Cephalopod resources of the Southern Ocean are considered to be distinct from other oceans with high levels of endemism in squids and particularly in the Octopods (Allcock et al., 2001; Collins and Rodhouse, 2006) Loliginid squids, sepiids and sepiolids are reported to be absent in Southern Ocean and all the squids are oceanic pelagic species. Cephalopods play an important role in the ecology of the Southern Ocean and act as a linkage between abundant mesopelagic fishes, crustaceans, sea birds and whales. Cephalopods are exclusively marine predators and voracious carnivores with very high metabolic and conversion rates. They feed on live prey throughout their life cycle. The commercially important cephalopods under the phylum Mollusca include nautilus, cuttlefish, octopus and squids. Our knowledge on the food and feeding ecology of cephalopods in the Southern Ocean is limited to commercial species including neritic octopuses, cuttlefishes and loliginids, and squids of the family Ommastrephidae (Rodhouse and Nigmatullin, 1996). In the Southern Ocean, the dietary habits of only a few species have been investigated (Rodhouse et al., 1992; Jackson et al., 1998, Philip, 2001). More work is needed on the cephalopod biology for a better understanding of their role in marine ecosystems of the Southern Ocean.
Squid jigging accounts for nearly 40 per cent of the world cephalopod catches followed by trawling, which contributes 25 per cent of the catch. Gillnets are also used for catching the squids, which accounts for nearly 10 per cent of the catch (Mohamed and Sarvesan 2004; Mohamed 2008). Gears like shore seines, boat seines, hooks and lines and spearing are the popular methods to catch cephalopods (Mohamed 2008).
Cephalopods are considered as an important source of marine fishery resource and many of the species are exploited as bycatch by trawlers along the Indian coast and the fishery forms 4-5 per cent of the total marine fish landings (Mohamed, 2008). Nair et al., (1990) highlighted the importance of the oceanic species in the Arabian Sea and Bay of Bengal waters. India government with the association of private trawlers conducted exploratory trawling for the cephalopod resources in the Indian EEZ since 1977-80s (Silas et al., 1985). Arabian Sea is considered as one of the richest fishing regions for Sthenoteuthis oualaniensis (Mohamed, 2012). The preliminary studies on the oceanic squids in the Arabian sea indicated that the area around Lakshadweep Islands is a major spawning grounds for oceanic squids (CMFRI, 2011). These species are known as the masters of the Arabian Seas due to its high abundance and large oceanic squids occupy and monopolise the trophic niche of apex predators in the Arabian Sea (Mohamed, 2011). Fishermen started hand jigging for squids along Pak Bay coast of Tamil Nadu since 1990 (Lipton 1990). Balasubramanian et al. (1995) reported the hand jigging for catching coastal squids along Tuticorin coast.
Fish aggregating devices (FADs) are traditionally used by the fishermen to attract and aggregate the fishes closer to the shore. Fishermen from Karnataka started FAD assisted cephalopod fishery in coastal waters of Karnataka (Sasikumar et al., 2006). The authors indicated that the FAD associated cephalopod fishery increases the vulnerability of spawners to exploitation. Venkatesan and Shanmugavel (2008) reported hand jigging operations for catching squids and cuttlefishes from themocole float along the Palk Bay and at Keelakarai in the Gulf of Mannar, southeast coast of India. These fishing operations are carried out at a subsistence level. The introduction of high opening bottom trawl nets leads to an rapid increase in the cephalopod production from the Indian EEZ (Sundaram and Deshmukh, 2011). Coastal cephalopod resources in Indian are facing tremendous pressure due to fishing. The exploitation of untapped or under exploited oceanic squid resources from the Arabian Sea will reduce this fishing pressure taking into account the relative huge quantity of the unexploited resources (Mohamed, 2006).
Materials and Methods
Squid jigging operations were carried out by the Central Institute of Fisheries Technology, Cochin, (Indian Council of Agricultural Research) during the 6th Southern Ocean Expedition conducted the National Centre for Antarctic and Oceanic Research Goa during 23 December, 2011 to 6 February, 2012. The experimental jigging was carried out to understand the scope of squid jigging, species diversity and biology of the oceanic squids inhabited in the Southern Ocean waters.
Squid jigs of various makes and types were rigged onboard for hand jigging during the first week of January 2012 (Figure 2). Hand operated squid reels were fabricated onboard using available materials and the same rigged with various types of jigs and loaded on the reels for the fishing operations.
Squid jigging operations were carried out for eleven nights and one fishing operation was carried during the day using a hand reel fabricated on board. All the ship lights were operated (12000 W) during night operations. Three different types of jigs were operated (local jigs, jigs with LED lights and imported jigs). Hand lines were operated for most of the stations while hand reel operations were carried out only in two stations.
The details of the squid jigging operations are given in Table 1. Catch was obtained only from the hand jig operations. The percentage catch from various jigs operated is shown in Figure 1. A total of 71 squids, weighing approximately around 60 kg (total weight) was landed by squid jigging. Three species were identified namely; S. oualaniensis, S. bartrami and T. filippovae. S. oualaniensis was caught at 0oS and 77o 3’ E. S. bartrami was caught at 40o S and 53o to 58o E. T. filippovae was caught at 43oS and 53o to 58o3’ E. S. ovalaniesis and S. bartrami are widely reported from the tropical Indian Ocean and T. filippovae is typically a Southern Ocean species.
Due to very rough seas and strong currents and winds during the cruise, squid jigging was not possible in all the sampling sites. Squid aggregation was notedly very less and therefore most of the squids had to be caught by throwing the jigs far away from the ship. Due to non-aggregation of squids close to the vessel the hand reel jigging operations could not be carried out. However, hand reel jigging operations were tried during day time by sending the jigs at deeper depths (up to 100 m). During hauling operations 10 squids escaped owing to strong currents and rough sea.
The development of distant water fishing operations is one of the main options for increasing marine fish production in the country. Most coastal stocks of the Indian marine fisheries industry has been fished to their maximum potential. There is good scope for expanding fishing for the oceanic stocks like oceanic squids. There is abundant stock of oceanic squids in the deeper waters of Central Arabian Sea and is considered as one of the richest regions for the oceanic squids. Squids are fast growing, short lived and are known to withstand high fishing pressure. Commercial fishing for oceanic squid is non existent in the country due to lack of information on abundance, distribution, and suitable fishing methods. Techniques for harvest and post harvest handling and processing of oceanic squid will have to be developed for successful commercial fishing operations of oceanic squids.
The study was carried out as part of the India’s 6th Southern Ocean Expedition Programme conducted by National Centre for Antarctic Ocean and Research (NCAOR), Goa. The authors are thankful to the Coordinator of the Expedition for his cooperation throughout the expedition. The authors are grateful for the encouragement given by the Chief Scientist Dr. C. T. Achuthan Kutty and all fellow participants in the Expedition. The authors would like to thank the Captain and crew of ORV Sagar Nidhi for their support onboard for sample collection. We also thank the Director, Central Institute of Fisheries Technology, Cochin for providing the necessary facilities.
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