Molecular identification and genetic variation studies in economically important cephalopods at Beypore Fishing Harbour (Kozhikode), South West coast of India

Cephalopods are ecologically and economically important marine groups in the world. Biodiversity description is essential for sustainable utilization of natural resources and to characterize biological entities for conservation. DNA barcoding is an effective tool used for identification of organisms at species level and is been widely used for delineate several ambiguity species. In this study, partial sequence of mitochondrial cytochrome c oxidase 1 (CO1) gene with a mean size of 680 bp was amplified by universal primers. Totally 13 individuals of Cephalopods comprising of three species, were barcoded and genetic variation was analysed. The maximum A+T content (67.60%) was recorded in Cistopus indicus and minimum (63.70%) in Sepioteuthis lessoniana. The maximum K2P distance (0.268) was found between the genus Cistopus and Sepioteuthis whereas the minimum distance (0.188) was observed between Uroteuthis and Sepia. The neighbour joining tree revealed three distinct clades represents Loligonidae, Sepiidae and Octopodidae with high boot strap values. However, Sepioteuthis lessoniana is showing a bifurcated branch and it may due to the co-occurring of cryptic species and till date this species is treated as Sepioteuthis lessoniana complex.

DINAMIKA POPULASI DAN LAJU EKSPLOITASI CUMI-CUMI (Sepioteuthis Lessoniana) DI KEPULAUAN SPERMONDE SULAWESI SELATAN

Squid Sepioteuthis lessoniana is a sought-after fisheries commodity, leading to a high exploitation rate. This affects the sustainability of Squid (S. lessoniana) resources in wild, especially Spermonde Island. The aim of this study was to determine the population dynamics and the exploitation rate of Squid (S. lessoniana) in the Spermonde Islands of South Sulawesi. The results of the study are expected to provide information on the level of utilization of Squid and as a basis for sustainable management of squid in Spermonde Islands. The present study was conducted from March to July 2019 in Spermonde Islands, South Sulawesi. A survey was performed by direct measurement of the fish captured by local fishermen and merchants. Data collected on length and weight of squid were carried out for 3 or 4 times a week. The results showed length of squid ranged from 06 to 28 cm, the relationship between the length of the weight was negative allometric, the age group consisted of 4, the growth rate (K) of 0.37 per year, the maximum length (L max) of 31.5 cm, the total mortality rate (Z) of 2.85 per year, the natural mortality rate (M) of 0.95 per year, the capture mortality rate (F) of 1.90 per year and the exploitation rate is classified into over-exploitation.

Evaluation of the 137Ba mass-marking technique and potential effects in the early life history stages of Sepioteuthis lessoniana

The use of mass-marking techniques of enriched stable isotopes has increased in studies of ecology, movement patterns and the dispersal of marine organisms. However, the efficacy of this technique and its potential effects on hatchling size and statolith chemistry of cephalopods are yet to be investigated. Sepioteuthis lessoniana egg capsules were collected from northern Taiwan and assigned randomly to 137Ba-spiking experimental groups at 0.2, 0.5 and 1ppm and three immersion durations (1, 3 and 7 days). Immersion duration >3 days produced significantly lower 138Ba:137Ba ratios, with 100% marking success, indicating that it is a reliable marking technique. The 137Ba mass marking had a positive effect on size at hatch and was likely to affect statolith trace element incorporation, including Cu, Zn and Pb. These findings highlight that it is necessary to consider the species-specific effects on hatchling size and physiological responses in when using stable isotopes mass-marking techniques.