An analysis of 15 specimens of the oceanic squid Sthenoteuthis oualaniensis caught by hooks and lines from

the Arabian Sea showed that the growth pattern was isometric with the length-weight relationship W = 0.0276

L"'. The von Bertalanffy growth parameters estimated were L_ = 49.1 cm; K = 0.83 yrl and to, -0.06 yr.

Other population parameters such as optimum length for exploitation, length at maturity and natural mortality

rate were also estimated. Relative fecundity was 125 no. /g body weight. The egg diameter ranged from 0.7

to 0.9 mm. The scope for exploitation of the oceanic squid is discussed.

Alloycious, P S

Joseph, Mathew

Mohamed, K S

CMFRI Digital Repository

J. Mar. Biol. Ass. India, 48 (2) : 256 - 259, July - December 2006 Note Population characteristics and some aspects of the biology of oceanic squid Sthenoteuthis oualaniensis (Lesson, 1830) K.S. Mohamed', Mathew Joseph and P.S. Alloycious Central Marine Fisheries Research Institute, P O  Box. 1603, Emakulam North P.O.,Cochin 682018, India 'Email: ktmohamed@vsnl. com Abstract An analysis of 15 specimens of the oceanic squid Sthenoteuthis oualaniensis caught by hooks and lines from the Arabian Sea showed that the growth pattern was isometric with the length-weight relationship W = 0.0276 L"'. The von Bertalanffy growth parameters estimated were L_ = 49.1 cm; K = 0.83 yrl and to, -0.06 yr. Other population parameters such as optimum length for exploitation, length at maturity and natural mortality rate were also estimated. Relative fecundity was 125 no. /g body weight. The egg diameter ranged from 0.7 to 0.9 mm. The scope for exploitation of the oceanic squid is discussed.. The purpleback flying squid Sthenoteuthis (=Symplectoteurhis) oualaniensis (Lesson, 1830) is dis- tributed in the tropical and sub-tropical areas of the Pacific and Indian Oceans. The Arabian Sea is considered as one of the richest regions for these oceanic squids in the. Indian Ocean (Zuyev et al., 2002; Aravindakshan and Sakthivel, 1973). These squids are pelagic animals living in the open ocean, usually absent over the continental shelves (<200 m), and first appear over continental slopes at depths above 250-300 m (Zuyev et al., 1985). Chesalin et al. (1995) termed this species as the master of the Arabian Sea due to its high abundance, large size, short life-span, fast growth and near monopoly of the higher trophic niche. However, commercial fishing activity for this resource is still low due to insufficient studies on its abundance and distribution (Chesalin and Zuyev, 2002). Globally, the stock of S. oulaniensis has been assessed as 3-4 million tonnes (Zuyev et al., 1985) and 25000- 50,000 t in oceanic Indian waters (Silas, 1986). Materials and methods The study is based on15 specimens of S. oualaniensis caught by hand lines operated from mechanized gillnet boats operating from Cochin Fisheries Harbour. On 5 May 2006, five mechanized gillnet vessels landed 25 kg of these oceanic squids. These 44-60 footer boats oper- ated hooks and lines (No.718 hooks) at a depth of 50 m. All specimens were examined externally and sexed, and then measurements of body proportions, and indices were obtained from the whole body as described by Roper and Voss (1983). Measurements were made in millimeters (mm) and weights were taken to the nearest gram (Table 1). Indices of length were expressed as percentage of dorsal mantle length (ML), e.g. HWI (Head Width Index) = HWIML x 100. Indices of organ weights, viz., gonadosomatic index (GSI), mantle weight index (MWtI), nidamental gland index (NGI) and hepatic (liver) index (HI) were also collected from 2 specimens. The specimens were cut open to examine maturity stage and stomachs were cut open to examine the food contents. The morphological features of the pen or gladius were also examined. The ovary and oviduct of 2 specimens were preserved in formalin