Growth and Mortality of the Oceanic squid Sthenoteuthis oualaniensis (Lesson, 1830) off the south west coast of India

Abstract

The study attempted to understand the difference in growth and mortality rate, between two phenotypic variants of the oceanic squid Sthenoteuthis oualaniensis. Specimens (1015 nos.) of the species collected off the south-west coast of India (lat. 07 to 11 o N; long. 74 to 77 o E) at a depth range of 180-2601 m were used in this study. Data on dorsal mantle length (DML) of dwarf and medium forms of the species were collected and analysed using the length-based FiSAT routine. L ∞ varied from 17.37 to 18.05 cm with an average of 17.89 cm for the dwarf and 29.5 to 30.49 cm with an average of 30.08 cm for medium form. Dwarf forms had a higher average K value (3.65 cm y -1 ) with � of 3.06, whereas, medium form had a lower average K value (2.38 cm y -1 ) with � of 3.33. Growth curve and longevity study indicated longer than a year life span for medium forms (461 days) with growth rate of 13.3 cm DML in three months (91 days), 20.8 cm in six months (182 days) and 25.0 cm in nine months (273 days). Dwarf form attained maximum length in ten months (302 days) with a growth of 10.5 cm in three months (91 days), 14.9 cm in six months (182 days) and 16.7 cm DML in nine months (274 days). The average total instantaneous mortality (Z) was estimated as 4.58 y -1 for dwarf and 6.03 y -1 for medium form. As there was no commercial fishing for this species, fishing mortality was considered nil. Therefore, total mortality rate Z was considered equivalent to natural mortality.

Genomes of Two Flying Squid Species Provide Novel Sights into Adaptations of Cephalopods to Pelagic Life

“…Morphological studies provided evidence that Sthenoteuthis sp . was distinguishable from S. oualaniensis concerning external features, including variables of the head, carcass, arms, as well as the shape and size of fins [31, 32]. Our results corroborate the conclusion that Sthenoteuthis sp.…”

Biogeographic role of the Indonesian Seaway implicated by colonization history of purpleback flying squid, Sthenoteuthis oualaniensis (Lesson, 1830), in the Indo-Pacific Ocean

“…A divergence level of 1.99% was observed between clade II from the northern East Indian Ocean and clade III from the southern East Indian Ocean, which is far lower than that (10.33%-10.81%) observed between the dwarf form (clade VI) and middle-sized form (clades I-V), suggesting that both of these East Indian Ocean clades likely belong to different lineages of the middle-sized form in the Indian Ocean. Although the dominant middle-sized form and the dwarf form were found north of 10°N and south of 7°N along the neighboring southwest coast of India (Chembian and Mathew, 2014), no dwarf form was observed in the present sampling from the East Indian Ocean. Further studies will be needed to further distinguish these populations including the three middle-sized forms in the Indo-Pacific and the giant form in the Arabian Sea (Nesis, 1993;Snÿder, 1998) through integrating molecular and morphological data on a larger spatial scale.…”

“…S. oualaniensis exhibits a complex and often debated population structure across the Indian and Pacific Oceans due to high levels of regional and intraspecific variations (Nesis, 1977;Snÿder, 1998;Chembian and Mathew, 2014;Jiang et al, 2015;Liu et al, 2019;Wang et al, 2019). In the West Pacific, two groups with different ecotypes and morphological characters have been described (Nesis, 1977): a small early-maturing group (EM) without dorsal photophores occupying the tropical Pacific 10°-15°N/S, and a large late-maturing group (LM) with a big dorsal mantle photophore occurring throughout the species range.…”

Biometric Characteristics of the Siboga Squid Uroteuthis (photololigo) Sibogae (Adam, 1954) from the South East Coast of India

“…The details are furnished in [Table 1 ]. Length-weight relationship of DML to Twt, and DML to MWt, for both males and females, were studied and compared by the equation W= aL b , where 'W' is the weight in 'g' , 'L' the DML in mm, 'a' intercept and 'b' slope (14,15) . The relationship between other linear variables were studied by applying a simple linear regression equation, Y= a + bX as recommended by Ricker (16) .…”