-scale ongrowing culture in the two
species under consideration. Given the rather expensive food required (Tables 16.3
and 16.4), it is not surprising that no industrial squid culture using L. vulgaris and D.
opalescens has ever been achieved. What potential market should be interested in
these two species? The year-round production of squid that must be kept alive until
consumption (e.g. as Sashimi) can be achieved much more easily with other species, especially Sepioteuthis (see Chap. 17). Only for D. opalescens the complete
life cycle was close under laboratory conditions (Yang et al. 1986). For any attempt
to set up a large-scale culture of L. vulgaris or D. opalescens, the following conditions would have to be fulfilled.