to determine the fecundity and ova diameter measurements were also taken. The length-weight relationship was estimated by using the equation, W = a Lh, where W = weight in gram, L = mantle length in centimeter and 'a' and 'b' are con- stants. The relationship was fitted using the software ABeeTM (Pauly and Gayanilo, 1997). The population parameters (asymptotic length, L_; growth coefficient, K; to, age at zero length; optimum length, LOP,; length at first maturity, Lm; natural mortality rate, M) were determined from the maximum length (Lmx) observed earlier from the region (Nair et al., 1990) using the empirical formulae given by Froese and Binohlan (2000) since maximum length is a good predictor of life history parameters. The depth at station ranged from 1000-1500 m (Lat Ruults and disolssion 1 1 ". 10'-11 O.49.N; long 71 O.51'-72".05'E). The fishing eround was 450 km west off Cochin near the Lakshadwee~ On the basis of the dorsal photophore and gladius u Island (off Cheriyam and Kalpeni islands) and the voyage morphology five intraspecific forms of S. oualaniensis duration was up to 10 days. have been described (Nesis, 1995). Accordingly, the Journal of the Marine Biological Association of India (2006) Population parameters and some aspects of biology of oceanic squid 257 specimens examined presently belong to Type 4 which is a middle-sized late-maturing form with dorsal photophore and with double lateral axes of the galdius (Fig.1). This is the most common form in Indian and Pacific oceans (Zuyev et al., 2002). All the squids obtained were females with the dorsal mantle length ranging from 220- 268 mm and a wet body weight range of 406-81 1 g. Based on the size these animals can be placed in the Vth ontogenetic phase out of a total of VI phases (Zuyev et al., 2002); which is a middle-sized adult of nektonic habit. All the animals had empty stomachs, although they are known to be active predators with a wide mesopelagic food spectrum. The preponderance of empty stomachs may be due to the fast digestion rates in the stomach of this squid (8-10 h in middle-sized squids; Chesalin et al., 1995). All the animals sampled were in fully mature condi- tion with the oviduct full of mature eggs and well devel- oped nidamental glands. Fecundity was estimated as more than 100,000 eggs in each specimen (relative fecundity 125 no. Ig body weight) and the egg diameter varied between 0.7 and 0.9 mm. Zuyev et al. (2002) reported that middle-sized S. oualaniensis had a potential fecundity varying from 100,000 to 500,000 eggs and had egg Table 1 .  Mean indices of length and weiglit qf fernale S. oualaniensis togetl~er with standard deviation (SD) and range Indices measured Mean SD Range Mantle Width Index - MWI 29.7 2 .2  27.5-33.6 Arm Length Index - ALI 58.8 7 .9  40.0-73.1 Tentacle Length Index - TLI 167.4 24.2 130.4-207.7 Club Length Index - CLI 44 .2  3 .2  40.0-49.0 Head Length Index - HLI 22.5 0 .6  21.6-23.1 Head Width Index - HWI 21.2  0 . 7  20.4-22.4 Fin Length Index - FLI 42.0  2 .3  38.0-44.8 Fin Width Index - FWI 80.4  1.3 78.4-82.4 Mantle Weight Index - MWtI 47.8 - 47.0-49.0 Gonadosomatic Index - GSI 1 1 .0  - 1 1  .O-  11.0 Nidamental Gland Index - NGI 5.98 - 5.9-6.1 Hepatic Index - HI 4.63 - 4.5-4.7 diameters varying between 0'65 and 0'85 mm. Fig. 1.  