Distribution, age and growth of the diamondback squid, Thysanoteuthis rhombus (Cephalopoda: Thysanoteuthidae) from the tropical Arabian Sea

• Published in: Fisheries Research
• Main Authors: Sajikumar, K K, Sasikumar, Geetha, Venkatesan, V, Vidya, R, Alloycious, P S, Jestin Joy, K M, Sahib, Karamathulla, Nataraja, G D, Mohamed, K S
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2020
• Subjects: Gastropods; DML
• Online Access: http://eprints.cmfri.org.in/14132/; http://eprints.cmfri.org.in/14132/1/Fisheries%20Research_2020_Sajikumar%20K%20K_Distribution,%20age%20and%20growth%20of%20the%20diamondback%20squid,%20Thysanoteuthis%20rhombus.pdf; https://www.sciencedirect.com/science/article/pii/S0165783619303339; https://doi.org/10.1016/j.fishres.2019.105478

Individuals in all life stages of the large oceanic diamondback squid Thysanoteuthis rhombus were observed in the southeastern Arabian Sea. A total of 82 individuals were collected from the Arabian Sea between February 2013 and December 2018. The length-weight relationship follows an allometric growth pattern. Age and growth were estimated by statolith increment analysis (n = 77) and demonstrated a rapid growth rate ranging from 1.42 to 4.80 mm dorsal mantle length (DML)/day. Based on back calculated hatch dates, T. rhombus spawned from May to December with a peak in July. Male and female squids matured at 6 months of age. The oldest individual was a mature female (655 mm DML) that was 220 days old with a growth rate of 2.97 mm DML/day. Differences in size-wise (DML) instantaneous growth rates were evident. Stomach content analysis revealed that fish and squid were the major prey of adults and sub-adults, while in juveniles, crustaceans were the dominant prey item. Ontogenetic differences in the diet were apparent.