Inter-cohort growth patterns of pharaoh cuttlefish <i>Sepia pharaonis</i> (Sepioidea: Sepiidae) in Eastern Arabian Sea

Abstract

Abstract:Sepia pharaonis is an important commercial species endemic to the tropical Indo-Pacific region. Despite its commercial significance, only few information on natural populations is available. This study was aimed to describe the aspects of size-composition, length-weight relationship, catch rates, seasonal recruitment and inter-cohort growth patterns of S. pharaonis population (Clade C), distributed along the Eastern Arabian Sea (South-West coast of India). For this, the Dorsal Mantle Length (DML) and weight of cuttlefishes was obtained from commercial trawl catches, from April 2002 to October 2006. Data was analyzed by normal length-weight methods such as von Bertalanffy. A total of 12 454 cuttlefishes, ranging in length from four to 41cm were analyzed. Size-composition patterns discriminated two pulses in recruitment to the fishery, discernible by a decrease in the monthly mean size of the population. The DMLs of the two seasonal cohorts were subjected to modalprogression analysis using the Bhattacharya's method for the estimation of growth. The estimated parameters L∞ and K in von Bertalanffy Growth Function (VBGF) were used to model growth curves in length for the cohorts. The first cohort, (post-monsoon cohort) which supports the major fishery, was composed of mediumsized, fast growing individuals, whereas the second cohort (pre-monsoon cohort), comprised of slow growing and large-sized individuals. There were differential growth characteristics between the sexes and the life span was estimated at less than 2.3years for males and 2.1years for females. Negative allometric growth in weight (W) with length (L) was observed for males (W=0.33069.L 2.5389 ) and females (W=0.32542.L 2.6057 ). The females were heavier compared to males at any given mantle length, and the males were found to attain larger ultimate lengths. The major fishing season for cuttlefish was from May to November, when higher monthly catch rates of 1.67-13.02kg/h were observed in comparison with 0.03-0.85kg/h in December-April. Seasonal catch rates indicated a migratory life cycle of S. pharaonis between offshore and inshore coastal zones. Rev. Biol. Trop. 61 (1): 1-14. Epub 2013 March 01.

Reproductive Biology of Sepia pharaonis Ehrenberg, 1831(Cephalopoda: Sepioidea) from the Suez Gulf (Red Sea), Egypt.

“…Ghazvineh et al (2012) recorded that the spawning season of Sepia pharaonis from the Persian Gulf covers the whole months with two maximum peaks in May and June (spring-summer). Sasikumar et al, (2013) recorded that the peak of spawning of Sepia pharaonis in the Indian waters (Eastern Arabian Sea) is reported in October/November (Autumn). Sasikumar et al (2013) stated that the spawning season of Sepia pharaonis from the Eastern Arabian sea is reported during October/ November (Autumn) and in February/March (winter).…”

“…Sasikumar et al, (2013) recorded that the peak of spawning of Sepia pharaonis in the Indian waters (Eastern Arabian Sea) is reported in October/November (Autumn). Sasikumar et al (2013) stated that the spawning season of Sepia pharaonis from the Eastern Arabian sea is reported during October/ November (Autumn) and in February/March (winter). Thus it is clear from the above mentioned results that there is marked variations in the spawning season of Sepia pharaonis regarding different localities, for the same species.…”

Inter-cohort growth for three tropical resources: tilapia, octopus and lobster

“…Differential growth patterns between aquatic organisms of different sexes can also influence on population dynamics and stock assessment, particularly in cases where fishing incidence is higher for one of the class groups (Sasikumar, Mohamed, & Bhat, 2013). This is the case of the red octopus Octopus maya (Voss & Solís-Ramírez, 1966), where females show parental care to their young.…”

Can an aggregation-fishery be responsible for recruitment overfishing? A case study on cuttlefish stock associated with moored fish aggregation devices (FADs)

“…The commercial fishing grounds of S. pharaonis are in coastal waters up to a depth of 130 m (Reid et al, 2005). The bathymetric variations in distribution patterns of S. pharaonis documented in exploratory surveys (Chembian and Mathew, 2011), and the seasonality of abundance in commercial fishing grounds (Aoyama and Nguyen, 1989;Sasikumar et al, 2013) indicated migration of S. pharaonis from offshore (depth: 100-200 m) to inshore waters (∼38 m). In the southeastern Arabian Sea, the presence of higher proportions of fully mature and spawning individuals of S. pharaonis in commercial catches (Sasikumar et al, 2013) and occurrence of egg clusters attached to the inshore rocky substratum (Anil et al, 2005) suggest inshore migration of the species for spawning.…”