Ventral view of the gladius of S. oulaniensis. Inset shows to neretic squids, the fecundity of S. oualaniensis is high detail of the central reg,on and arrowhead shows the double and therefore, these animals can be considered as r- lateral axes of the gladius strategists as opposed to k-strategy of the neretic squids. All animals were also in mated condition as evident from the presence of spermatophores in the buccal region. Since all the squids were mated and in mature condition, it can be concluded that May is a peak spawning period in the southeastern Arabian Sea. Earlier reports (Silas, 1969; Okutani and Tung, 1978) also suggest that S. oiialaniensis spawning occurs throughout the year with peak in March to May (summer) in the Arabian Sea. by Nateewathana et al. (2001) were considerably smaller and therefore could belong to the dwarf form of S. oualaniensis. The maturity index (GSI) is reported to vary from 11-15 to 25-30 for S. oualaniensis and the orangeback flying squid S. pteropus worldwide (Zuyev et al., 2002). In the present case the GSI of fully mature females was estimated to be 11, which is close to the lower maximal range. Most length indices were in conformity with those The length-weight relationship was found to be W = observed by earlier workers from other regions of the 0.0276 L3I0". The b value close to 3 indicates the iso- world (Nateewathana et al., 2001). except that of tentacle metric growth pattern of the squid (Table 2). The values length index (TLI). The TLI was considerably lesser in compare well with S. oualaniensis from Hawaii (Suzuki S. oualaniensis from the South China Sea (Vietnamese et al., 1986) and central Arabian Sea (Chesalin, 1993). In waters). This may be because the specimens examined contrast, in most neretic squids the growth pattern is Table 2. Estimated parameters of the length-weight relationship of S. oualaniensis. Mantle length a value b value Goodness Authors range (mm) of fit(R2) 200-472 0.0276 + 0.01 1 3.1056 + 0.107 0.985 Present study 100-297 0.00001 8 3.150 0.959 Suzuki et al. (1986) 150-300 0 .082 2.699 Chesalin (1993) Above 300 0.005 3.506 Chesalin (1993) Journal of the Marine B~ological Association of India (2006) - - pp -- - - - - 258 K. S. M o h a m e d  a n d  others clearly allometric, with the value of b closer to 2 than 3 Lakshadweep waters, the lights from the boats attracted (Meiyappan et al., 2000). the squids, and below the dense mass of squids, tunas and sharks were present to feed on them. According to The von Bertalanffy parameter L-was determined as Chesalin et  al. (1995), the most promising region to 49'1 cm (SE range 41'4-58'3) and as 0.83 3). develop a fishev for these squids is the Arabian Sea, The average life span of the animal is estimated to be where the squid biomass reaches several tonnes per km2. around 2 years. Considerable work has been done on the The estimated squid stock in the Arabian Sea varies in the age and growth of various intraspecific forms of S. range 0.9-1.6 million t (Zuyev et  a l . ,  2002). At present oualaniensis in the Arabian Sea by Soviet investigators the fishermen do not bring back the squid catch from using recordings on the gladius (Zuyev et al., 2002). these voyages-due to the lack of market demand and grew faster than and the growth appreciable price structure. The prospects for developing pattern was either slightly sigmoid or linear depending on a new fishery for oceanic squids in the Arabian Sea based the maturity stage. from west coast fishing ports, either by hook and line or The length at first maturity (L,) was estimated as 27.6 cm. Nair et al .  (1990) estimated the Lm as 1 1  cm for females of S. oualaniensis from the Indian EEZ. Al- though the present estimate is an empirical one, the large difference could be because the latter estimate may be primarily based on the dwarf intraspecific form of S. oualaniensis available in the Indian Ocean. The ratios of LmL_, L,/L,, LOp,/L_ and M K  are all well within the limits of an unexploited population. The present mean length of the catch (24.3 cm) is close to the estimated Lop, (30.8 cm), which is the length at which highest biomass of this unfished population is available. S. oualaniensis form large shoals of up to 1000 individuals in the open ocean. They are attracted to light and undertake diurnal migrations rising to the epipelagic layer at night for feeding and descending up to 800-1200 m depth in the morning. The present