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J. Nabhitabhata and Y. Ikeda
the mantle length (ML), and the fin width is more than 75 % of the ML (Jereb et al.
2010). The bigfin squid is a demersal neritic species and is found between the surface and depths of about 100 m. Its habitats include coral and rock reefs, seaweed
and sea grass beds, and estuaries. Its geographical distribution covers the IndoPacific region, 20°E–120°W, 40°N–40°S (Dunning 1998; Jereb et al. 2010; Okutani
2005). The maximum body weight (BW) of S� lessoniana is about 2 kg, while the
maximum ML is 422 mm for males and 382 mm for females (Jereb et al. 2010).
In the shallow waters of the Gulf of Thailand, the maximum ML of these squid is
around 305 mm, and squid that are 70–260 mm in length are commonly caught
(Chotiyaputta 1995). The first maturation size of female squid is 130–140 mm and
their fecundity is approximately 1,000 (400–3,500) eggs (Chotiyaputta 1984, 1988,
1995; Nabhitabhata 1996; Roongratri 1997; Segawa 1987; Segawa et al. 1993b).
S� lessoniana is of commercial and artisanal interest throughout the Indo-West
Pacific region. It constitutes about 7 % of Indian east coast cephalopod landings and
5 % of Thai landings (Jereb et al. 2010; Supongpan et al. 1988; Supongpan 1995). It
is captured using a variety of fishing gear and comprises about 10 % of the catch by
offshore trawlers and purse seine. In the Southeast Asian region where S� lessoniana
is the most abundant, i.e. Thailand and Indonesia, squid traps are popular inshore
gear for capturing this species. Squid trap fisheries in Thailand annually yield about
7,000 t, and 90–95 % of the catch is comprised of S� lessoniana, the main target species (> 6,000 t). The remaining 5–10 % is comprised of by-catch pharaoh cuttlefish,
Sepia pharaonis (Supongpan et al. 1988; Chotiyaputta and Yamrungreung 1998).
The trap used to capture these squid is artisanal, can be made from local materials, and reflects a good understanding of squid behaviour by local fishermen.
In Thailand, two types of traps are used: the semicylindrical type (Fig. 17.2; for
details, see also Chap. 7, ‘Aquaculture to Restocking’) and the rectangular box
type. Both types are 500–800 × 800–1,200 × 500–650 mm, and most of them are
600 × 1,000 × 500 mm (Boongerd and Rachaniyom 1990; Chotiyaputta and Yamrungreung 1998). Trap frames are made of locally available wood and are covered
by a polyethylene fishing net that has a 25-mm mesh size. In fishing operations, the
trap is suspended in the water column 2–3 m above the bottom using rock sinkers
with Styrofoam and bamboo floats. The fishing depth is approximately 6–40 m,
depending on the local fishermen’s experience regarding the optimal trap depth. Coconut fronds are used to cover the trap, making it look like a shelter. S� lessoniana
egg clusters are hung inside the trap to persuade squid to enter. When egg clusters
are scarce, stripped plastic shopping bags are sometimes used as a substitute. Female S� lessoniana, escorted by mated males, enter the trap in search of appropriate
substrates for spawning. After entering the trap, a female attaches her eggs to the
net covering. Chotiyaputta (1984, 1988) and Roongratri (1997) reported that the sex
ratio of squid captured in traps in Thai waters is close to 1:1.
The squid trap is an appropriate fishing gear in view of natural resource conservation, as only full-grown stocks are exploited. Chotiyaputta (1988) reported that
80 % of the squid captured in traps are larger than 140 mm and are therefore fully
mature. The fishing period consists of 20 days per month for about 9 months each
year. The remaining periods are reserved for natural stock recruitment.
J. Nabhitabhata and Y. Ikeda
the mantle length (ML), and the fin width is more than 75 % of the ML (Jereb et al.
2010). The bigfin squid is a demersal neritic species and is found between the surface and depths of about 100 m. Its habitats include coral and rock reefs, seaweed
and sea grass beds, and estuaries. Its geographical distribution covers the IndoPacific region, 20°E–120°W, 40°N–40°S (Dunning 1998; Jereb et al. 2010; Okutani
2005). The maximum body weight (BW) of S� lessoniana is about 2 kg, while the
maximum ML is 422 mm for males and 382 mm for females (Jereb et al. 2010).
In the shallow waters of the Gulf of Thailand, the maximum ML of these squid is
around 305 mm, and squid that are 70–260 mm in length are commonly caught
(Chotiyaputta 1995). The first maturation size of female squid is 130–140 mm and
their fecundity is approximately 1,000 (400–3,500) eggs (Chotiyaputta 1984, 1988,
1995; Nabhitabhata 1996; Roongratri 1997; Segawa 1987; Segawa et al. 1993b).
S� lessoniana is of commercial and artisanal interest throughout the Indo-West
Pacific region. It constitutes about 7 % of Indian east coast cephalopod landings and
5 % of Thai landings (Jereb et al. 2010; Supongpan et al. 1988; Supongpan 1995). It
is captured using a variety of fishing gear and comprises about 10 % of the catch by
offshore trawlers and purse seine. In the Southeast Asian region where S� lessoniana
is the most abundant, i.e. Thailand and Indonesia, squid traps are popular inshore
gear for capturing this species. Squid trap fisheries in Thailand annually yield about
7,000 t, and 90–95 % of the catch is comprised of S� lessoniana, the main target species (> 6,000 t). The remaining 5–10 % is comprised of by-catch pharaoh cuttlefish,
Sepia pharaonis (Supongpan et al. 1988; Chotiyaputta and Yamrungreung 1998).
The trap used to capture these squid is artisanal, can be made from local materials, and reflects a good understanding of squid behaviour by local fishermen.
In Thailand, two types of traps are used: the semicylindrical type (Fig. 17.2; for
details, see also Chap. 7, ‘Aquaculture to Restocking’) and the rectangular box
type. Both types are 500–800 × 800–1,200 × 500–650 mm, and most of them are
600 × 1,000 × 500 mm (Boongerd and Rachaniyom 1990; Chotiyaputta and Yamrungreung 1998). Trap frames are made of locally available wood and are covered
by a polyethylene fishing net that has a 25-mm mesh size. In fishing operations, the
trap is suspended in the water column 2–3 m above the bottom using rock sinkers
with Styrofoam and bamboo floats. The fishing depth is approximately 6–40 m,
depending on the local fishermen’s experience regarding the optimal trap depth. Coconut fronds are used to cover the trap, making it look like a shelter. S� lessoniana
egg clusters are hung inside the trap to persuade squid to enter. When egg clusters
are scarce, stripped plastic shopping bags are sometimes used as a substitute. Female S� lessoniana, escorted by mated males, enter the trap in search of appropriate
substrates for spawning. After entering the trap, a female attaches her eggs to the
net covering. Chotiyaputta (1984, 1988) and Roongratri (1997) reported that the sex
ratio of squid captured in traps in Thai waters is close to 1:1.
The squid trap is an appropriate fishing gear in view of natural resource conservation, as only full-grown stocks are exploited. Chotiyaputta (1988) reported that
80 % of the squid captured in traps are larger than 140 mm and are therefore fully
mature. The fishing period consists of 20 days per month for about 9 months each
year. The remaining periods are reserved for natural stock recruitment.