catch of squids using small hook and lines was obtained as incidental catch by fishermen who were targeting tunas and sharks during dusk and night. Fishermen reported that in Table 3.Estimated population parameters with standard error (SE range) of S. oualaniensis caught from Arabian Sea Population parameter SE range L... (cm) 47.2 L- (cm) 49.1 41.4-58.3 '-ma!L- 0.96 Lm (cm) 27.6 20.6-36.9 LmlL- 0.56 Lop, (cm) 30.8 26.0-36.4 Lop,"-- 0.63 K yr" 0.83 to Yr -0.0607 M yr-I 1 .34  M/K 1.61 squid jigging, is substantial, taking into account the rela- tively huge magnitude of the unexploited resource. For this, a concerted effort through the formation of an oce- anic squid task force with fishery biologists, fish proces- sors, market developers and planners is recommended. References Aravindakshan, P.N. and M. Sakthivel. 1973. Tl~e location of cepl~alopod nurseries in t l~e  Indian Ocean. Inter- national Indian Ocean Expedition, Handbook to the International Zooplankton Collections. IOBC, N10, CSIR 5: 70-75. Chesalin, M.V. 1993. Hydrobiol. J., 30(2): 61-73. and G.V. Zuyev. 2002. Bull Mar. Sci., 7(1): 209-221. -- . G.V. Zuyev and V.N. Nikolsky. 1995. Squid Sthenoteuthis oualaniensis (Cephalopoda: Ommastrephidae) is the 'master' of the Arabian Sea. In: Guerra,A., .E Rolan and F. Rocha. (Eds.) 12* International Malacologiral Congress, Vito, Italy p. 161-162. Froese, R. and C. Binohlan. 2000. J. Fish. Biol., 56(4): 758-773. Meiyappan, M.M, K.S. Mohamed, K. Vidyasagar, K.P.Nair, N. Ramachandran, A.P. Lipton, G.S. Rao, V. Kripa, K.K. Joshi, E.M. Abdusamad, R. Sarvasen and G.P.K. Achary. 2000. A review on the cephalopod resources, biology and stock assessment. In: Pillai, V.N. and N.G.Menon (Eds.) Marine Fisheries Research and Management. p. 546 - 562, Central Marine Fisheries Research Institute, Cochin, India. Nair, K.P., K.S. Rao, R. Sarvesan, M.M. Meiyappan, G.S. Rao, M. Joseph and D. Nagaraja. 1990. Pror. First Workshop Scient. Resul. FORV Sagar Sampada, 5-7 June, 1989. Mathew,K.J.(Ed.). CMFR1,Cochin: p.403- 407. Nateewathana, A., S. Siriraksophon and A. Munprasit 2001. The Systematics and Distribution of Oceanic Cepha- lopods in the South China Sea, Area IV: Vietnamese Journal of the Marine Biological Association of India (2006) Population parameters and some aspects of biology of oceanic squid 259 Waters. Proceedings of the SEAFDEC Seminar on Roper, C.F.E and G.L. Voss. 1983. Memoirs of the Na- Fisherv Resources in the South China Sea. Area IV: tional Museum o f  Victoria. 44: 49-63. Vietnamese Waters, Southeast Asian Fisheries Devel- opment Center, p. 169-180. Silas, E.G. 1969. Bull. Cent. Mar. Fish. Res. Inst., 12: 86. Nesis. K.N. 1995. Population structure of the purpleback . 1986 (Ed.). ibid., 37: 195 pp. squid (Sthenoteutltis oualaniensis) in the Arabian Sea Suzuki, T., S. Yamamoto, K. Ishii and W. Matsumoto, and adjacent areas. p. 11 1-1 14. In: Goldman, J.C. and 1986. Bull. Fac. Fish. Hokkaido. Univ., 37(2): 11 1- H.D. Livingston (Eds.). Biogeochemiral proresses in 123. rhe Arabian Sea. US-CIS Arabian Sea Workshop, Sevastopol. Zuyev, G., C. Nigmatullin and V.N. Nikolsky. 1985. Agropromizdat, Moscow. 224 pp. 0kutani.T and I.H. Tung. 1978. Veliger, 21(1): 87-94. -., C. Nigmatullin, M. Chesalin and K. Nesis. Pauly. D. and F.C. Gayanilo, Jr. 1997. ICLARM Software 2002. Bull. Mar. Sci., 7(2): 1019-1060. 8. ICLARM, Philippines. Received: 19 October 2006 Accepted: 20 December 2006 Journal of the Marine Biological Association of India (2006) -- -- - - - -- -- I -  - 

Population characteristics and some aspects of the biology of oceanic squid Sthenoteuthis oualaniensis (Lesson, 1830)

http://eprints.cmfri.org.in/2097/1/Mohamed_26-259.pdf

Population characteristics and some aspects of the biology of oceanic squid Sthenoteuthis oualaniensis (Lesson, 1830)

Abstract

Similar works

Full text

Available Versions

CMFRI Digital Repository